What's Wrong With Raptor's Compound Turbo System?

[@jaymenna]

Peter has a lot of people telling him what to do. The signal to noise ratio is really bad. But this seems very well thought out and very well presented. Perhaps this will get thru.

[@thomasaltruda]

Nope, Peter will ignore it and carry on with what HE wants to do! Too bad though..nice video!

[@onethousandtwonortheast8848]

@@thomasaltruda Jay Menna is correct though. The noise floor is so high, sifted through and qualifying remarks made would become a career. I’m the end, you’d never get anything done at all. My opinion is Peter already admitted that using a conventional engine would wipe away the excitement for him. It would just be another plane. So he is trying to create a paradigm shift. I say good for him. I see in 10 years after production has started, a major manufacturer will make engines properly for this application. Until then, it’s the Wild West.

[@DealerD8vE]

@@onethousandtwonortheast8848 It’s one thing to break new ground. It’s another thing altogether to ignore irrefutable engineering principles.

[@bryceb8331]

Yes saying he wants to break new ground is not related to this issue. He is just straight up ignoring or rejecting proven principles that could significantly improve his performance and eliminate some of his temperature issues. I know he is probably way over budget and overtime, and just trying to get the 40 hours in he needs to get it to production. but still, this seems so clear and obvious. It’s a shame he isn’t Making this change while he’s swapping the engine

[@Jwmbike14]

Unlikely. Peter has had many aerospace engineers, previous kit designers, test pilots, production engineers, etc, all chime in. He ignore their advice or often even blocks them. The signal to noise ratio is not the problem (it's actually self induced because Peter deletes so many comments). The problem is that Peter is suffering from confirmation bias. I wish for the best but I am fearful that this project will have the worst outcome.

[@keithturner3859]

Ross, I think your channel has become the “go to” place for those of us that have been in the aviation business for a number of years - have some idea of what works and know how to run the numbers. Muller’s behavior of blocking those that question his methods and judgment is consistent with someone that is finding himself boxed into a corner, running out of money, just needing to get out of the constraints and taking bigger and bigger risks by shortcutting all reasonable processes and procedures. I think he is close to the end of his rope so maybe we all need to stand back - give him space and hope he doesn’t kill himself in this unsafe prototype.

[@dbhyslop]

You do a great job breaking down a really complicated engineering topic to make it easy to understand. Compounding the turbos essentially turns it into a jet engine, just with a piston engine instead of a combustion chamber. And every cutaway of a jet engine shows the second stage compressors and turbines a lot smaller than the first!

[@jackspratt4343]

The modern automotive turbo diesel is the linear descendant of the jet engine.

[@hansieslim1000]

The older I get, the more impressive people seem to me. I so wish Peter would buy you a beer and ask for help. I salute your complete knowledge and experience on this subject.

[@TeemarkConvair]

one wonders given the way elliot was treate. i give muller props for al the effort put into this project, some situations had me squirming a bit, but this turbo situation,, this is a biggie

[@bingosunnoon9341]

Peter doesn't need any help. Free advice is a distraction.

[@brianschaer]

Peter doesn't care.. Peter's a know-it-all

[@blowinkk9396]

Even tho everyone has donated from him to have that plane

[@leoa4c]

I tried to help with his aero instability. I hope he listens.

[@Mike-01234]

He's flying it now.

[@fargley001]

I'm honestly not sure how anyone could downvote this video - truth hurts, I guess. Perhaps one of the most constructive and caring technical criticisms ever created on the topic. Always impressed with your contributions to the autocon/exp community, Ross.

[@markmark5269]

Peter has 8 x KZbin accounts?

[@fargley001]

@@markmark5269 Ah yes. Perhaps Peter has 10, and even he had to throw a couple of up votes to sleep well. 80% spite...

[@Mike-01234]

Why does anyone spend this much time making a video about someone he never even met in person?

[@stevegiboney4493]

@@Mike-01234 , because he’s talking about the Raptor? 🤦

[@COM70]

@@Mike-01234 the joy of sharing hard earned knowledge, the challenge of improvement maybe??

[@martinmusial7428]

Spot on! I've been doing work with turbocharged high performance engines for about 20 years and this is dead on.

[@rafiqsaid4297]

Nice and simple explanation. Like my late father said, one must have a lot of knowledge and experience about a matter to be able to explain that complex matter in a simple understandable way

[@okgo8315]

Rafiq said.... your father was quite right and not every expert is capable of explaining in simple language, even though he may have the expert knowledge.👍🇬🇧

[@nssherlock4547]

45 yrs of knowledge available for free, I'll sub that. Now i have a backlog of 90+ videos to watch.

[@patrickroher4760]

I sooo relate. I, on the other hand will need a much larger brain. I'm looking into turbocharging for more brain power.

[@aviator267]

So sad that when priceless, accurate information like yours is freely availble ....there are people out there who choose to ignore this ... pity.

[@nevillecreativitymentor]

45 years of INTENSE Experience and KNOWLEDGE compressed into just 16 minutes. that is some compression ratio!!!! (see what i did there) 🥰🥰🥰 .. Thank you for the video ..From India

[@johnwausau64]

Wow... not only is there an immense amount of knowledge on the topic, but the calm, documented, easily understood delivery is the best.... just the very best. None of the I am a big shot, ego here.

[@tilmaen]

Ouch. This is exactly what I've been saying in the comment section on The Raptor Videos. My suggestions for peter would have been to stick with one Turbo in the first development stage of the airplane. As soon as the airplane is ready to fly and safe in Lower altitude, he could start implementing a revision with two turbos. I. E just drop another bigger turbo in front of the already existing small turbo for lower altitudes

[@geoffreymckenzie5561]

Wow, outstanding video. Arguably the best video I've seen on turbocharging. I hope he listens to your advice. Well done and thank you!!!!!

[@someoneelse7629]

I have watched the raptor build series, and I get more and more concerned as i go along. I have seen delaminated carbon fibre, electrics that would look bad on a bicycle light, hydraulics that clearly didn't work (so he made a workaround), aerodynamics that does not work, instruments that does not work, cutting new holes to get moore cooling, an left out c-clip that made the engine blow up, a serious wingstrike without an inspection, an test start of an enginge that was clearly blown up, an engine replacement without flushing the remaining oilsystem and the list goes on... I'm watching the rest of the series with horror...

[@John-rw9bv]

I don't know anything about the raptor but damn that sounds like good television to me :P

[@sprebound3805]

Cool video and appreciate the explanations on everything. I imagine you attempted to bring this to Peter's attention, but was most likely ignored. I used to be really interested in the Raptor project but as time goes on it gets harder to watch, especially after that last engine failure. I wish him the best but he doesn't seem to want to listen to anyone other than himself and that is really unfortunate.

[@DoRC]

Agreed. After his first engine blew up I mentioned many times that he needs to go through everything that oil touched and thoroughly clean or replace it. So far metal particulate has caused one of his turbos to seize up temporarily and now it's taken out the bearing in his redrive. It's just a matter of time before another catastrophic failure.

[@tujmeister]

This is great & important information. Thank you for the time you put into this video. Getting this right would go a long way to getting Peter's project moving in the right direction. I know that he is deep into his current setup, but it seems inevitable that he will need to make this adjustment to the turbo system for his design to have a chance at success. It simply can't go into production without getting this issue solved.

[@simoncorporation3]

Your presentation enlightened & intrigued me.

[@fraserhardmetal7143]

An excellent analysis of the system required - the problems with the engine in the raptor , and the re-drive , are the potential points of failure in the overall system. For a diesel engine , which is intrinsically a basic compression combustion engine, the added systems and sensors in the raptor installation; add another level of potential failure - that and the belt driven re-drive do not make for a fail safe set up.

[@PeteZoot]

Awesome vid. Thx! Pity the raptor has more than a few similarly rooted design issues.

[@therabbi75]

This is another in a long line of problems with the Raptor. I have pointed out the problem of the integrated hydraulic system. The reason for the last engine failure was that the prop system failed , oil leak, causing the engine to loose oil pressure. The engine should be separated from the prop hydraulically. Simple to do . Yes it will cost a little.

