Well I had my car smogged the other day and did not come anywhere close to passing. (infact one of the requirements I was 11x over the legal limit.) I've taken care of the major problem, but I still want to be sure that I will pass. Anyway I'm going back soon I was wondering what the maximum air-fuel ratio I can run for a short period of time without hurting the engine. I'm running a 91 350 TPI and can burn my own chips so I can just pop in the new chip at the smog station. The most it would be run is for like 15 min. Right now I have it set to about 14.9:1. Thanks guys.


Jim

 

Why use duct tape when you can fix it right.


Get a new cat.

 

First, I have a 8 month old random tech high flow cat. It might not be good any more because I've dumped so much gas into from running rich for so long. I would replace it, but the guy that installed it welded it to my headers and my borla cat-back. Even if I could get past that, I don't have the money right now to buy another cat. I have 2 G's in credit card debt that I have to take care of because my tranny took a dump on me in Jan. Ok say that I do get a new cat. I don't have anytime to install it with school and 2 jobs. I can't pay someone to do it because the camaro is my daily driver and I can't have any down time on it. Even if I could pay someone to do it, I have to present proof of reg. to the courts on may 15 and I don't think I could get it shipped here installed, smogged, registered, and get to the courts by the 15th. I need to make sure that I pass because I have failed once already as a gross poluter and I can't afford to fail again because then I would have to take it to a state referee station and then I would never pass.

So please do not give me any more "get a cat" answers I don't have time for that.


Back to my question, I need to make sure that I pass. How much can I safely lean out my mixture only running it for a few minutes. Thanks again.

 

I'm not being an A5S here.... but the cat is the gold..


Ask traxion, his car is fairly wild, and he tried through just prom tuning (risking his engines life) I think tried twice, then came back with a new cat and passed with flying colors that would be impressive for a honda civic.


So, if its that important that you pass this time, prepair to buy a cat.

 

Ok but I have taken care of the main problem the exhaust leak, that should get me close. But I just have to make sure. I'm not trying to pass on just the chip alone. I'm just trying to be on the safe side, hoping that the combination of things will get me past.

 

If it didn't pass with a new cat then your tuning has to be WWWWAAAAAYYYYYY off. Or something else is all crapped up like the cap/rotor...plug wires...scummy oil. Just leaning it out won't do. Too lean will cause detonation and that drives the temp up real fast...too hot and you'll fail the NOx limit.

What are your mods? I passed the IM240 dyno test with no EGR, aftermarket intake and the limits were for a 4.3 V6.

Even after I took the cat off and changed the cam it would still barely pass. I know from the "drive-by" tests they do here.

 

The reason I failed so bad the first time was that there was a huge exhaust leak right next to the O2 sensor causing fresh air to get into the exhaust stream. The O2 sensor sensed raw O2 and dumped massive amounts of fuel into the engine. I took care of that and ran my datamaster program and everything fell into place. Before the BLM's were maxed at 160 almost everywhere. Now most of them aren't above 7% high. I'm tuning that right now to get 128's everywhere, but I just want to be 100% sure I'm going to pass before I take it in again.

 

Ugh... "gross pollutor"... who cares about that bit of industry dumping hazardous waste into the river down the road, this guy's a gross pollutor! Get him!

HC: Make sure your igniton system is in top notch condition... the plug wire ohmage should all check out to be near the same, plugs clean and gapped to spec, distributor cap/rotor clean of carbon deposits.

CO: The air filter should be NEW and clean (aka the "emissions test air filter"!)

NOx: (dyno emissions test?) Make sure your EGR works.

The cat does nuke a few of these. Hot Rod did a test a few years back on a big block 502. They found that while an aftermarket catalytic convertor added about 2 HP, the new factory convertor reduced emissions by more than 3 times!! They said that the newer a cat is, the better it flows, so a new GM cat might add performance over an old 80's original GM cat.

Just something to chew on...

 

Thanks Tom, I'll go over all that before I take it in.

BTW, what did you mean by the "emissions test air filter"? I have K&N filters in there now, should I switch them out with something else?

I have the NOx taken care of I was allowed 1056 ppm and I had like 250, and that was running pretty hot so I'm not to worried about those.

 

99,

So, exactly where did you fail? I'm guessing HCs, due to the "Holy Exhaust System" - (Holy Crap, look at that LEAK!"

Since you have K&Ns over the radiator, just make sure they are cleaned and lightly oiled.

And I hate to jump on the "cat converter bandwagon", but...

It may be very helpful if you could get your hands on a sniffer to verify what you are seeing on your scans. Remember that before, the ECM thought it was seeing good numbers. If you know someone that has an older Sun 920 or 1120, or a newer sniffer, that would work fine for indicating actual AF ratio in the exhaust and HC levels.

If not, take a lesson from your "Holy Exhaust System", and pray...

Incidentally, I'm guessing that you could safely go to 16:1 with a fully functional EGR system - for a short time. Just keep the load low and pedal pressure light so you don't melt any aluminum.

I've had cars with marginal fuel pumps and filters that were running (although making no respectable power) that were probably worse (higher ratios) than that, and had been driven for weeks that way.

 

I failed the worse on CO max was .71% @ 15 mph and .53% @ 25 mph. Mine were around 6.83% and 6.52%. The HC were not that bad 103 and 84 max mine were at 253 and 211. Still a gross poluter in those areas but the CO is what really suprised me. Now that I have fixed it and started tunnig the VE tabels. MY gas milage has improved dramatically. We're talking like 6-8 mpg. Now I don't have to fill up 2x a week

Thanks Vader I really appriciate your straight forward answer. Also thanks to everyone else. Sorry that I got a little agrivated but I have had a difficult week.