How One Decision Ruined British Aircraft Engines

The lack of a fuel injection system in early British aero-engines is often criticised as giving pilots a disadvantage in the air against German Bf 109 fighters. But why did Britian not have a fuel injection engine, when it had developed this technology?
- Reading Recommendation
Calum E. Douglas, The Secret Horsepower Race - Western Front Fighter Engine Development, Tempest Books: 2020
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- Sources -
Calum E. Douglas
- Timecodes -
00:00 - Intro
00:45 - Calum E. Douglas
01:00 - Fuel Injection
01:31 - What's a carburettor
04:03 - Problems with carburettor
06:37 - Timeline
08:44 - Why did Britain fall behind?
17:46 - The War Starts
20:58 - Temporary fix and RAE carburettor
22:59 - What is direct fuel injection?
26:42 - Recommendation

[@herrakaarme]

The whole thing reminds me of the American torpedo scandal, with the Bureau of Ordnance claiming Mark 14 is perfect and any troubles are user errors or individual odd cases.

[@Battleship009]

Wonder why anyone at the top weren't sacked for their actions.

[@Hachaimenesch]

@@Battleship009 you must not wonder about this. If errors of such ridiculous magnitude are being made, there have already been failures in judgement in the hiring process years before. You don't end up with someone like this Dr. Morley in a position as a decision maker, without others already messing up big time by selecting such a person for the job he had. In such an organization you cannot expect those responsible being sacked, because everyone involved will be busy covering up their own mistakes

[@Battleship009]

@@Hachaimenesch The BuOrd refused to admit its mistakes until Admiral King stepped in as the BuOrd''s incompetence cost the lives of many servicemen.

[@Hachaimenesch]

@@Battleship009 the important factor in case of those faulty torpedoes is that Admiral King intervened. If there is no one to intervene, who actually knows, what he is doing, people get away by acting surprised that everyone else is replacing carburetors and since even a stupid person can follow a trend, introducing fuel injection following the lead of other, much more competent engineers, eventually resolved the issue

[@sakukullberg2697]

@@Battleship009 Because they're at the top.

[@user-qf6yt3id3w]

This is an example of what happens when you have one expert whose decisions cannot be questioned by anyone else.

[@stanthology]

Like old J. Edgar!

[@trauko1388]

And a camel is a horse designed by committee... it ALWAYS comes down to the type of people you have up there.

[@primmakinsofis614]

_This is an example of what happens when you have one expert whose decisions cannot be questioned by anyone else._ Sounds rather like what's gone on over the last year and a half or so in regards to a certain virus.

[@jimwoods9551]

You just have to hope you have more correct people than Dr Morley’s. It’s human to have Dr. Morley types. You could add the demise of mass automobile manufacturing in the UK to his list of achievements due to prejudice against fuel injection.

[@iangascoigne8231]

@@primmakinsofis614 Really? The one expert who the vast majority of other experts happen to agree with him? You’ve shot your own argument in the foot. You need a better example. Though what this has to do with an aviation film is beyond me.

[@cncshrops]

Callum's book is as good as you might imagine from this presentation. It's worth pointing out, however, that none of the combatants in ww2 got it all right. The German advantage from fuel injection was balanced by a failure to appreciate the benefits of high pressure cooling systems. This required larger radiators with consequent increased drag. It's worth remembering just how much time pressure everyone was under, particularly once war had been initiated. Mistakes made in the runup to war had to be lived with as there was simply no time to start down a different path.

[@TheHarryMann]

@cncshrops … but it may not have been a mistake. Might have been a conscious high-level decision that it was just a bridge too far

[@DC.409]

@@TheHarryMann indeed the other side of the coin is Cold Charging which all other nations pursued using carburettors. The supercharger heats the air under compression, introduction of fuel, through thermal dynamics the evaporation of the fuel, it cools the air consequently a greater volume of air and fuel enters the cylinder producing a bigger bang. The Merlin with 100 octane fuel generated more power at a greater height than the DB 601, because the air from the German supercharger was hotter, no cooling so around 9,000 feet against 5,000 feet. In combat power at height is king, consequently the greatest engines are the Merlin and the PW 2800, they powered the most successful allied fighter aircraft, Spitfire, Mustang, Mosquito, Corsair, Hellcat, and Thunderbolt.

[@CalumDouglas]

@@DC.409 You can also obtain all of that with injection. BMW801 had a 15th injector in front of the supercharger, (has 14 cylinders) which obtains a similar benefit (slightly less as its not the full fuel charge). DB and Jumo did the same but with Methanol-Water or Nitrous through the supercharger, which also obtain similar effects. Also remember that when you go to injection you delete the chokes, which are by definition flow restrictors, this also buys you back a lot of that gain, and, in a well designed system, you will make more power with injection overall, this is clear from nearly all the experimental data.

[@DC.409]

@@CalumDouglas Indeed but the penalty is extra weight 109K has a 118-liter tank behind the cockpit for MW50. Though the performance was called incredible, it was outclassed by the Mustang and Griffon Spitfire. Didn’t Stanley Hooker run similar tests on the Merlin but rejected the development, I believe because it would cause too much disruption to production. I think you then run into the pragmatic British strategic and operation philosophy of the war, good enough today, excellent tomorrow. A number of proposals were rejected because of that principle when the German designers proceeded to progress them, but at what cost to production.

[@JimChamp]

@@DC.409 Indeed. As with almost all engineering there are tradeoffs. The charge cooling effect of the cab gave more power all the time. The negative g benefit of fuel injection was only useful under negative g. Emotive language like ruined makes for a good headline, but I suggest the engineering reality is much more nuanced. One might look at the headline photo and suggest that without the extra power the Spitfire might not have got there in the first place.

[@lukelee5385]

11:38 I feel like for every major invention in military history, there is a guy in the higher ups decide he doesn't like it personally

[@hunormagyar1843]

ikr lmao

[@joevignolor4u949]

Admiral Hyman G. Rickover, who is known as the father of the nuclear navy, was often asked what was the hardest part about building the Nautilus, which was the first nuclear powered submarine. He said that it was convincing people to build it.

[@moosemaimer]

See also Brigadier General William Crozier, US Army Chief of Ordnance, whose job explicitly involved adopting and procuring machineguns but seemed almost incapable of doing so.

[@SheriffsSimShack]

this is just great and I like that Chris provides the plattform here.

[@Tigrisshark]

Again, a wonderful piece of content- I really enjoy the mix between modern stuff and historical debate! It seems as if the more of an expert you are in a field, the more your desire to facepalm at certain errors increases. Seen it with Dr. Franke and here again with mr. Douglas. I just love the amount of learning is being presented in these.

[@RaduB.]

On 13th of November 2021 it says that you posted this comment 12 days ago... Yet the video came out on the 11th. Interesting! I really agree with you, though!

[@trauko1388]

@@RaduB. Patron

[@donjones4719]

In an interview Elon Musk said he tells every engineer to assume every piece of work handed to him is flawed, because nothing is perfect. The engineer should be even more aware of this if the work was done by one of the brightest (higher ranking) engineers on the company - because no one's perfect.

[@spitfiremark1a768]

It is worth reading Sir Stanley Hoooker's book "Not much of an Engineer". Worked at RR from 1938 and instrumental in developing the Merlin. He mentions carbs and fuel injection. Our fighters were designed as bomber destroyers. At the time, German fighters did not have enough range to reach the UK from Germany. Bombers cannot do fighter manouvres hence our fighters did not need fuel injection. Obviously the fall of France changed all this.

[@markdavis2475]

Great book. Had my copy for years. Questionable ethics later on but the WW2 stuff is great.

[@spitfiremark1a768]

@@markdavis2475 Yes a good book. Most interesting. I also recall an account by an aerodynamacist who evaluated the Spitfire in the 30s saying that they were more concerned about how aircraft performed on perfectly sunny days doing nice aerobatics. Screaming downhill at ones maximum permissable was frowned upon and academic The realites of war brought these naive ideas home to roost.

[@genericpersonx333]

Really points out the problem that at some point, someone has to make an arbitrary decision on whether doctrine focuses development of technology or technology informs the development of doctrine, and if you don't have a brilliant synthesizer in charge, someone who can see both sides of the process, you end up with equipment that doesn't really do the job needed. People will obsess about the politicians and others interfering which is a real problem of its own, but even when the "professionals" are the ones making the decisions, it is unfortunate that the professionals tend to also not have a wholistic view of the problem either. The real marvel is any weapon system ever works well in the end.

