The car had back to back runs over 3 hours at MSL while they adjusted the box settings.
The car actually makes slightly more 239hp on 373nm... it made 243hp on 373NM but the LOWEST reading was 239hp on 373 and that's what I've gone with.
It still hits 60 in 5.7 seconds (GPS stopwatch). It still hits 155mph. It wouldn't be able to if it didn't have that kind of power.
Sorry Uz, but you have been fed erroneous information.
Power, torque, acceleration and top speed combine to make a difficult subject. Power and torque on their own are meaningless figures. You need weight, gear ratios and the final drive ratio to make the complete picture.
The car manufacturer will determine what is optimum for its customers - eg for a small engined car, light body weight, 4 door shopping car, they will decrease the final drive ratio to produce economy at the sacrifice of top speed and acceleration. On something like an SLK2s, they will reverse this to a certain extent to give either acceleration OR final speed. You cannot have both! Here is where power comes in - you need power (bhp) to acquire both acceleration and speed. All this is done by altering the final drive ratio and nothing else.
So, a 200 has a 3.07 final drive giving 7 odd secs 0-60 and 147mph top speed. You can get the acceleration better through more power. You cannot increase the top speed as this is dictated by the RPM and the final drive (OK, you can increase the RPM, but this only by nitriding the crankshaft and steel conrods etc - an extremely expensive procedure) So your car will never exceed 147mph with the standard 3.07 final drive and limiter. To get 155mph, you will need to switch off the factory limiter (highly illegal) and then determine what the RPM allow on a 3.07 final drive and change it accordingly - maybe down to a 2.9. But this change will drastically reduce acceleration time.
Now the 55 has a 2.8 final drive BUT it also has an excess of power - some 400 odd bhp. This overcomes the drag of a 2.8 final drive to give a sub 5 second acceleration AND as it is a low final drive, able to produce the 155mph.
As WJA says, the dyno people - and sales people - will give the best figures. The first point here is 'what is being measured' - so you are told you have 239 bhp. Where? At the wheels or the crankshaft. What loading was applied to the rollers? More often than not, no loading is applied. In real life, the road condition and wind resistance will dramatically hit the acceleration times. If they tell you the bhp is at the wheels, this means your engine is producing some 300bhp at the flywheel. Just not possible I am afraid. I would ask questions of when the dyno was last calibrated and by whom. Most dynos are not regulated, so treat them as indicators.
By no means am I saying you do not have any increases in your figures, I am simply confirming what has been said already, and advising you to be cautious.
Now, if you were to have a genuine 50bhp increase at the wheels, and top speed is not an issue, you have enough to allow you to change the final drive to a 3.27 that would give you a genuine sub 6 second acceleration. This ratio was fitted to the early 250CGi cars but change in late 2013 back to 3.07 as the only difference in acceleration was half a second but there were a lot of complaints from owners (I think in Germany) that top speed was more important, so the drive was changed to 3.07!
As I say, a complex subject, and if I may observe, one that you are worrying too much on…your car is already nippy - why not leave it as is?