[@golfmaniac]

That redrive system is the weak link in the chain. That will be a constant failure point.

[@henry41493]

Why stop there? You could have different oil system for the engine top end, a different system for both top ends, different oil system for the turbos, different system for each turbo, you could have a different system for each crank bearing, you could have a high volume low pressure system for cooling oil. How do you know what is the right number of segregated oil systems?

[@therabbi75]

@@golfmaniac YOU are correct!!!

[@sl66ggehrubt]

@@golfmaniac and it's the only selling point.

[@beewagyu]

Excellent presentation. I just wish he would listen to men that know what their talking about. Thanks for opening most eyes.

[@jmaridon]

My wife keeps asking my why I keep watching the Raptor videos. It's for the same reason that people gather to watch a train wreck. I just hope Peter doesn't kill himself or someone else with that airplane.

[@mattym8]

It seems possible he will run out of money or time before he crashes it. It flies now, just irreparably poorly.

[@mackdlite5900]

This is good analysis, but as big of an issue as it is, Raptor has even bigger problems. Very sad airplane!

[@Swarfman64]

Thank you very much for this, many watching knew and have made comment on the turbo set up but your explanation/ presentation nails it. One would hope some changes are made before we see a catastrophic failure in the air.

[@tacticalrabbit308]

He already had a failure in the air after loosing oil pressure , now he has had to replace the engine because of it . He had a leak in the redrive unit for the prop .

[@John-rw9bv]

Wow i learned a lot about turbos and compound turbos from this video, thank you so much for making it! Also you use my fav. engine, the EJ22, haha, would love to see how you turbo'd that :) My dream is to put the EE20 (Subaru's high-efficiency 2L diesel) in a LongEZ, and just try and max out the miles-per-gallon. Actually i was going to make it a dual-fuel diesel/propane because that gets even better efficiency, and the propane can take high boost and has a better weight-to-btu than diesel/petrol, but i'm rambling now, thank you for teaching me more about turbos and helping me get closer to my dream :)

[@keithturner3859]

Excellent explanation and discussion on the raptor shortcomings on turbo sizing and matching. Mullers solution to hearing dissent and criticism is to ban those trying to set him straight. There are so many areas in the design and development of aircraft where he just doesn’t have a clue. Flight controls, structures, aerodynamics, stability and control to name but a few. His approach to returning to flight after having an in flight engine stoppage after a major oil loss is mind boggling. Fortunately there was significant internal damage to the engine that manifested itself on the ground run up after fixing the oil leak and just adding more oil. Maybe the next significant in flight engine failure will not end so well - he did get very lucky on the last one. He just thinks he is way to smart to listen to anybody about any subject and maybe he is. For those of us that have been involved with aviation for 40 plus years, lost some capable and careful friends and colleagues in aircraft accident - what do we know. Maybe we have just been unlucky. Everything tells me the raptor program and Peter Muller are going to come to an abrupt and unpleasant end if he carries on with the “suck it and see and press on regardless approach” . I don’t for one moment believe he will listen to your efforts to help him. Sheep were made to be sheered.

[@simonbaxter8001]

"Mullers solution to hearing dissent and criticism is to ban those trying to set him straight." ... He's banned me! His loss, I'll share my experience with someone who appreciates it. Your other comments are spot on. I gave up following when he just refilled the engine oil and fired it up ... no inspection, no strip down, no oil analysis. Sadly it's a matter of time before something really bad. Hopefully not at the expense of an investor or 3rd party.

[@keithturner3859]

@@simonbaxter8001 yep banned me too. Just bad for business when he got told that he needed to stop putting patches on top of patches. I am surprised he hasn’t had a visit from the FAA revoking his airworthiness certificate and his pilot licenses. If (when) he has the next major event with the unsafe prototype raptor and somebody else gets hurt I can just see the lawsuits piling up. His approach and behavior is just plain reckless and unsafe. Best to watch from a distance.

[@apocalipsboy21]

I started having doubts when the empty weight went trough the roof. Now I see velocity’s are the way to go.

[@philpotter6388]

Thanks, Ross. I hope your knowledge, and willingness to share same, will benefit someone. Sadly, not likely to alter Peter's configuration.

[@normancole3415]

Peter is a hard head and if he isn't careful that thing will be the end of him he's been lucky so far but things can go from good to bad in a heartbeat

[@antonudrp707]

I am getting the same vibe. He does all this intricate engine diagnostics but he gets bog down with data and information.

[@don_sorensen_santa_barbara]

@@normancole3415 and as witness the seal blowout that caused the engine failure and near disaster of his last flight, he is not careful. The seal seemed ok, until it wasn’t. If you get a chance to fly with him, pass.

[@georgeingram2143]

@@don_sorensen_santa_barbara Peter didn't check anything else after finding the blown seal. It could be something else that failed. He didn't even take a head off to check the valves and pistons that many, many people have told him were being tortured to death. Compressor turbo seals don't usually see much pressure, they are effectively at an inlet pressure point. But with compound turbos, the second stage compressor seal sees about the pressure of the first stage outlet. That is likely going to need a different seal to the ones put in speed shop turbos, which aren't compounded. Stuff is never as easy to do as it first seems. His luck has been keeping him alive, it can't last, though.

[@swlowry5277]

@@georgeingram2143 george, you may have missed the engine teardown where he looked at the cyl head and pistons. Incidently, to prior comments, hard heads is what causes those few adventurers to risk all to do awesome work that has some chance of move humanity's needle. This video is a great way to present a well developed comment to Peter's work. I am with the many who hope this video will make it to Peter. At the same time kudos to Peter for being one of the rare humans who try something - anything to make a difference!

[@golfmaniac]

I have been following Peters build for a few years. Several people, that had good experience in turbos, tried to tell him his setup was wrong. Peter will not listen, its like he is getting bad advice from somewhere, but he believes it. It is obvious from the test flights that it is not making enough power. He reaffirmed in a video a couple months ago that the turbo setup was good. I do not understand the unwillingness to listen to people that know more about a subject than you do.

[@ulbuilder]

My observation is that he is overly focused on getting the first 40 flown off, a requirement before going into production. So he focuses on easy quick fixes only. While he seems like an intelligent person I suspect this build has taken him into many areas he knows little about and he simply does not know what knowledge he lacks. One cannot sift through what turbo change suggestions are helpful if you don't have the fundamental knowledge required to assess the suggestions.

[@aGabay]

Even on of the original designers of this very engines told him the exact same thing! He just ignores everything that doesn't suit him.

[@rocketplane]

Thanks for the introduction to turbocharging. I had to go look up what "corrected airflow" was, but in combination with some of my own reading, I've got a much better understanding of matching a compressor to a particular application.

[@rocketplane]

I was just thinking, since it took me a little bit of time to wrap my head around "corrected airflow." I'm pretty sure the designer of Raptor just looked at the fact that the turbo Audi draws 30 lbm/min of air at maximum power and said, "oh, that will work great!" without understanding the "corrected" part of corrected airflow.

[@rv6ejguy]

@@rocketplane The main rub is that Peter failed to understand that the 1st stage compressor must take in about 2.68 X the amount of air and compress it roughly to SL pressure to feed the 2nd stage compressor at 25,000 feet, which then compresses it a further 2.68 times to achieve the 80 inches.

[@scarter176]

Great Video ! Very good explanation of ratios and efficiency of turbos

[@johncalhoun358]

Priceless info,,,, thank you!

[@ronkluwe4875]

I have commented on Peter's videos multiple times about his lack of engineering understanding, especially of first principles that drive engineering design decisions. I want to say your video is clear and succinct about the dual turbo set-up Peter currently has installed on the plane and is exactly what I, and many others, have been trying to tell him. I have to agree Peter is definitely a "not invented here" guy and that is a very dangerous trait for any engineer or person trying to perform design development. Based on my many years of very successful large engineering project management, I see a person who is now at the point of using bad logic to justify his decisions rather than listen to anyone who is not on board with his views. In my world, this is someone I remove from my project as there will be a bad outcome sooner or later. I really wanted to see Peter succeed, but I have no doubts at this time this plane will never make it to production unless someone takes over the project. Peter is way beyond his capabilities and unfortunately appears to not have the money (otherwise why purchase a suspect used replacement engine?) to hire people who can help him to success.