[@spitfiremark1a768]

@@genericpersonx333 They had no concept of modern dogfighting. Just look at the RAF fighting area attacks that they were trained to fly prior to the war. All lining up to take a shot at a single bomber, then go round for another squirt. Not thinking enemy fighters might have something to say about it. Also, the first 109's were apparently inferior to the Hurricane. The Spanish civil war, and other improvements in manufacture or service meant that the Hurricane was surpassed by 1940.

[@BunkerFox]

I misread that as "He mentions *crabs* and fuel injection." I re-read and was very disappointed

[@tisFrancesfault]

Dr Morley should have been awarded an Kriegsverdienstkreuz for contributions to the war effort....

[@genericpersonx333]

In fairness, the fact that British industrialists simply accepted his report and quit bothering is the bigger issue, as it fed into a cycle of British industry complying with the government rather than challenging it to the detriment of both. In the USA or Germany, a definitive report from the Government frequently inspired someone in industry to prove the report wrong. So the real culprits are arguably the industrialists for letting one government report have more weight on their decisions than all the engineers those industrialists were employing who were telling the industrialists that there was clearly potential.

[@drstrangelove4998]

🥳

[@Selvariabell]

It's like saying Hitler should receive the Victoria Cross and Admiral Yagumo the Congressional Medal of Honor.

[@michaeloneil2379]

@@Selvariabell no

[@Selvariabell]

@@genericpersonx333 It's more on British conservatism rather than compliance that is the issue. The British has a traditionalist mindset when it comes to engine development, especially if they're foreign in origin. The British lagged behind in adopting newer technologies such as fuel injection, turbocharging, etc. People always think of the Americans to be the "no replacement for displacent" muscle-car loving guys, when the Brits are in fact more reactionary when it comes to engine technology.

[@TchaikovskyFDR]

I know a lick of nothing on engines and Mr Douglas explained it such ease that I was able to come to a meagre understanding of such complex machines! W o w

[@davidbrayshaw3529]

Yes, an excellent display of knowledge and eloquently conveyed. Now if he could just explain the workings of governments and bureaucracies...

[@TheSulross]

david brayshaw that would defy any rational manner of understanding

[@cap10bc]

As always, Calum is explaining things so that everybody can understand. I think he has a gift.

[@CzarOfMars]

fascinating! as an engineering student who's also a history buff this is just perfect. Loved the way he explained technical concepts in a very approachable manner without dumbing it down.

[@grimgorkeisenpelz9392]

This was great! He is really great in explaining technical details so that everyone can understand this. Many thanks for inviting him.

[@ddegn]

Agreed!

[@generalharness8266]

Ice'ing was something I did not even consider but yea reduced pressure in going to have all kinds of problems.

[@EllieMaes-Grandad]

@@generalharness8266 My VW Golf2 had a replacement carb [Weber]. Performance was much improved over the factory-fitted Pierburg. However, icing was a problem, especially in cold, damp conditions, leading to fuel starvation and engine failure. Several minutes at the roadside allowed it to 'thaw out' and I could continue driving. The problem was exacerbated by the use of a more efficient, free-flowing exhaust manifold. A look under the bonnet/hood when stopped showed condensation on the carb body. Never seen a comment on carb icing in WW2 aircraft . . .

[@derekr6124]

Very glad you were able to have Mr Douglas present this. Was interesting and a topic I had not considered before. Cheers!

[@zoeytasker6078]

Just got home after walking 2 hours I’ve watched ur channel for about 4years roughly and I’m looking forward to finally learning y the spitfire had no fuel injector big up to Bismarck and to the guests and helpers over the years on the channel

[@tobiaskarlsson9094]

Once the merlin was developed there would have been substantial redesign required to fit a direct injection system. However it would have been easier to design and mount a injectionsystem similar to a multipoint injection system from a car. If you can't put the injector tip in the combustion chamber put it in the intake before the valve. Some one should have that dr asshat keelhauled.

[@johnburns4017]

@@tobiaskarlsson9094 The supercharger also pre-mixed air/fuel, which is great advantage. The charger mixes the air/fuel very well before it enters teh cylinders, which is not the case with _direct_ fuel injection, as the engine only draws in air not a well premixed charge, relying on mixing inside the cylinder. A supercharger also delivers the same amount of fuel equally to each cylinder, as does multi-point direct fuel injection. The supercharger only needs one point for injection of fuel - using either a suction or pressurised carburettor (a pressurised carb was entry level fuel injection). Once supercharging advanced, such as twin chargers, twin-speed, multi-point _direct_ fuel injection gave no advantages whatsoever. It gave disadvantages such a bore wash. The vid is about pre and early war engines.

[@tobiaskarlsson9094]

@@johnburns4017 yes it is. But they could have fitted something once they realized their mistake. Instead of having a carb with an orifice in it. Throw the carb mount the injectionsystem before the charger if you want those advantages. Doesn't the fuel going thru the supercharger give a cooling effect to the air/fuel mix also?

[@johnburns4017]

@@tobiaskarlsson9094 Firstly Mrs Shilling's fix had to be retrofitted to fighters ASAP. Then a pressurised carburettor was fitted to fighters. Would a bomber need a retrofitted pressurised carburettor? Doubtful. You also need the products available. They are not made overnight.

[@tobiaskarlsson9094]

@@johnburns4017 jupp there is that and yes a bomber doesn't need a press carb. But they could have done it. Once you have the press carb you might not need a simple multipoint injection system because there is no gains to be had over the press carb.

[@davebarrowcliffe1289]

In the film, "Battle of Britain", in the opening credits, there is the sound of a Spitfire engine cutting out... Once you've noticed it, you'll never NOT notice it... 😀👍

[@benjaminbuchanan7151]

It’s a Hurricane… but similar engine system yes.

[@davebarrowcliffe1289]

@@benjaminbuchanan7151 Memory fades! Of course it is!

[@Nick-ye5kk]

@@benjaminbuchanan7151 If it's the hurricane doing a flat roll with a cough and puff of smoke then it wasn't the Battle of Britain, I forget the name of the film unfortunately.

[@givenfirstnamefamilyfirstn3935]

@@Nick-ye5kk It is over the retreating British soldiers in the opening of Battle of Britain, it is on KZbin.

[@Nick-ye5kk]

@@givenfirstnamefamilyfirstn3935 Thanks for that, the film I'm thinking of was Reach For The Stars, so presumably the Merlin coughed at every opportunity.

[@JimChamp]

In "not much of an engineer" Sir Stanley Hooker states that a major reason for retaining a carb of some kind was that the charge cooling provided by the carburetor provided a significant horsepower boost and was a key reason for retaining carburetion. Extra power = faster time to height. The design philosophy of the Merlin (27 litre) and DB601/5 (34/35 litre) were significantly different and its hard to make comparisons.

[@johnburns4017]

That may be the case in atmospheric engines, however... When using a supercharger, the air is compressed then heated, then taken through a radiator to cool the air before entering the cylinders (done on turbo charged trucks these days).

[@givenfirstnamefamilyfirstn3935]

@@johnburns4017 The 109 didn’t have an inter/after cooler. The direct injection fuel was added after the comparatively hot and less dense supercharged air mass had already filled the cylinders so there was little cooling while the inlet valves were still open.

[@johnburns4017]

@@givenfirstnamefamilyfirstn3935 Which was a disadvantage.

[@MrHobbit60]

I was just going through the comments to see if someone has mentioned this. Yes, Hooker stated quite plainly that the charge cooling effect from the accelerator pump on a carburettored motor meant that the pilot got a significant power boost just when needed, and that in the context of the Battle of Britain, in particular, (Being jumped by 109's) this advantage outweighed the disadvantages of the engine cutting under negative G. That problem was solved by Miss Shilling's orifice, of course, so was well in hand by late 1940.

[@anthonywilson4873]

@@johnburns4017 The air being compressed gets heated if it’s cooler to start with it will be cooler after its boosted its an aid to the intercooler.

[@jameslawrie3807]

I suspect the British authorities were concerned with *Bore Wash* Bore wash is a problem that plagued early injectors. It is where excess fuels wash away the lubricant of the cylinder wall and cause a loss of compression and possible seizing. Remember, military aircraft don't just run while in the air doing combat stuff but also get many hours on the ground. Bore wash, while mainly concerned with engines that have just started can conceivably cause engine seizure during take off with catastrophic results. I might also note it's unlikely the Germans and the Americans were sharing their data with the British. :) Bore wash and similar injector problems also kept injectors out of motorcycle engines, another engine type that must be lightweight, put out large amounts of power and changes orientation (although obviously nowhere near that of an aircraft) until digital injectors became available.

