Movie Theater "Why was the BF109 so slow compared with the P51?"
- Thread starter steve podleski
- Start date
If you listened to the video, high octane fuel was the main source of speed. Better aero helps mainly increasing range.
I have to believe it was more than fuel. The engines, design, weight and of course aerodynamics played a part
p38
corsair
p51 were all racehorses
Don’t discount the P-51 being designed 5 years-later than the bf. That’s a long time in the engineering world for better/faster/more reliable product to be designed.
Kurfurst - Your resource on Messerschmitt Bf 109 performance
The Messerschmitt Bf 109 Performance Resource Site. Wartime reports of the WW2 Luftwaffe fighter Messerschmitt Bf 109. Performance tests and tactical trials, and related information.
www.kurfurst.org
the 109 was on it's 5th or 6th upgrade in 45. the p51 on it's 2nd or 3rd. we got alot of engine input from the brits who had been playing with the spitfire for a few years. i believe the 109 was designed in mid 30s,before the spanish civil war. p51 in 1940 or so. germany just did not have the industrial capacity to compete with the US and england and russia. they made some bad decisions along the way as well. the 109 was pretty successful-hartman,marseille,galland and others. the p51 was the best fighter in ww2 for sure and was a product of the huge american military/industrial/enginering colossus. same applies to japan. at wars end they had come up with some extremely effective fighters but couldn't do much with them due beaten on the industrial and military fronts by us. essentially the 109 was an end product of long upgrading of an "old"design. the 51 the product of essentially "modern" engineering. my take on it anyway.
P51 was not the best fighter of wwII just the most recognizable thanks to Hollywood
fastest airplane bf163
most kills hellcat
the mustang just had the longest legs….
has anyone listened to the video?
It's a great analysis of engine performance of the Merlin vs the BMW.
It's a great analysis of engine performance of the Merlin vs the BMW.
Great resource but many documents in german. I suspect that the video author has access to these types of documents in his analysis of the 109 engines.
And I do agree with you; most of what I've read indicates that the Germans were hampered by poor quality fuel, and in a war where performance and superiority were measured in inches, it made the difference.
Mercedes is the german name you intend, BMW is bavarian.
Daimler Benz....does it sound close to Mercedes Benz ?
Thot sew.
The fuel did squat.
Higher boost is what caused the power increase. The fuel did allow less detonation (or pre-ignition) when running the higher boost.
They could have run the higher boost with the lower octane fuel but it would have required ignition retard which would have killed *some* of the benefit of the higher boost.
BTW, those were terribly designed superchargers and were more in line with a gear driven turbo than anything.
Exhaust driven turbos would have been much better to use but bearing technology was not up to it in those days and cooling would have been a problem too....once again due to damn near dinosaur level technology.
That same engine today could easily put out 5x-6x the amount of power with some simple tweaks and newer tech.
You cannot run the higher power levels safely on shit fuel. You can’t retard the timing crank the boost up and think it’s gonna be safe it doesn’t work like that.
The problem is cylinder pressure is causing the fuel ignite diring the compression stroke before the spark plug fires. Which will damage/destroy the engine. Retarding the timing ain’t gonna do shit
Pre-ignition and detonation are two completely different things. Your are speaking like they are the same...
Seriously... lol
Wow, go back to sniffing smokeless powder dudes and leave engines to us that build them.
Go google 'volumetric efficiency' and *maybe* it will help you understand what and how a boosted engine works.
Pre-ignition causes detonation but it is not the only cause of it.
Efficient cooling and precise timing are the cures for detonation.....cooling is not just a radiator, timing is not just ignition.
Obviously I would be wasting time to try to explain 40 years of experience and a masters in engineering to....well.....you'se.
Go google 'volumetric efficiency' and *maybe* it will help you understand what and how a boosted engine works.
Pre-ignition causes detonation but it is not the only cause of it.
Efficient cooling and precise timing are the cures for detonation.....cooling is not just a radiator, timing is not just ignition.
Obviously I would be wasting time to try to explain 40 years of experience and a masters in engineering to....well.....you'se.
