Here in Quebec, it looks like the winter will come sooner than before. I'm getting outside temperatures of 5 degrees during the day (around 40F).

The OTTP tune command an AFR of 11.8 at WOT in my case. During the summer I could read 11.6 with my wideband with my stock catback. Our summer are pretty like many american summers, from 70 to 85F. But now, with the colder air, around 40F during the day, I'm getting 12.2-12.3 instead of 11.6 at WOT!!! That is quite a difference. I installed my new OTTP catback at the same time than the colder days.

So we all know that for an LSJ supercharged setup, 12.2-12.3 is on the too lean side. But what about the colder weather??? Because the air is colder, would this be as safe as before with hotter temp and 11.6? My IAT2s as a results are a lot colder too, around 60F when cruising on the highway.

And because the air is colder, I boost more. I could see like 16-17 PSI before and now its more like 18-18.5 PSI !!!! I'm getting some hesitation from 6200 RPM and up. Something that I didnt experience before. Maybe because I'm boosting more and I should tighten the gap of my spark plugs? They are gapped at 0.34.

Thanks in advance for your opinions

 

Thats leaner than I would be corfortable running on straight pump gas.. (ie, w/o methanol)

 

yeah i would get it retuned

 

....or keep your foot off the gas until spring. High speeds + ice = bad things.

 

I cleaned my spark plugs today, the one for the cylinder #1 and #2 was really carbonized!

From 6200 RPM and up before, I could hear multiples pops from the exhaust, the car was hesitating a lot and since the plugs are cleaned, this is less worst. However I have some hestiations again but this time more at the end of my RPM range. They are gapped at 0.34 now and I have a setup with a 2.7" pulley.

Do you know what happens if the gap of a spark plug is too small, or too large? What happens in both case? I don't know how I should gap them...

 

If they are gapped too far you can get spark blowout, too small and you can predetonate

 

I don't know what to do anymore... they are gapped at 0.32 now and I'm still getting hesitations from 6300 RPM and up. Could this be because I'm too lean at 12.3 of AFR?? My gauge tells me that I have still no knock retard...

 

stop getting on the gas you are going to blow up your car get retuned or keep you foot off of the gas you are to lean

 

It doesn't matter even if this is 40 degrees F outside? Cooler temp so cooler intake charge. I'm not living in Arizona where the temperature is still hot nowadays...

I don't know exactly why I'm running this leaner... I don't know if this is the cooler temp, I don't know if this is because I changed my stock catback for an OTTP 2.5" one (basically a 2.5" Magnaflow)... I'm confused

 

it is because of the colder temps it make the air more dense so the motor is getting more air now then it used to you need to get retuned for the winter then tuned again for summer

 

Get Retuned, colder weather shouldn't affect your afr that much. its always good to have a winter tune and a summer tune, both files will be different.

 

Colder time shouldnt affect my AFR that much, someone said. So do you think that changing a catback can affect the AFR?

And I have to add that anyway, for the winter, I planned to go back to GM Stage 2, their tune is much richer so this will be ok for me.

However, if my catback is the problem and is the source of why my AFR got changed... I'm not sure cuz my AEM wideband gauge wasnt installed for 2 months and during that time I couldnt see my AFR of before I just installed my catback and after + the colder time. But I knew that when my gauge was installed during the beginning of the summer and with my stock catback, the AFR was dead on around 11.6...

So again if this is because of my catback, I should get retuned ANYWAY even for the next summer... ? What do you think guys?

 

If you didn't retune and you had the stock exhaust when you got your tune, then yes you should retune and the exhaust will affect it.

If when you got tuned you had a different size exhaust then you do now and the exhaust you have now is bigger that will affect your afr. Get retuned.

 

Point made earlier get retuned...and no the cat back will in no way have that much effect on your afr...its the colder temperatures, when air is cold it is more dense (more air entering the supercharger) and when its hot its less dense (less air entering the supercharger). now with air being a compressible gas and the supercharger being an air compressor, its common sense after the description above. you need to get re-tuned and get more fuel in the motor or you are going to blow it up. and the hesitation is detonation which is very bad!!!! if you keep beating on it like you are then your going to burn a hole in a piston before you know it.

 

13.8 man.

Feels good man. Feels good.

 

huh?

 

yea cold temps will make it run leaner. the air is more dense, its no different than tuning your car for 7000' elevation then going to sea level, it will run lean.

another option would be to drop to a larger pulley. id guess you have a 2.8, go up to a 2.9 or 3.0, ive heard of guys doing that for winter.

 

Someone says here that a new catback can change the AFR... following people say that it doesn't affect too much the AFR. Now, who is right?

And So I can have detonation even thought I see that the PCM doesnt decrease timing (knock retard on the Interceptor gauge)?

But I think that I'm gonna put back my GM Stage 2 kit tomorrow or next tomorrow. In brief, as soon as I can. The AFR will be for sure really better with the GM Stage 2 tune, during the winter time...

 

new exhaust can change the AFR, I have seen the GMPP exhaust change the AFR by about .2-.3 on stage 2 cars, if the car is tuned properly then the colder air will not affect your AFR. Your fueling is controlled by the MAF in your tune at the top end or from whatever point they command it to start from. In colder weather you will just be moving more air (mass) so if they tuned the MAF through the entire scale then your AFR would remain constant as you would just be higher in the load tables (more boost). This also puts you into different timing as well. Make sure you have no knock, that is what I think is happening to your top end.
I have the same AFR through the spring, summer, and fall which gives me anywhere from 5*C to 35*C.

 

wow thanx for that complete answer Rippin07! That puts me in different timing? This is something I would have to check... I hope that I'm not higher than 18 degrees at WOT because with 91 octane I could get knock while with 93, I was fine. It's quite weird that most of the time, I'm not seeing any knock retard at all when I feel the hestiations up top!

 

Detonation can occur at any time with a boosted car. a bad batch of fuel will do it, to hot of a plug will cause it to preignite, a hot spot in the head will cause it to preignite, don't get me wrong preignition and detonation are two different things but they both can really screw some **** up.