FM's the State of Play with empasis on Climb performance.

[Crumpp]

My E4 Climb test flown at 250Kmh IAS 1.35/2350RPM (AUTO)

Did you write down the climb speeds you used as well?

AFAIK the best speed for climb for the 109E in the sim is 270-280 kph IAS. This would be correct for the 109G, but the E's best climb rate was at 250 kph IAS.

Kurfurst is correct. All aircraft performance occurs at a specific velocity and it fixed by the design.

If the relationships of lift and drag are correct in the model, it will reflect in the best rate of climb speed.

Those airspeeds are listed in the appropriate Operating Handbook for the type.

I would also suggest conducting saw tooth climb schedules to determine the Vy and Vx of the models in the game.