Have you ever built tuned turbocharged engine before? I have, what you’re saying is ridiculous.
I don’t care how much engineering you have, I’ve actually done it before.
PRE IGNITION FROM SHIT FUEL WILL DESTROY AN ENGINE.
Denying that is utter stupidity!! 40 years of engineering... What did you engineer so I never go around those projects
130 and 150 octane fuel is the shit when making a high performance aircraft engine. The Germans did nitrous oxide, turbos, superchargers and methanol injection to boost power and stop detonation but they lacked the ability to make large quantities of high performance fuel.
The BF-109 was an older design and in war things move fast, very fast occasionally. FW-190 was a faster, better plane in most respects and Germans used cannons which made them better at destroying our planes with fewer shots. But they were hard pressed to train and deliver high quality pilots by the end of the war.
If they made a BF-109 fly 480 mph they would have still lost, speed was not their problem. The problem was they had very few pilots, even less fuel and they were losing the war to a numerically superior enemy which had the ability to make planes and train pilots in complete safety and deliver them to the war zone fully equipped with very good equipment.
The BF-109 was an older design and in war things move fast, very fast occasionally. FW-190 was a faster, better plane in most respects and Germans used cannons which made them better at destroying our planes with fewer shots. But they were hard pressed to train and deliver high quality pilots by the end of the war.
If they made a BF-109 fly 480 mph they would have still lost, speed was not their problem. The problem was they had very few pilots, even less fuel and they were losing the war to a numerically superior enemy which had the ability to make planes and train pilots in complete safety and deliver them to the war zone fully equipped with very good equipment.
First of all the examples below are gonna be measured at sea level using30” of manifold pressure.
Me-109 had a 7:1 compression ratio.
44” of manifold pressure is around 7lbs of boost or 1.5 bar. This is the pressure run on the ME-109.
So at full tilt boogie, it had a boosted compression ratio around 10:1. Pretty modest and not needing high octane fuel.
IF you were to crank up an Me-109’s engine to say 60” of MAP, 14.7psi, 2bar you are now up around a 14:1 compression ratio.
You are not going to run 60 inches a manifold pressure on one of these engines and get there by some tricks with the ignition timing... aint gona happen
During World War II Germans re-engined a Spitfire with a DB 605A. It was found to be better than the Merlin version.
https://theaviationgeekclub.com/dur...s-found-to-be-better-than-the-merlin-version/
Aluminum heads, just the material allows for higher boost w/o issues.
Intercooling allows for higher boost w/o issue.
Switching to methanol allows higher boost w/o issues.
Intake air chillers (not the same as intercooling) allows MUCH higher boost.
Instead of posting screen shots of idiots that have no clue, let's start with all the clueless things posted.
BAR means barometric, which at sea level is 14.7PSI.
Strangely that is exactly the same as the stochiometric air fuel ratio.
Inches of vacuum is measured with mercury as in how high it will lift mercury in a given tube diameter (*if* I remember right it's in a 1/8" tube but that obsolete measurement I have long since forgotten).
Manifold PRESSURE (not vacuum) is measured in PSI and has nothing to do with inches.
44" of manifold pressure is not a valid measurement.
7psi is *about* .5BAR
Compression ratio is static based on combustion chamber size and swept volume of piston diameter and stroke, it is not 'theoretical'.
Intercooling allows for higher boost w/o issue.
Switching to methanol allows higher boost w/o issues.
Intake air chillers (not the same as intercooling) allows MUCH higher boost.
Instead of posting screen shots of idiots that have no clue, let's start with all the clueless things posted.
BAR means barometric, which at sea level is 14.7PSI.
Strangely that is exactly the same as the stochiometric air fuel ratio.
Inches of vacuum is measured with mercury as in how high it will lift mercury in a given tube diameter (*if* I remember right it's in a 1/8" tube but that obsolete measurement I have long since forgotten).
Manifold PRESSURE (not vacuum) is measured in PSI and has nothing to do with inches.
44" of manifold pressure is not a valid measurement.
7psi is *about* .5BAR
Compression ratio is static based on combustion chamber size and swept volume of piston diameter and stroke, it is not 'theoretical'.