[@johnburns4017]

I had a Mercedes Benz 230SL with a mechanical fuel injected engine. It suffered from bore wash. The injectors needed constant cleaning to ensure a proper atomised spray cone. Later, superior oils reduced the problem as they were more _sticky,_ keeping oil on the cylinder walls.

[@CalumDouglas]

Bore wash is concerned with direct injection (unless its an astonishingly badly designed port injection system), and since I have rather obviously read all the reports, I can tell you the British were not interested in bore wash - the Germans were, as they`d been forced into using fuels with too high an evaporation end-point, which then caused oil dilution. Also, up until an astonishingly late date, the British, Americans and Germans WERE sharing all the details, as huge amounts were published in academic journals which were available to all. Britain even kept reading them after the start of the war, because they managed to get copies of the journals (which were still being published inside Germany) sent to them through various "friendly" Embassies in Germany.

[@johnburns4017]

@@CalumDouglas The Mercedes Bosch system, apart fro the first in the 300SL, was spraying into the ports, not direct. But if the injector was not a fully clean spray in a 60 degree cone of fuel, it never full atomised, then bore wash. It was clear looking at the cylinders, especially one of them, bore wash was occurring. Using contactless electronic ignition made a _hell_ of a difference. It worked better when at high constant speeds.

[@johnburns4017]

@@CalumDouglas Callum, why were the Germans producing inferior, or unsuitable, fuels?

[@SheepInACart]

@@johnburns4017 That ones easy to answer, they didn't lack refininging knowledge, but rather access to quality feedstock. Germany doesn't have much oil resources domestically, meanwhile the USA was the worlds largest exporter of oil at the time. They actually made a lot of oil products from coal, which was amazingly advanced, but also more difficult, expensive, and limiting than just having a huge amount of high quality oil, especially as US wells and infrastructure was outside of the threats of bombing or capture, while allies directly attacked power infrastructure (including fuel) in Germany for much of the later conflict.

[@DBSTH0R]

More content with Callum please. Excellent video. You can tell he knows how to explain things, when even non technical people can uderstand it. This is one more reason what makes his book worth well the read. :)

[@nickdanger3802]

In 1936, the first Bendix-Stromberg pressure carburetor (a model PD12-B) was installed and flown on an Allison V-1710-7. The engine used in most P40's and early Mustangs. Wackipedia

[@4evaavfc]

I wonder if Dr Morley ever knew that Allied pilots lost their lives because of his decision not to support injection.

[@CalumDouglas]

I would think it is highly likely he did. It was a huge controversy in 1940 in Britain when the deficiency became clear in combat. See page 174 of my book. "“The engine defect of cutting at the commencement of a dive...been a sore point for some months, and has probably saved the lives of many enemy pilots who have traded on it." February 5, 1941, Sholto Douglas

[@hansvonmannschaft9062]

@@CalumDouglas Hope you get to read this comment sir. You just gave an amazing class. Both on the subject at hand, and on how to be a top-of-the-line university professor. In respect to the latter, hopefully some university professors happened to see this video and learnt the importance and difference between repeating a book from memory until the students fall asleep, and using simple yet also rich and precise terms to bring to life their topics, while also instilling curiosity and learning enthusiasm in the classroom. Bravo, and thank you extremely much!

[@andrewgause6971]

@@CalumDouglas Thank you for your explanation. You did a great job!

[@farrier2708]

@@CalumDouglas I understood that British pilots overcame some of the shortcomings of the carburetor by using aerobatic manoeuvres that maintained the correct G-force on the fuel system. I'm no historian, so I do stand to be corrected.

[@firstlast9384]

@@farrier2708 yes I read that in the 1990's magazine Take Off … they had an illustration of that problem with the Messerschmitt doing a straight dive and the Spitfire/ Hurricane would have to roll over and invert to dive down

[@gort8203]

Superb video. The depth of content on this channel has been increasing and the collaboration with other experts really adds a lot.

[@rokuth]

IIRC, just prior to the start of WW2, someone had tried to smuggle the fuel injection system of the Daimler Benz engine to a British Embassy (Consulate?) in a European country. However the British staff had refused to accept it.

[@jimjardine4705]

Oh no!! Bloody typical British bureaucracy!!

[@tr1sh2tom]

Best book on wartime engine development: The Secret Horsepower Race, by Calum Douglas. If you thought carburetors were a bad idea, imagine Germany trying to make aero engines out of garbage pot metal, due to mineral shortages....

[@kurttappe]

Morley had a choice. The Germans didn't; they were handcuffed by their material shortages. Morley had no reason to deny fuel injection was better.

[@Bartonovich52]

The Germans also needed direct injection (not just any type of fuel injection like sequential port, multi port, or throttle body) because they had no access to high octane fuels. While the RAF were able to secure high octane fuel from the USA enhanced with tetra-ethyl lead to make up to 145 octane performance… the Luftwaffe was running on 87 octane until well into the war. Of course.. had the u-boats been more successful.. the Brits would have had to reduce the amount of boost they were allowed to use.

[@jacktattis]

@@Bartonovich52 The UBoats were being sunk left right and centre

[@nickdanger3802]

Attention: The Stromberg pressure carb was invented in the USA and first used on the Allison engine in 1938.

[@bobsakamanos4469]

Rolls Royce created their own fuel pump for the Bendix on the Spit IX that solved some of the issues with it (eg. using a vane type fuel pump that could clear the airlock). Bendix then copied that to produce a better pressure carb - the Bendix PD18 used on Packard Merlins.

[@nickdanger3802]

@@bobsakamanos4469 "For the next important and powerful Merlin 66 engine, Rolls Royce finally decided to use the Bendix-Stromberg Injection carburettor. The American Bendix-Stromberg pressure carburettor was developed in the mid 1930’s and was in production from 1938. This carburettor was designed to operate as a fully pressurised fuel system that dispensed with the problematic float controlled fuel level with its emulsion tubes and diffusers. Negative G had no effect on fuel flow or carburettor function. The pressurised and metered fuel flow was delivered as a spray into the inlet air stream just in front of the supercharger inlet. This feature virtually removed the risk of carburettor icing, in fact the throttles and chokes of the injection carburettor did not need heating by hot oil or coolant circulation at all and their deletion removed several other problems associated with the previous provision of those heating circuits. Rolls Royce had been aware of the Bendix-Stromberg Pressure type of carburettor for several years and versions of the carburettor were used on many American engines including the Allison V-1710. Notably, Packard built their Merlins in the USA with a version of the Bendix PD16 from the very start of Packard Merlin production. For the high power Merlin 66, Rolls Royce needed an even larger choke carburettor and decided to modify the Bendix PD18 type Pressure carburettor to suit. Suitably modified, this carburettor was fitted as the Stromberg 8D44/1. There were some problems with the Bendix pressure carburettor, particularly if excess air was allowed into the fuel system, but this was resolved with internal bleed venting of the D chamber of the carburettor and, by using a vane type fuel pump that could clear the airlock." ROLLS-ROYCE MERLIN CARBURETTOR DEVELOPMENT © Chris Starr 2023

[@jayklink851]

Brilliant video, I'm sure the community would enjoy more appearances from him. Concise information that is easy for the laymen to understand while still entertaining.

[@DanielWW2]

And that is another €35 down the drain for yet another book that won't fit in my bookcase. I hope you are happy now. 😅 This one was already on my "to get" list and this confirmed it. Because this is exactly the type of detail I like in my books. I love collecting those special books that just cover a subject very well.

[@malcolmmoy]

You will love it, but warm your arms up before you read it, it's a heavy book. In both senses of the word :)

[@DBSTH0R]

You won't regret it. One of the best books written on the subject, with so many info in there. I bought it from one of the earlier videos Chris did with Callum. :)

[@TheSulross]

well, the women ought to even love this book as will see how the woman got it right and the man that was the presumed expert got it tragically wrong (by evidently just being stubbornly bull-headed instead of objective)

[@jeremyohara5707]

@Danielww2 its comforting to know its not just me with books....I have over 200 i am trying to slim down, so far, trying to find books to throw out has been slim pickings :D

[@TheSulross]

jeremy O'hara I rationalize it that I am serving humanity as when the current digital civilization crashes these printed books will be our resource of knowledge for a civilization reboot. So just explain it to the spouse that way.

[@CarlosTehJackal]

An excellent and informative video. Thanks for having Calum on to talk about this.