[@mikegofton1]

Yes Ron, I came to the same conclusion. I really wanted Raptor to succeed and put up some cash to keep the project rolling, however Peter is not applying sound project management principles and engineering decisions are being made without the benefit of experienced and qualified practitioners. I hope for everyone’s sake the project ends before there’s injury or loss of life.

[@kwittnebel]

Best video I have seen on the subject. Glad I am doing a car rather than a plane; you might also consider mentioning that other applications e.g. automotive can run the turbos sequentially to broaden the combined compressor map and spool earlier then hand off to the large compressor, because they almost never run over PR 4. This is achievable by a single turbo, rather than compounding boost all the way up to PR 7 due to low ambient pressure at altitude. Kind of a shame the raptor guy went to all the trouble to build a compound without bothering to size the first stage appropriately.

[@davidmintun]

This is certainly constructive criticism. Good information well presented.

[@jamesperedo5699]

awesome, please consider reaching out and helping the builder and let's make this open source project best in class so we can all benefit from all that hard work

[@rv6ejguy]

The designer won't be listening to me or anyone else here. It's his project and he can continue on his own path any way he likes. Open source makes no sense on a complex aircraft project like this.

[@judd_s5643]

@@rv6ejguy I think Peter is nuts for doing this development online. Anyone that has any engineering experience knows what the outcome will be when a project is designed by committee.

[@rv6ejguy]

@@judd_s5643 He's done most of the design himself but lacks any real-world background or formal education in the multiple disciplines required- aerodynamics, structures, systems design, engines, cooling/ thermodynamics, turbos, stability, flutter and flight testing. This is a complex project and he needs serious engineering help if he expects it to be successful. I don't know any single aviation person who could do this project successfully by themselves- and I know a lot of smart aviation people.

[@tonymatthews4853]

Hi - Question on the calculation of required airflow - at about 6:20 you do a calculation to get to about 80LBS/MIN. Why does the second turbo (ie engine) need 2.68 times the pounds per minute of airflow? It seams like you are saying that the second turbo needs 2.68 time the flow rate of the first turbo (I would think that both turbos have to have exactly the same flow rate) or the engine needs 2.68 times the flow rate at altitude (which I would think is also incorrect, it needs the same flow rate). I might be just be unaware of what the term "Corrected Air Flow" means. Thanks

[@rv6ejguy]

2nd stage will always be smaller so not 2.68 times the flow rate. We work the calcs backwards from stage 2 to see how the stage 1 compressor needs to be sized. Perhaps I didn't make that clear. Compressor maps are based on corrected inlet flow- that is the ambient temperature and pressure present at the inlet. Stage 1 is at about 11 inches and 0F. Output from stage 1 into stage 2 will be at about 2.68 X the pressure (we're ignoring intercoolers here). Mass flow is the same throughout the system, only pressure, temperature, volume and density changes. Stage 1 needs to be larger to squeeze down a greater volume of that low density air to feed the smaller second stage.

[@tonymatthews4853]

@@rv6ejguy Thanks for you reply. So - What is the 80LBS/MIN referring too? Why did you time 30 LBS/Min x 2.68? Wouldn't the flow rate through both turbos be 30 LBS/Min. Sorry if I am missing something

[@rv6ejguy]

@@tonymatthews4853 The difference is the inlet conditions at each compressor. One is at 11 inches, the other at about 30 inches. Air molecules further apart at stage 1. Flow is 'corrected' for air density. The mass of air inducted remains the same throughout the system. Remember Boyle's Law I talked about- double the pressure, half the volume, double the density.

[@DoRC]

The big problem with his turbos right now is that he has metal particulate flowing through them. I'm pretty sure that when he blew up his last engine he never went through all of things the oil touched and cleaned or replaced them. I'm pretty sure if the old engine had managed to start again he would have just carried on using it.

[@H60ace]

Interesting, and accurate. I will say that I had to restart the video in the morning because it made me fall asleep last night! True story!

[@garywhitman2540]

Have you talked with Peter about this?

[@markmark5269]

bahahahaha! You know how a conversation works? One person talks, the other person listens, and there is the issue.

[@simoncorporation3]

Good presentation of your point of view.

[@ptrsrrll]

Odd choice of words - this is not his point of view (suggesting there may be others) This was - Good presentation of the FACTS.

[@deemsdavis7811]

I believe that Peter's problems extend beyond the turbo, and reduction system. Didn't he tell us a short while ago, he was out of money . He was able to round up some more, but that had to come with tighter stipulations and progress way points. He's in a catch 22, stop and fix the root issues and loose his financing. Not a good place to be.

[@sl66ggehrubt]

Who would buy this aircraft when DarkAero will get to market faster with a regular proven engine?

[@danielwaddell123]

@@sl66ggehrubt Someone who wants more than two seats?

[@gordo1163]

@@danielwaddell123 I would rather purchase a 2 seater over an airplane Peter has built. The DarkAero actually looks plausible, their team looks structured and has a smooth workflow. I can't say the same about Peter and his 'team.'

[@danielwaddell123]

@@gordo1163 What a ridiculous response. There are other alternatives for 5 place kit planes.

[@livetoshredhella]

How did we go from 80 in absolute (pressure) to 80 lbs/min (flow rate)? Or did I miss something?

[@jaws2858]

I’m not a pilot nor do I have a plane I do love turbos though. I have never heard someone know so much about them. Enjoyed myself.

[@avshiloh2438]

EXCELLENT presentation!!!

[@gerardmccarthy2432]

Would a correctly matched vnt turbo eliminate the need for compounding?. 25000' is way optimistic. Peter needs to get to 15000 first then go from there. Very good technical insight video. I learnt quite a bit. Thanks for going to the trouble.

[@rv6ejguy]

No centrifugal compressor is this size range can make much over 4.5 pressure ratio, so it really needs 2 stages for a diesel engine. I'm working another video now which will explain this a bit more.

[@yukon4511]

Peter needs to get out of the traffic pattern between overhauls. 300 knots is a pipe dream.

[@mackdlite5900]

@@rv6ejguy I subscribed and I'm looking forward to that video.

[@kaecycorbin6399]

VERY fascinating video. Thanks for sharing all of your wisdom with us! You've earned my subscription!! I began watching Raptor being put together right at the end of assembly and missed all of the engine testing - surely this turbo mismatch should've reared its head during engine testing.... I began to realize what kind of builder he is when he was bumping up against problems, getting loads of helpful advice from his KZbin comments, and then pushed on (ignore any advise) with an inappropriate "fix". Then that came all to a very heated, red-faced point with trying to get Wasabi to do the flight testing!! There's a reason that Elliot isn't flying that aircraft.... Certainly seems to me that the turbo mis-match is another case of excellent advice being blatantly ignored. And truly a shame, because I think the Raptor is a beautiful plane - but looks to be doomed to fail.

[@richard8181]

I have followed Raptor (Peter M) since beginning and you would know from following that there HAS been good info given but NOT taken on board. Sometimes you just got to think about input suggestions and there SOURCE. 🤔🤔

[@chrism9976]

I was initially excited about the project, not so much now. Aircraft weight aside, do you think the Audi engine is the best choice?

[@rv6ejguy]

No, it never was a good choice. Way too heavy and with Peter's mods, it has less power and stock, burns more fuel and is less reliable.

[@petesinclair5653]

Great video. I’m not sure why you assumed the aircraft needs full power at 25,000 feet. Pretty much all turbocharged aircraft engines choose 18,000 as a critical altitude, above which power output drops off. That still provides enough power to climb into the mid 20’s, albeit at a slower rate. Given the thin air up that high, dissipating the engine heat at full power in the mid 20’s would be very hard. Thus, the decreased power output also helps the cooling question. So designing around a 5.6 PR may be a better choice. Not sure how that affects your turbo recommendations.

