6 Various Examples Of The Highest Possible Compression Ratio

[@dogstar234]

My inboard boat motor from the 60s has a compression ratio of 4.5:1. Can run it on anything mildly flammable 😂.

[@RJARRRPCGP]

@Dogstar_DogOfWar That's like a flathead from way before the 1960s, wow! More like the 1920s or the 1930s!

[@f.b.i73]

Put sum bacon grease in it.

[@THESLlCK]

@@f.b.i73 that would work only as grease

[@jamest.5001]

I guess the compression bis so low , they was attempting to get it to run on water eh, ha-ha!!/!!;

[@DM01710]

@@jamest.5001 you can use fractal distillation run it on hydrogen for a little while anyways lol

[@djungelskog2654]

Highest PSI in factory Turbo cars? Largest turbos in racing history? Awesome video as always

[@straight_intro]

The highest boost pressure in PSI is probably in 2018-2019 Mercedes Benz A45 AMG, it's just slightly above 30 PSI from factory, thus it's officially world's most powerful 4-cylinder engine in a production car - over 400 horsepower (420 or so, I don't remember exactly).

[@3800S1]

I designed and helped build a race engine for a friend. We settled for 14.5:1 since we use E85 fuel, but later in testing we found it was no where near knock limited and could of easily opted for 15-16:1, but valve to piston clearance was already challenging as it was due to the large cam. End results were pretty good still.

[@NousagiMechanic]

I like how you're branching into more technical aspects of automobiles. Your videos have been pretty interesting in the past, but I'm always ready to listen to engineering info.

[@VisioRacer]

I don't feel like the perfect one to example engineering info, I personally don't quite understand many aspects of engines and how they work, I like Jason Fenske from Engineering Explained, he's good at this, but I try to show interesting stuff within the engine and automotive business which haven't been explained or shown yet. Thanks

[@tihomirpranjic812]

@@VisioRacer my 70cc scooter did 15:1 and its a 2 stroke

[@b_mb4948]

Engineering Explained would be proud...

[@VisioRacer]

Jason is a better guy in this stuff, I only like to show specific examples and if so - topics which I haven't seen explained or shown yet

[@doc.voltold4232]

VisioRacer you two are my favourite car channels. i dream for the day i can see a collab of some sort

[@snek9353]

Engineering Explained, is dumb, too much of what he says is either dumbed down too far or flat out wrong.

[@doc.voltold4232]

Howard Rourke it may be too ease down or dumb for some enthusiast but he is a good resource for guys just getting into the car scene

[@snek9353]

Doc. not if it's to the point of being incorrect.

[@blurglide]

The Mazda 14:1 compression ratio is misleading because it's Atkinson cycle. The intake valve remains open for a while during the compression stroke, pushing some of the air backwards back out of the intake valve and reducing the amount of air and pressure in the cylinder at the top of the compression stroke. It's more accurately understood to have a 14:1 *expansion* ratio and the *effective* compression ratio is probably more like 12:1. You lose power but gain efficiency with this cycle as you give your explosion more room to expand.

[@joakimvhes302]

So basically Mazda made engine that will last longer thanks to lowering expansion pressure, which also lowers the forces on the piston, connection rod and the crankshaft, so they wear off slower. Is that right, or have I just deduced some bullshit?

[@blurglide]

No- it just gets more energy by letting the explosion expand more. It does this by having, effectively, less displacement and compression than the numbers would suggest. Basically a longer effective power stroke than intake and compression stroke.

[@fajar8230]

mazda use long pipe exhaust 4-2-1 and use scavenging effect ...

[@colindoyle5778]

you are wasting your time but thamks

[@177SCmaro]

The highest compression ratio I've worked with is 23.5 to 1 in a small, NA desiel engine. The problem is that you start getting into diminishing returns over around 20 to 1 - meaning at some point it takes more energy to compress the air then you get from the extra expansion of the fuel durring combustion.

[@787brx8]

A good portion of those diminishing returns is caused by low level knock. My anti-knock prototype let's me advance ignition timing to the maximum factory setting. A short test run video is on my page.

[@hurvinekspejbl6229]

@@787brx8where?