[@Completeaerogeek]

Stanley Hooker, developer of the Merlin 60 series points out that fuel and air leaving a carburettor, cools the inlet charge allowing higher boost. When the Bendix injection carburettor came along it was the best of both worlds. And let's not forget Miss Shilling's orifice (the RAE restrictor) !

[@dianedougwhale7260]

Spot on ! The facts .

[@richardhart9204]

I know next to nothing about aeronautical engineering; however, it strikes me the phrase "gravity-fed" should form no part of a combat aircraft's planning or design.

[@moosemaimer]

stupid squishy pilots and their inefficient pumping systems

[@everTriumph]

Even dry sump engines need to know where to draw oil from. Oil also causes problems if it accumulates in the wrong bits of the engine. Even modern fighter jet engines have only a limited time they can fly inverted before the engine destroys itself. Can't escape gravity that easily.

[@danielcamacho1913]

Considering having gravity go the wrong way can cause capillaries to rupture in a pilot’s eyes and brain, it hardly seems useful to design an engine to maintain power during a negative G maneuver the pilot didn’t want to do in the first place.

[@Ro-zn6um]

Fascinating stuff! And the book is great idea for a present for my father. One of his favourite topics for storytelling is when he studied to be an aicraft mechanic just after WW2. I know he will like this. Thanks!

[@topiasr628]

Wow. What a great, great presentation! Thanks to you both!!

[@tsegulin]

I've read Calum Douglas's superb book (I don't think I've been quite as impressed with an aviation book since I discovered Heinz W. Nowarra's books on the Fw-190 and Bf-109 when I was a kid in the sixties) but this is the first time I've understood how overlapping valve timing made sense and why it only worked with direct injection and why that dramatically improved fuel economy. Excellent episode gents - thank you so much!

[@johnburns4017]

I looked again. The pressure carburettor _continually_ injects fuel (like a non-pressurised carb), so the valve overlaps have to be the same. The direct injected fuel system only injects the correct amount of fuel when the valves are closed, which is not a continual injected process, so needing different valve overlapping.

[@2lotusman851]

You are correct, on the pressure carb. But only a portion of the fuel is continually fed into the the engine. The balance of the fuel is metered in like a regular carb. I dont remember the percentages. This reduced the chances of the carb misbehaving while doing aerobatics. I think the first engines in the US that were fuel injected were on the B-29s Wright 3350s. This improved the fuel distribution, and the overheating problems largely went away.

[@BIGparge]

Another side to the story is that during the Battle of Britain, the more complex German fighters were produced at about 180 a month. British fighters were produced at about 450 a month, with less material, factories and workforce. Obviously a lot of variables, but as an Air Force, keeping it simple may not have been such a bad choice.

[@danielcamacho1913]

I think Allied fighters were also easier to maintain. The German engines, especially the wonky noise inverted V-12s, needed to get shipped off the front lines for depot maintenance way too often, while the Allies were doing damn near everything their engines needed right on the flight line.

[@robstone4537]

@@danielcamacho1913 the inverted V was an advantage for Maintainance. You could stand on the ground and work on the engine top end, which was were most of the work happened. With an upright V you need scaffolding or ladders to do that.

[@danielcamacho1913]

@@robstone4537 Oh, no! Not a *ladder*! XD The alleged maintenance advantages of the inverted engine were rendered useless because, again, many procedures required the engine to get shipped off the front lines for depot maintenance by guys in white coats, while the Allies were doing damn near everything their engines needed right on the flight line. ...With a ladder next to the plane, out in the weather. response Allison, Rolls Royce, and others just left their V12s rightside up, they had better ratios of flight time to down time than their German counterparts, and that kind of logistics had a part in determining the winners.

[@nicktecky55]

Exactly. War is not about being best, it's about being most. Or: "God is on the side of the big battalions", as someone once said.

[@nikoscosmos]

Nothing more complex than a Spitfire to produce! It's a matter of where resources were placed. The Germans were busy building advanced gliding bombs and ballistic rockets.

[@jannesoderholm]

Great video! Many thanks for this!! Hope you do more videos with Calum.

[@jcorbett9620]

What is rather interesting about the improved fuel economy of the German engines, is that without the "extra" 15 mins flight time the Direct Fuel Injection gave them, the German fighters would have been unable to escort the bomber formations to London at all during the later stages of the Battle of Britain as it was so close to their maximum range. As it was, they only had around 10 mins of combat time over London, before needing to return to base. Would have been a nightmare for the German bomber force to have to fly undefended to their targets, once their escorts had been forced to turn back - a bit like the later B-17 and B-24 formations until the advent of the P-51 Mustang.

[@anotheruser676]

You don't think that if the German engines were carbureted they would have stationed the fighters closer to put them in range? or the bombers too? (in retrospec I should have said 'built them with bigger gas tanks')

[@jebise1126]

@@anotheruser676 closer where? in the english channel? there is no closer point at where they already were. still bf109 fuel tank was too small since they only got 10 minutes over london

[@jcorbett9620]

@@anotheruser676 Don't you think if they knew they only had 10mins combat time over London, they would have moved them closer to give them more time? There was a slight problem called the English Channel (plus the North Sea for those units stationed in Norway), which meant they were physically unable to be any closer, unless they either operated from underwater or built a fleet of carriers to launch from.

[@anotheruser676]

@@jebise1126 and J Corbet Okay, your right, that was dumb. The fighters were based mostly in Calais-ish area. (I had thought Germany) But you did hit on the key point. The Bf 109e only had about 410 miles range with a more efficient engine, but the Spitfire Vb had 460 miles range, because of a larger fuel tank.

[@jebise1126]

@@anotheruser676 i believe germany had doctrine of fast bombers that would just outrun any interceptors. thats why they didnt develop proper escort fighter. yes now we know they made a mistake. not that spitfire was all that better i mean for proper attacks on germany allies had to wait for mustangs. also its not only range. germany was short on fuel for whole war. or them 10-15% less fuel consumption was huge deal. much bigger deal than for allies.

[@garywalker447]

I think it overstates the problem to say it ruined the Merlin. It was a hanicap that could be exploited in some situations, but "ruiuned" is a bit much.

[@jacktattis]

They are Trolls They cannot or will not quote a German engine that got their SINGLE ENGINE fighters above 38000ft Only the Bf 109K and TA 152 very late were able to do it. It was the Merlin that got the PR planes well above any interception And later the Griffin PR MkXIX that got to 49000+ft

[@rare_kumiko]

Excellent video and excellent presentation from Mr. Douglas!

[@johnscarpa5116]

Great video....glad you are willing to share your platform!

[@Bernie_747]

Excellent presentation/explanations & research work - thank you, Calum !

[@zxbzxbzxb1]

I always assumed that it was deliberate to deter negative G manoeuvres in order to stop the brave, moustachioed, tommy pilot spilling his cup of tea

[@jerribee1]

One only drinks g&t when flying old chap

You meant to say Sir it was to stop those magnificent man in their flying machines to go up diddley up and go down diddley down ?

[@BAGHEAD1995]

@ Still won old boy.

[@HiVoltish]

Bravo!

[@SheepInACart]

