951 running rich
08-13-2011, 01:05 AM
#1
951 running rich
86 951 I recently got runs very rich. I don't kknow much of anything about thhe cars history but when I got it I saw it had the boost set over 15 psi and I also noticed a billett cycling valve and a 3bar fuel pressure regulator. The car was very fast but you could not boost very long before overboost protection sut things down. I checked the dme and the klr and they do not appear to have been opened so I don't think the car is chipped. I reduced boost to stock 11psi and the car runs fine, but give it any boost and you can smell the rich exhast. The muffler is always black. I passed a buddy under full boost thhe other day while his window was down, I let off the throttle and spooled the turbo up as I went by. Later I asked how the turbo sounded and he said, sounded fine but you filled my damn car with stinky exhaust. I am wondering if just the 3bar fpr is responsible or is it something else? Can boost be enriched with fuel without chips someow and the culpret is hidden somewhere in my car besides the dme?
08-13-2011, 12:46 PM
#2
Proprietoristicly Refined
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Absolute and pure guesses.
You recently got the '86 951...
Could the PO have adjusted the FQS switch in the DME for any reason?
http://www.motronic.ws/fqs.htm
NA rich problems start at the O2 sensor being defective/worn out
DME engine temp switch defective wornout----constantly sends "cold" reading to DME to keep fuel rich
Or take your pick...
http://www.oz951.com/public/broken.htm
From...http://www.oz951.com/public/index.htm
GL
John
You recently got the '86 951...
Could the PO have adjusted the FQS switch in the DME for any reason?
http://www.motronic.ws/fqs.htm
NA rich problems start at the O2 sensor being defective/worn out
DME engine temp switch defective wornout----constantly sends "cold" reading to DME to keep fuel rich
Or take your pick...
http://www.oz951.com/public/broken.htm
From...http://www.oz951.com/public/index.htm
GL
John
08-13-2011, 08:24 PM
#4
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A 3bar fuel pressure with a stock DME chip will cause the car to run 9-10% richer. If the FQS was also set to add fuel, you can be running as much as 15-16% more fuel (total with the 3bar FPR).
If the car is running very rich under boost only, then you have a pressure leak. The air is getting measured by the AFM, but escaping the system before entering the combustion chamber. The DME has no way of knowing there is a leak, and will supply the fuel fot the air as measured by the AFM; resulting in a rich condition under boost.
It's a wise idea to pressure test the intake system, a lose hose clamp, a cut hose all can cause a pressure leak.
If the car is running very rich under boost only, then you have a pressure leak. The air is getting measured by the AFM, but escaping the system before entering the combustion chamber. The DME has no way of knowing there is a leak, and will supply the fuel fot the air as measured by the AFM; resulting in a rich condition under boost.
It's a wise idea to pressure test the intake system, a lose hose clamp, a cut hose all can cause a pressure leak.
08-13-2011, 08:59 PM
#5
Proprietoristicly Refined
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AA-Ezra posted a simple DIY intake pressure tester--Post 7
http://forums.pelicanparts.com/porsc...ml#post6182468
Recent user results:
http://forums.pelicanparts.com/porsc...oooo-easy.html
GL
John
http://forums.pelicanparts.com/porsc...ml#post6182468
Recent user results:
http://forums.pelicanparts.com/porsc...oooo-easy.html
GL
John
08-14-2011, 12:59 PM
#7
I have already pressre checked the vacuum system, I guess a will install an air fuel mixture guage to get a better idea of what is going on. Can anyone reccomend a good one? I see the ones at the atoparts stores that wire into your o2 sensor and have a series of lights that light up. Are these worth a crap?
