951sickness

Well, I passed the dreaded California dyno smog test today. I was hoping to say "with flying colors" but "by the short hairs" is more accurate. What I did first was to replace the APE chips with the stock chipset, remove the LBE, Set the Fuel Quality switch to position #7, and replace the spark plugs with a set of a colder heat range. Here are the results of this test:

15 mph (2466 rpm)
HC 65 (116 Limit)
CO .68% (.74% limit)
NO 822 (791 limit)

25mph (2376 rpm)
HC 32 (91 Limit)
CO .29 (.62 Limit)
NO 724 (730 Limit)

Upon switching the Fuel Quality to position #3 the NOx went to over 1000 ppm. This was done on the dyno but not under a official test. That concluded testing for the day.

Today I had the Catalytic Converter changed out with one from a 55K car (thanks alpenweissisnice). The results of the test were as follows:

15 mph (2408 rpm)
HC 84 (116 Limit)
CO .46% (.74% limit)
NO 787 (791 limit)

25mph (2390 rpm)
HC 39 (91 Limit)
CO .28 (.62 Limit)
NO 566 (730 Limit)

So I passed.....but by a really close margin. The smog tech said that it failed the first try but passed the second time he ran the test. He also mentioned that since the used cat was inactive for a while....further driving and heat cycles might clean things up a bit more.

Here are my unqualified observations on this whole deal and a question to all those with 951's that were tested for NOx. It seems that all 951's run high on NOx values. I have yet to read about a 951 with NOx even under the 400 ppm range. Anyone who has run a test for NOx on a 951.....what were the test values? Please post your results as the curiosity is killing me.

This leads me to believe that these cars are just that way and the State is trying to make these cars pass standards it was never designed to pass. Also I was under the impression that in stock form...the 951 wastegate will begin to open as soon as any boost begins to build...thus the benefit of the LBE. If this is the case, the basic design of the Catalytic converter for the 951 will make the cars harder to pass on a rolling dyno test. The wastegate dumps after the cat....so anything that goes through the wastegate will never hit the cat. That would surely lead to higher NOx and other gasses. Well, at least I'll have a break from this insanity for two years.

Waterguy

Recently tuned car with aftermarket (Autothority?) chips:

2400 rpm 2nd gear:

HC 36 ppm
CO 0.10%
NOx 76 ppm

I don't have a full history on the car, but it had 103k miles on it when I had it tested in April. Stock Porsche cat, not sure if it is the original. O2 sensor looks fairly new. The car had failed the previous year (PO.) The local Porsche specialist (Weissach) re-connected the O2 sensor, tuned the car, adjusted the idle CO. It passed on retest, then passed for me. I made sure the car was fully warmed up (hot!) prior to the test; not too hard with that little turbo thingamy atttached to the side of the engine.

So I don't agree that you can't get decent emmision numbers with these cars, and I don't think aftermarket chips hurt if your O2 sensor is working. These same chips ran very rich at WOT on the dyno.

Bill

NOX is a byproduct of a lean mixture. High HC, a rich mixture.

The cat does not clean up Oxides of Nitrogen, meant to seek and destroy Hydrocarbons.

It appears that with all the changes you made, you screwed up your air/fuel ratios. Better get your fuel curve checked before you get the dreaded milk shake.

Oh......congrats on passing. Mine is still in fail mode prision. Not due to the emissions test (perfect fuel curve), but due to the visual (smog **** does not like my MAF modification, oh and the cat was missing.....can you say test pipe). Keep in mind, with a good fuel curve, our cars can pass without the cat. Mine did. Of course it will fail the visual (WTF gave it a try).

Hopefully my car will not be in smog jail for long though. The cat is back in. And Danno just sent me the Guru Racing stealth MAF kit, which adapts the MAF so it can use the stock airbox (thus looks stock).

The standards used today for our cars, are the same ones that were in place in 86. Yes, The same guidelines that Porsche used to design our cars. These guidelines do not vary. An 86 model year car is not allowed to use 1970 guidelines (less stringent). Nor is it required to meet 2000 model year requirements (more stringent). All the air quality board is asking for, is that your car perform close to the level that it did when it left the showroom floor.

Or in my case, about a 100 or so more ponies........yeah baby!

That is if I can get them to buy off on the MAF.

951sickness

Thanks, it is a great relief to be done with his crap. Best of luck getting yours through

According to the smog techs (I ran the numbers by four different smog shops) NOx is caused by high combustion temperatures and not necessarily a lean condition. If you look at the CO readings they are right about where they need to be.

Not really. I didn't change the fuel/air ratios at all. The fuel quality switch is on the DME and a eight position potentiometer. The fuel/air adjustment hole is still plugged just as it came from the factory.

Actually they do vary. Just do a search on this board where people post their results compared to limits and you will see differing values. In early October 2003 the pass/fail limits (cutpoints) were reduced further because too many cars were passing the rolling dyno test. The first guy told me this as he said, "too bad you didn't come in before November...you would have passed".

joseywhales

Just passed myself on 3rd attempt. Change cat for 3rd attempt, failed at 1st attempt on 15 mph (same as others) and I ask tech what gear he had in, told me 2nd I asked him if he would retest and leave in 1st, he did and it passed w/ a 561 nox. I'm running stage 2 chip and tail 38 wastegate. Picked up the 1st gear tip from a fellow Rennlister, Thanks.

turbite

Congrats on passing, I'm scared to take the test. (and I don't wanna bother taking the test pipe out)
Ironically I think I'd pass emissions even without the cat, but I doubt the visual.

I just registered my car in Tennessee.
Do you guys think I'm gonna get pulled over all the time?