I feel treating the British report as if it where intentionally downplaying benefits of fuel injection because of conservative nature of the examiner, while not without merit, is unfair because the over simplification fails to mention the advantages which the system chosen had to instead focus only on the disadvantages. Meanwhile putting up the narrative that aviation carburetors where somehow preferenced due to perception as "the older proven concept", despite still being a fairly new/rapidly developing field at the time (as can be seen on the timeline chart within video even, look how close wicks still being used was to the first injection planes testing). Period documentation in Britain heavily references the benefits in the Merlin design of spraying the fuel BEFORE the supercharger, this was what precluded multi-point injection (not the complexity), as if you where looking for to optimize continuous power per engine size/weight (instead of power for a given fuel amount as the US mostly tested) especially at higher altitudes (lower ambient temperature is more than offset by lower density, thus more work compressing, resulting in HIGHER induction temperatures than superchargers set up for peak performance at a lower altitude), then the superchargers accumulation of heat was extremely significant, which is one of several reasons why the max continuous power of Merlin is much closer to WEP power than it is on the DB601. While its undeniable that post war injection development resulted in engine designs simply not possible running a carburetor (and superchargers ceased to be a primary limiting factor), Its not like during the course of hostilities the lack of injection would hamstring the Merlin's max power compared to other nations contempories, with ever newer superchargers and higher manifold pressures they would push power beyond not only the DB601, but even the later (and larger/heavier) DB605 series, meanwhile mitigating the worst of the handling impacts during acrobatic maneuvers (themselves not all that common in military use). Duel stage supercharged Merlins where even adapted to be built in the USA, and where chosen for their most prolific wartime construction (P51-Mustang) because of superior high altitude performance to US designed engines of simlar volume (turbocharger plumbing resulting in sizes prohibitive to a small fuselage fighter, using almost all of the length of the twin boom layout of P38-Lightning). So why? Well adding an air-air heat exchanger for post supercharger charge air cooling failed to realize as low of a intake temperature (thus density for a given pressure) on direct injected engines as a fuel wetted supercharger system, and would embody extra drag, weight and packaging/plumbing concerns that wet superchargers simply didn't have. The work around by Germany was to install water/methanol mixture sprayers to get the same cooling effect (plus an anti-knock boost that helped offset fuel limitations vs allied supplies later on, it was injected post supercharger, but continuous flow in intake manifold runners, rather than direct into cylinders, being intended to fully evaporate before intake valves), but this was far more limited in runtime (limited to 10minutes use, some planes carrying 2 charges, but you must wait for supercharger to cool off between), and embodied more weight (indeed the direct injection system alone was heavier than carburator, even before MW50 injection system was added). Also because the point of fuel being added was pre-supercharger your fuel systems working pressures could also be very low, letting simpler systems get massive flow rates, while period direct (and even multi-point systems with timed pulses, rather than continuous flows) where struggling to realize enough fuel capacity to be as rich as desired at maximum military power settings intended. Finally injecting closer to cylinder was one reason for the poorer evaporation which also lead to more concerns with fuel entering engine oil and causing premature failure due to lubrication issues (which would lead Germans to not run even emergency power mixtures as rich as British did in maximum military, and this drawback was further compounded by synthetic fuels, and would have been in other if nations if they had opted for a low volatility fuel in response to fire hazards).

[@ArneChristianRosenfeldt]

About the temperature in the superchargers: The hotter the air the more (parasitic) intercooling happens into all the walls. The video has one picture where the injector is in the center of the 4 valves. After all air is in the cylinder the fuel can be shot at the piston. The biggest drops hit the piston. Fuel pressure needs to match air pressure, in order to keep the amount of fuel lost on the piston surface on the optimum. In this way no fuel hits the walls or anything oil. Any drops in the air may lead to soot. So the fuel pump shown: I don't quite understand how fuel pressure matches air pressure. Looks more like fuel pressure matches RPM, which is not what we want. Port injection is a simple way to increase the flow because the injector can be open all the time ( -retraction of the pump piston ) so half the time. It looks just like a small V12. In direct injection the pressure needs to rise as air enters the cylinder ( we want more time for injection ). Then it plateaus until it drops of sharply when enough fuel is injected. Edit: So now I think I understand fuel injection a bit more. Fuel injection is simple if the fuel pump creates all the pressure. A single centrifugal compressor in the tank can do this already. Then we need to match the fuel pressure to air pressure .. that means that we need to regulate the fuel pump and because this may lead to stall we need a blow-off valve instead. F1 cars have injectors which point into the intake runners. Those are straight and thus it is possible to have stratified mixture: fat in the center and lean near the walls. With long intake runners the charges of consecutive strokes overlap. Thus we have no problem with the big drops. They just get sucked in earlier. For port injection we need to go from 0 to full pressure, hold, and then back. Thus a valve is the correct answer. Thus EFI or before that: Kugelfischer. A volumetric pump sounds nice, but this pump is what you really criticize. At full power the valve just stays open. With a V12 the intake runners of opposing banks cross each other. This is for high performance, especially with slow direct drive. Sadly, Enterprise solutions try to avoid this. For volumetric fuel injection a compact and efficient gasoline pump is a radial piston engine with some fancy mechanics for the crankshaft to change stroke.

[@alan-sk7ky]

@Alfred Wedmore Very good points, it's something Greg brings into his videos, the P38/merlin springs to mind as also the German 3 blade prop etc.

[@CalumDouglas]

A few comments Hamish. "...especially at higher altitudes" Putting fuel through the supercharger is a benefit which is maximised at sea level, and thereafter, steadily decreases in effectiveness, until (in the case of a Merlin 46) the gain in power virtually vanishes by -44C external air temperature, because the fuel doesnt get hot enough, quickly enough to evaporate inside the supercharger. So, it is in fact the reverse. You say that MW50 was injected after the supercharger, it wasnt, in anything other than some very late model Jumo213F experiments which were never in combat. German use of MW50/GM1/C3 injection into the blower, was not a "workaround" for intercoolers not working on "direct injected engines". The best German engine of the war which was actually mass produced and saw combat (the Jumo213E) in a few very late engagements has direct injection, two stage supercharger and a water/air charge cooler. Direct injected engines (if the spray pattern and such) are done badly, certainly doesnt like intercooling, so the DB601E reacted very badly to low charge temperatures, but it is quite wrong to say that "direct injected engines" dont work with intercooling, etc as a general rule of thumb. Thats very misleading indeed.

[@SheepInACart]

@@CalumDouglas Altitude wise, your correct, the word I was missing was design. As manifold pressures "for a higher DESIGN altitude" not a higher flown one. Charge air temperatures climb with increase in pressure, so optimizing a plane for power higher up means hotter intake charge (before inter-cooling or other systems), in spite of the cooler ambient temperatures. In face even when throttling the engine intake charge air will be hotter, one of the myriad of efficiency reasons that would before wars end see 2 stage supercharger gearing become near ubiquitous in new designs (even if many nations didn't get to actually field them). But for reference also,-44C occurs under standard atmospheric conditions at almost 9km (a bit shy of 30,000 feet), the early supercharger design was for just 4.9km. No Merlin was designed for peak power beyond 5.8km until 1940, long after the ship had already sailed on pre-war injection system choices. It should be noted on the German side the variable speed drive of the BF109 superchargers (at least for DB-605AS) mean intake charge temps DID increase with altitude, even though 1.7ata pressure remained till 6.8km, so the behavior would follow as my original text reads. I'll need to look back at injector locations, I'd distinctly remembered the Fw190a had used multi-point MW50 (unlike C3, which was into supercharger eye), but it'd been a while, so this might just be my derp. Finally regarding direct injection vs inter-cooling we agree, I did not say inter-cooling didn't work on direct injected engines, they actually have MORE demand for inter-cooling than systems where fuel in intake path with enough time to evaporate. What I said was air to air inter-coolers "failed to realize as low of an intake temperature.. as wet intake systems", and also noted that evaporating fuel didn't add drag liter inter-cooling would in order to reach the same temperatures.

[@johnburns4017]

Chris it is fantastic that you teamed up with Callum in historical technical matters. It blows away many myths. And makes it easier for non-techies to understand. Not only blowing away myths, it adds more to the party.

[@IanSinclair77]

Great presentation. Rich content, interesting and very articulate. The man just got a new fan.

[@yereverluvinuncleber]

At least we didn't have Lucas fuel injection during the war...

[@CalumDouglas]

A small mercy, agreed.

[@birlyballop4704]

Joe Lucas. To motorcyclists in the 60s and 70s, The Prince of Darkness. 6v dynamos, c'mon!

[@johnburns4017]

Merlins were injected using Lucas injection.

[@yereverluvinuncleber]

@@johnburns4017 Damn.

[@johnburns4017]

@@yereverluvinuncleber You are still sucking in this 1970s US propaganda to discredit imported cars after the 1973 oil crisis. I, and many other people I know, have had cars with Lucas electrics which performed flawlessly. RR used them. Most UK cars used them: Ford and GM (US companies) cars made in the UK. It must be the air in the USA that affects them. Also this odd air in the USA makes British cars leak oil. Listening to Americans British roads are full of broken down vehicles and swilling in oil.

[@darreng745]

I think you will find that one of the reasons that Rolls-Royce did not go with a direct injection system was that the primary manufacturers were Bosch through their UK sudsidaiary and thus RR would have been in the position of paying them royalties on the use of the technology even up to the start ot WWII. A dear friend of mine since deceased worked for Bosch UK during WWII and said what they did was took the sign down saying who owned it and continued on with production.

[@nickjung7394]

A bit like Ford and GM in Germany then!

[@jacktattis]

Source please It is easy to cast dispersions this late

[@SouperAsH]

Brilliantly presented, informative, and digestible. I really enjoyed this one.

[@kenbellchambers4577]

Thanks so much for these amazing insights. If I had to do my life over again, I would probably have gone into aviation engineering. My father was a machine gunner on a Catalina, and afterwards worked in aircraft manufacturing, so I must have a bit of it in my genetics. Great presentation.