[@rv6ejguy]

Raptor had been talking 350-400HP. I was assuming around 300HP at altitude to even have a hope of getting close to the original performance claims. That's 75-85% power. The problem with the diesel is that it requires much higher PRs to make the same power as an SI engine. Even at 5.6 PR, still can't do it with a single turbo. The next video will explore some of these points.

[@gerardmccarthy2432]

@@rv6ejguy Lets not forget that engine is going to be runnung an ac compressor also. They rob power.

[@yashmanwani6232]

Thanks for taking time to share ur knowledge!

[@yukon4511]

Great informative video. Try to remember Ross, "Complexity is the Mother of Failure".

[@rv6ejguy]

I agree, Raptor is overly complex but that's the least of its problems.

[@yukon4511]

I'm concerned that he is taking people's money with a highly deficient prototype. This thing is heavy, slow, unstable and unreliable. Experimenting is fine, but do it with your own money.

[@ernies7174]

@@yukon4511 I'll give peter credit. Unlike Jim Bede, he actually put the money into escrow, and then told people to take the money out of escrow. Bede ran a ponzi scheme. Peter doesn't know what he doesn't know. And the last statement from Ross was a beautiful dog. Bravo Ross

[@antonudrp707]

Quite interesting and educational. I follow the raptor aircraft channel on KZbin. Hopefully, Peter finds this helpful with his intricate engine diagnostics.

[@jeffrobodene1485]

Nice Job! Interestingly enough that turbocharger system on the Raptor was designed for a automobile operating at normal conditions...say under 5000 AGL. I am surprised this was not thought of my the engineer who designed and manufactured the Raptor. Anyway, this was a very informative video. Thank you for sharing.

[@rustyshackleford7022]

He didn't use the stock turbo setup from the Audi but cooked up his own. Also, usually automobiles operate under 5 AGL...they would seriously lack traction any higher.

[@grandenauto3214]

@@rustyshackleford7022 not sure about that....the computer mapping should be infinitely expandable to what ever pressure (height)... most autos computer take information from a wide variety of sensors and monitor operation constantly, as you go up and have less air the computer would compensate by leaning the mixture or upping the boost.

[@rustyshackleford7022]

@@grandenauto3214 I think you missed the joke...we're talking AGL. An automobile above ground level usually lacks traction because its tires are off the ground. The computer mapping can't counter that.

[@grandenauto3214]

@@rustyshackleford7022 I get haha

[@richardperry21]

I forgot to say that again but great job Ross

[@ronboe6325]

Thanks! I didn't know what forlks were going on about the turbo's and this is a huge help. There really should be a shop converting these Audi engines to aero use so they are suitable for the application. With each video of Peters' we get a glimpse of the limits of his knowledge so it's painful to watch him set up for failure. I suppose he can't afford to pay for good advise (and maybe figures free advise is worth less). This whole experiment to get this plane off the ground with an Audi engine may just prove you shouldn't use an Audi engine. :P

[@scarter176]

What is the best turbocharger for 10 to 1 static compression 540 CI lycoming to maintain 25 inch man press to 15,000 feet ?

[@PatrickJWenzel]

Fantastic resource. Thanks for posting this.

[@shortribslongbow5312]

Well done.

[@dankennerson2080]

Great video- I've been interested in compound turbocharging for awhile in the diesel truck world, and am becoming interested in aviation- which leads me to a question: Is the mass airflow in the efficiency island graphs the same at different altitudes with the difference being final absolute pressure? or does the mass airflow also scale with altitude for the atmospheric turbocharger?

[@rv6ejguy]

I've answered this one several times here. Mass flow is at the compressor inlet so the lower the inlet pressure, the higher the inlet flow must be to deliver the desired outlet flow at the desired pressure ratio. Boyle's law applies here roughly with corrections for air density with temperature change from compression. Since inlet flow and pressure ratio changes with altitude, you'd see a change in point on the compressor map.

[@silasmarner7586]

The thing is, retrofitting the two turbos in Peter's setup wouldn't be a tragically difficult switch, but would provide dramatically better HP.

[@kscipkkkk]

Better HP an less heat to deal with.

[@MrBryansa]

In this case, why couldn't a single sizable turbo with a substantial impeller work since quick spooling is largely unnecessary? Maybe you covered this in which case apologies but it seems you're saying that a compound system is necessary.

[@rv6ejguy]

No compressors in this size range can efficiently produce pressures ratios over 4 and we need 6-7 here.

[@MrBryansa]

@@rv6ejguy Would we also want to add fuel then?

[@rv6ejguy]

@@MrBryansa The diesel requires excess air to operate efficiently, more fuel just raises EGTs further.

[@rileyswing9731]

Great video

[@nielsf2743]

How do you calculate ideal turbo charger combinations when there is the big unknown of how much bleed air will be required to pressurise the cabin? Seems to me you can’t until you take the aircraft up to FL250 while keeping the cabin altitude at something under 8000. Only then will you have the necessary data to make selections of the better turbo charger combinations.

[@rv6ejguy]

I believe Peter was feeding the pressurization system with a 1/4 line in ground testing which may be too small unless he has exceptional sealing. In any case, most small cabin class twins leak something less than 30 cfm. Since this compressor is putting out around 1230 CFM, that would only be 2.4% of output which is inconsequential.

[@nielsf2743]

@@rv6ejguy Ah ha! Thanks for clarifying. I had no idea what leak rates could be expected. It is indeed surprisingly inconsequential.

[@stevec7596]

Great video. I'm sure you know that people who comment on this subject in one of Peter's videos gets bkocked. There should be a club!

[@DavidAndruczyk]

Excellent presentation, thank you.

[@gregorykusiak5424]

So what I’m seeing here is that the Raptor’s capabilities will be limited in terms of power and efficiency - it won’t efficiently push itself to the proposed altitudes, and it will have a hard time staying there. It might even be why cooling has been an issue. And maybe was a contributing factor to the engine failure. These are not minor issues. I truly hope there is the potential for things to change.

[@henry41493]

Really nice video, thanks for making it. Good to know that raptor has some low hanging gains to be made in the future, he has an whole air frame to finish developing first. Do you think he's flying with dangerous egts or just suffering poor efficiency and output in the meantime? Is there other dangerous damage he could be doing?

[@rv6ejguy]

The piston crowns and exhaust valves will be taking a beating like this which can't be good for longevity and the high temps generally increase the thermal loads on the oil and coolant as well. The engine never spends more than a minute at true climb power because of the thermal challenges.

[@davidgreenfield1476]

@@rv6ejguy absolutely agree, a properly sized compound setup would solve his thermal difficulties in stead of being a heavy bandage. I've seen him compare his fuel rates to horsepower output without talking into account the absurd exhaust pressure and temperature readings proving inefficiencies.

[@rv6ejguy]

@@davidgreenfield1476 The thermal difficulties go far beyond the improperly matched turbos. The oil, water and charge air heat exchangers and ducting for them are all improperly done as well. Agree, judging HP from fuel flows is invalid without dyno numbers. The estimated HP was much higher than what the ground acceleration or ROC would suggest for this weight of aircraft. I've run the ground accel numbers myself almost 2 years ago and those show 250hp at best.

[@keithturner3859]

@@rv6ejguy Ross, I think 250 HP is being optimistically kind. Based on static thrust measurements, take off acceleration and his demonstrated performance following the engine failure, raptor is developing somewhere in the range of 160 to 200 HP at full power and in the the range of 120 to 140 HP when throttled back in the climb. Truly pathetic for a vehicle that is expected to operate at 25K.

[@rv6ejguy]

@@keithturner3859 Yes, probably slightly optimistic. Remember that prop efficiency isn't 100% though and acceleration will be based on the average force delivered throughout the run. I've working on a new video which will cover this.

[@adrianluis6590]

I totally agree that the engine setup and especially turbo setup needs to be different , and I do think that peter has to contact someone like you Sir in order to make them better. the engine on raptor doesn't that good this is a fact.

