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Having lived in Illinois almost all my life I have never had to take my car in for any sort of emissions testing. Well I did today because I now live in the wonderful state of California. My results are here:
I'm pretty sure I need a new cat and o2 sensor. I already have the o2 sensor in my possession. Any recommendations on a cat? And any suggestions on anything else I should look it. Vacuum lines are new as of last summer. I also have another afm off another car if I need to swap that. Car is an 85/2. My Illinois registration is up on the 30th so I really need to get this taken care of.
You guys rule and I look forward to one day being able to contribute more to the forum. Thanks a bunch!
Yes you are running very rich, which normally would mean that your NOx number would be lower, but if the cat is bad then it is high as here.
In CA you have to use a CA-approved cat.
Walker and Magnaflow (among others) make such a part for the 944, it is a universal weld-in replacement. But you HAVE TO USE the specific part number catalyst that CA says for your car.
It is possible to tune the car to the point you can pass without a cat. (I have done this on my car.) I'm not saying I recommend this, but saying it to point out that you have other problems beyond just a bad cat. It's good to see you looking at more than just the cat, since it is just one piece of the problem. It looks like only NOx is classified as GP, the other 2 are just high.
Originally Posted by V2Rocket
Yes you are running very rich, which normally would mean that your NOx number would be lower, but if the cat is bad then it is high as here.
I'm not an expert, but without a cat I know the NOx goes up when you lean it out (low HC) and down when you go rich (high HC). With a cat, the cat will be less efficient converting NOx when the car is lean, helping NOx, go high when lean, but should be very efficient if the car is rich? Is this why you say high NOx & HC indicate a bad cat? A working cat will reduce HC, NOx & CO. Since all 3 are high I could see the cat being bad. I wouldn't expect the NOx to be so high while running rich, just because of a bad cat. What else causes high NOx?
I'm not an expert, but without a cat I know the NOx goes up when you lean it out (low HC) and down when you go rich (high HC). With a cat, the cat will be less efficient converting NOx when the car is lean, helping NOx, go high when lean, but should be very efficient if the car is rich? Is this why you say high NOx & HC indicate a bad cat? A working cat will reduce HC, NOx & CO. Since all 3 are high I could see the cat being bad. I wouldn't expect the NOx to be so high while running rich, just because of a bad cat. What else causes high NOx?
The O2% is an indicator of cat efficiency...it should be very low.
To process HC/CO the cat needs free O2 to do its reaction.
But after the cat there shouldn't be much O2 left because free O2 was used up to convert the HC/CO into H2O/CO2.
Thanks guys. So new cat o2 sensor should get me on the right path, which i have kinda figured all along. I have checked out the walker and that seems like my best bet. I will recheck for vac leaks too. Any other suggestions?
Looking at those numbers, there's no amount of tuning or adjustments you can do that will have it pass.
1. new cat, make sure it is stamped with CARB EO# D193-117. Interestingly enough, all of Magnaflow's universal weld-in cats for 944/951 from 2.25 to 3.0" has the same number.
2. adjust FQS-switch to -3% fuel and -2.77 ignition position. The ignition-retard will lower combustion-temps and reduce NOx. Less fuel will lower HC as well.
3. dump in 1/2-gal of denatured-alcohol or E85 in 1/4-tank gas. The alcohols carry along extra O2 and reduces emissions
4. when going to smog-shop, run the car HARD at full-throttle for about 30-seconds to heat up the catalytic (I just go WOT with left-foot on brake). Then when pulling in, leave car idling, do not turn it off. Best to make an appointment for non-busy time so you won't have to wait too long and have the cat cool off.
Looking at those numbers, there's no amount of tuning or adjustments you can do that will have it pass.
That doesn't make sense. If you get everything working right it could be made to pass with a bad or no cat. My point has just been to not expect a cat to fix everything, fix the other problems, too. Which the OP sounds like he is trying to do.
Originally Posted by JacRyann
1. new cat, make sure it is stamped with CARB EO# D193-117. Interestingly enough, all of Magnaflow's universal weld-in cats for 944/951 from 2.25 to 3.0" has the same number.
2. adjust FQS-switch to -3% fuel and -2.77 ignition position. The ignition-retard will lower combustion-temps and reduce NOx. Less fuel will lower HC as well.
3. dump in 1/2-gal of denatured-alcohol or E85 in 1/4-tank gas. The alcohols carry along extra O2 and reduces emissions
4. when going to smog-shop, run the car HARD at full-throttle for about 30-seconds to heat up the catalytic (I just go WOT with left-foot on brake). Then when pulling in, leave car idling, do not turn it off. Best to make an appointment for non-busy time so you won't have to wait too long and have the cat cool off.
Great suggestions. I used about 4 gal of e-85 in a full tank when I got my car to pass without a cat. In addition to what you said it also leans it out some while helping it to burn cooler, which helps both HC & NOx.
That doesn't make sense. If you get everything working right it could be made to pass with a bad or no cat. My point has just been to not expect a cat to fix everything, fix the other problems, too. Which the OP sounds like he is trying to do.