I'm thinking its probably pretty obvious *why* I registered it in Tennessee.
I just hope they don't hassle me.

cas951

Bill, I.ve been curious to see this setup. Do you have it installed yet? I really want to see the result of this kit.

alpenweissisnice

951 sickness, glad you passed...Hope the Kentucky Cat had a lil sumpin to do with it...All I ask is that if there is a fellow r'lister out there in sunny California with the same issues, pass it on!

turbo944

LOL....let me know how it goes Turbite!! My car is currently registered in TN and I'm figuring it won't take long before I'd have to before getting hassled a lot once I move out there....well, once you have established residency and have a job, according to the law it looks like you have to have it registered or they can actually charge you penalty and interest from the point that you "should" have registered it. A monetary hardship might get a little leniency, but maybe not. Hard to prove that you live in TN and commute into CA to work as well in your car....unless you can show that you are driving back and forth every other week or something and that your primary residence is still in TN. My car doesn't have a cat on it now and so I've been considering doing the full SFR exhaust with cat if I move out there myself so as to get both a performance upgrade and a cleaner exhaust at the same time.....

I had hoped to keep it registered here since I will have an address to keep it registered at and it only costs $24 a year to keep it registered here.

951sickness

alpenweissisnice, I definitely beleive the Kentucky cat had a major role in getting the car through. Not only did it clean things up in the 15 mph test...but if you look at the 25 mph test, it scrubbed the NOx down to 566 ppm from 724ppm. The car seems to idle a bit higher and revs up a bit easier.

Bill

cas951,

Not installed yet. The kit is due to arrive on Tuesday 1/27.

951sickness,

Keep in mind when you are getting advise, there are two levels of a smog licence. The lower level is a test only licence. At this level, minimal knowledge is required. Just push the button on the smog machine and watch. The higher level is test and repair. This requires theory, as knowledge of the combustion process and how the manufactures equipment deals with this process, is required to trouble shoot and repair. A test only mechanic can not troubleshoot or repair smog equipment. Also like any field, there are good ones and bad ones. I hold a test and repair licence, passed the California state test on the first attempt (rare), and was top in my automotive technology class, of which I hold a BS degree and ASE master technician certifications.

I am not a mechanic by trade. But I took a Ford factory training program at a local JC, because I was tired of the bad repairs I was paying for, and decided to learn how to, and do the work myself. No one will take the same care and extra effort on you car, than yourself.

"Not necessarily" is a true statement. Lets looks at possible causes of high combustion temps.

1. Advanced timing - Not likely with stock chips. Timing is not externally adjustable on a 944.

2. High compression - Does you motor have carbon build up that takes it from the low stock 8 to 1 compression, up to say 11 to 1 compression. Unlikely, that would be a huge amount of carbon.

3. High boost - Did the smog tech boost your motor to 18 psi for the test (again more air, less fuel). Unlikely you could get high boost at 2500 rpm.

4. Poor fuel quality - Unlikely, the stock chip coupled with the O2 sensor should be able to keep up with the differing California fuel quality. That is, at the low rpm and boost levels the test is performed under.

5. High ambient air temp - Unlikely in San Francisco in January.

If you changed from APE chips to stock chips, you changed your fuel curve. Fuel and timing ARE the reason for chips. The DME fuel switch is only a small means of adjusting the stock chip fuel program, to account for regional fuel quality. By no means does the switch control fuel management. That is the job of the DME as guided by the chip.

6. Lean mix - Could occur with chip swap. Could be a bad O2. A lean mixture causes high combustion temps, which causes oxides of nitrogen to form. Add fuel and the mixture will cool.

I don't intend to be melodramtic, just warning you. High combustion temp can burn through your head gasket, melt valves, rings, or pistons.

But hey, its your motor.

Jake951

According to Autothority, their chips use stock fuel and ignition maps at idle and part throttle. Therefore, unless your emissions test goes beyond part throttle, there is no reason you should be failing the test if the rest of the car is in good running condition. When I had Autothority chips I always passed the MA smog test (originally at idle and more recently on the dyno) with flying colors. Perhaps CA limits are tighter?

One common cause of failing smog tests is a bad O2 sensor. It is absolutely critical that the sensor be functioning correctly (including having the sensor fully warmed up to its operating temperature) to control the A/F mixtures.

951sickness

Bill, In do understand what you are saying here. I my point was that the air/fuel mixture screw was not touched. The fuel quality switch was touched only to see if that would allow the car to get by the test. The switch is now returned to it's original position. Okay so I agree with you that a lean ratio will cause the combustion temps to rise thus increasing the NOx readings. The rational behind ruling out the lean A/F ratio is that the CO reading was at .46% and .28% for the 15 and 25 mph test respectively. Somehow this doesn't indicate a lean mixture. Also, i was told that if there was a lean condition that there would more than likely be higher HC values as well. So in a perfect world, what should the CO readings be? And is it possible to be running dangerously lean and still have HC's in the lower boundary? Right at this point the car is back to the way it came in 88....are you saying there is still a headgasket risk? i never thought I would want to learn about all this crap but it looks like a necessity if one lives in California.

Bill

951sickness,

The smog check program is just an indicator as to the condition of your engine. Kinda like a doctor taking your blood pressure. If it is near or outside the required limits (good running 944's are usually well under the limits), something is not functioning correctly.

A rich turbo engine is not as big a concern as a lean turbo engine. And that has nothing to do with which state you live in.

Waterguy

The local smog facilities provide data on what an "average" car should read at idle and 25 mph (2nd gear.)

CO: 0.02% idle, 0.08% 25 mph
HC: 6 ppm idle, 23 ppm 25 mph
NOx: not measured at idle, 174 ppm 25 mph

Has your idle mixture been adjusted? There is an idle adjustment screw on the AFM. You adjust the mixture to get 0.6 +/- 0.2% CO upstream of the cat. This reading would indeed pass without a cat.