German C3 Fuel, Uber Octane or Synthetic Crap?
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- Опубликовано: 11 авг 2021
- There is a lot to cover here, the first 20 mins just go over the basics of calculating equivalent compression ratios in supercharged engines, I start with automotive examples because they are easier to understand. At about the 20 min mark we get into airplanes.
How good were the German B4 and C3 aviation fuels? We have allied reports on them, but they don't answer all the questions. Were the Luftwaffe aircraft really held back by low fuel quality, or was it something else like metallurgy?
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Hey Greg, looking forward to watching this episode. Thanks very much for your kind words and showing off our book project! We are very happy to see so much interest in German primary documents and hope to do more of this in the future.
Thanks Chris.
Two channels with extraordinary content. Thank you .
Cool to see you here
Thanks for another fantastic video, Greg! And this is Chris approved!
I wish I could support more, but I already bought the book before those video came out.😅😅
Hey kids. What's your dad doing?
He's watching a long video about the octane ratings on WWII German aviation gas.
????????
LOL.
Great video, Greg, but my wife and kids will never understand.
I never knew fuel could be so fascinating. I learn more in any single video from Gregg on WW2 aircraft than most entire books I have read on the topic. Most books recycle the same generalized info and rarely get into the minutiae of these videos. It appears that often these small details and finer points of design and performance made much bigger differences in outcomes than is usually appreciated. Thanks so much Gregg for all your time and effort!
Or destructive?
There was some anti-knock research in the 1920 that looked at quite a few potential anti-knock compounds and rated their effectiveness. Among them was triaryl-bismuth, which was about a fourth as good as tetra-ethyl lead, thus requiring four times more concentration for the same knock reduction. I think I once calculated that switching to it would add about 10 or 15 cents a gallon to the cost of 105 octane, or something close to that. I wouldn't think it would effect valves or bearings any differently than lead, and the worst the exhaust might do environmentally is just make Pepto Bismol.
Doolittle's early drive for high octane fuel points out one sometimes neglected aspect of the man. Doolittle was not only a great pilot. He was also a great engineer. Doolittle had a doctorate from MIT. He did much of the work developing early instrument flying. He also had the foresight to see that with higher octane fuel available, higher compression engines would follow. This is often the case with technology. Develop a method for producing a chip with greater device density and electronics taking advantage of that device will follow.
😂 WE OWE A LOT TO JIMMY DOOLITTLE ‼️🇺🇲🗽
The decreasing quality of motor oil in the last years of the war("resembling water") is frequently mentioned as a factor with the poor reliability of the Tigers and Panthers tank engine, so that might be the reason for not exploiting the octane potential of c3..
That could be, a lot of the factors tie together.
And sabotage undertaken by slave labourers working in assembly plants.
I heard it was mostly drive train / transmission problems.
@@2lotusman851 Bad oil wouldn’t help with transmission reliability either (particularly under high load).
@@2lotusman851 Combat records by Tiger/Panther crews often mention how they found debris deliberately hidden inside the transmission(by slave labourers) to reduce its efficiency and cause breakdowns.
Between Calum Douglas and his new book, Chris at Military Aviation History & you Greg with your content we have reached a Renaissance of information on WW2 aviation. This knowledge which has not been available since the end of the second world war when people with first hand experience were available to write on these aviation subjects. Now we have multiple You Tube channels with all 3 of you gentlemen doing excellent in depth research on these subjects. Well done & thank you.
I learnt so much from Ricardo's book. I found it in the local library when I was a schoolboy. Years later I bought the 4th edition (1953)
Greg with Another big hit
I wouldn't have believed that one could talk *interestingly* about one specific type of WW2 aviation fuel for an hour and a quarter, but you pulled it off. Thanks a lot for your knack of diving deep and separating the wheat from the chaff.
Good points about the life expectancy of the German fighters later in the war. I was reading about the Luftwaffe's Autumn 1944 attempts to stop the 8th Air Force Raids, and they are horribly lopsided bloodbaths for the Germans. In November 1944 they only go up 4 times in attempts to defend their oil installations, and are suffering loss rate of ~25% each engagement. Essentially the life expectancy of their fighters and engines are a couple of hours. That realization would probably make them less cautious with trying to preserve their engines when it came to the fuel.
Watching this at 10:30PM on a Sunday night, the wife of 36 years walked by and asked what I was watching and if it was for work. It was right at the point of the fuels evaporation point in relationship to engine oil temp which I explained. She shook her head said "I can't believe I married such a nerd" and closed the door. Keep up the great videos!