Great suggestions. I used about 4 gal of e-85 in a full tank when I got my car to pass without a cat. In addition to what you said it also leans it out some while helping it to burn cooler, which helps both HC & NOx.
Actually leaning mixtures results in hotter combustion and higher NOx. It's the ignition-retard that results in cooler combustion and lower NOx.
This is California Enhanced Area emissions standards. Look at the actual limit numbers. Then compare it to yours. And compare the actual measured emissions. The high NOx numbers indicate that the cat is not working. The oxygen is stripped first from the NOx and is stored. That's then used to combust with excess HC to convert to H20 & CO2.
High NOx and high HC is a sign that the cat is bad. This is due to the criss-cross of HC vs. NOx; you can tune down one and the other will go up; no way to do both. That's where the cat comes in. Low CO2 is also sign of bad cat, which should be in the 14.5-15.0% range for a good working cat. Also O2% should be practically zero with a good cat as it will use all available O2 to combust with HC.
Here's my car 6-years ago with failing cat, it barely passed CA Enhanced Area standards.
Then I installed new cat before the next test 4-years ago. Nothing else was replaced on the car other than the cat. Note the significant decrease in both HC and NOx, which cannot be done with any kind of tuning (fuel adjustments). Also free-O2 coming out tailpipe decreased significantly showing the cat using all oxygen for converting HC.
Again compare the actual measured HC, CO and NOx of these tests with your car.
It isn't possible to directly compare CO & CA emissions because they are measured differently, but Rogue, who is one of the most respected tuners here has said that the way they do it in CO it is harder to pass than even CA.
I understand that many changes have the criss-cross effect, but it is possible to lower all of those numbers. I've seen it done. I'm not saying the OP should go through to the extremes I did to pass without a cat, but you make absolute statements, like "can't" that just aren't true. They can all be lowered at the same time through tuning. It's been done. Not saying you'd want to use the tune for anything but emissions, but it works fine.
I agree the cat is bad, and again, my only point is that from the numbers the OP has more wrong than just the cat.
It isn't possible to directly compare CO & CA emissions because they are measured differently, but Rogue, who is one of the most respected tuners here has said that the way they do it in CO it is harder to pass than even CA.
I understand that many changes have the criss-cross effect, but it is possible to lower all of those numbers. I've seen it done. I'm not saying the OP should go through to the extremes I did to pass without a cat, but you make absolute statements, like "can't" that just aren't true. They can all be lowered at the same time through tuning. It's been done. Not saying you'd want to use the tune for anything but emissions, but it works fine.
I agree the cat is bad, and again, my only point is that from the numbers the OP has more wrong than just the cat.
One way to simplify it...
"You cannot pass California Smog test without a Cat, period."
As in,
You have to have a cat installed, and the appropriate cat for that matter, to even start the test (visual inspection).
I have never said he shouldn't have a cat. (FYI, we have visual too, mine is just gutted.) Why would you just throw a cat on a car that has something wrong and leave it at that? The cat will just get worn out faster if you don't fix the other problems. Plus if you are too far off from the ideal AFR even a good cat will be unable to keep up on either HC or NOx.
I'm sorry if I've confused people by mentioning no cat. I was just using that as a reference point to show that our cars can be pretty clean even before the exhaust goes through the cat. I do NOT recommend trying to pass emissions without a cat. When we did it, it was more of an experiment to see how far we could go with just changing the tune and adding some e85. In the end all numbers were very good. My everyday tune wouldn't pass current emissions without a cat (passed in '08 on old standards), but wouldn't be close to GP either.
I have never said he shouldn't have a cat. (FYI, we have visual too, mine is just gutted.) Why would you just throw a cat on a car that has something wrong and leave it at that? The cat will just get worn out faster if you don't fix the other problems. Plus if you are too far off from the ideal AFR even a good cat will be unable to keep up on either HC or NOx.
I'm sorry if I've confused people by mentioning no cat. I was just using that as a reference point to show that our cars can be pretty clean even before the exhaust goes through the cat. I do NOT recommend trying to pass emissions without a cat. When we did it, it was more of an experiment to see how far we could go with just changing the tune and adding some e85. In the end all numbers were very good. My everyday tune wouldn't pass current emissions without a cat (passed in '08 on old standards), but wouldn't be close to GP either.
Please post some actual numbers of before and after your "tuning".
If you want a direct fit CARB legal cat, look at DEC part # PO82603. Available on PartsGeek for $425 shipped, look around online and you can get like a $20 coupon also. I bought a DEC made cat for my '88 911 for smog as well. The welds are not pretty but for the price (911 one was $300) and only needing it every 2 years i was happy with it.
Also i suggest you have them do a test only next time you bring it in. They will test the car as normal, but not submit the results. You may get flagged and have to bring the car to a STAR center where it does not get any easier to get the car to pass.
I am replacing the cat and o2 sensor once the cat gets here. I ordered the walker cat. Once I get those in I guess ill try again and see where I am at? Anyway to know otherwise?
04-26-2016, 05:56 AM
Gross polluter Cali smog
