Almost passed smog test, how to reduce HC in tuning?
03-09-2006, 05:14 PM
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Almost passed smog test, how to reduce HC in tuning? Yet another question for the experts...
I almost passed the smog check, but failed the HC @ 25mph (I had 50ppm vs. 37 max allowed).
I did all the usual tricks (got it really hot, etc), and it came pretty close.
So my questions:
1) What impact does ignition timing have on HC? If I back out 6 degrees across the board, will that help or hurt?
2) Both the 15mph and 25mph test were done at 1700rpm (due to my torque converter). I could theoretially rig the shifting tables so that the the 25mph test was at 2500rpm. Since I have a cam, would that help? Would having the torque converter lock up during the test help?
Thanks,
Terry
I almost passed the smog check, but failed the HC @ 25mph (I had 50ppm vs. 37 max allowed).
I did all the usual tricks (got it really hot, etc), and it came pretty close.
So my questions:
1) What impact does ignition timing have on HC? If I back out 6 degrees across the board, will that help or hurt?
2) Both the 15mph and 25mph test were done at 1700rpm (due to my torque converter). I could theoretially rig the shifting tables so that the the 25mph test was at 2500rpm. Since I have a cam, would that help? Would having the torque converter lock up during the test help?
Thanks,
Terry
03-09-2006, 06:40 PM
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Oh yeah it failed the visual all over the place, they noticed the AFR heads, the LS6 PVC system, the MSD wires, and everything except the headers. It is a Corvette though, so headers are harder to see.
03-09-2006, 07:10 PM
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Oh yeah it failed the visual all over the place, they noticed the AFR heads, the LS6 PVC system, the MSD wires, and everything except the headers. It is a Corvette though, so headers are harder to see.
MSD wires and LS6 PCV are visual fail...?
PS. The PCM controls the fuel mix so there is no way to lean it.
03-10-2006, 09:05 AM
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You can try advancing the spark at the points where its too much.
You can also consider looking at the 02 switchpoints at the closed loop mode that corresponds to the airflow at the point it failed. (ie) Set the switchpoints at a lower mv
Let us know how you go.
You can also consider looking at the 02 switchpoints at the closed loop mode that corresponds to the airflow at the point it failed. (ie) Set the switchpoints at a lower mv
Let us know how you go.
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03-10-2006, 04:26 PM
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I agree with ringram, advance the ignition.
I'm blown away that the tech noticed your aftermarket heads and PCV. Take it somewhere else next time.
Post back your results please.
I'm blown away that the tech noticed your aftermarket heads and PCV. Take it somewhere else next time.
Post back your results please.
03-11-2006, 07:18 PM
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It's just a 232 114ls comp cam. The AFR heads should have an EO, but I didn't have it with me, and the car failed emissions anyway. To be honest I have no idea if MSD wires are legal or not, but its easy to sway back to stock. 
CA is a real bitch!
Anyway, someone else told me to retard the timing. Which is it?
CA is a real bitch!Anyway, someone else told me to retard the timing. Which is it?
03-13-2006, 12:57 PM
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Find a cool smog guy, go early or late (when there aren't a ton of people) and give him some money to let you try out a few things on the dyno. After you figure it out drive to another place and take the test.
03-13-2006, 06:23 PM
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Well first thing i have to ask is does ca have the put $300 in it and you pass any way rule i know ohio did in that case just show them the recipts for you injectors and spark plugs and wires and that should do it. If you dont have that rule then use hp tunners to tune your ltfts to be a little lean (this may cause nox to go up so dont over do it) as for spark i wouldent take any out i might add a little but taking it away will raise co and you dont want that.
03-13-2006, 10:20 PM
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Originally Posted by Terry Burger
It's just a 232 114ls comp cam. The AFR heads should have an EO, but I didn't have it with me, and the car failed emissions anyway. To be honest I have no idea if MSD wires are legal or not, but its easy to sway back to stock. CA is a real bitch!
Anyway, someone else told me to retard the timing. Which is it?
CA is a real bitch!Anyway, someone else told me to retard the timing. Which is it?
03-14-2006, 09:33 AM
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Retarding the timing will probably make it worse. I'd go the other way.
If the HC's are being caused by misfires, then you have a chance of helping by cleaning up the plugs and running a tighter gap <.040".
Make sure you air injection is going into the CAT during the test. That will burn up more HC's as well.
If you're not running 87 octane in it for the emissions test, then definately do that! it will have the effect similar to increasing your spark advance and your HC's should go down.
If the HC's are being caused by misfires, then you have a chance of helping by cleaning up the plugs and running a tighter gap <.040".
Make sure you air injection is going into the CAT during the test. That will burn up more HC's as well.
If you're not running 87 octane in it for the emissions test, then definately do that! it will have the effect similar to increasing your spark advance and your HC's should go down.
03-14-2006, 11:51 AM
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Quick update: I pulled 4 degrees of timing out, and ran a 5% alky mix, and it barely passed the emissions test. Unfortunatly since I had reset my PCM none of the readiness tests were ready, and I need to bring back a Carb EO # for the AFR heads. This guy didn't seem to care about the PCV or anything else. I'll reupdate this next week when those stupid PCM tests run. It seems taking out timing helps HC (consistant with research I did on google).
T
T
03-14-2006, 12:25 PM
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IMO the only way taking advance away could help is if you were really over-advanced in the first place... which is unlikely.
Over-advance would not only ping, but supposedly raise the NOX out of range.
I've tried alcohol too, but made my HC much worse due to increased misfires, so my experience is pretty much opposite what you're getting/seeing right now.
Over-advance would not only ping, but supposedly raise the NOX out of range.
I've tried alcohol too, but made my HC much worse due to increased misfires, so my experience is pretty much opposite what you're getting/seeing right now.