And that's why only about two percent of my subscribers are women. Of those, one is my wife, one is my daughter, and neither of them watch my videos. Also a few flight attendants subscribed to show support when I started this channel. I think I only have about 25 actual female subscribers.
The amount of engine variants, aspects like temperatures evaporation etc etc is incredible… the detailed discussion you perform is just beyond what I can grasp and understand properly… I wonder how much the expectation of own over enemies performance actually influenced a pilot’s approach to an air fight.
In terms of the US aircraft like the P-47, a lot of the performance depended on the pilot being able to set things correctly.
When comparing the Merlin to the DB601A, keep in mind that the direct fuel injection on the DB601A can take advantage of the heat of vaporization of the fuel injected directly into the cylinder to cool the cylinder charge. On a modern spark ignition engine, the difference between direct and port injection (assuming approximately the same overall level of F/A mixture control) allows approximately 1.0 to 1.2 higher CR for the same RON fuel.
Well that assumption just got shattered...
I have thought for a long time the German engines just used port injection and the direct part was a changing in terminology.
Well thanks for these comments and making me look/learn
@@TheAneewAony we used fuel injection during the timeframe just to the best of my knowledge not direct injection
Love the teachings Professor! Between you and the Chieftain debunking WW2 armor myths, I’m starting to feel like I “know” very little about the long held truths of the war. Thanks! (any update on possible sleeve valve engines?)
I have been waiting 43 years for this video. Go, Greg!
I remember reading a book on P-83 and early in the war they were using 122 octane. They switched to 150 and took off on a mission only to have all the spark plugs plate with lead and foul out.
From an instrument engineers perspective 2x DIFFERENTIAL pressure produces 1.414x the volumetric flow through an orifice (Bernoulli’s theorem). Pressure loss along the intake and exhaust manifolds are significant to flow rates.
Increasing temperature decreases the mass flow as you stated.
(47:20) it was about Oil Fumes and the Oil Separator design. Spark Plugs getting hot was also an issue. In late 1943, after all of this has been addressed with newly designed components, they released the 1.42 ata again. Of course, this doesn't mean that they didn't push the limits of the engine with this kind of fuel too far, in general.
When the R+M/2 method,took over in the USA,Sunoco 260 was
initially rated at 97.5,dropping to 96,and eventually disappearing altogether.
Thanks for another informative video.
Was it "260 GT" or did Sunoco reuse the branding? If it's the former, it's still for sale as a race fuel in cans.
@@andrewahern3730 It was Sunoco 260.
yes still available in cans as street legal 100 unleaded,and all their other race fuels
Cheers
Your videos deserve to be in A&P shops. I have learned so much more things from them. I'm still building A&P hours so it helps a lot. Thank you
First, I must say Bravo! to your newest video, Greg. Second, there are two factors beyond a fuel's octane ratings that may influence heavily on it's resistance to knock/pinging, i.e., the fuel's latent heat of vaporization and it's resistance to ignite because of a hot spot or lack thereof, such as a carbon deposit or a glow plug. A high fuel's latent heat of vaporization, specially in a direct fuel injection engine, favors an increase in ECR because it reduces the air/fuel mixture's temperature more than in a fuel with a lower latent heat of vaporization; this works just the same as an intercooler or W50 and also may explain at least some of the difference in motor and research and lean and rich octane ratings. For example, because of methanol's very high latent heath of vaporization, intercooling was not used for a long time in turbocharged Indianapolis 500 racers, fueled with methanol, but was, out of necessity, in all turbocharged Formula 1 racers, fueled with many mysteryous concoctions they called gasoline, for marketing reasons. The other factor is the fuel's resistance to knock due to hot spots and that may explain Mr. Cullum's remarks about exhaust valves temperatures and also the reduced ECRs on air cooled engines as compared to liquid cooled ones, I guess B4 and C3 might have low and maybe very unpredictable resistance to knock due to hot spots, what might force a reduction in ECR. That's why you may dare throwing a lit cigarette butt on avgas without much risk of setting it on fire, but don't even think trying to do the same with E85 or methanol. I also venture an educated guess and a very long shot in face of our lack of solid information, and try to explain the very high ECRs of DB engines as being due to fuel's high latent heat of vaporization and high resistance to knock to hot spots. Of course, that's just a guess. Sadly, available data sources are lacking information on both factors.
Top fuel cars use a similar trick to the turbo indy-cars where they will spray some of the nitromethane/methanol through the super-charger to help cool the air a bit.
