Speedtoys

Get the ones roger has...IIRC, thats what I have on my Xpipe I got from Rob, and...I just breezed emissions with room to spare..could have been 4-5x dirtier, and still passed.

safulop

Gotcha, Roger's been helping me out lately. I'm sure as can be it's this dang Cat, there is nothing else wrong with this car. Really! Nothing at all! I'm just going to keep saying it until it's true.

Speedtoys

Just thought of a neat experiment.

Get a car that passes smog well, and have a shop get samples PRE cat, to see what good cats are doing specifically.

Then have people use that to sorta...judge..or at least help.

danglerb

People in non visual inspection states have passed smog with a well running 928 and no cats, the 928 isn't a dirty motor by nature.

safulop

With my car running as nicely as it is, whatever problem it may have is so well masked it will just be easier to get a newer cat to clean up the soot. You know how it is with Porsches, stuff that ain't right can seem fine for a long time. I have those funky chips installed; those don't cause smog problems do they?

Andre Hedrick

I had high HC and CO and lately NOX in the past tow smogs :-(

I had leaky injectors, fuel pressure regulators, O2 sensor, and new FlowMaster CAT, and narrow band A/F gauge added to try and get his under control.

If you pull your CAT and look up the manifolds and they are black/wet you to likely have injector issues.

Hilton

The autothority ones? They may explain the high HC's - IIRC they advance the timing a heap and compensate for increased knock count by dumping in a lot more fuel (as the EZ-K can't pull timing back as far as it can on the stock maps).

I'd certainly put the stock ones in for smog - it should make a noticeable difference. Then carefully take the autothority ones and put them underneath a 4lb sledge (doesn't need to be a big hammer).

If you want chips, by far the best bet is to find someone within a few hours drive who has a sharktuner II, and actually tune for your car.. see Jeff's thread he posted in today about his latest emissions test and previous sets of results a couple of years ago

Also note that high NOx can also be caused by carbon deposits - they raise the compression and affect the evenness of the burn.

In your shoes, before buying cats, I'd be putting in stock chips, and then getting a does of BG intake clean to remove carbon buildup.

WallyP

A cat only works with mixtures very near stoichiometric. If the fueling is faulty because of injector problems, leaking regulator/dampener, high fuel pressure, etc., and the oxygen sensor/LH ECU can't trim the mixture enough to get to stoichiometric, the cats can't help.

If the oxygen sensor or its connection is faulty, and you get no fuel trim and are running open loop, the cats can't help.

If the WOT switch is maladjusted or faulty, the cats can't help.

To sum up - anything that puts you in open loop, or over-fuels past the trim capabilities of the system will cause your problem.

I agree on going back to stock chips as a first step.

Speedtoys

I did not pass until I got into stock tune after finding some non stock chips in the computer.

Get some PEMs from Jim Corneman with a stock tune on em.

dr bob

Sean--

I'd put the stock chips in before anything else. That will help mileage too.


----

I fiddled with NOx numbers that were growing slowly test to test, flirting with failing. I coaxed the tester into doing the dyno runs with the car locked in second gear, and it would just squeak by. Did an in-the-car FI nozzle flush with BG, and it got a lot better, enough to pass without resorting to holding the gearbox in second. Then did the intake refresh a year or two ago, including new injectors. NOx is now less than half of the "average" number as of last September test. HC dropped some too, back to below that "average" number.

My theory is that it only takes one injector with a weak spray to make enough extra NOx to fail. If any one spray is weak enough to have even the occasional lean misfire, HC will go high too. Remember that the oxy sensor reads the --average-- CO from all cylinders combined, and adjusts mixture dynamically. One or two lean cylinders won't move the average CO enough to compensate completely for the one or two poor injectors. So it's easily possible to have one or even a few weak cylinders causing the failure symptoms you are seeing.

----

One of our San Diego brothers was having the same problems you are facing, and is fanatical about keeping the car perfect. His local mechanic suggested the BG cleaning. I wasn't a fan of the process at the time, but he did it and reported complete success.



YMMV, of course.

safulop

Yeah, I think I'm gonna get rid of these autothority chips, there is definitely some amount of overfueling happening, and there always has been since the chips were put in by the PO. HC numbers have been crap since then.

Good to know that the Cat only works when mixture is good. Why why does every mechanic and smog repair tech go straight to the Cat as the cause of the problem? They like to sell parts instead of solving problems. I'm glad the car passed and is running OK, gives me time to sort this through step by step.

-Sean

Speedtoys

Well, a shot cat would do what you see, they dont know you have super-fat running chips in there.

dr bob

The "challenge" with fat-running chips is that, in the end, the fat-running only happens when the car is open-loop. It won't get there during the Cali rolling emissions test. What does hurt is the more aggressive ignition map, which does not discriminate between open- or closed-loop modes. It sees low load .and. .not. idle on the closed-throttle switch, and the timing is advanced.

Sean--

IIRC, the brain we put in that car has the limited early diagnostics on it. Might be worthwhile finding a diagnostic tool to plug in, just to verify that stuff like the knock sensors and the Hall sensor are functioning correctly. While those will cause timing to retard when they fault, it might possibly be part of what you were seeing.