[@Mike-01234]

How much experience do you have with a turbo diesel? Diesel can take lot more boost with the high compression they can produce lot more torque. My Cummins 6.7 produces 850lb of torque yet only 375 hp. I suppose a gas engine of that size could produce lot of torque if it was using a turbo charger, but it would require high octane fuel to do it.

[@rv6ejguy]

I have turbocharged diesels in the past. Torque isn't so important here. Hp is the measure of rate of work done and what we need in aircraft. SI engines put out more hp and torque per unit boost than CI engines. You can watch a comparison video on this subject on my channel.

[@michaeltranchina6358]

Great job...👏 Excellent all around! I am confident Peter will come around...

[@rustyshackleford7022]

Good one

[@gerardmccarthy2432]

@@rustyshackleford7022 HAHA

[@jetshine9985]

Thanks for the explanation, I learned a little more about turbo design! It wasn’t super clear to me why the Raptor was using a serial turbo setup, but now I understand a little better. The choice of engine for the Raptor is really the bigger stumbling block for me. The 3.0 TDI engine hasn’t been made since 2015, so even the best example out there is 6 years old, and likely a buyback from the dieselgate scandal. That doesn’t bode well for long-term support, spare parts availability, and general technical support of the base engine. I think Raptor serial #1 and maybe #2 will probably eventually get to a successful point, but it will need to be re-engined for anything after that, in which case I hope your turbo suggestions are taken into consideration if it’s another car engine conversion.

[@gerardmccarthy2432]

Look at Darkside developments in the UK. 3.0 tdi engine can be a powewrhouse if done correctly.

[@davidgreenfield1476]

3.0 TDI engines are abundant worldwide, and they are a benchmark in power and efficiency. When referring to outdated technology, please consider the faa regulations for general aviation craft: typically using 1940's technology and shunning innovation. Two valves per cylinder, constant spray manual adjusted mechanical fuel injection. Mechanical spark advance. Research diesel aviation engines and you'll see how much of a hindrance the faa has been on affordable personal aviation. At least Peter's goal is in the right place, even if he's missing the forest of valid advice.

[@jetshine9985]

@@davidgreenfield1476 I don’t doubt it is a wonderful engine, but it has been obsoleted by its manufacturer. In fact, both Audi and VW announced they will no longer develop new ICE engines, which further reinforces that this engine’s days are numbered (and it’s already 6 years on borrowed time!). I think that is a pretty serious demerit for a brand new, clean-sheet airplane design. Maybe you can source engine parts for the next 5 years, but what about 10 years from now? 20 years? Trust me, I’m all for high tech engines. I’m currently building a plane myself, and it is powered by a Rotax 915iS, which is one of the most advanced GA engines you can buy right now. But it’s also backed by an engine company that’s been around for a while that will probably still be producing this engine 10 years from now.

[@neeema3]

Thank you for the video! I followed most of it--can anyone help explain how/why at 6:15 we multiply one turbo's pressure ratio (~2.68) by corrected airflow to get the 80 lbs/min figure? I'm guessing that's part of an equation for compound turbos?

[@rv6ejguy]

Compound compressors are typically matched from the 2nd stage airflow first and then multiplying by the first stage pressure ratio (2.68 in this case) Using Boyle's Law, volume delivered by the 1st stage to the 2nd stage will be 1/2.68 (0.37) 0.37 X 80= 30. Note that Boyle's law assumes constant temperature during changes in pressure and in reality, we won't have that in a compound turbo system, which isn't a closed system either. The video also ignores the fact that there is substantial temperature rise during compression and does not take into account any intercooling of the charge air which we'd certainly need to do to have a functional system. The video is illustrative only (which I'm sorry, I didn't make clear) and is not about solid numbers for compressor matching for Raptor. My main purpose was to show that the equally sized compressors cannot work at 25,000 feet and the required pressure ratios. I tried to make that part clear by using the analogy of the 2 stage air compressor and showing photos of the size difference on actual compound turbo setups. I also tried to explain why the turbines used here are too small and also greatly impacting performance. As a data point, my 2.2L Subaru uses a turbine wheel about 10mm larger than Raptor where Raptor should have something around 10mm larger than mine with almost 50% more displacement and around double the HP. I think many people are confused when I use the term compressor mass flow. Compressors are rated by CORRECTED INLET flow- either CFM (volume) or mass of air (usually lbs./min). Corrected meaning inlet pressure and temperature are taken into account and often specified on the compressor map. If the map was developed at or near sea level, that will be the correct inlet mass flow processed by the compressor down there. Now move the compressor up to 25,000 feet where in the inlet pressure and density is about 1/3rd of SL conditions and compressor won't process the same mass of air as at SL at the same compressor rpm. Up high, we need to intake a greater volume of less dense air and compress it back to near SL pressure to feed it to the 2nd stage compressor so it can then increase that pressure to the required value in the intake manifold to make rated power. There are a myriad of other factors involved but a simple, short video can't cover all those things and that wasn't the intention of this one. I'll try to touch on some other factors in subsequent videos on turbocharging and intercooling as this seems to be a popular topic.

[@neeema3]

@@rv6ejguy I follow now. Great explanation. Thank you

[@letmeseeit66]

Presumably the people at Garrett would know this too. I wonder if when choosing turbos, other considerations took precedence, such as actual physical size, in order to fit them inside the cowling. I'm not saying that this is a valid line of thinking, just speculating on how we got here.

[@rv6ejguy]

I believe Peter chose these turbos himself based on his flawed understanding of the topic. Had he consulted Garrett engineers with aviation matching experience, he would have ended up with something a lot different.

[@kenandzana]

The challenge Peter has undertaken is testimony to the tenacity and determination of the man, so it is my assessment that Peter will embrace this advice as he may be many things but one thing he is not and that's a fool. So expect Peter to respond in the same manner that this advice was given. graciously.

[@DealerD8vE]

How long have you been following this project? You sound more delusional than Peter!

[@airtightindustries]

Excellent follow up to a well intentioned comment, I'm sure! I spoke the design of the redrive and the foreseeable issues with oiling and pressurization within redrive causing hydraulic power loss..... Yadda yadda yadda. Peters an amazing man, and it's great to see him succeed with flight but... It's hard to watch and listen to these days..... As someone who has followed the Reno Races push all types of engines to the limits the only turbo charged car engine I'd want on a runway is those Saabs in 06!

[@austinbowman1433]

I feel like I could learn a lot from you.

[@rmatthews8161]

I heard that Bernoulli put Raptor down in a cornfield in Iowa

[@davidhanson3288]

Well done. I doubt Peter will listen.

[@rickfeehery7722]

Back in October 2018, I had the opportunity to visit the Raptor prototype and see what all the fuss was about. Peter was mobbed, but I had great talk with Jeff Kerlo his right hand man on the composite side of things. There was a couple of questions that I had, especially since I had built and flown an Express Aircraft (Auriga). I thought that the prototype was engineered poorly, especially the doors, which were way too complicated and heavy, the lack of radiator cooling, and the cantilevered seat mounts which were extremely heavy. The whole plane smacked of a computer generated fantasy, with no real knowledge of engineering. I asked Jeff point blank why Peter insisted on an experimental engine on an experimental aircraft prototype, he just shrugged and said that Peter wanted it that way. Just look at the Dark Aero boys--are they putting an experimental engine on an experimental prototype? Of course not, they are ENGINEERS. I have no qualms with being self taught, hell Elon Musk is primarily self taught--but he hires really smart and talented engineers to get the job done. If you are going to design and build an experimental aircraft start small say a two seater, and work your way up. Don't go full bore with the most complicated thing you can think of, dupe people of 25 grand a piece, and then claim that prototype 2 will be better. Give me a break.

[@YeshuamyKing53]

Rick Feehery, I'm really impressed with the Dark Aero brothers.

[@willhibbardii2450]

@@YeshuamyKing53 , Yep!, me too!