@@666Blaine and that’s what many aero engines did too. Late Merlin sprayed most into the supercharger eye, I think. Will check that though. Callum Douglas points out that injected Daimler engines had an extra injector nozzle into the supercharger inlet
Extremely enlightening!
Consider the naturally aspirated GAcontinental IO 470 engines are 8.6:1 compression on 100 LL. They appear to be right at the top of the detonation envelope!! It is amazing to see where today's piston engine technology comes from! How difficult would it be to obtain more information about piston design? Whether they used cast or forged pistons, piston ring design and what clearance tolerances were adopted? Thanks for all the time and effort you put in to these presentations!
This is going to take some concentration. I'll save it for when I'm stuck in a hotel
I do that too. I'm saving MAH's new Brewster Buffalo video for my workout later today.
Great video. I don't know if you've changed up your audio setup, but the sound quality was just awesome.
"Knock Knock"
"Who's There?"
"U Need"
"U Need Who?"
"U Need More Octane".
I'll show myself out.
Excellent video Greg! Thank you and giid job mentioning Chris and his Stuka book project at the end.
Fine , Greg about B4 and C3 Fuel, my wet dream!
Have you considered spraying the house down with MW50?
@@KR4FTW3RK Does a great job at cleaning windows.
This is by far the best channel for technical review of aircraft, thanks.
Would love to see some more early jet aircraft featured as the developments in the late '40s and into the '50s were imo some of the most interesting in all of aviation history (both in terms of engines and aerodynamics).
Greg,
That makes total sense, I like your explanation, and agree with your conclusion about the 2 formulas
I suspect one of the reasons the "linear" formula for effective compression ratio doesn't work is because in pretty much every scenario of a compressed charge, some heat is always removed by the interface between the charge and the materials around it.
Obviously with an intercooler, the charge temperature is greatly reduced (and therefore it's tendency to detonate). But even in the worst imaginable configuration, such as a draw through supercharger mounted directly to the intake manifold, the supercharger body and intake manifold, short in length and limited in time interfacing with the intake charge as they may be, will draw SOME heat from the intake charge.
An NA engine with a compression ratio of say 16:1 will compress the charge on the compression stroke in a very small window of time, and the charge will remain inside the combustion chamber, which is a relatively hot area of the engine.
Where as a (theoretical) supercharged engine running 14.7PSI of boost with an 8:1 compression ratio, even without an intercooler, and even with a very short distance between the supercharger and the combustion chamber will bleed off SOME amount of heat from the intake charge before the charge is compressed again inside the combustion chamber.
Therefore it makes total sense that when it comes to a compressed intake charge + an engines compression ratio: 1 + 1 does not equal 2.
I've always wonder what might have been achievable if engines such as the DB 603 had access to 150 octane fuel and used technologies like two stage supercharging and intercooling.
There are a few unreliable records of a test variant of the DB 603, the N model which was supposed too have exploited C3 fuel, a 2 stage supercharger, and various tuning improvements, supposedly this achieved a take-off power of 2958hp
Its hard to imagine the increase in performance the German heavy fighters might achieve going to that from 1726 HP, notably what speeds would the Do 335 have achieved with such a performance increase?
Would the German idea of, heavily armed aircraft that weren't maneuverable but could outrun single engine fighters be possible?
Regardless, a very interesting subject
Great series you have here! Your videos are so unique and informative. Learning so much more than the stock documentaries out there.
I always wondered where your wealth of knowledge on these subjects came from, now I know! Thanks for these in-depth videos on what I know are decades-old debates among ww2 aviation enthisiasts
Another great video thank you Greg. A video about sleeve valve engine's would be very interesting, just an idea. Keep up the great work!
I do want to get to that, but it will be a while.
@@GregsAirplanesandAutomobiles
In aircraft that would see a usable lifespan of very low hours I'm of the opinion that sleeve valves while superior especially in larger bore diameters due to the limitations that poppet valves put on the ability of the engine to breathe were in many ways a waste of the second most precious resource a nation at war has. First of course is the lives of its servicemen. Second is the manhours required to produce the weapons that your people need. In a fighter that might see very limitied hours it doesn't pay. Napier might of built a great engine but the role could easily ben handled by the Griffon at probably less manhours to produce. However in aircraft used primarily in the transport or naval patrol roles the sleeve valve makes perfect sense due to its lower specific power output in terms of fuel use per hp per hour. The same could be said for long range bomber aircraft.
@@mpetersen6sleeve valves cost the lives of plenty of pilots. I don't fully understand sleeve valves but it seems to me that they were just asking for trouble with the available machining technology, particularly during wartime. I have read that the main problem was a failure to properly warm them up.