[@iliaslamari7315]

"Ambition is a dream with a V8 engine" - Elvis Presley

[@afoxwithahat7846]

Happiness is a dream with a V10

[@jbcowherder6210]

for the top possible, the award goes to Top Fuel dragster engines, where the fuel/air is compressed to the point of hydro-loc just before it fires

[@1elijawon1]

Top Fuel Engines Are Only Around 6.5:1-7:1

[@SalveMonesvol]

@@1elijawon1 But boosted to hell

[@russbilzing5348]

In the '70s, Chrysler brought out an engine, a 318 or 383, (can't recall), that employed a 19-1 compression ratio. It was normally aspirated and my friend's mother drove it for years after buying it new. I was amazed to find the 19-1 cr claim boldly advertised under the hood. We spent an afternoon tuning it up, plugs, filters and fluid changes, added a bit to the a.c. coolant level. I believe that it had about 56,000 miles on it then, and until she died, she never had a bad word to say about it.

[@505197]

Turbo cars typically have lower compression due to the fact that when they get on boost the cylinder is "overfilled". The "working compression" can be calculated, cylinder head volume and how many atmospheres are crammed into it..........detonation kills engines, some chamber designs can tolerate more compression without causing detonation. Thanks for the video, as always it's informative and well done.

[@mr.petrolhead5432]

The reason why modern F1 is using compression ratio's up to 18:1, is that the engines are doing HCCI (homgenous charge compression ignition). basicly the engines work like diesels, only burning petrol, so they want the engine to knock, only controlled. mazda is bringing hcci engines on the market in 2019. the benefits of hcci are much higher thermal efficiency, reduced emissions and also able to get more power.

[@steeler1168]

Mr. Petrolhead F1 engines are not HCCI. They are still required by regulation to use a spark plug. The efficiency comes from using a Turbulent Jet Ignition system. A pre-chamber with fuel injector and spark that lights a tiny amount of rich a/f and uses its flames, dispensed from holes around the pre chamber to light the lean mixture from cylinder.

[@mr.petrolhead5432]

HCCI engines do have spark plugs, but don't use them all the time, but on a other note, TJI is nearly the same as HCCI, it's something similar to what old diesels had too, it's like one step behind actual HCCI, if you listen to onboard engine sounds from today's f1 you can hear the engine's knocking sound. F1 is going to need to change their rule about ignition to allow HCCI in the future, or they basicly are keeping IC enginges from evolving and getting better, which would make F1 a completly unessesary and uninteresting motorsport formanufacturers for years to come, as HCCI is most likely the way to go in the future

[@snek9353]

Mr. Petrolhead, a more accurate comparison from the past would be the CVCC. Comparing to the Ricardo chamber isn't accurate. While mechanically it may share a few attributes the design goals are completely different.

[@stevenjohnson1692]

Mr. Petrolhead in HCCI you wouldn't want knock. Just because it wouldn't use a spark doesn't mean it would be knocking.

[@snek9353]

"Mr. Petrolhead in HCCI you wouldn't want knock. Just because it wouldn't use a spark doesn't mean it would be knocking." Steven, uhm what, that does not compute? HCCI is Homogenous Charge COMPRESSION IGNITION, you know another term for COMPRESSION IGNITION? It's called KNOCK!

[@davidblalock9945]

VisioRacer you are almost correct. Thermal efficiency is not the product of an engine's compression ratio, but its expansion ratio. An engine's power output is based solely upon how much air it can pump. Compression is the enemy of efficiency. The higher the compression ratio, the more energy the engine uses just to maintain operation. Expansion ratio on the other hand is key to high efficiency. In 2 and 4 stroke engines compression ratio and expansion ratio are unavoidably linked. Fortunately, the gains from expansion ratio are always greater than the losses from compression because of Pascal's law. The 5 stroke engine, invented by Gerhard Schmitz, does not have this limitation. The prototype engine has a 7.5:1 compression ratio and a 15:1 expansion ratio. The engine requires 3 cylinders. Two cylinders operate on a 4 stroke cycle, firing 360° out of phase. each in turn exhausts into the 3rd cylinder, which uses a 2 stroke valve timing, and is 180° out of phase of the other two. The ratio of the compression cylinder to the expansion cylinder will determine the overall expansion ratio. This also gives the engine 360° of expansion stroke. Also, in reference to the FIA Formula1 rule limiting compression to 18:1, that's referring to total compression. So an engine with a cylinder compression ratio of 12:1 is limited to just 1.5:1 boost compression, while an engine with 9:1 compression is allowed to have up to 2:1 boost compression. The thinking behind this rule is that it will improve engine longevity, as it caps the amount of stress the engines can be subjected to. It also forces the teams to make a choice between higher specific efficiency (high compression, low boost) or higher raw power (lower compression, higher boost). Teams will over time find the best balance between the two. This drives innovation and accelerates the rate at which this technology can trickle down into production cars.

