Spit/109 sea level speed comparisons in 1.08 beta patch

[MiG-3U]

Originally Posted by Kurfürst

Nope, this is just your opinion and has nothing to do with any test report's contents.

The facts:
1. Prototype aircraft V15a, tested well before production started
2. Tested speed 493kmh at altitude of 440m, gives 485kmh at 0m
3. The supercharger has two fixed speeds:
- boden- and hohenlader are claimed and the optimal change altitude is determined
- manifold pressure drops above the FTH of the bodenlader, until hohenlader is set on
- the speed test confirms that the supercharger has two fixed speeds
- according to Flugmotoren und Strahltriebwerke by Kyrill von Gersdorff, Kurt Grasmann, Helmut Schubert the first order of the DB601 was the pre-series of 150 motors, A-0 ie Baureihe A (carburator engine with fixed speed supercharger), so based on engine number of 140, the V15a had one of these instead a A-1. The hydralic clutch came later with the Baureihe B along with fuel injection.

Originally Posted by Kurfürst

Unfortunately it is test data and it is relevant. Unless you want to dream up specifications.

It's not a test, just a piece of paper, no test data nor kenblats of production planes support 500km/h at sealevel. Everything else is around 460-470km/h including swiss planes with the 601Aa.

Originally Posted by Kurfürst

Oh but an 500+ kph Spitfire I as fast as the 109F *IS* logical, riiiiight?

Calculating the speed of the the Spitfire I at +12lbs the same way as done in the V15A report:

Density at sealevel: 1.225 kg/cubic meter
Power at sealevel at +6.25lbs: 880hp
Power at sealevel at +12lbs: 1180hp
Speed at sealevel at +6.25lbs: 280mph

r = ((1180/880)*(1.225/1.225))^(1/3) = 1.103

V0 = 280mph * 1.103 = 309mph = 497kmh

However, that is a crude, unaccurate and partially wrong way to calculate it.

Originally Posted by Kurfürst

Thank you for admitting that your remark about supposed two speed superchargers was just speculation.

The only speculative but logically correct part in my post is the size of the oil cooler, and it was there only because you asked it. The rest are facts.

Originally Posted by JtD

Regarding level speed performance of the 109, a question raised by I think MiG-3U puzzled me, maybe you have a good explanation, I'm at a loss for now: How come the 109E is faster than the 109F at less power, if you accept the 498 km/h for the 109E at 990ish hp from the V15 test and the 495 km/h for the 109F at 1065ish hp from the 109F Kennblatt?

Thanks for correcting the power of the 601N.

We do have several datapoints for production 109E giving 460-470kmh at 1.3ata and 990hp.
Calculating again the speeds of the 109E same crude way using 470kmh as base line:
601Aa 1045hp = 479kmh
601N 1060hp = 481kmh

Then we have the 109F doing 495kmh ie about 15kmh faster than the 109E at same power, that difference is roughly same as found at FTH. These values match very well while 500kmh is clearly an outlier and not supported by any test or kenbalt of the production planes.