[@anthonyburke5656]

This question puzzled me for years, why did the Brits and US use carries and the Axis use injection? By way of comparison, Mercedes cars used fuel injection years before most other manufacturers. Mercedes used mechanical injection which was prone to malfunction, eenthoughwhen it worked it was better than a carbie. The ONLY time Mercedes got this right was the 1985 model. That is, it took from 1950 to 1985 for Mercedes to get mechanical injection right. By 1985, electronic injection came on line. Carburettors, on the other hand, are much simpler and easier to both manufacture and tune, although less efficient. So, the Allies made a decision. Irony, the Engineer that solved Te most pressing problem for aircraft

[@johnburns4017]

The Mercedes cars used Bosch _mechanical_ injection. It was fuel thirsty in cars. It was not high pressure _direct_ injection as German plane engines were, being _indirect_ low pressure as it injected into the inlet ports. The operating conditions in cars are quite different with constant revving up and down, cooling and reheating. A car engine rarely operates at its peak performance or efficiency. I had a Mercedes Benz 230SL with this injection. I rebuilt the engine. The Bosch system was very reliable needing no tuning. The injection pump calibration was done at a Bosch dealer. The lines from the injection pump to the cylinders were not the same length. Number 6 cylinder was the furthest away and occasionally this cylinder would flood not firing. Wear rate of the cylinder liners was more on this cylinder. They were pigs to start needing an starting injector in the inlet manifold. *But!* Third party, electronic contactless ignition using quality ignition plugs, made a massive improvement in starting, acceleration and general performance - I disconnected the starting injector as it was not needed any longer. Number 6 cylinder always fired. The six cylinder long-stroke Mercedes straight-six engine was not particularly refined - rough and noisy. Some design defects for sure. The Jaguar straight-six was a far better engine. The ultimate Jag straight-six engine was the last of the series being electronically fuel injected. If people think I am being pro British I drive a Mercedes Benz, provided to my daughter who is employed by Mercedes Benz.

[@everTriumph]

And Ferrari used Lucas mechanical (along with Triumph) fuel injection, if I remember correctly. It was only with the advent of electronic, in particular computer control of all the variables relating to correct combustion that fuel injection became more efficient/correct than the best carburettors. Carbs are magic in action.

[@V8_screw_electric_cars]

Actually early mercedes cars used the fuel injection system from the Bf 109 it was exactly the same unit that's how they got it.

[@johnburns4017]

@@V8_screw_electric_cars Correct. It was improved and changed as it went on. Very reliable, as I know.

[@anthonyburke5656]

@@V8_screw_electric_cars We all mistakenly take it as a technical question, when it’s a logistical one. It isn’t generally appreciated that Merlin (and other Allied engines) were designed to function with different octane rated fuels, Merlins were actually physically altered depending on the Octane rating of the fuel they were using. Another indicator is the Manifold Pressure of Allied versus Axis engines. This all harks back to the Axis lack of oil and reliance on synthetic fuel, which was very inferior to oil based fuel.

[@wadejustanamerican1201]

A really good episode. I honestly liked the details.

[@johnburns4017]

*1)* Premixing the air/fuel charge ensuring the charge was fully mixed and atomised was far better than direct fuel injection. *2)* Keeping the premixed supercharged charge as cool as possible was beneficial. *3)* The supercharger gave equal charge to each cylinder, as did multiple fuel injection, so no advantage of multiple injection.. *4)* Supercharging only needed one fuel injection point, not multiple as per direct fuel injection. *5)* The one fuel injection point did not matter so much if it was from a pressurised carburettor or a pumped fuel injector.

[@givenfirstnamefamilyfirstn3935]

Point 3 is weak. Point 4 ignores carburettors working perfectly well with superchargers.

[@johnburns4017]

@@givenfirstnamefamilyfirstn3935 Premix supercharging did give equal mix to each cylinder. When I say injection, that can mean any type. The Merlin was single point pressurised carb (continuous) and pumped injection (Lucas) into the supercharger - like multi-point but using a single injector nozzle.

[@Leon_der_Luftige]

Callum also made a thread on Twitter recently why the jumo 213 engine was the best engine for propeller driven aircraft of WW2. It would be really nice, if he could go more into detail about that topic in another video. 👍🏻

[@CalumDouglas]

You will find copious details on that in the book, but perhaps I will also try to make a video too.

[@Leon_der_Luftige]

@@CalumDouglas Good to know, thanks a lot.

[@NLBassist]

What a great video. Well explained, thouroughly researched, easy to understand and still technical enough. Loved every second of it.

[@givenfirstnamefamilyfirstn3935]

Shock Horror Probe!

[@oesypum]

In all branches of science, there are many instances of those at the top refusing to accept new findings/discoveries.

[@Horaczkocom]

Ideology.

[@Horaczkocom]

They prefer their own ideas than others even are wrong In movie "King's speech" Doctors had advice to smoke cigarettes for King.

[@charlesflint9048]

That was an really good explanation of fuel injection v. carburettor. I’ll have watch it again. Thank you.

[@dart3409]

Very enlightening information. Thank You!

[@andypdq]

The irony is that the injection pumps used by the Germans were very similar to pre existing inline plunger pumps used in diesel engines of the time, established technology which the British already had.

[@drstrangelove4998]

The Germans having invented the Diesel engine of course, had been ahead of the game with fuel-injection.

[@andypdq]

@@drstrangelove4998 In 1931, British company CAV partnered Robert Bosch Ltd., became CAV-Bosch Ltd and began making fuel injection pumps for the diesel industry and later fuel systems for aircraft. Bosch produced the injection system for the Daimler Benz engines used by the Luftwaffe, CAV had their technology, the RAF had access to the same technology chose not to use it. The Germans were not ahead of the game regarding technology, they just had people with unbiased, objective views in charge of design, unlike the British

[@jacktattis]

​@@andypdq When will you get it through your heads The Merlin did not need it The Spitfire was getting to 4500ft + with the MkIX Sept 11 1942 No single engine fighter got that high with Fuel Injection until very late in the War

[@JohnRodriguesPhotographer]

You have to wonder how many people died as a result of this stupidity.

[@lorrinbarth1969]

As soon as the pressure carburetor was introduced in British and American fighter aircraft the problem was solved (modern terminology would be single point fuel injection) . The reason the engine makers went with pressure carburetors is that the intakes on these engines had originally been designed (in come cases) for regular carburetors. So, it was simpler to install a single point injector into the eye of of supercharger wheel. This provided good fuel distribution using fewer parts than the German design.

[@wm811]

Great movie Guys. i love to watch this channel, whenever i have time.

[@nicwilson89]

11:02 It sounds like there may be some...less than savoury dealings taking place there. I find it hard to believe that they'd suddenly decide that carbs are totally fine and not recognise the benefits from other countries and the independent research taking place on fuel injection like that This has been fascinating. Would love to see more from stuff like this! I'm gonna have to buy yet another book now :D

[@jimfisher5856]

While I'm not privy to all of the details, fuel injection did have some disadvantages with WWII era technology. The precise control required was difficult to achieve with purely mechanical system. Machining tolerances were required to be extremely tight. These tolerances were something that plagued the Japanese in copying the DB601. Also the tiny ports could be subject.plugging. This problem plagued the fuel injection systems for the diesels in German tanks.

[@jacktattis]

What is to believe Rolls Royce did not want or need fuel injection

[@elmariachi2979]

hey chris i love your content, and i have an idear for a future video.Maybe you could show us a selection of good aviation books. Would really love that especially considering christmas is right at the door

[@MilitaryAviationHistory]

I can always recommend my own stukabook.com but it only ships after Christmas I am afraid. If engines are your thing, strongly consider Calum's book! Otherwise all my videos have the sources in the decription and you can find a good selection there imo

[@nickdanger3802]

For the next important and powerful Merlin 66 engine, Rolls Royce finally decided to use the Bendix-Stromberg Injection carburettor. The American Bendix-Stromberg pressure carburettor was developed in the mid 1930’s and was in production from 1938. This carburettor was designed to operate as a fully pressurised fuel system that dispensed with the problematic float controlled fuel level with its emulsion tubes and diffusers. Negative G had no effect on fuel flow or carburettor function. The pressurised and metered fuel flow was delivered as a spray into the inlet air stream just in front of the supercharger inlet. This feature virtually removed the risk of carburettor icing, in fact the throttles and chokes of the injection carburettor did not need heating by hot oil or coolant circulation at all and their deletion removed several other problems associated with the previous provision of those heating circuits. ROLLS-ROYCE MERLIN CARBURETTOR DEVELOPMENT page

[@AdmiralQuality]

Great video! Thanks guys!

