More dyno results

[wibble]

Here are my results from dyno:-
http://i158.photobucket.com/albums/t81/mrfigs/Dyno/dyno1a.jpg
http://i158.photobucket.com/albums/t81/mrfigs/Dyno/dyno2a.jpg
http://i158.photobucket.com/albums/t81/mrfigs/Dyno/dyno3a.jpg
http://i158.photobucket.com/albums/t81/mrfigs/Dyno/dyno4a.jpg

'90 944 turbo with Brodie Brittain chip. I hasten to add my next job is to confirm which chip is fitted.

The tests seem to imply my car is running lean. Are any of you able to confirm this from the links above? However, there were also three 964's testing with me which also ran lean, so I am slightly dubious these were mis-readings.

I was told to check air flow sensor, fuel pressure or chip itself. From Clark's garage, I think my next job is to check AFS with a multimeter.Thoughts?

 

[Diver944]

Yes you are quite lean.

For a Turbocharged car the holy grail when on boost is 11.8:1 but it's a bit safer to be slightly richer at 11.5:1 or lower. Yours never gets below 12.5:1 and as the revs increase towards the redline you are dangerously lean at 14.5:1 []

From memory the BBR chips has been around a long time, so if everything else checks out I would suggest changing to a more modern one like Promax, or MaxHP

 

[nick_968]

Unlikely to be the chip that is the problem as no one would map a chip to do those afrs. Either the computer is not getting the correct air reading and hence not giving enough fuel, or there is a fuelling problem at higher rpm. 12 to 12.5 is fine afr for the boost levels you are running but past 13 is definately not. Get a second check done on the air fuel and do not drive your car hard until you know what is wrong and have fixed the problem or know the reading to be false. At extended use in the 14 range your car will not last long before you do some damage to the bottom end.

 

[John Sims]

Could be a duff or under valued Fuel Pressure Regulator. I'd swap it for a 3 bar and see what happens.

 

[wibble]

Thanks for your advice - I'll investigate.

 

[Diver944]

ORIGINAL: John Sims
I'd swap it for a 3 bar and see what happens.

The 3 bar FPR could ring the AFR to a safer lever after 4000rpm but it would make it too rich further down under 4000rpm

Looking at the graph the AFR looks just about spot on in the lower RPM as it is spooling up and is slowly getting richer all the time, but just as it hits 4000rpm it starts to get lean. If it could maintain itself around 12:1 or a little richer from that point it would be fine.

I wonder if a split in the j-boot between the AFM and the turbocharger is opening up at high RPM and sucking in unmetered air? [&:]