[@DRAGOSMAN95]

You always talk about very interesting topics, notification on

[@VisioRacer]

I appreciate it very much, thanks!

[@joe125ful]

Next:Fastets reverse gear cars? Probablly noone do that before:)

[@joe125ful]

I really want see that,pls someone!

[@matthewweisenburger2095]

I nominate my truck for that list, it’s like taking off in second when it’s in reverse.

[@combee23]

The fastest reversing car is the old DAF car. It was as quick (slow) backwards as it was going forwards.

[@DBHHellhound]

Probably the French... 😂

[@dsimila1]

@@combee23 Yes. They use a variator transmission. Like a scooter.

[@_..-.._..-.._]

A lot of the newer vvt cars and direct injection engines have a physical compression ratio that is way higher than the actual compression ratio, they use late intake valve timing to lower the running comp ratio and make it like a pseudo-Atkinson cycle engine. My wife’s 2020 Hyundai accent is that way, but it also has a physical engine displacement of 1.8 liters and only uses 1.6 liters of “intake air” so the power-stroke can have a longer stroke with more efficiency. Car has a terribly weak heater output though, being “too efficient”

[@edilson1234567890123]

In ethanol engines the compression ratio is about 10:1 to 14:1.

[@RoobehTunes]

For comparison, a jet engine can have a compression ratio in excess of 40:1

[@gen3v8]

I`d rather fly in an aircraft with a cr under 30:1

[@fidelcatsro6948]

yeah they dont have pistons in them, they use fan blades to compress....different football game

[@ariesmight4141]

RoobehTunes. They have a tremendusly high torque to hp level.

[@fidelcatsro6948]

yeah they're basically open pot bolt on self propelled super/turbochargers, like comparing a cat to a Lion!

[@jacquesblaque7728]

Bit of a prob when they up the CR, though. Power turbine entry gas temps run above the melting-point of the blades, even with super-sophisticated nickel-hafnium alloy blades w/internal cooling. For one, P&W has a huge investment in making such blades. Airlines LOVE the reduction in fuel consumption.

[@wylieisnothere5062]

I had a yz426 with stage 1 hotcams and a wiseco high compression piston. it made 12.1 compression stock and when I built the motor I could not even pull start it in 6th gear without the decompression. lets just say when it kicks back, it REALLY kicks back

[@saxplayingcompnerd]

Compression ratio does not mean much these days. All the engines run atkinson-cycle variable cam timing. Meaning they delay intake valve closing to lower effective compression ratio to avoid knocking on regular fuel. This allows them to keep the expansion ratio high for efficiency.

[@miguelmatos8574]

Atkinson is a Joke, Why reduce the Dynamic compresion ratio?

[@ChasingTheeDragon]

Atkinson is important to keep quench and burn characteristics proper whiteout inducing knock on pump gas.

[@miguelmatos8574]

the variable timming is For linear torque and HP trough revolution range, if you reduce Dynamic compression ratio loose thermal efficiency, Power and torque can be module with the gas pedal why reduce de CR? better use a small engine

[@miguelmatos8574]

+Chase Watkins Pump Gas had the 8.5 to 9 DCR Limit depends engine stay little under this limit is safe for Street car Atkinson System only bring more cost engines, repairing and maintenance the benefit i$ for the manufacturer$ and Autopar$t

[@mrburgermaster]

Miguel Matos It reduces pumping loses, which is especially useful for light loads in larger engines.

[@MrPizzaman09]

I've made a few gasoline engines with a 16:1 compression ratio engine running on 100 octane. A few friends later pushed the engine to 20:1 and it was running like a diesel on a carburetor. It was pretty close to the same efficiency as the 16:1 C.R. version.

[@no-damn-alias]

More than 15:1 doesn't make sense in an engine as it will decrease efficiency above that. A turbo or diesel engine approach that from the top and a petrol from the bottom. Also depens on your application and which load range will be used much. The reason behind that is the adiabatic index in the equation that determines the thermal effeciency of an engine

[@jag7371]

Dude!! Every video your English keeps getting better!! Keep up the great work!!

[@mihkus]

Mustanglvr007 - Still accent I cant take. Im not sure how hard he is trying but everyone will get used to it anyway...