The sleeve valve is basically a sleeve inside the cylinder with holes in the side. You twist the sleeve so that the holes in it line up with holes in the cylinder head or in the side of the cylinder, and that's how mixture gets in or exhaust gets out.
The actual engines (e.g., the Centaurus) actually moved the sleeves up and down as well as twisting them, but the idea is that the sleeve is what covers and uncovers the openings to let air flow in and out.
Sealing between the sleeves and the bore, or between the two sleeves (intake and exhaust), and there is definitely some complexity in making the sleeves move correctly.
Here's an animation of a Centaurus in action: ruclips.net/video/_vrvep_YOio/видео.html
@@davedarling4316
For some very good CAD drawings and animations look into the Aircraft Engine Historical Society's web site
Love everything on the channel greg the trips and history combined with the cool educational content just absolutely top notch
I was wondering if you and Chris were aware of each other. A collaboration between the two of you would be epic.
We don't know each other, but we have communicated a few times via email. I have a lot of respect for his work. Same with Bernhard.
I have definitely seen other references to their work in Greg's videos, and I think I've read correspondence from Chris (MAH) that he has seen Greg's videos.
Not exactly a surprise, as they cover a lot of similar material from very different viewpoints and different levels of detail!
This needs to happen. Collaboration is an understatement; a full loop closure would better describe the many detailed connection that would be made.
Chris can't even pronounce "Junkers" or "Jumo" right most of the time. I's embarrassing since he is German.
@@Ausf.D.A.K. -- Chris has addressed that in one of his about-the-channel videos. He is using the English language style of pronunciation, because his videos are in English. It is a stylistic choice that I personally disagree with, but it is why he deliberately mis-pronounces "Junkers" and "Jumo".
Now if only he wouldn't use the German pronunciation of "GMBH", it would be a bit more consistent.
Yet another amazing video. Not only your work is great but you also appreciate the great work of other RUclipsrs.
I just want to say thank you for such a well researched interesting video with content no other RUclips channel or creator is offering. Much appreciated :)
I've got a copy of Secret Horsepower Race on the way and I am *beyond excited* . I missed out on a copy of the first printing and am very pleased to get one second time round
I saw an errata sheat from Collum Douglas, and you will probably get a slightly improved version of the book. -- I plan to go throgh the errata sheet after I have read the book, just as a repitition and as I guess I will understand details better at that point 👍
@@MultiZirkon Can you please link where one can obtain an errata sheet? Thank you.
I've been looking forward to seeing this video since you mentioned that you were working on it. Thanks for the great content.
Thank you for this beautiful hour of informations. Please go one. geatings from Germany
Thank you for an extremely informative video. Across the theaters, in the air, at sea and on the ground, it seems that the decisive Allied edge was the American ability to make and supply war materiel in abundance.
Man you sure put a lot of research into all your videos and it is greatly appreciated. 👍
Blue skies and tailwinds Greg. ✈
Another top notch video full of quality content. I always learn new things when watching these. It's amazing how much of an effect natural resources and access to them along with logistics affected the war.
One of your best videos yet. Very, very insightful and informative. Thank you!
19:00 I like the way of thinking with the compression formula that lacks a correction for a temperature increase that has to be there. I think Greg could do well in teaching physical chemistry...
Amazing content Greg. Just so well done. As always I have watched this video several times and learned more each time. I have so enjoyed Callum Douglas's book...and really appreciate you insights. And thanks to you I have ordered the book on the Stuka. It is a fine time to learn about WWII aircraft...and you lead the way by miles and miles. Thanks for all the hard work, insights and amazing gift of presentation. I keep thinking you have maxed out how amazing your videos are, and then you just blow me away.
Great as always, thanks Greg , keep going, many thanks from the uk.
I have listened to a lot of your talks ... and I found myself seriously excited for this one. I am totally down the rabbit hole. Best explainer ever.
Greg either you are getting better at explaining these technical issues or I have actually been learning something this whole time but this was an excellent dissertation on the subject and I found i could keep up!
Haha
Coming back for a second view of a complicated subject after a few months, fascinating as always Greg 👍🏻
Love your posts and Bismark, through flight sims years ago , you have prompted me to look him up again !
Algo boost! Great content as always Greg, digging into this now!
Great video. Thank you. I supported the Stuka book before watching this exploration of German WW2 octane and aircraft engine issues. Chris’s recent (not) in the cockpit video on the Ju 87 is an excellent introduction for anyone who wants to learn about the Stuka.
Thank you Greg... You are a dude with quality information delivered in a technical yet easy manner. Please keep on posting. Cheers.
