Seeking lost power
I was pretty unhappy (make that 'gutted') about the power output of my car on Saturday - 192bhp (same as wrinx, coincidentally) while it should be about 40 more than that.
Kershaws diagnosed fuel starvation which made power drop rapidly above about 6400rpm, but comparing the plot against the original one for the engine the curve seems to flatten off over about 4500rpm.
So far I have two possible theories - I think this might become an obsession unless someone else want to take the car off my hands along with the 'problem'!
Fuel tank venting problem. When I filled up on Sunday (the tank was almost empty when the car was on the rollers) there was a huge 'implosion' when I took the filler cap off suggesting significant negative pressure in the tank. Could this be sucking against the fuel pump and restricting fuel flow? I'm not convinced by this one as the car didn't seem to perform significantly differently with a full tank on the way home - I'm sure I'd notice a 15% power difference.
Air-flow meter. Idling on the car deteriorated over the weekend - now it's pretty awful. Symptoms are classic sticking air flow meter - I've cleaned and lubricated it fairly recently so maybe it needs replacing. What if the flap was sicking at high air speeds? Maybe it wouldn't open fully, therefore the ECU wouldn't know to let more fuel in. This is my best theory so far, other than a weak fuel pump.
Anyone else got any theories? Next weekend I will carry out a full investigation because it's really bugging me!