[@willhibbardii2450]

Your numbers for petrol fueled engine is spot on my friend...

[@willhibbardii2450]

@@ryanthomas2472 , Yep, getting the boost on the money is the goal! That's what experimental is all about! At least it's spurred intelligent working knowledge of innovative discovery of upgrading light aircraft propulsion... Many discussions are now happening... The compression ratio that's engineered into engines is called "static compression." When boost is combined in conjunction with compression ratio, the result is known as the "Effective Compression Ratio." Low compression engines will facilitate higher boost than high compression engines. An aviation solution that one company has employed with Diesel engines is a low compression aviation Diesel engine requiring spark ignition which will accept higher boost. With any application of serial compound boost it becomes a balancing act of engineering compromises concerning aviation FL (Flight Level) operational environments. Presently I'm spending time with a commissioned project calculating series compound boost for a proposed aviation 4 cylinder 150 KWH auto ignition Diesel propulsion unit. I've found the numbers skewed counter intuitively with high compression engine applications fed with railed fuel injection systems... I'm convinced that Boosted Aluminum Block Diesel aviation piston engines will gain a considerable market share like they have with the marine propulsion industry. Bottom Line... Experience with petrol boost low compression SI engines isn't an equivalent benchmarked Horsepower conversion when working with boost... Torque is the master of KWH conversion. The goal in X country aviation or marine propulsion operation is to use less fuel for distance traveled... Correct? The balancing act that's paramount to this aviator's awareness is average fuel burn consumption for weight transported. I've found that Torque fuel flow of Diesel piston engine propulsion KWH output is almost 1/2 that, of it's petrol burning cousin... In other words... 20 gallons of Diesel fuel (timewise) will just about do the work that it takes 40 gallons of petrol to perform... Rule of thumb speaking! rv6ejguy with his presentation is spot on for petrol... He's a sharp guy that's very detailed oriented. I've been working with boosted diesel marine propulsion at about sea level since the 1970s. The Mercruiser TDI 3.0 V6 Mercury Diesel TDI marine propulsion system is similar to the Raptor's Audi 3L TDI. I only became aware of Peter Muller's Raptor project June of 2020. I never considered employing Diesel engines for light GA aviation till I discovered Peter's remarkable work at that time. Since then I've been experimenting with different configurations on the Mercruisers to get my base data from, thanks to his work. I've spent many enjoyable hours with aviation since the late 1960s. Primarily with certified manufactured aircraft. Mostly avoiding experimental machines... love flying at FL-24 in a private 4 place turbocharged aircraft, cruising at a calibrated IAS of 100 ~ 120 kts tracking groundspeeds north of 200 Kts sipping an average 11.5 GPH fuel flow petrol in strait and level cruise configuration... But that's only 20 MPG with a tail wind... With Diesel the MPG would be closer to 30~40 Statute Miles Per Gallon in real-world applications... When I crunch the numbers... Series compound boost Diesel piston aircraft propulsion becomes a no brainer decision for light private aircraft operations... Good thing that Turbos are relatively inexpensive in the scheme of things... We need real-world test to verify what seemingly looks good on paper. At least now we have a working premise to tackle the solutions...

[@rv6ejguy]

@@willhibbardii2450 Present SI aero engines can deliver .38 BSFC in cruise LOP, the best light diesel aero engines about .33. That's only about 15% better. You're saying here the BSFC will be half with a diesel... Diesels output less torque and HP per unit displacement and boost than SI engines. I did a video on this some months back. Diesels have several drawback for high altitude aviation compared to SI engines. I may do a video on that sometime in the future. The big draw for diesels is no lead, cheap fuel in my view.

[@willhibbardii2450]

@@rv6ejguy , Yes, I prefer inexpensive thrifty clean burning fuel... A rule of thumb I've adapted for the marine and aviation propulsion is remarkably accurate and simple... BSFC (Brake Specific Fuel Consumption) with gasoline propulsion I've found to be directly relatable to (GPH Fuel Flow)... Multiplied by 10 is close to horsepower being employed by the engine, with an engine running LOP (Lean Of Peak)... Example: If the Gasoline fuel is flowing at 20 GPH (Gallons Per Hour) the so called horsepower being employed is about 200. Not perfect but there about... 200 HP I equate to on the dyno to be about 150 KWH... At Standard Temperature and Standard Pressure with naturally asperated engines. Supercharging and turbocharging simply equate to expedited climbs... The trade offs for the amount of fuel needed to get to FL- Cruise altitudes then trimmed clean is a stepped process of performance finding the sweet spots. With every 10 gallons of fuel burned (Gasoline) the aircraft loses 60 pounds and the aircraft will climb to the next step... The Guy that taught me to fly little airplanes drilled something into me that's been very handy. The Aircraft I trained in was a Aero Commander 100. He had a fuel flow indicator installed. On a cold day below standard temperature 0 C at sea-level the engine, a Lycoming O-320-A air-cooled flat-four, 150 hp (110 kW) would consume just over 16 GPH on a hot day that number changed dramatically reduce to under 14 GPH at about sea-level. A large portion of may aviation training was operating at 14,000 feet MSL and above in that little aircraft especially in winter months. When I started doing my solo cross country work it was no problem getting through 14,500 and above (Yes we carried supplemental Oxygen) It amazed me that the naturally asperated engine LOP would sip fuel at less than 6 gallons per hour throttle to the fire wall at full altitude. The translation to horsepower was about 60 hp employed but yet we could track ground speeds well over 120 MPH. A great trade to my thinking. Though the Corrected TAS was 65 ish. He taught me how to enjoy little airplanes and keep the cockpit quiet with very little stress on X - Country flights... The cruise accent to altitude was 1/8 FOB (Fuel On Board) of the fuel consumption and the decent 90 MPH at 300 fpm decent with the engine loafing. No need for headphones. Guys that fly with me comment how well they can hear without allot of engine noise and appreciate hearing the controllers on the overhead speaker. He taught me to use weather as my friend and navigate the VOR Rhumb lines taking advantage of the wind components and shifts in the winds aloft FD (Forecast Data)... He was a fighter pilot during the Korean War and became an instructor. Many controllers would hear Aero Commander and relate it to the twin 500 which he also flew. I know he enjoyed that aspect dropping in hot from altitude with a 30 kt tail wind to the downwind leg with a 150~160 MPH ground speed turning a quick base and final on an expedited approach in the 100. He taught me how to dump energy, land like a bird and clear the runway. My grandmother called it landing on a dime and leaving 9 Cents change... Handy Safe maneuver when landing little airplanes in big bird (Bravo) domains. Jets behind me have been warned by control towers of my propwash🤣 I've fooled many towers over the years in Cessna 150s thinking I was a twin Cessna arriving. I've actually had controllers ask me what kind of souped engine I had in it. Seems unusual to see a 150 at 14,500... Just stock 115 HP and knowing how to ride the chop... Ok Marine Diesel topic... The first marine Diesels I worked with were Perkins TV8 540 twin turbo. Rated only 145 HP. (109 KWH) yet sip fuel at 5.5 GPH under full load. Ratings in the marine industry diesel world are curious... This same engine block is very capable of delivering 300 HP (225 KW) though the fuel consumption dramatically increases to 15 GPH... In the Super Yachats this same block is reported developing over 2,000 HP... I don't know the fuel consumption flow rate... But I imagine my rule of thumb calculation is out the window. A Stock Mercury Marine 240 HP (180 KWH) 3L TDI @ 3,950 RPM propped to full load (verified) sips fuel at 12.5 GPH ADL (All Day Long) yet at 2,500 RPM sips fuel at 5.5 GPH ADL~ANL (All Night Long)... My findings indicate that with Diesel fuel Power that a multiplier of 20 concerning fuel flow GPH is ED (Every Day). Example: 10 GPH Diesel fuel consumption X 20 = 200 HP (150 KWH) Work Employed... Compared to Gasoline's multiplier of 10. Example: 10 GPH Gasoline fuel consumption X 10 = 100 (75 KWH) HP work employed... It's known in the marine industry manufacturing engineer circles as reserved torque! Rule of thumb speaking. OMC V4 two stroke Gasoline Example: Same Block but 80, 88, 90, 95, 100, 110, 115, 120, 125, 130, 135 and 140 Full out same bore and stroke. inexpensive minor changes facilitates this wide range of performance values. I work with 4 strokes also... Horsepower ratings... Guess What? Fuel consumption divider of 10 nails their respective GPH fuel consumptions @ WOT (Wide Open Throttle) under full load in their RPM classifications between 4,500 ~ 5,750 predictably... ADL... 3,000 ~ 3,200 is the sweet spot for planing fuel economy. I look forward to your presentations... Persistence with endeavors is the path to recreation! Cheers