[@mediocre-motorcycle-modifi6818]

A lot of those engines run variable valve timing. If you close the intake valve early or late you can reduce the effective compression ratio, which prevents knocking. It also gives you a longer expansion stroke which is more efficient.

[@danielescobar7618]

Isn't that just the miller cycle engine at that point

[@RoobehTunes]

Thanks for taking my suggestion and making a great video out of it! I think we all learnt something!

[@HomebrewSubaru]

Nice one Visio! My Impreza is 10:1 with 5psi on top. Effective compression is like 13:1 ;)

[@Ms.Fowlbwahhh]

Homebrew Subaru my 2010 civic si is 11:0:1 with a turbo pushing 12psi.

[@HomebrewSubaru]

Damn that's high! What engine? Hondata?

[@Ms.Fowlbwahhh]

Homebrew Subaru that's stock engine compression. The stock engine is the k20z3. It's only been used in the 8th gen si and ariel atom as far as I know.

[@HomebrewSubaru]

Mine is stock NA as well. Maybe I'll build a Civic some day, so cost effective.

[@Ms.Fowlbwahhh]

Homebrew Subaru all the k series engines with around 175 to 210hp have at least 10:0:1. The guys who get real serious with all motor builds go all the way up to 14:0:1 compression. Those things are crazy

[@peterpimmelmann3330]

i love those lanz bulldogs

[@b_mb4948]

Possibly the only vehicle in history that you use the steering wheel in that particular manner to start...

[@vtecpreludevtec]

Peter Pimmelmann big piston

[@1001speedster]

Lmao same.

[@ojlgarage]

Video of engines with lowest compression ratio would also be interesting :D

[@heathbauerle2787]

Rocket engines unless you considered combustion chamber pressure or fuel pressure.

[@TheBikemaster94]

American work truck special

[@jakubbarta5826]

fresh breath of air :) more of those technical videos :) dobrá práce, jen tak dál!

[@antoniovillanueva308]

Your videos are getting better and better! This is good stuff.

[@paulellis7533]

The engine I am building has an expansion ratio of 30:1 but with only a 5:1 compression ratio, using 3.1 bar of boost to achieve an effective C/R of 15.5:1 The piston therefore does less compressive work and more expansive work, increasing efficiency towards the theoretical maximum of 44:1 for a spark ignition (gasoline) engine, leading to an efficiency above 70%. And all this in a Two-stroke!

[@fidelcatsro6948]

make a video and show us amigo....till then its all only cat talk about 70 percent efficacy

[@paulellis7533]

I am only claiming theoretical efficiency gains. The proof of the pudding is on the dyno. I haven't finished the build yet, I'm still machining parts for the auxiliary drives.

[@johngialampoukas311]

How did you calculate that? Because 3.1×5 is not so correct.

[@paulellis7533]

3.1 x 5 does not equal 15.5 ???

[@johngialampoukas311]

3.1×5 equals 15.5. But the result is not CR, is pressure, since you multiply pressure with a dimensionless number and is not correct because 5 has to have an exponent, usually something between 1.3-1.4 .

[@GModBMXer]

Every video your voice gets better and better. Aside from that. Go cars!

[@saltysteel3996]

The 6.5L V8 non-turbo diesel in my M998 Humvee has a 35:1 compression ratio. Also my Duramax is 18:1, but it is turbocharged.

[@xavierrodriguez2463]

813cc per cylinder compressed to 23 cc at tdc fuckin wild

[@Greyline_ENG]

I recently built a 42cc compression ignition engine with variable compression from 10:1 to a compression ratio of 30:1. it was almost impossible to pull start it with the compression turned all the way up, and on cold days I had to use a propane torch to warm the cylinder head.

[@63turbo]

Its probably more accurate to list the actual cylinder pressures the engines operate at, than it is to list compression ratios, because there's numerous factors that allow one engine to run at only 10:1 and another at 12 or 14:1. For example, in NASCAR, the races that are run using restrictor plates, the compression ratio might be as high as 19:1, but the non restrictor plate races are run at lower compression.... something like 15:1. In 2010, F1 was still a N/A configuration, and both F1, NASCAR, and Motogp all ran near identical cylinder pressures, despite having different compression ratios. An interesting aside... Pro Stock drag racers run higher cylinder pressures than either NASCAR or F1 did when it was still naturally aspirated. The normal way of stating "cylinder pressure" is to use Brake Mean Effective Pressure, which is basically the average cylinder pressure at the horsepower peak.