Fantastic piece of work sir. This is one of my favourite channels and articles like this is the reason why.
Oh this will be interesting! Thank you Greg!
Greg I don't know how you do it but I'm glad you do! Another excellent video and enormous amount of research is indicated here. Well done and thanks for sharing.
Interesting video. I liked your question about why did the Germans run their fuel mixture so lean, when it would promote knock? Perhaps they had to run their mixture lean to try and save as much fuel as possible, it being so expensive and in such short supply? Whatever the reason, it must have really hurt those perfectionist German engineers, to have to build something that they knew wasn't as good as it could have been...
Something you obviously wouldn't want the pilots hearing as the reason for deceased performance, but in combination with all the other factors, it makes a lot of sense
I wondered this too. How "rich" is rich though in these circumstances? I doubt it's more than a few percent. And of course they would only be running at these mixtures during takeoff and combat, which occurs only a few percent of the time. Added to that, I'd expect a few hundred horsepower would always be worth a few percent extra fuel - even the Germans in the later parts of WW2 would be unlikely to deny their pilots competitive performance as a means of saving a few pints of fuel.
I had no idea of your credentials. That's really awesome congrats. Great videos keep up the fantastic work. Your content helps me sleep at night.
I was listening to this video while I'm working on a 1/48 scale Bf109G-10, I really like these video's! So much so that you've got another Patreon!
Excellent, outstanding; thanks. Greg finds answers and reasons to fill in the gaps, and makes it understandable. Raises the bar.
Very enjoyable to see the graphs and listen to your presentation. Thank you!
Another great video,Greg.Dummies like me really appreciate someone doing the math for us.Complex subject matter, excellent delivery and explanation.
Thanks Greg, a vid I have been waiting for
Yes!!! Finally....I have looked forward to this for weeks...thank you so much Greg...love your research...
Greg, I love your Videos! Nice that you used the picture at 43:43! It was made at Schleissheim Airport and I live just 10 min away from this place :)) Greetings from Germany!
Thsnk you very much for your videos. I am learning a lot through your work!
Wonderful Greg! Absolutely loved it
My three favorite under square non racing stock 92 octane motors from 1969, the 10.75 to 1 Pontiac 400 and 10.0 to 1 383 Mopar & Ford 9.5 to 1 390 . These were in everything from
a coupe to a pick-up and were not the largest displacements or highest output available. All are a joy to drive!
I like the video and the presented information very much. A long needed explanation on that topic, with a lot of additional Information on comparing different fuel type's Octane number / detonation resistance, and on how many factors it depends. It also opened up a lot of new questions, like on how rich mixture did the german engines fly.
Well done.
+ please have a look at the 2013 Supercharging Book by the same Greg.
After watching this I'm motivated to go back an re-read my thermodynamics textbooks on combustion.
Greg you do such a good job of slowly and carefully explaining you subjects so well that I think even a non-technical person can follow along.
Astonishing
Thanks Greg :)
Magnificent work, as expected!
When you’ve literally wrote the book on supercharged engines. Great videos! I really appreciate all the information your able to share and the research you’ve put into it.
Thanks Greg, its Rob here from Christchurch, South Island New Zealand! You have answered my questions! Thanks Cobber from Down Under!
Thank You for a very detailed video. Well understood even for a viewer without a formal engineering background.
Great video. I came across this video after my comments on another, so all the points were covered here.
Thanks Greg for another superb video! Maybe inter future you could do a video on the A-26 Invader. It definitely deserves a video from you imo.
Love your Videos Greg!
Terrific video as always. Thank you
Nice getting that interesting background sketch some of us were wondering about; A pilot & flight engineer with a years of experience flying supercharged piston engine aircraft as well as having a specialty shop for turbo charges & super charged car engines and authorship on the subject.
Excellent. Nice to see your knowledge base and writing credits.
Thanks Greg. Excellent video as always 👊
Fascinating and very thoroughly explained with added proof and calculations. Thank you for this educational aviation video. I picked up some new insights about the inner workings of engines.
Any plans on making a video looking at fuel injection or fuel delivery systems on WW2 fighters in depth? I know you mentioned the German injection versus the Allied carburation a few times and it seems like it could be a good topic.
I probably should, and to be clear, I mentioned British carburation. The US was using a primitive form of fuel injection in the examples I cited.
Great again 👏 I knew about fuel and comp ratio . But it really give a good insight into what the German had to deal with and how Geography and resources . Determined the outcome of the conflict before it even started
As a mech. Eng. I appreciate your information and presentation style!
