First, I am not saying the Merlins were better than the DB or Junker inlines.
I simply observed these engines reflected a different design philosophy and these continued in their subsequent refinement. The British opted for very high manifold pressures, The Germans for more displacement.
By paying very careful attention to design, Rolls Royce came up with a very fine two stage supercharger, which made the Merlin a great high altitude engine. In the fighter engines, the Germans opted for smaller changes to their superchargers, instead focusing on boosting systems for high altitude performance. But their best solution for this problem was using bomber engines optimised for high altitude performance - hence the Dora.
Yes the BMW801 was a fine engine. Most of the thread is about the inlines however.
Yes both sides obtained better fuels than they expected before the war broke out. The effect of these improvements is to increase maximum BMEP without detonation. The chemistry does not care about the nation of origin. Remember the allies only had access to an abundant supply of 100 octane fuel becuase a guy name Jimmy Doolittle insisted the company he worked for at the time (shell) build factories in anticipation of airforce demand.
As for the data, people asked for data and I provided a good deal of it. I happen to think the data is pretty good. It has the virtue of being assembled by one source, over many editions (Wilkinson). In particular, the measurement methodology is common across engines. The disadvantage is that not all the engines are there, and there are more axis engines missing than allied ones. (Wilkinson had to wait until the end of the war to get the data on later axis models).
Now the data is maximum (gross) horsepower devleped by the engine. These are typically sealevel numbers taken off the bench, although some are reported for low altitudes (0-4k ft). Depeniding on the engine, this is either "wet" (using ADI) or not. The numbers typically correspond to maximum horsepower for take-off. These powers can only be used for a short time in any engine (typically 2-5 minutes).
Yes actual comparisons of aircraft performance are going to depend on the relative performance of the engines at different altitudes. These threads are full of such comparisons. The question is whether you want to talk about planes or powerplants. We were talking about powerplants. When the discussion is about the engines, and not the installations, the metrics I am reporting are the ones typically used by scientists and engineers. The data is only misleading if it is used in a misleading way.
As you point out, without a continuously variable clutch, multispeed superchargers result in a shark's tooth performance curver. DB avoided that, at the price of using only a single stage supercharger on the fighter engines.
-Blogs
Originally posted by Knegel
Hi
the DB´s used with C3 fuel(DB601N and 605DC) clearly show that they wasnt behind the Merlins.
The two speed supercharger had as many advantages over the DB system like disadvantages, good for high alt and high power peaks, but a not steady powercurve and missing exhaust thrust, the weight and ammount of maintaince probably also wasnt that smal.
Of course in high alt the supercharged planes had advantages, but up to rated altitude they dont had, with GM1 the DB´s was rather even again.
btw, the BMW801 had more then 2000hp(with C3 injection) and why there is no DB605DC or Jumo213+MW50 listed in your engine performence graphic??
The DB610A was also a very powerfull engine, though heavy.
Anyway that power comparison graphic isnt much worth. Or would we compare the MerlinII(max 890hp) and DB601Aa(max 1160hp) at sealevel??
Or would we rate the Jumo213A only by its "Sondernot" power at sea level(2250PS)??
Such single point comparisons are nothing more than missleading.
Only powercurves for usefull or comparable powersettings should get listed.
What are the 1160HP of the DB601Aa worth if its only available for 1 min??
All this need to get seen in the contex of the tactical need.
What was the excelent high alt performence of the Ta152H worth in 1945, when the high alt fights stopped??
What was the great low alt power of the Ash82 and BWM801 worth in 7000m?? What was the good power of the MerlinsIII worth if the fight was in low alt?? What was the Merlins good high alt power worth in the low level tactical Airwar in Africa? etc.
The great power of the US radials, the DB610A etc also are not always that much worth cause their high weight and fuel consumption.
Powerload(in different altitudes), airframe(aerodynamical potentail of the engine, how good to maintance the engine), fuel consumtion, reliability, price and much more are needed to rate the value of a engine.
With C3 fuel the DB605 + MW50 also was in the 2000hp + class, the Jumo213 was above it with B4 fuel + MW50.
Imho RR, BMW and Junkers had the best inline engines in the war. Reliable, good powerload and fitting to the available airframes.
But also the Russian VK-105 in combination with the Yak3 airframe was very good(at least in low alt).
How important the airframe is while rating the engine, you can see if you look to the VK-107. A very nice engine, with much power, but no russian fighter airframe was able to use it(not enough space for the needed radiators).
At the end the performence of the different fighters in europe was rather similar. There was no superfighter that was supiriour in all altitudes, usefull for intercepts, dogfight and escort missions. Same like every engine brough some limitaions to the airframe, also every airfame brought limitaions to the engine.
Greetings,
Knegel