[@johngialampoukas311]

bmep is highest at max torque btw.

[@snek9353]

Yes and no, in this age of late intake closing the old compression ratio terminology isn't really accurate. Today we need to separate static compression ratio from dynamic compression ratio, and similarly dynamic compression ratio from expansion ratio. The ratio numbers used in this vid are all likely static compression/expansion ratios. Not the more important dynamic compression ratios.

[@johngialampoukas311]

Though since you don't know the actual valve timings you can't say anything about the dynamic CR. Except that is lower than the static.

[@snek9353]

I don't know the exact valve timing any more then I know the BMEP, I'd have to research that. But I can tell you the timing would not only be easier to find but be more important to the topic. BMEP while of course important has a limited range of functionality for a given fuel and quench design.

[@johngialampoukas311]

bmep can be calculated just by knowing max torque and max power. I have no idea what you mean by quench design.

[@michaelconnerlone5668]

Really nice video Visio, keep them coming man

[@pdr5926]

There is a concept called dynamic compression. This is ruled by intake closing degree ABDC. The longer the intake the lower the dynamic compression value, so you need to compensate by increasing the volumetric compression otherwise the engine would not run as intended. Dynamic compression (the real compression value) is always smaller than volumetric compression on NA engines. It gets more complex on boosted engines as it also plays a role how much boost pressure is run. The idea with this is that you need to make space in the combustion chamber (lower volumetric compression) for the extra air/fuel charge so you end up with a decent effective compression ratio.

[@perfectentrytrading]

14:1 wow mazda must be good at eliminating that valve piston friction

[@tomashton7208]

compression ratio is done by cylinder volume and head displacement, (the bore and stroke volume) and head cc,s, what Mazda is doing is closing the intake valve and exhaust valve timing to reduce cylinder pressure, also check out what is called the Miller cycle where valve timing is changed to reduce compression.

[@hoost3056]

Static compression ratios versus dynamic compression ratio. With modern fuel injection, knock control and cam phase control engines can get away with higher static ratios on pump gasoline. Factor in alcohol based fuels and the sky is the limit. I think Volvo experimented with 28:1 static ratios using ethanol fuel in a concept engine

[@monteiro5306]

By far one of the best videos you'd published. Awesome.👍👍

[@pedrobranco974]

you have 1.8T VAG engines with CR of 9:1 OR 9.5:1 depending on engine version, some doing 1.7bar on stock components (stock boost goes from 0.6 bar to 0.9 bar depending on engine version) .

[@joppy232]

My personal race car has a b series engine i built running 14.8:1 static compression . Tuned on e85 of course. Love it!

[@mrfd6182]

How much u get if test on psi?

[@joppy232]

@@mrfd6182 something like 270

[@mrfd6182]

@@joppy232 👍👍

[@SuperSunnyB210]

I was always taught that lower compression ratio works better with high boost, as in more air and fuel can be crammed into a larger space and reduces stress on pistons and heads. But like the other comments state, I guess it's altered timing that can compensate for a higher compression. Computers are amazing...

[@SalveMonesvol]

There have been engines pushing 300HP per liter with 10:1 compression, but that's about the limit with normal fuels. F1 engines did 300 per liter naturally aspirated, but that took 20k rpm. The the lower your compression ratio, the higher boost you can have. Usually you can go really low, like 7 to 1, and the added boost ends up increasing power despite the loss of efficiency.

[@fjodorgrenz1428]

Why do some people still complain about his voice? It's getting better and better!

[@VisioRacer]

Thank you

[@mrdiesel6303]

3:04, the combustion chamber in a diesel is usually in the piston, not the cylinder head.

[@RJARRRPCGP]

When I think of high compression ratios, especially 13.0:1, 12.0:1 or the like, I think of Audi roughly 10 years ago, when they seemed to pioneer that, with the very high-revving 4.2 N/A V8s, (RS4 at that time, and the R8) and the 3.2 V6s in their more upscale A-series... I honestly think that VW was the starter of mainstream high compression ratio engines...

[@Roy123lol]

That's pretty much your best video so far! Keep it up!

[@TheS1PikesPeak]

Good Video (as always) but why did you not talk about the Mazda "Biesel" Engine ? Starting 2018 in the Mazda 3.

[@VisioRacer]

Too few details about it are known yet, I'd like to wait, I do not even know how high its compression ratio is going to be.