Greg I really enjoy you're presentations. I look forward to them with great anticipation. I love the detail. Dispelling long held myth with analytical precision. I been thinking of signing up with Patreon and tonight's the night.....2mins later......What only 484 Patreon's!. That's a travesty. By the way what was the Japanese fuel like during the war? I notice presently your main focus appears to be the European campaign. Love your work.
I'll get to the Japanese stuff at some point. Their fuel was generally poor, but as always it's a bit complicated.
@@GregsAirplanesandAutomobiles In his Stalin's War, Sean McMeekin makes a case that our Soviet "Allies" traded US Aviation fuel to the Japanese for other needed goods during the Second World War. The Japanese left cargo shipping from the Western US ports to Vladivostok unmolested during the war. A quick look at a map will show that Vladivostok is on the west coast of the Sea of Japan, and would have been easily subject to interdiction by the Japanese. A fascinating claim to be sure.
It was indeed a very interesting video and had me looking for motor car figures.
The owner's handbook for the Ford Cortina Mk1 claimed a 16:1 compression ratio for the 1500cc engine in the mid '70s. It used 95 Octane leadef petrol (gasoline in some parts).
At that time the upper limit for displacement in Formula 1 was also 1500cc but these engines screamed their way round the track at high revs.
More recently Nissan claim they use engines in everyday cars taking 95 Octane unleaded petrol with a 12:1 and a similar engine but turbo/super charged running 13:1 .
They claim.
@@myparceltape1169 Keep in mind that there are two different systems for measuring Octane number in widespread use, the Motor and the Research methods. The Research method is widely used in Europe and in the UK.
The Research Method generally returns Octane numbers up to 12 points higher than the Motor method.
In the US, Octane number is usually presented as the average of the two methods.
Hence 95 Octane Petrol in the UK would likely be equivalent to 91 Octane Premium Gasoline in the US. 16:1 is some serious compression to be running on any pump gas, especially before the advent of variable valve timing and digital engine controls.
My hat is off to the engineers at Ford UK!
@@jaym8027 Thanks for that Jay, I started thinking about what I read so long ago after I heard Greg talking about the two methods of measurement.
Specifically it made me wonder how the Ford people arrived at the number. At the time I was aware that the USA cars were large with rather sloppy engines. In the UK most of the cost of fuel was and is, Tax. Fuel economy was a big selling point.
Even in those days however, many contemporary cars could be plugged in to the garage machine for engine diagnosis.
Thanks for noticing it.
(Oh, not much later we could buy a Honda motorcycle which revved up to 9000. Not as much as the racing cars, but they knew they could thrash it).
In the comments under your alert post I said I'd be here as soon as I got off of work and here I am. :D
This has been an outstanding video, and I appreciate you making it.
There are always so many factors which contribute to the outcome of the war, but the analysis of one factor can often illuminate many others. The subject of German aviation fuel highlights the simple fact that Germany likely had lost the war almost as soon as it begun. Their assumption that combat excellence would overcome their serious lack of many strategic resources, their absolute failure to adequately prioritize logistics when developing war plans, and their inability to get their economy on a proper war footing, (not to mention their inability to manage or even profit from the economies of their newly subjugated territories) meant that they were essentially doomed to lose the day Hitler opened a second front with the Soviet Union. Hell, even had they not, simply holding on to Europe with a belligerent Britain was not a foregone conclusion. As it was, they had their hands full with the British, so they did not have the economic might to also take on the world's second biggest economy, and that's before they even *thought* of tangling with the first place one.
Meanwhile the United States had the largest known oil reserves at that time, the most advanced fuel industry, and the luxury of being able to drill as much as they wanted without worry of incoming fire. Furthermore their economic output was swiftly and efficiently moved to maximize war production, and they commissioned twice as many logistics officers as they did combat officers throughout the war. Combine these factors with reasonably secure supply lines most of the time, and with rare exception the supply of fuel, just like every other strategic resource, was simply not a serious concern to the American and allied aviator. The lack of high quality fuel was a constant drain on the Germans, and the common occurrence of completely running out routinely crippled them.
The totality of their fuel issues, the way they were handicapped when forced to use substitute metallurgy, the way synthetic fuel negatively interacted with other systems in their aircraft, the simple economics of turning coal into gasoline, all of them exemplify the absolute shit show which was German economic and logistical planning in the Second World War, and the hopelessness of playing the hand they dealt themselves.
Thanks Craig. I always enjoy your well thought out posts.
Also the insane depraved effort used in mass murdering target ethnic groups as if it was an _integral war aim_ and the prolonged years of effort and gigantic amount of material wasted on the static Atlantic Wall which contributed absolutely nothing after the allies got ashore on the first day.