[@jonathansmith6050]

I love these insights into the technical / development history -- and this one has the hook of a bit of inexplicably bad decision making

[@peterstickney7608]

Thank you both Chris and Calum. I find it interesting that the RAE and the British Aero Industry not only sloughed off the U.S. and German efforts in Direct Injection development, but also ignored the Bendix Pressure Carburetor efforts - as Packard Merlin production demonstrated, that was essentially a "drop-in" replacement for the SU carburetors, solving many of the problems. Calum, have you found any evidence that the Brits tried to obtain one of the Pratt & Whitney direct injection R1340s? I'd think that that being able to actually run a fully built-up engine would provide indisputable evidence. The issue with a Brit Ministry Boffin stamping a good idea as not worth following is, unfortunately rather common. When mechanical ballistic computers were first being evaluated for fire control on Royal Navy ships, the leading design was evaluated and rejected by the designer of its main competitor. When Frank Whittle first brought forward his concept of the turbojet to the Air Ministry in the mid 1930s, the Air Ministry handed it over to their tame Gas Turbine Expert, Dr. A.A. Griffith, who rejected the idea - apparently finding Whittle's simple centrifugal design as "too simple" after the repeated failures of his baroque multi-axial compressor, multi-reverse flow efforts. This set back jet engine development in the U.K, by about 2 years.

[@flakmag1004]

as always it seems politics ruin the greatest inventions in the uk, time and time again.

[@jimdavis8391]

The class system was and is the main reason the UK underperforms.

[@fenrisgrins]

Thanks so much for this, really engaging!

[@tomasrom9073]

Great informative content and a super presentation, will have to buy that book now

[@stephengloor8451]

I really think the word on this should go to Sir Stanley Hooker who became the chief engineer of Rolls Royce during the war. He personally increased the power of the Merlin with supercharger changes and was a world expert on it “Let me now add that the Germans paid a large penalty for their fuel injection. When the fuel is fed before the supercharger, as on the Merlin, it evaporates and cools the air by 25°C. This cooling enhances the performance of the supercharger, and increases the power of the engine, with a corresponding increase in aircraft speed, particularly at high altitude.” From “Not much of an Engineer” Additionally the fuel injected DB601 was 34 litres in displacement whereas the Merlin was 27 litres for roughly the same horsepower so it was considerably smaller. So clearly the fuel injection didn’t give as big a performance boost as the author is trying to make out. More important was the fuel used. Britain had access to high octane fuel from the USA whereas German fuel was lower octane and got worse during the war whereas Allied fuel just got better as the war continued. Fuel octane rating and supercharger efficiency was far more important to aircraft performance then fuel injection V carburettor. BTW the main solution to carby icing is carby heat which is universal on all carburettor equipped aircraft.

[@paulgush]

Indeed. To sum up, with a carb you get cooler air going in to the supercharger, which improves its efficiency, allowing the engine to swallow more air, giving a better power to weight ratio.

[@cannonfodder4376]

Yet another excellent and informative presentation from Calum on this topic. On the topic of Carburetors, when going through my A&P training I and others had to carry out a engine function test for a Cessna 150. The amount of fiddling and complications involved with fuel mixture control, RPM and carb heat makes me question how these engines and systems remain popular. That AVWeb video that explained carb icing failures accounted for 6% of engine failure related crashes in GA is illustrative in itself.

[@benjaminbuchanan7151]

Yes. I had a similar experience. Carb engines are easier to start in hot conditions and on warm engines, in which injected ones may suffer from vapor lock, but all in all there aren’t many other reasons why the “Caburburetor” as my prof would call it, was a better choice.

[@Skyfighter64]

@@benjaminbuchanan7151 And yet somehow, I tend to have the opposite experience with Carbureted vs Fuel injected engines. My primary experiences are with Lycomings, ranging from 235-360 Cubic inch displacement, Most commonly O-235-L2C, O-320-E2D, IO-360-L2A, and IO-360-C1E6D (both left and right spinning versions). Tuning a Fuel injected engine is effectively no different from tuning a Carbureted one. Adjust the idle stop until you get the RPM range you need, then check the idle rise. Tweak mixture, clear cylinders (2K RPM, then pull mixture until engine loses RPM, then back to full mixture), then check your Idle and rise again. Rinse and repeat until you reach the correct range for that engine application. The biggest problem with fuel injection, as a mechanic who works on these engines, that I notice, is that the fuel injection system is a maintenance sink. I don't know about injected Continentals, but with just the 172R, fuel injection means you have to have 2 fuel pumps, one mechanical, driven by the engine, and one electrically driven one, mounted behind the firewall, underneath the copilot rudder pedals. You also have a fuel servo that meters the fuel flow, which is then sent to the top of the engine and the flow distributor, where it is then divided into the lines leading to all the cylinders. These lines, on Lycoming engines at least have a rather specific 100 hour Airworthiness directive and inspection requirements. Lastly, you have the injectors that actually interface the fuel lines to the cylinders themselves. This is a very complicated system that also has additional lines and sensory information sent to the instrument panel to add extra wrinkles. Also consider that the 172R model engine, with the fuel injection, only gets 10 more horsepower than a IO-320-E2D (160HP vs 150), all that crap is a LOT of weight to lug around. The Carbureted engine on the 152/172M's I work on, on the other hand, have one line going to the carb from the fuel filter bowl. Gravity does all the work, so there's no fuel pumps in the design at all, except for the maybe if you're reaching, there's a primer pump that can be used from the cockpit for helping to start the engine. I work at a flight school. We put our aircraft through the wringer year after year. The sheer amount of labor we save on 172M's compared with aircraft that are 20 years at minimum newer (172M models stopped production in 1976, 172R production began in 1996) because of the fuel injection systems would astonish you. That doesn't even take into consideration how expensive it is to fix the various parts involved when they fail... Long story short: Carbureted engines are popular in aviation because they are so much simpler to maintain and so much lighter than comparable fuel injected engines. At least as a comparison of the lycomings I've been working on (doing annuals, 50hr and 100hr inspections) for the last 6 years. I've only done work on one Continental, a Rolls Royce built O-200, so I can't speak for those as much.

[@CalinCETERAS]

@@Skyfighter64 "The biggest problem with fuel injection, as a mechanic who works on these engines, that I notice, is that the fuel injection system is a maintenance sink" Maybe it is. However, this entire maintenance cycle done - let's say - every 10 flight hours on warbirds - is so much cheaper than losing an air fight. Or allowing a bomber to pass. Many fighters in WW2 had limited engine space volume, limited engine weight and limited fuel capacity. The early war birds were also fighting at the end of their "leash". Getting another 10% extra range, or fight time, or anything else was important, or even crucial.

[@Skyfighter64]

@@CalinCETERAS you read my comment, but missed the point. I was talking about civilian general aviation aircraft operating on carbureted be fuel injected engines. Private pilot's often don't have the resources required to pay for the extra maintenance needed in terms of fuel injected engines in aircraft. They also weigh less as a result. I was not talking about the super high performance side, where the maintenance costs are a much lower factor.

[@Bartonovich52]

Carbs are super easy and simple on light aircraft. The only adjustment other than making sure the throttle and mixture controls go from stop to stop is idle and idle mixture. Idle just so the engine will run and not stall (you never idle an aircraft piston engine except for testing during runup, live mag check, and just before touchdown… the reason being because of the aforementioned valve overlap which will contaminate the intake valves and cause them to leak because the deposits won’t be burned off like the exhaust valves) and idle mixture you simply adjust it rich so it produces a 50 RPM rise on shut down. Compared to the PFM and all of the gauges you need and the adjustments to be made on fuel injection.. plus you need two pumps (vs zero on a high wing aircraft), throttle body, flow divider/manifold valve, injectors.. all for it to not start and drain your battery when it’s warm. Carb ice? Put on carb heat. Carb ice is mainly a Continental engine problem. Lycoming puts the carb right on the oil pan so it’s not an issue. This is even shown by the fact that Pipers (traditionally Lycoming) say you don’t have to put on carb heat for low power settings. Cessna only does because they were mostly Continental and by the time the 172 and 152 swapped to Lycoming, legal liability had taken hold.

[@up2tech]

Exceptional explanation and thanks for all the information!

[@daylyt100]

Outstanding explanation, thank you!

[@homecornerforge6970]

아돌프 갈란트 자서전을 번역하면서 영국 전투기들이 치명적인 단점에도 불구하고 기화기 방식을 왜 썼는지 궁금했는데 의문이 풀렸습니다. 정말 유용한 정보였습니다. 감사합니다.