[@TheS1PikesPeak]

VisioRacer ok, cr will be 18.1. HP or Nm not confirmed

[@fajar8230]

mazda called Skyactiv x

[@stephenmwyatt2]

in the U.S., we have E-85 that will allow 16:1 compression, and it is sold at the pump and for about 20% less than gasoline or petrol

[@keithw4920]

The 12.5 CR version of the VW 1.5 Evo runs 130hp. The 150hp version uses a 10.5 CR. In addition, the 12.5 CR version uses a Miller cycle, which expels part of the intake charge in the initial compression stroke, so you cant compare it directly to a standard 4 stroke Otto.

[@sentinelcheese3420]

NOT FIRST! :D Awesome video! Speaking of compression ratios, maybe you can make a video next on turbine engine? Like the largest/smallest/mass produced/ powerful turbine engines. :)

[@gert106xsi]

Direct injection engines generally have a higher compression ratio because of the cooling effect in the cylinder. The Toyota 2NR-FKE has a 1:13,5 compression ratio but with indirect injection.

[@petergarratt9645]

Ford's old NA 7.3L diesel (not the powerstroke) is 21:1 if I recall correctly, and the last year they made it they did add a turbo

[@boboutelama5748]

A thing that I'm not sure but should ask. Older car had lower compression ratio, and their reliability tended to be better. Today's car have higher compression ratio, but a far lower mechanical reliability. Are the reliability and the compression ratio related ? And what are the other mechanical factors related with the actual reliability issues ?

[@boboutelama5748]

Hello Sothere. We use ten thousands of car in the army. In general, Honda, Subaru, Skoda, Peugeot, Volkswagen, Audi, Ford, Fiat and Mercedes are the more represented (without entering the range of combat vehicles of course). When speaking strictly about the engines. We had less reliability issues before 2005 than after.

[@tomashton7208]

static CR is based on bore and stroke, plus combustion volume, now if the intake valve closes after bottom dead center the compression will go down, full blown sprint cars run 14 to 1 on alky

[@joakimvhes302]

VisioRacer gone more educational. Thumbs up

[@sidecarbod1441]

2:58 A 25 litre cylinder compressing the mixture into a 1 litre cylinder head would not give a CR of 25:1. The CR is the swept volume PLUS the head volume divided by the head volume (The volume above the piston at TDC). The CR for the engine would be (25+1) / 1 which would be a CR of 26:1

[@nolanjudkins7151]

Not quite sure if you are quoting the Hp output for the European model of the Mazda 3, but in the US it has a power output of 155 hp. Just thought you should know. Great Video as always!

[@VisioRacer]

Those were the figures of the most powerful 1.5 Skyactiv in the Mazda2. By the way, the more powerful two-liter in the Mazda3 has 165 hp in Europe, the other one has 120 hp.

[@SonpreetSingh]

Visio rocks man Hands down...

[@fullbadboycompany]

I think i have read that the Extrem Tuners from Greece use special pistons forfith the vo 9 with a compression ratio of 18.5:1 as i know they use e85 or e100

[@Kalvinjj]

Yes, Ethanol also uses a higher compression ratio than gasoline, hence they manage 18.5:1.

[@fullbadboycompany]

Yeah iam totally fan of Ethanol. e85 is 107 Octans and e100 should be around 115 Thats really sick even for the cheap price you get it. Iam planning to switch my n/a Honda Crx ed9 to it. Maybe when i learn more about cars i will get new Pistons with a lot more of Compression.

[@HotForgeChaos]

Alcohol based fuels like the higher compression. Drag cars running on methanol don't typically have a high static CR though, of that around 6:1 to 8:1, but they boost the bejeesus out of the engine with turbos or blowers; upwards of 50psi is common

[@barath4545]

Careful with Octane ratings. There are two ways to measure it, RON and MON so the US use an average of RON/MON while Europe use RON only. Hence why American gas is regular at Oct ((RON+MON)/2) 87 and EU is regular at Oct (RON) 92, but they are the same as RONMON 87 = RON 92. And E85 is just 102-105 RON (EU) and 94-96 RONMON (US). E100 is 108 RON and 99 RONMON. You need to go to C16/Import race gas to get 118+ RONMON as even methanol is too low at 108/99 octane. You can run xylene as well but it gets exotic then. Usually the best is Methanol and then you got built-in cooling for your engine as well. Just need more space as you burn more volume of fuel.