Contrast the ruthless axing of overlapping complex programs such as Rolls Royce’s dead end upgrade improvement and attempted X-24 layout development of the old Kestrel V-12, cancelling the Westland Whirlwind, Hawker Tornado and the Avro Manchester with all the unorganised, unrestrained hare brained waste in nazi Germany which was so out of touch with hard reality that it later spawned all the Wehraboo super ahead of its time myths such as the Horten brothers useless but wacky _stealth fighter._
Thanks Greg. Fascinating information
Nitrous, water or methanol injection are neat ideas for boosting power.
Greg, thanks for this jam packed full of data about fuel video. A lot of this was helpful for my understanding of some issues I have with my 3.0 L Twin Turbo automobile motor. It also helped me get a better feel for the nuances of my 3.8 L hopped up (LOL) flex fuel GT-R . I do have ECU maps for 93 and 100 octane for my 3.0 L. Now understand how and why the HP gains are so significant when using E85 and 100 octane fuels, with 70-73% alcohol giving me the most gain in my GT-R . Your video was very insightful!
Perfect cont pet usual- have to re- watch this one, as with many others of Greg’s videos.
Great video, Greg!
A couple of things I remember from Callum Douglas’s excellent book that are also relevant to this video:
- The allies were able to run much higher coolant temperatures due to being able to manufacture coolers that could withstand higher coolant pressures. Can’t remember the specifics, but he suggests that it drove German designers nuts, especially with their C3 evaporation problem,
- the conservative Merlin power levels may have been due to larger overlap values the Germans could run with the direct fuel injection.
I do like Callum Douglas' work. Of course that doesn't mean I agree with him on everything and I don't think he is right about the Germans inability to manufacture radiators that could handle the higher temps and pressures. That's a good theory, but it doesn't seem to hold up.
Greg, great video. Thank you for all the time you spend researching and putting these together. I've got some books relating to aircraft that maybe you've read, but maybe not. If you want them I'd be happy to give them to you. I'm not a Patreon supporter but I would give them to you just to say thanks if you're interested in them.
Wondeful deep dive ,,, Thanks 👍
Thank you Greg!
Hi Greg, another great video. I’m a technical manager for an oil company who knows a bit about gasoline formulating. I have a hypothesis about why C4 might not have had quite the performance that the bare octane rating might imply in some of the German engines. Not sure how to reach you privately to discuss….
feel free to email me at gregsairplanes at gee mail
Altered Attitude: Please share this with us :-) I have a hypotesis fusing a a guess of more cyclo-alaknes and "iso-octane" in Allied fuel, and more aromatics in German fuel; combined with shorter "energy-steps" in the molecular-orbital (MO) energy level diagrams; combined with the statistical population of these levels as the temperature increases during compression (Boltzman distribution?); which then eventually leads to the German fuel being tipped over the edge to pre-ignition first. -- It would be gratifying to know if I wasn't that far off.
@@MultiZirkon Good knowledge on the radical development side Ole, but think it’s perhaps worth considering this more empirically. Essentially octane tests measure detonation under conditions defined by the test. The different tests (MON and Supercharge Methods) result in very different temp/pressure relationships in the end gas at the point of detonation. What then needs to be considered is what is the octane index of the engine you care about both in terms of absolute value and relationship between T/P (which can be expressed as a function of MON and RON in today’s world, but could equally be expressed as a coefficient MON / Supercharge Ratings which then can be derived through testing fuels of various sensitivities and applying linear regression.
In the case of C3 we know it was predominantly cyclic (the synthetic Bergius process used produces cycloalkanes, but dehydrogenated to give higher octane aromatics). The allied fuels relied more on alkylate which is predominantly substituted liner alkanes.
The difference is that the cyclic fuel is more likely to result in a higher Supercharge rating (low T/P)for a given MON (or vice versa) and so would advantage engines with low end gas temps. Think liquid cooled, carb engined (enthalpy leads to inlet cooling) charge air inter cooling. The opposite (air cooling, non inter cooled etc) would result in a higher demand that would have to be offset by lower compression ratio or boost.
Add to this that other factors add to an engines octane index (e.g. low engine speed, larger cylinder bore) then we can start to see that many of the German engines might have to back off on the boost / compression ratio to compensate for the other factors that increase OI and others that drive the T/P ratio higher which would disadvantage them (air cooling BMW801, no inter cooling etc.)