[@PhilipFly11]

There is also a difference in density, diesel is about 10% denser, so that when measuring fuel flow in GPH the difference will be around 25%, at cruise power. With a power setting of 70% plus, an air cooled Continental, will not have an SFC of 0.38 and then probably will run about twice the GPH. I don't think Lycomings get as low as 0.38 and more like 0.42. As you say, cost of fuel and availability are a major factor. In most of Europe AvGas is about 3 x the cost of Jet-A and in most of Africa you cannot get AvGas at all. Diamond have been building certified aircraft, powered by certified automotive diesel engines, for 20 years. They are fuel efficient and now have turbine like reliability. The DA-52 has a 3.0 litre V6 turbo diesel based on a factory standard Mercedes-Benz block. It has a solid geared reduction drive, runs cool in the climb and cruise and it can descend fast without shock cooling. That engine is made by Teledyne Continental Motors!

[@rv6ejguy]

@@PhilipFly11 I've done a detailed comparison of various aero engines, both CI and SI. See vid #93 on my channel.

[@bartofilms]

From this it sounds like Raptor could conquer its engine cooling issues quickly by downsizing the 2nd stage turbo, or up-sizing the primary, if there is room in the engine bay. It doesn't seem like it would be too expensive to fab. an adapter for a smaller 2nd stage. I'd try that first.

[@rv6ejguy]

Changing the turbo system would only make minor improvements to engine cooling. Raptor will have much bigger cooling problems as it climbs into thinner air and at higher than 65% power like it's using now on a summer day. The coolant, oil and charge cooling systems are all poorly designed and would need a complete re-design from scratch to be functional on a 100F day, climbing to FL250 at climb power (say 80-85% power.

[@bartofilms]

@@rv6ejguy I'm sorry to hear this, however, it sounds like Peter already has a complete redesign in the works. This is also a very sensitive topic over there...

[@rv6ejguy]

@@bartofilms It will need a complete re-design to get anywhere close to original performance predictions.

[@satguy]

I honestly doubt Peter would listen, after all he is now his own test pilot. The one thing he did do, was listen about an airport change. Which probably saved his life on the first flight.

[@richard8181]

Very informative, I have followed Raptors development. I think a little more collaboration would be very helpful to the successful future of Raptor 🤔🤔

[@AnarchyEnsues]

Double intercooling? Imagine that increase.

[@jeffhines73]

Damn thing isn't anything but a death trap

[@FreeSpeechWarrior]

Have you tried to contact Peter? I have been following him for several years, and he used to take advice from people who comment. Starting late last year I think, he has started to show a little disdain for people's comments. I really like Peter, he's a nice guy, and he's very smart about a lot of things, but he's clearly stubborn and close-minded when it comes to anything related to engines and turbos. Seems like he doesn't want to hear anything about it. I think he thinks that he's the smartest man in the room all the time when sometimes, he's clearly not. I'm really a big fan of his project, and I really wish you would contact him. If you do, please lead with your experience, like you do here in this video, so he doesn't dismiss you automatically.

[@rv6ejguy]

I commented several times on his videos but he dismissed the suggestions as, like you say, he's knows it all after a few hours on Garrett's site... His project, his call, but it's destined to failure unfortunately IMO if he stays on his present path. There's lots he doesn't know about many aspects of aerodynamics, structures, engines, system design, turbos, cooling etc. We can see the results of that lack of knowledge so far.

[@FreeSpeechWarrior]

@@rv6ejguy I don't know if there's a way for you to reach out to him directly, maybe if you contact the airport where he has his plane stored. There's got to be a way for you to get in touch with him. Your comments are probably getting lost amongst all the other comments from guys who don't know as much as you do. There has to be a way for him to watch your video, and see how much experience you have. He's a software engineer by trade, and I've been in his business for more than 21 years. I know the type, they always think they're the smartest person in the room, and you can't tell them anything. I posted a link of your video in his comments, he used to listen to me, so hopefully he'll see it.

[@rv6ejguy]

@@FreeSpeechWarrior He's free to take or dismiss my advice or that of any other person. There's lots of nonsense advice posted on his YT by other people with no experience in these fields as well so who do you listen to if you don't know any better yourself? Peter doesn't know me and I don't know him. I made this video more for other interested folks rather than Peter. I don't see him changing turbos at this point in any case, maybe in the future on the 2nd prototype if there is one...

[@keepyourbilsteins]

I followed Peter's build and my concerns grew as the project evolved. I contacted him and volunteered my experience and help with EABs and TDIs. He wanted nothing of it. He has a devoted fan base in his comments section that rail against any constructive or seemingly critical commenters as simply being "haters". There could be nothing further from the truth. I want his project to succeed, everyone I know that has been following it does.

[@FreeSpeechWarrior]

@@keepyourbilsteins Yeah JP, I guess it's just one of those things, you can lead a horse to water, but you can't make him drink. You can't help somebody that doesn't want help. Well you know what's going to happen? There's one good thing he's stubborn about, and that is testing. He's going to continue to test, and test, and test, and that engine is going to keep overheating and failing. Eventually he's going to have to either listen to the experts, or scrap the whole project all together. Because even though he's closed-minded, I don't think he's going to try to put out a plane that's clearly not ready for prime time. I just hope he doesn't get hurt going through the same futile exercise as he did with the last engine.

[@andrewcox3686]

Thank you #rv6ejguy Russ, for your time, experience and expertise.

[@jekader]

Hope Peter sees this vid and takes action.

[@BLAMBERRY]

he would never acknowledge it as helpful and would downplay its information. He’s an idiot and an asshole. Did you see how he treated the test pilots?

[@labgrunt1961]

@@BLAMBERRY Was there actually a video that showed him mistreating the test pilots? If there was, I didn't see it. From what I could gather watching Peter's Wasabi videos, he basically "dismissed" them and decided to do it all himself. I think the title of the video where he had discharged the test pilots was called "I'm Making The Call" or something similar. I'm not disagreeing with your assessment of him, and I'm saddened by the realization that I have devoted several years to watching Peter's videos and dreamed of having a functional Raptor only to see that dream crushed by a narcissistic egomaniac with a god complex who, apparently, can do no wrong in his own eyes...

[@BLAMBERRY]

@@labgrunt1961 Critical thinking. These test pilots were willing to put their lives on the line to test peters POS aircraft. Peter didn’t want to be bothered with the safety aspect of flight testing. Peter treated the professionals like a couple of assholes.

[@labgrunt1961]

@@BLAMBERRY Roger that, Blamberry. I also felt like the test pilots were treated poorly. Peace, my friend.

[@BLAMBERRY]

Noone seems to be mentioning the fact that this is a pressurized aircraft that will rely on those turbochargers -which is probably going to cause peter alot more stress.

[@deanhowell6730]

I found this dissuasion is Fascinating,

[@donaldasayers]

Sigh! This is not new knowledge, it is not cutting edge nor even something you need anything more than a slide rule to compute. Read Stanley Hooker's book "Not much of an Engineer" which details his time at Rolls Royce and how they added compounded superchargers to the Merlin engine. Same calculations same results and Hooker did it all from first principles. He was a newly graduated engineer, in his first job designing compounded centrifugal compressors for the first time. Problem is that if you go too far down the turbo diesel route you end up with the Napier Nomad and then you reinvent the jet engine.

