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boosted 89's Avatar
 
Join Date: Nov 2009
Location: Ontario Canada
Posts: 132
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frustration mounting

Hey All

Yes I'm still trying to get the 930 to pass emissions here in Ontario Canada. I've adjusted the CO screw down to the point where my wibeband o2 sensor says I'm running 15.2 afr at idle. Its passes the idle test with 0.02 reading but during the 25mph test it fails miserably with 2.95%CO output. It doesn't have the air injection pump any more(not sure if this is the reason why its failing) and the 3rd last time I tested it, the car ran a 0.72 CO%(which still fails, but is the closest I've been to the 0.33% required) at 25mph but failed with a 2.91CO% at idle. I was using my WB output for a lambda signal but later found out a fault with an output of only 0.032volts at 14.7 afr. Tried an aftermaket O2 (narrowband) and got a 0.455 volt output at the same afr which I used for the lambda signal and it still failed with a 2.95%CO...but passed at idle. I guess what I'm asking is...what does the O2 signal act on to adjust the afr to 14.7 during the idle and lower rpm/loads. does it signal the WUR using the bimetal strip to adjust the control pressures..is there a lambda module of some sort. I've been screwing around with this thing and it seems like I take one step forward then 3 steps back. All my CO adjustments are done at N.O.T and before the cat through the O2 sensor hole. If my afr's are 15.0/1 before the cat then I would think it would at least be close to passing.

Any input would be greaetly appreciated

Chris

it may very well end up at a Porsche dealer if I can't get this resolved..i'm just to anxious to drive it!
Old 05-28-2010, 05:15 PM
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Join Date: Jun 2005
Location: Colorado
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I have to do the same thing here in Colorado.

First of all, you have to maintain right around 14.7 AFR to let the cat work, no more, no less. Your 89 has a computer under the seat that reads the O2 sensor and adjusts the AFR by a bypass valve on the fuel head. This bypass valve controls the fuel pressure in the chambers of the fuel head for fine tuning of the AFR. It does not control the WUR.

I tried to pass emissions without the lambda working and using careful tuning, and it didn't work. It's just not possible to maintain an almost perfect 14.7 with tuning alone, you need a functioning lambda system to get precise control.

You need to tune the WUR to factory specs first, then set the idle CO per the manual, and plug in the O2 sensor. Make sure your O2 sensor is good. Log your AFR for normal driving and see if it hovers around 14.7. If it does, and your cat is good, it'll pass.

I have 964 cams and no air injection, but once mine is properly tuned it passes at about 1/3 to 1/2 the limits.
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Old 05-28-2010, 05:38 PM
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+1 on above. fresh O2 sensor and a fresh cat. I just went through that with another older non-turbo vehicle in CA. It was a long process, but in retrospect I should have started with CAT and O2 replacement and just saved lots of time.......and get it adjusted for the 14.7 AFR
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Old 06-02-2010, 09:46 AM
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Thanks for the info.
I was originally told that I was getting a new performance cat and muffler system with the car, then when it was delivered it had the original exhaust system that was on the car when I test drove it.. Nice stainless twin outlet muffler assy, but obviously not good for emission testing being catless. They then shipped me at my exspence an oem muffler /cat assy which looks ok but who knows..They said the performance system they had purchased( which was apparently $2k and was supposed to be thrown in with the sale of the car) didn't fit so they threw the oem style one on to pass it in Arizona..which it apparently did( I think it was fudged through because it was coming to Canada). Now here in Ontario it fails misably.
Needless to say I think I'm at a loss for any more adjustments and I don't have the proper tools to test control pressures and such so its going to a reputable Porsche repair place to get figured out.
Old 06-02-2010, 05:38 PM
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