[@vaclav_fejt]

Great video! At first I thought this was just another sensational video title (a sad necessity for KZbin) and there was a good reason for carburated engines. Little did doctor Morley know...

[@TheHarryMann]

There was a good reason for sticking with carburettors… the latent heat of evaporation of the fuel in the inlet tract (in and ahead of the supercharger) With the amount of fuel going into an aero engine at high power, this is a very powerful effect and equivalent to an inter cooler in itself, increasing the charge density significantly. Even Sir Stanley Hooker of Rolls Royce fame stated this was a key reason to stick with carburrettion, especially those injecting fuel straight into the eye of tiger ( oops, I meant eye of the cyclone, oops I meant eye of the supercharger)

[@neilwilson5785]

A fantastic explanation. Really good content.

[@tomfey6020]

Thanks for that. Love the original-source documents.

[@kurttank_1909]

Having flashbacks to my early spitfire days in War Thunder before I had a key bound for starting my engine

[@mauricedesaxe1745]

I know right! I ended up binding it to Right Alt. Wore the button off my keyboard.

[@ktipuss]

Also the effect on performance of ICE caused by the difference in air pressure at altitude caught out U.S. companies selling diesel railway locos to Andean railways in South America. These railways quickly discovered that the diesels' performance deteriorated once above 10,000 feet. Two diesel locos had to be put on a train to replace one steam loco (steam locos are not internal combustion powered so are unaffected by altitude).

[@2paulcoyle]

I would imagine the coal burn would increase at altitude regardless of incline.

[@simonrisley2177]

Really well presented. Thank you!

[@dtengineering1]

Great, easily understood info. Cheers

[@1337penguinman]

Whats funny is that in the automotive world, GDI engines (direct injection) are a relatively new thing outside of diesels. Yes we've had fuel injection for quite a while, but it works a lot more like a pressure carburetor than these designs as it simply injects into the intakes rather than directly into the cylinder. Funny to see how far back the lineage actually goes.

[@Bartonovich52]

Youll also notice four valves per cylinder. These weren’t common on cars until well into the 90s.

[@Nerezza1]

It's all cost and complexity versus actual gain. Port injection works just fine and keeps your intake valves cool, clean and gets you excellent fuel atomization. Significant valve overlap is not a concern unless you have to take emissions into consideration. A bit of your charge pissing out is inconsequential really. Four valves had been done back in the 1910s and provided better aspiration, but as power went up as did the heat which smaller valves don't cope with as well as larger valves. This is why it was so much cheaper and simpler to stick 2 valves on most regular cars and they frankly didn't need four valves

[@michelguevara151]

dr morley was also the one responsible for rejecting frank whittle's jet turbine engine in 1933-34. enhgland could well have entered the war with jet aircraft.

[@kurttappe]

I'm sure it would be difficult to do 90 years later, but it might be interesting to analyze Morley and what his motivations were. In short, WTF was wrong with him?

[@5metoo]

@@kurttappe - Yeah that would be interesting. Unless and until we know more about it, I do think saying he was "a stick in the mud" (describing behavior only) is about as good as we can do.

[@paultraynorbsc627]

Excellent Chris thanks for sharing

[@RaduB.]

Outrageous title!... 🙂 Great video! Never knew how bad the carburetors were when compared to the fuel injection in an aero engine... Thanks a lot!

[@jacktattis]

Well they lied

[@jimdavis8391]

Rikardo and his company were genius, the toffs that make the decisions in Britain are numpties.

[@nickjung7394]

Germany had its numpties as well....starting from the very top!

[@mtskull59]

Quote from Rolls-Royce engineer Stanley Hooker: “Let me now add that the Germans paid a large penalty for their fuel injection. When the fuel is fed before the supercharger, as on the Merlin, it evaporates and cools the air by 25 ° C. This cooling enhances the performance of the supercharger, and increases the power of the engine, with a corresponding increase in aircraft speed, particularly at high altitude.”

[@actually5004]

Mr. Hooker, however, was ignorant of the fact that the Germans were indeed using charge air cooling with a water-methanol injector placed before the supercharger inlet.

[@mtskull59]

I am sure that neither Hooker or any other Allied aero-engineer was “ignorant” of that fact when deciding not to add the extra weight, cost and complexity to what were highly successful engines. Sure, there is a valuable discussion to be had about the relative merits of carburettors v direct injection and charge cooling and NO2 injection, for that matter but to state that this “One decision ruined British aircraft engines” is not only inaccurate but crass. After all, aircraft powered by those same “ruined” engines shot down a lot of German aircraft, inflicted a lot of damage to German cities and belonged to the side that ultimately prevailed….

[@pourlemerite]

A cracking exposition on the engineering aspects of the two systems 👍👍👍

[@jsfbr]

Great class! Thanks!

[@lovetolearn5253]

As a mechanic and someone that builds things on the side, I'm wondering if the head of Britains aircraft was just really comfortable with carburetors. For me I truly start to understand a system and build ideals. Then all the sudden it changes and frustration sets in. Now adays it seems every 2 years systems changes. Some are very little and easy to adapt others is different all together. At first I wanted to quit. It just seem to get over whelming. Then I realized if I keep up with technology it's not that bad. Sorry I got off topic. All I was saying is maybe he felt confident in carburetors and didn't want to leave that aside and start basically new.

[@5metoo]

Yes I think human factors like that are understandable and the most likely explanation. What's less forgivable is that he didn't get pushback from peers. The debate that should have happened didn't. Not sure why.

[@christopherrowe7460]

I can appreciate your argument about the frustration dealing with a new technology, but peacetime is when new things should be tested and adopted (or rejected). His decision was made in 1935, and an alternative decision would have allowed the R.A.E. and related end-users to work out the problems.

[@crabmansteve6844]

Mr. Douglas was a great presenter. I am going to be purchasing his book, I didn't realize how interested I was in the subject.

[@shawn6860]

Nice video. that was a very good explaination of a complex topic made easier to get the grasp of.

[@givenfirstnamefamilyfirstn3935]

Click Bait

[@otpyrcralphpierre1742]

Bloody good explanation of valve overlap. That's one thing I've heard but couldn't quite wrap my mind around. Now, I'm Fully Wrapped. That music in the background is Wrap Music.

[@199diesel]

Good thing the design of a certain mans fire spitting plane was more than enough to compensate for this issue. I think you are right. I think the dude just loved Carbs. There are many people today who love them. Love the sound of them etc etc etc. There is one good thing. The sound of the spitfire inspired a lot of young kids to fly :) Very smart analysis. Well done

[@britishamerican4321]

And yet the Spitfire (with a carburetor engine) nonetheless proved more than fit for purpose.

[@britishamerican4321]

... Shot-down 109s nod in sad agreement.

[@CalumDouglas]

Indeed, and they would have been even MORE fit for purpose with a pressure carburettor which they were mostly equipped with from mid/late 1943 onwards thanks to Bendix-Stromberg.

[@michaelguerin56]

Thank you Christoph for inviting Calum. Great video.

[@rangie944]

Excellent presentation of facts. The more information like this I come across the more frightening the thought of "what iff?" becomes. You are being generous when you say you feel sure the scientist wasn't working for the other side. Where where all the other engineering experts? Thanks for posting Chris yet another point for long debate.

[@TheHarryMann]

Gawd! There are plenty of non conspiracy reasons for him making these recommendations…

[@billmmckelvie5188]

When the Germans captured an almost complete Spitfire they decided to make a Frankenspit and put a Daimler Benz engine onto the aircraft they had a faster aircraft than both the ME109 and the Spitfire, proving that both NACA and the Non-government labs were correct in their conclusion!

[@johnburns4017]

That was in the first year of the war, which this vid is focussing on. The later Merlins outstripped the German engines without direct fuel injection.

[@jacktattis]

Funny that Beatrice Shilling fixed the first problem in the bunt. Then Rolls Royce stayed with Carburetion because the fuel stayed denser therefore gave more power. It is explained in Haynes Rolls Royce Merlin workshop manual page 46 and its states : Charge cooling was a fundamental feature of the Merlin and one reason why it was able to maintain a power advantage as even in early Marks The cooling from evaporation of the fuel also helped maintain charge density This was not possible with direct fuel injection . There you go I just saved watching a video that is fundamentally wrong

[@dianedougwhale7260]

These old German Engineering stories- makes one puke !

[@Humbertusmarius]

Enjoyed the video, and just ordered a copy of Callum's book.

[@daseladi]

My compliments for another great video, to you and to your excellent guest.