[@barath4545]

Also, the Extreme Tuners from Greece have quite a sketchy reputation so I would not take anything from them as fact. Instead, go check out the YT channel, High Performance Academy. Probably the best racing channel on YT from a tuners perspective. The level of depth in the interviews and stuff they teach is astonishing, kzbin.info

[@LordMekanicus]

I once rode a Maico 440 than had 16:1. You absolutely needed the compression release to even kick the silly thing.

[@marvinblankinchip2535]

You did a wonderful job on this one. What am I saying? You always do a great job. You did a lot of research for this.

[@CSLFiero]

comparing turbo to na on CR is a little bit of a misnomer because it can't alone fully express the volume of the charge and therefore the "true" CR. Regardless, it seems pretty clear 14:1 is the limit for pump prem, which is quite good. however, e85 has become very available and also quite cheap. it, theoretically, could have a CR limit closer to 14.5 or 15. Combine this with a run of the mill water injection system dosing out 90% isopropyl, a liter of which can be bought at any drugstore for 8-10 dollars and should cover 150 miles or more. there's really a very good case to be made for 15:1 in a car that can run well off very available and affordable fuel sources (e85 with iso shot). compare this to race fuel, which I think runs well over 10 a gallon. e85 is 2.20, and a 600 mile range of iso is 36. thats maybe 60 dollars for 14 gallons. compare to 150-200.

[@robertvanderlinden2813]

3:00, the thing is, you may actualy find diesel engines with those exact sizes

[@marceloho1984]

VW EA111: 1.0 8v has 13:1 compression ratio. Very economical engine, but has some valves issues and lose compression by the 70.000 km. A few years laters, VW decreased to 12,8:1 and the this problem was solved.

[@raymondj8768]

my super omp dragster has a big block chevy engine it has 18:4:1 comprsion and runs on 119 race gas it has 1045 H.P. and man is it fun !!!!!!!

[@snailze6761]

Kool video man! I enjoyed the topic and the comparisons used. Thxz.

[@AudioOrchardMusic]

Cool video! It might be worth noting that Oldsmobile made some very high compression engines in the 60’s on leaded gas.

[@theosudarja]

I would like to see more the Hot Bulb Engine. As I never heard that before. It's good to know that.

[@giuseppec8158]

I think that the highest compression ratio for road legal motorcycles (four stroke) are KTMs : -14.5:1 for 125 Duke or RC 125. -14.4:1 for 250 SX-F. -14.2:1 for 350 XC-F. Also Husqvarna : -14.4:1 for FC250. -14.2:1 for FC350.

[@bornhunter100]

I love a high compression ratio!

[@beargibson3100]

really enjoy the new intro.

[@ChainsawChuck13]

Don't know how it is in Europe but here in the US regular is usually 87 octane by (R+M)/2 method which I assume is the same as AKI. In some states such as my home of Alaska, premium is *90*, which is stupid as I've never seen a car that recommends more than 87 but less than 91 octane, and many ask for/require 92 or 93. (93 seems to be a common US premium, 94 appears in some places, one station that I know of in California sells 100 from the pump, don't know why Alaska's is so low considering we literally have multiple oil refineries in state).

[@d.c7464]

If you notice all these high compression engines are direct injection. The motorcycle racing engines (MotoGP) are making 260+ HP. The engine specs you quote are showroom bikes.

[@VisioRacer]

Yes, I know, and?

[@ariesmight4141]

The big two stroke diesels in freighters. Have a compression ratio of 110.00.1or 140 bar.

[@fodaogamer1]

Daily drive mitsubishi 4d56 engine, 21:1 compression ratio. 2.5 tb diesel. The heat generated is pretty high, the cooling system needs to be on perfect conditions.

[@monoracer_]

@ visioracer You forgot the vw caddy ecofuel which has a vw 2.0 8v engine very similar too the azg, aeg, bev.. but has high compression pistons to be more efficient on compressed natural gas, it also has a small tank for gasoline This engine is the bsx and has 13.5:1 compression ratio

[@craigg4246]

The 14:1 C.R. In the Otto Cycle Ferrari is a lot more compression than in the Atkinson Cycle Mazda. An Atkinson Cycle engine pumps a considerable amount of it’s intake charge back out of the cylinder before the intake valve closes. Effectively lowering the calculated C.R. I doubt the Mazda engine has more actual cylinder pressure than you would achieve in an Otto Cycle engine with 11:1 compression.