Speed isn't everything. Even these days, rarely does top speed come into play during dogfighting (and even BVR combat).
Also with the P-51 being the "best fighter...
The Pacific theater has a few candidates for you--that's a whole other topic. And then there's that German Focker....
Also with the P-51 being the "best fighter...
The Pacific theater has a few candidates for you--that's a whole other topic. And then there's that German Focker....
I don’t have a master’s in mechanical engineering, but my pap does. I did grow up in a shop and have been around drag racing since I could walk. Never heard of retarding ignition timing to cure detonation. Interesting concept, and might play a role in octane limited classes? But in the real world(at least in racing) the answer is always to move on up to VP 110,etc or E85 or VP M1(meth). Meth injection helps, water injection also(but those are usually limited to lower performance street applications). In the limited realm I have knowledge of, it’s kinda already a prerequisite that you’re running a intercooler..
You could always just run a diesel tho and boost that thing to the sky with a compound turbo Cummins or the like lol
You could always just run a diesel tho and boost that thing to the sky with a compound turbo Cummins or the like lol
Reducing/increasing ignition timing usually has a dramatic effect on pre-ignition. Years ago I used to time my truck engine by ear, stopping short of pre-ignition. However when I was an Alfa Romeo mechanic, I was surprised that this was not effective. Needed to use a timing light on the Alfa engines, they would not ping/pre-ignite until ignition was way too far advanced.
Here, in case someone needs independent verification from a respectable company.
BTW, this is a technique that was well known in the 40's.
Exactly nothing new, nor is it a rare idea.
BTW, this is a technique that was well known in the 40's.
Exactly nothing new, nor is it a rare idea.
The Germans had a diesel bomber, it held the altitude record for a while if I remember correctlyI don’t have a master’s in mechanical engineering, but my pap does. I did grow up in a shop and have been around drag racing since I could walk. Never heard of retarding ignition timing to cure detonation. Interesting concept, and might play a role in octane limited classes? But in the real world(at least in racing) the answer is always to move on up to VP 110,etc or E85 or VP M1(meth). Meth injection helps, water injection also(but those are usually limited to lower performance street applications). In the limited realm I have knowledge of, it’s kinda already a prerequisite that you’re running a intercooler..
You could always just run a diesel tho and boost that thing to the sky with a compound turbo Cummins or the like lol
I am not sure what you are trying to say whether the standard method of measuring manifold pressure is psi and not inches? In the video, military manuals are presented showing manifold pressure in inches. That may have changed.
DB605 had more engine displacement if that is the correct term (more cubic inches) but don't understand why the DB605A Spit had better performance than with the Merlin, since the Germans had bad gas and one stage superchargers.
The only thing that has ever mattered.
Power to weight ratio.
If you have a 1000 lb car with 500 horse
vs
2000 lb car with 750 horse
Which is able to accelerate, decelerate, and corner better *as a general rule* ?
(there it assumes same gear ratio, trans, braking, suspension setups, etc.)
Power to weight ratio.
If you have a 1000 lb car with 500 horse
vs
2000 lb car with 750 horse
Which is able to accelerate, decelerate, and corner better *as a general rule* ?
(there it assumes same gear ratio, trans, braking, suspension setups, etc.)
Nice try but wrong in the piston aviation world. MAP is measured in inches of mercury. It is a vacuum in normally aspirated engines because it is measued after the butterfly valve. So at low rpm/idle butterfly closed high vacuum. As the throttle valve opens MAP increases. When you boost you get into positive pressures.
Car guys think in terms of vacuum and positive pressure (psi) in the case of forced induction.
In aviation, we use manifold pressure whether naturally aspirated or supercharged/turbocharged.
Put it this way…. If, in aviation, we used vacuum/psi, in a naturally aspirated aircraft with the throttle wide-open, the vacuum gauge would read “0” whether on the runway or at 20k feet. It would be a meaningless value.
However, using manifold pressure, with the throttle wide-open on the runway you could see 29” and at altitude you might see 17” on the gauge. It’s now a means of determining how much power you’re able to make.
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