[@martinrenschler4046]

The mass flow (lbs) per minute must be the same in both turbos (no air is added nor lost, so where should a difference in mass come from?) So why are you applying any kind of multiplication to the mass flow? If the engine needs 40 lbs per minute, then each turbo needs to transport 40 lbs per minute. Understood that the second turbo needs to be smaller since the air is more dense but I don't get why the mass flow should be different?

[@rv6ejguy]

Compressors are rated on inlet mass flow. First stage air will be compressed in volume to feed second stage. Boyle's Law, as I explained.

[@martinrenschler4046]

@@rv6ejguy All agreed - can you help me and state the lbs/min in and out for first and second turbo. In my mind all 4 numbers must be the same.

[@rv6ejguy]

@@martinrenschler4046 If you look at the relationship between volume and pressure (assuming no intercooling and disregarding temperature change from compression which is substantial in this case), in simple terms, double the pressure, you have half the volume and double the density. We are trying to take air at low density and increase the density back to SL conditions. The first stage essentially brings the 2nd stage compressor inlet back to SL at 25,000 feet so the 2nd stage can then bring the intake manifold up to 70-80 inches Ab. This may be easier to visualize volumetrically rather than thinking in terms of mass flow and you can see how gas turbine engines with multiple axial stages have large blades at the front and progressively smaller as you progress rearwards. you squeeze the air more and more and pressure increases at each stage. You'd have to consider the effects of intercooling and aftercooling to actually match turbos for Raptor. The point of this video was simply to show that you can't use two equally sized compressors for compound turbocharging as Peter has done. Don't take the actual numbers presented here as gospel, they are only for illustration of the concept.

[@martinrenschler4046]

@@rv6ejguy I again agree with everything you say but it doesn't explain why you would have different lbs/min numbers between the turbos. If it were so, we would either gain or loose mass in a turbo and that can't happen. If the engine needs 40 lb/min than that's the mass each turbo needs to take in and put out. No multiplying with some factor and getting to a higher lbs/min number for the other turbo.

[@martinrenschler4046]

I read up a bit and found that the charts only apply to the first stage. In order to use the same charts for the second stage turbo you have to calculate a different mass flow, not because there is a different mass flow but to be able to use the chart. The formula is mcorr = m*sqrt(T1/298)/(P1/1). This number is smaller than one, so a smaller turbo will provide that corrected virtual mass flow.

[@micjbaron]

I’d love to see this guy work his magic on my GMC 2500 Denali, forget the raptor, let’s have some fun making a fire breathing truck 😂

[@richard8181]

At least comments about RAPTOR issues won't be deleted here 🤔👍

[@richardperry21]

These kids should of reached out to people whom are experts in the different fields that they have issues with. Seems like they're just wing it sometimes.

[@rv6ejguy]

Well, Peter doesn't look like a kid but he certainly would have been further along in the project and more successful if he'd consulted some aero, structure, mechanical, systems, diesel and turbo experts. You can't start from zero knowledge in these fields and expect build a world beating pressurized, compound turbo, diesel powered canard design. There is so much to know here in multiple fields, it's almost impossible for one guy to get this all right the first time. You'll get a lot of hard lessons along a very protracted design and development process as we've seen.

[@okgo8315]

@@rv6ejguy ....👏👏👏👏👏👏👍👍🇬🇧🇬🇧

[@orbitalair2103]

@@rv6ejguy well said. I was going to comment the same, but you worded it better. Peter should be managing the project, managing experts in order to stay on schedule. the death of projects like this is dragging it out longer and longer and longer. momentum and interest eventually dies.

[@o0darkart0o]

Amazing video, I love the internet

[@gsxr1kmatt]

Thanks Ross!!!

[@chippyjohn1]

I've done a fair bit of design and research with regards to compounding for a a high altitude aircraft using 4 stages including 1st stage supercharger. There are few inaccuracies in this video. The pressure ratios do not have to be the square root. The high pressure turbo can be fixed pressure ratio with the second changing according to altitude. You also mention the 2867 being the first stage, maybe you mean first stage turbine, not first stage compressor. You also don't state what the second turbo is. You don't state the power goal for the Raptor either. I agree Compounding is more difficult, but not that difficult. Air density also changes according to temperature, consuming air that is -40 is beneficial to power at a lower pressure ratio. This is the closest I have seen, with most not explaining it at all. My current project is compound and successful, its for a helicopter to set a HOGE record of 13500 metres. I had to mix compressor and turbine wheels, make a custom turbine housing, Centre housing, modify the compressor housing. Ideally I would like to make my own compressor wheel in the future but it is only a one off flight. My intake to exhaust pressure ratio is about 1:1 with tuned exhaust, twin scroll plus much more. Even the consideration of 7075 (not used) shattering at high altitude must be considered. It is a bit too complex for the average aircraft, especially helicopter, I will change it to single turbo after the record. I haven't got off the ground yet, but it has proven very efficient with testing. I can't wait to fly at 26000 one day, that project utilises a 600mm exducer on the first stage which is a supercharger. It is capable of flowing 12000Kw at sea level, but will only power about 200Kw at altitude. Intercooling for that project will be a large consideration even with low intake temperatures.

[@rv6ejguy]

Matching of compressor flow the way you describe here would be difficult as PR varies as the square of the N1 but mass flow doesn't. I am talking about compressors mainly here and the 2867 was what was used as the 1st stage compressor here as shown in one of the Raptor videos. The 2nd stage was never revealed but judging from video evidence, it was similarly sized to the 1st stage. Raptor's hp goal was 350-400 hp. Properly matched aviation turbos will almost always use custom compressor and turbine sections compared to COTS automotive units as the Raptor guy used. I am not familiar with Kw being used as units of mass flow. Your project sounds cool! I hope you do a video of this when you make the record attempt.

[@chippyjohn1]

@@rv6ejguy It's not difficult, it is no different to having a single turbo. So you agree that turbos can be customized yet you think that because the compressor housings are similar that means the impellers are also. If the compressor housing on the smaller turbo is large, it makes little difference to flow. kW is the standard unit for the measurement of power, I exchange it with 1g/s.

[@rv6ejguy]

@@chippyjohn1 Every turbo I've used in the last 30 years has had mixed and matched compressor and turbine sections-a very common practice. While compressor inducer and exducer diameter doesn't tell the whole story for mass flow it is a rough guide within a series of stock type Garrett turbochargers like those used on Raptor. Wheel height is also another variable to be considered. You mentioned 12000 Kw flow. Mass flow isn't measured in Kw which is an expression of power- about 16000hp in English units. Centrifugal compressor mass flow or airflow units are commonly CFM, lbs./min., cubic meters/sec. or Kg./sec. I can only surmise that your helicopter engine only outputs a tiny fraction of this 12000 Kw number so this make no sense. Also, a compressor to supply this much mass flow (around 2000 lbs./min.) would take thousands of hp to drive it.

[@chippyjohn1]

@rv6ejguy The 12000g/sec 12kg/s is for a high altitude plane designed to fly at 26000 metres. That is what it would flow at sea level, but at 26km only about .2-.3kg/s. My helicopter is only two stage, much more simple with Max flow of .165kg/s. For the petrol I am using and all parameters, 1kg/s is equal to about 1000kW, or 1g/s = 1 kW. You have to love standard metric and its simplicity. Not sure why people still use the old measurement. Nice chat mate, happy new year. As far a compressor wheel sizes go. I am using the compressor wheel from a gbc 17-250, and s200-70. So a large size difference. Due to air density differences, and desired weight I use a custom compressor housing on the s200 making it look much smaller. Maybe what raptor did, although I quickly watched some of his videos and did not a power struggle even with increased boost.

[@simonbaxter8001]

Excellent explanation and walkthrough of the fundamentals, requirement, design and selection considerations rv6ejguy. I really hope Peter takes humble guidance from this and also stops blocking experienced aviators which try and provide invaluable advice on his own channel!

[@bingosunnoon9341]

You are not helping

[@simonbaxter8001]

@@bingosunnoon9341 Meaning what?