Hence my hypothesis is that allied engines like the Merlin / V1710 are more likely to have an easier time (or be able to use a higher boost / compression ratio) on a given fuel when compared to many of the German engines.
There are more issues related to organic octane boosters that I know the Germans were working with at the end of the war and how they are likely to also show a faster transition to severe detonation when compared to non organic inhibitors such as TEL. Hence operators may choose to operate their engines further away from the detonation boundary (i.e. back off on the boost) to avoid damage.
By the way it’s worth noting that the second, higher number used to define aviation engine ‘octane’ ratings is not a Rich Mixture number even though it is often referred to as such. It is actually a Supercharge test (ASTM D909) that uses fixed inlet temp and varying inlet pressure to reach knock and then varies mixture around the stoichiometric to get to peak knock and through bracketing with reference fuels, to derive a Supercharge Performance Number (performance numbers are octane numbers above 100 - because it’s not possible to have more than 100% octane as the reference point). So the test itself does not rely on the charge cooling effects of overly rich mixtures.
Rich Mixtures do affect an engine’s octane index / demand and therefore would also allow a lower octane rating fuel to be used free of detonation, so we should try to think of rich mixture charge cooling effects as being an engine Octane Index (engine demand) property and not a fuel (octane availability) property.
@@robmidgley Thanks :-) I have always known that "Octane"-numbers are to be found empirically. But I found this facinating stuff in Calum Douglas book, the chapter "Prelude to war" about the allied fuel have flatter curves/surfaces in "knock-resistance" vs inlet temperature; and I remembered it as a 2 dimensional graf of allied vs german fuel. But I misremembered: It was a 3-dimensional figure plus text. It was the steepness, not absolute values, of the relationship that made me ponder...
Thanks for the information about the name of the Bergius process. It was interesting to read what I could find fast on the internet. And very much thanks for the tidbit of allied fuel regarding the low cyclo-alkane content vs linear-alkane content.
Nearly halfway through another great video from you:
Two things:
You mention air density as the factor to calculate actual comp ratio in a charged engine instead of just multiplying geometrical comp ratio and boost pressure. You are definitely right about that because the hot air from the compressor/turbocharger has lass density.
But, as you metion earlier, higher temperature also leads to knocking.
Pressure is the product of density and temperature.
If pressure is the determinating factor of knocking (as in comp ratio in a N/A engine) doesn´t the hotter air in a charged engine make up for the lesser density?
More density just means there is more oxygen to let the burning process be more efficent. In a given engine you can run the mixture richer if you have colder air instead of hotter air, getting more power (more oxygen and more fuel in a given displacement). That´s why engines perform poorer in hot climate. Same for less air density in higher alltitudes, that will take away oxygen.
In addition, if you can run the mixture richer (because of more density) it will cool down the engine because of evaporative cooling, also preventing knocking.
Isn´t that the whole point about intercoolers, running the engine cooler with more dense air, so also beeing able to run it richer?
If more density regardeless of temperature alone would lead to knocking, who would need intercoolers in a charged engine? Then you would just increase boost pressure whithout an intercooler and don´t mind about temperature. I don´t think that´s how it works.
Second, you don´t mention ignition timing. As far as I´m aware it´s a huge factor. Early ignition gets you more power out of a given engine, but it also makes the engine running hotter, thus promote knocking. As far as I know, charged engines usually use less early ignition as N/A engines.
Greetings,
philpp
Great questions.
It's a complex answer but your.on the right track. And it varies based.on the specific engine design, what method it creates additional boost, (one, two or three stage, one two or three speed superchargers or exhaust driven Turbocharger, and whether the have an intercooler, or maybe an intercooler between each supercharger stage?).
The absolute best resource on the subject, written by a top American designer who worked on aero engines of that era. MITs Charles Fyat Taylor: Internal Combustion Engine in Theory and Practice Vols 1&2.
Keep an eye out for a used set, they can be spendy. Best book on engines of all sizes and how.to go about designing or reverse engineering them. Haha!
super super cool. awesome information and great insight on effective compression ratio. laid out and explained very thoughtfully, thoroughly in a very logical and sensible manner
Thanks, I was worried I spent too much time on ECR, but it seems like it worked out.
@@GregsAirplanesandAutomobiles I have actually re-watched the ECR segment several times, I recently acquired an older 01 beetle turbo 5 speed from a family member and it just so happens I am a mechanic/auto tech by trade and is still my day job. Very handy info not just for my own curiosity but for future engine tuning/ builds down the road :) the beetle is only the first turbocharged car I've been able to "mess around with' even aside from turbo'd applications the octane , compression and air/fuel information still applies across the board