I believe what he is trying to say is that the rpms stop increasing before the redline which seems to suggest fuel restriction.
This is due either to:
- a very dirty fuel filter
- a problem with the HPFP
I would suggest that since this only occurs at WOT, he attempts the cheaper solution of replacing the fuel filter. If that doesn't work, he should pursue the HPFP angle.
Sounds like good advice to me - always best to rule out the cheap / simple stuff first.
Not sure if it's the case on Minis but on Subarus (which is where my background lies), a faulty fuel pressure regulator isn't unheard of and that can also have similar effects.
It's also possible that the ECU is detecting knock at WOT and is pulling timing which would certainly feel like the engine was "choking". If the fuel pressure is down, then knock could well be a side effect of that.
Also, what fuel is being used? SUL obviously being more resistant to knock than normal 95 RON fuel. If you're using 95 RON, it could be worth putting a couple of tanks of SUL through to see if it makes a difference.
On Subarus, there's an open source application called ROMRaider that allows you to log via the OBDII port - not sure if there's a similar tool for MINIs / BMWs - but it's very useful when diagnosing issues to be able to log what's going on.
Now: 2005 R52 MCS
Plus: BMW X3 3.0d, BMW Z3 2.8, BMW F700GS, Vespa ET4 125
Was: 04 R52 MCS, 06 R53 MCS