[@eaglefat9398]

Pontiac had 13 to 1 compression in the 1950's and fuel injection.

[@demonic477]

with a proper crank and cam most engines will take 14 to 1 but you have to build it for the compression and make sure it can get the fuel and air it needs to use the compression .

[@jv6miata660]

Really a great and informative video. Thanks!

[@EstevanTH]

In case of forced induction, the boost value is valuable when it comes to explain the actual pressure in the combustion chamber. Unfortunately manufacturers often skip the provided peak boost when giving technical information. :-(

[@MotoMarios]

Motorcycle engines have had compression ratios of 11:1 or more (now they're at 12.5:1) for many years. I don't know how though as they can still use normal gas.

[@danzel1263]

Thank you for explaining!

[@meusana3681]

hey, do a video on the most powerful billet engines made. Billet aluminium has the advantage of being made from a higher grade aluminium than that which is used in casting.

[@rcadd1ct]

Nice video. I would add more info for effective compression ratio due to boost.......or an idea for another video.

[@someonebald2022]

That was very interesting. Nice job, well done.

[@TheNecromancer6666]

Well Compression Ratio is also the expansion ratio so yes it is basicly the measure for the possible energy exctration out of the combustion.

[@therandomrobert1842]

Prius 1.5 has a 13.5-1 but it’s Atkins cycle so I’m swapping the cam for a Yaris 1.5 cam for that high compression

[@tcmtech7515]

Years ago I did some homebuilt hydrogen fuel experiments using common and cheap lawn mower engines. On their stock ~7:1 CR they were dismally weak and inefficient on hydrogen gas but when the heads were welded in ot get the compression up to ~ 13 - 15:1 they were rather efficient (as small 1 cylinder B&S push mower engines go. ) Downside was that CR would blow the heads off or crush the connecting rods since they were not built to take that sort of abuse at normal power output. So when you see some claiming they are running their stock engine off of HHO or real hydrogen gas and getting loads of power and high fuel efficiency call them out for the bullshit it is. It ain't happening.

[@drewwill2650]

Great content, you're very knowledgeable

[@optimizticpizza8395]

Dangit 2 years old

[@MrAndrius12]

Correction: the OM603 that was in this video is not naturally aspirated. The naturally aspirated OM603 is 3l, 109-113hp, 185-191nm. The naturally aspirated OM606 however is 3l, 134hp, 210nm.

[@THEBOZZ1801]

NASCAR engines can go up to a comp ratio of up to 25:1 and they are N/A, pricing around 1000bhp on their highest setup, or the Aston Martin Valkyrie's V12 has a CR of 15:1, producing 1000bhp also N/A

[@The_Inspiration_86]

I just wanna say glad ur doin these videos keep up da great work & even though majority of da time I can understand what ur sayin I'm glad u do subtitles cause every once in a blue moon there's a word I have no idea as to what u said lol.

[@ariesmight4141]

Some carberated gasoline HCCI engines. Have a compression ratio of 20:1.

[@KuntalGhosh]

make a video about straight 16 engine if there is any in the world because I haven't seen or heard about anything more than straight 12 engine!

[@thetuber705]

google it. they're around.

[@rafaelz6632]

they usually in the big container ships one of them are wartsila sulzer RTA96-C

[@ariesmight4141]

@@rafaelz6632 Inline 14 with 18 on order.

[@Shoorit]

Had to watch the start 3 times because I thought you were saying a Mazda skyactiv engine was in a 458 speciale.

[@derickparrish833]

WHY! The Indy car. How about a car you really like but is a pain in the ass to go anywhere in because of the 14:1 compression needing 100octane gas? Is E85 sufficient or no? I'd try it myself but gotta fix it first. Bored broke asking.

[@marcusbewley1]

A petrol engine can have high or low compressions, as higher is not always best on most standard engines its all down to the camshaft,or shafts chosen put a short 260 duration cam in a engine it could be 10-1 put a 320 duration cam in same engine, then CR may well go down to 8-1 you need a compression ratio to match what your cams power band is at as a long duration cam will loose most of its power stroke power at low revs, due to the fact that both valves are open at the same time { valve overlap } So a high CR helps the bottom end a bit too. this is one of the reasons that long duration cams idle at a higher RPM than lower duration cammed engines doo if they did,nt, then there a good chance the engine will stall, and be v v difficult to re start whenst hot. its horses for courses regarding CR ratios