Spitfire makes only 300 mph?

Can you tell me how I get the 317 at SL in COD with CEM? My procedure is:
All out (max rpm, max boost with boost cut out) then trim aircraft. Optimize rpm (slightly lower seems to improve speed), let it settle, retrim aircraft, then close radiator just as much to stay at water temperature still acceptable (120°C). Retrim if necessary.

I only get 300 mph at sea level. And this with several trials.

[ICDP]

41Sqn_Stormcrow,

Make sure you use the no cockpit view. The internal speed guage jumps aroung quite a bit and the little info box only shows increments of 10.

So if you use the info box (move your mouse over the instruments) your speed might be showing a 300 but in reality it could be 309. My top speed has ranged from 311 to 317, there doesn't seem to be any reason for the difference apart from my varing flying skills

I open the radiator 5 or 6 clicks from fully closed for optimum cooling and speed. I am not sure if it is modelled in CoD but the real Spitfires would give slightly better speeds with the radiators slightly open. This position was known as the minimum drag position and was marked by a red or white triangle on the map box beside the radiator lever. Open the radiator further than the triangle and the increased drag would slow the aircraft down. Close the radiator further back from the read triangle and the decreased cooling would cause the engine to overheat, thus requiring a reduction in power.

Unfortunately the CoD Spitfire has the radiator lever slightly forward from the correct position so it wouldn't line up with this red triangle even if it did exist on the CoD Spitfire.