Well i went and got dyno today and after the first pull 13.5 A/F to 15.1 A/F?? WTF????? gm stage to is supposed to be 10.6 or something?? what the hell is going? i didn't even do another pull after that. I have the 2.8 pully but that has nothing do to with it. Hell i was reading a 13.5 from the start of the pull which was like 10 psi. WOW so what do i do buy a wideband and if the wideband is correct take that mother ****** back to the dealership??????

 

dont u need to retune when u go to a smaller pulley on the GM tune??

 

Did the dealership but the Stage 2 flash in? Sounds like they didn't flash the computer......

Do you have a 7k redline????

 

Gm stage two is tuned for a 3.06" pulley not a 2.8". Just becuase people do it does not make it right or safe.

 

And if you installed a 2.8 pulley on Stage 2, dealership doesn't even have to do anything for you.

No but that seems retarded lean. Most Stage 2's with 2.8 don't run that lean.

 

Where is the bung installed?

 

Bung installed at end of tailpipe. I know it was correct because it read the exjact A/F for my cavalier. Agian the 2.8 DOESN"T matter. It ran lean even at 3K. The computer is supposed to read pressure-MAF and add gas per pressure correct?

And also i had noticed a huge difference from a 2.9 from the 3.0. Went to the 2.8 yesturday and i didn't see any difference. What am i supposed to boost with a 2.8 with gm performace header and catback

 

the smaller pulley does have something to do with ur afr. the smaller pulley the more air ur sucking in, our cpmouters arent going to compensate for that extra air by itself

 

at the end of your exhaust?

 

Your wideband 02 reading should be 18inches from the cylinder head and before the cat, after a cat or further than 2 feet will give false readings

also if you have a 06 stage 2, its completely stupid from GM in the way that its tuned

if its a tailpipe sniffer the dyno is using those are worthless

 

Its an 07. It was a tail pipe sniffer. It worked perfect in the cavalier. The cav i ran 26 psi at 11.7 af with my wideband and then i look at there computer and it was the exjact same. Somethings fishey with the cobalt. I shouldn't have ran that lean. I thought i read on here 2.8 would be find but it makes ur injector duty cycle way higher which means it compensates for the 1 extra psi. but then dude just told me no it dont. ONly thing i can think is i have an exshaust leak or something. Im going to leave everything the same and buy a wideband and check this problem out. I'll let everyone know!!

 

Never trust a tail pipe sniffer. Put the wideband where it should be.

 

the reason it was lean down low is it wasnt into power enrichment yet, iirc PE starts at 4500rpm. my car does the same thing, its low 13s at WOT at 3000rpm. it hovers around there till i hit around 4500rpm then it drops to low to mid 11s. when i installed my wideband i noticed exactly this and was worried, however more knowledgeble people informed me thats it was normal.

with a 2.8 and 42s its gonna go lean above 500rpm as the injectors are maxed. my 2.9 starts creaping up to the high 11s and hits 12.0 just before it hits the rev limiter.

 

 

^^Agreed. That statement is awfully stupid.

 

a 2.8 on 42s is not maxing them out yet. I was running mid to high 11s with a 2.8 and 42s, and when I added the meth it dropped considerably til I got it retuned.

 

Anything over 90% on IDC is considered unsafe. 42's are not SAFE on 2.8. Can you do it, sure, but how long will you injectors last? Who knows.

 

I was at 87% with my setup.

 

pw>idc

 

My wideband only read .1 point richer then the tail pipe sniffer at my local dyno shop. So not all tail pipe sniffer are unreliable.

 

tailpipe sniffers cant be used if you have a cat. if your catless, they are fine. a local tuning shop has their test cars (they are an rx7 shop) driving around with the wideband wiring going through the hatch, they tune primarily with sniffers.

 

a smaller pulley will make a difference because it produces more boost earlier in the rpm range than the stage 2 pulley and thats what the tune is built around. also the be power enrichment starts 3000 and doesn't go fully enriched to almost 5500.

 

a 2.8" pulley, which provides more airflow has nothing to do with you going leaner on a GMS2 tune that is tuned for a 3.1 pulley.... right...

 

wait. Isn't a 13:1 a/f at wide open throttle considered pretty rich? JW.

 

no. 14.7:1 is the stoichiometric ratio of gasoline, meaning its neither rich or lean. ideal for part throttle and cruising can be from 14.7 to 17:1. under heavy throttle, gasoline will make more power when richer than stoich, ideal for a naturaly aspirated engine is 12.5-13.5:1, and a boosted engine is 11.5 to 12.0. those are just general theories, every engine is different.