Hi

Can anyone tell me what the stock AF ratios should be for my 98 Camaro:

Idle
partial throttle
WOT

I assume partial throttle should be 14.7 +/- .5 (14.2 to 15.2)?

Any help appreciated. My car failed the sniffer test and I plan to put it on a dyno to see what the AF is. I need a baseline for comparision.

Thanks JA

 

should be stoich, it may spike to the +/- values you listed, but the average production will remain pretty accurately at stoich. Just b/c you are running stoich, doesn't mean you will pass emissions. Stoich is the cleanest burn, but if you are using more fuel (such as most might after modifying the vehicle), you are still dumping more total emissions. Let's take a car with cats and without, even here, you take away they cats, and you are not using "that" much more fuel, but the amount of emissions released greatly increases. All the while, your PCM is managing fuel to remain at stoich.

 

get to know someone at a shop...

what mods have you done?

 

See signature for bone stock WOT A/F ratio.

 

Hi

98 Camarao A4
K&N induction
180stat
Mac headers
Mac cat y pipe
Borla catback

I know the car passed befor the Mac headers and Y pipe whent on. After I installed the headers and y pipe it failed. The HC and NOx are way up passed the limits.

I took it to a certified aircare shop here in my area. They scanned the **** out of it a few days and I did a few road tests. They said they checked the O2s, filters, EGR, ignition coils, plugs, wires, rich condition, timing, etc and found nothing wrong. In fact it runs great. They are trained at OBD II diagnostics and use a Tech 2 or Snapon scanner.

They did not use an exhaust analyser on the cats because they are brand new and they did not want to drill holes. However, they did measure the temperature before and after the cats and found it to be the same. In their opinion the cats are not liting off. I do not know if this is a valid check, but it seems to make sense.

So I am thinking 2 possible causes: shitty cats and/or incorrect A/F from the header install.

It is not easy to fix as I am in Canada and there are no established LS1 shops in my area. I found a shop that will put Magnaflo cats (EPA/OBD II certified) on for me, but they say they cannot save the Mac y pipe. Building a new Y pipe will cost $500 to $600. After that there is still no guarantee it will pass.

After that if I tune it, it means buying HP Tuners ($500 US = $650 CND). I found a local dyno shop but they do not have software or a commercial license. They will charge $200/hr for dyno time. I assume a dyno tune takes about 1/2 day so its big dollars. And even then no guarantees. ALso, they do not specialize in LS1 so I assune they have a learning curve. They may screw it up even more.

After all this, I could end up still having to put the stock exhaust back on. I am just woundering if I should just bite the bullet and put the stock exhaust back on now.

Any input appreciated.

Thanks JA

PS

I was thinking about installing an additional single down stream 3" cat immediately behind the Y pipe, where the slip joint is to the Borla system. This would give me an extra cat just for the testing, which I would remove after and put the slip joint back in. Does anyone know if this would set off a SES code?

 

Mine failed on emmisions, I thourgh tit was dodgy cats, so I installed new cats but in the process I got high flow cats and complete stainless sytem to add to my Corsa Cat back system.

The car still failed emisoins, they said it was 1.11 lambda, all other gases were good. I was trying to figure out why did it fail. I gave up with them after a couple of retests, plugging in the laptop during the test to ritchen or lean up the AFR, just couldn't get it passed. Went to another garage, they said I have a small exhaust leak near the rear corsa system, the exhaust gases were sucking in air and making their sensor system read too lean, so its failed, we blocked up these leaks and all was fine. Hope its only just a matter of exhaust leaks in your case. The car was running fine, as the leaks were right near the rear pipes.

 

Hi

My exhaust doese have a small leak that creates more of a rattle and sort of a hum. It must be quite small. I will get it fixed. Thanks

JA

 

did you perhaps hit the sensor on the drivers side by the headers and not notice it?..forget what its called

 

Hi

I think you mean the O2 sensors. They are new and undamaged. Unfortunately it is regulated with govenment drive in centers. No chance of getting past any other way.

JA