Steves flutter / PowerFC problem

[AJ4]

Not sure where else to put this, and its only of interest to Steve but someone else might find it useful.

I'll let Steve add to this if he wants with the setup and history of the problem, but basically he was getting an odd flutter at a certain RPM range that was holding the car back.

The problem seems to be that the MAF he is using is not scaled properly in the PFC, causing the engine to knock. In the graph below, the point at which the AFM voltage flutters and the point at which the knock starts is when the engine load is over 27000 ( scaled on the PFC ). Basically what we think is happening, the load is going off the scale and the engine is possibly running lean as it doesn't have a load point to referance for the fuel.

As soon as the load came back under 27000, the AFM voltage flutter and knock stopped. The load peaked at 30000 and the trace can be seen disappearing off the bottom of the screen.

I think the first thing to do is re-scale the MAF so that the load stays on the map, and see if that cures the problem ? Don't rush out and buy a Q45 just yet

Any comments, thoughts, suggestions welcome.

Ross.

 

[Rishi]

See i thought it was the fact that he was flowing exceptionally well and that the turbo housing was causing back pressure... But it could very well be running lean for a similar reason although i thought the mapper would have corrected for this...?


Rishi

 

[CruiseGTi-R]

It looks like knock is still registering when the load is under 30000 and is worse when the load is back within range?

I know very little about this sort of thing, but just going by the graphs.

 

[Mad]

I think its the new turbo, its too good Steve can correct me on this if I'm worng, but I think it was mapped with the smaller turbo, you can see that the MAF correction table has been fiddled. My guess is that it was scaled to use the last row with the small turbo, and the bigger turbo just pushes it off the map as it flows a lot better.

The knock is fine, it hard to explain it with the scale of the graph above, but there is always a small amount of 'knock'. Its not knock really, its just background noise in the engine etc. When the loads goes over 27000 there is a clear jump in the knock, its just not very easy to see from that graph. Its possibly not even knocking but just vibrations from the engine stalling thats causing the spikes.