Well I've got stage 2 and its seems pretty obvious that a 2.9 is safe with stage 2. Has ANYONE had a problem resulting from putting a 2.9 pulley on? I'm sceptical about putting it on.

Problems anyone???

 

I have 2.9. 15 psi comes at 4 grand instead of 4.5 But Still not boosting over 15. Maybe limited i dunno.

 

your injectors will go static, but go ahead and do it sense everyone else seems to think it is that great

 

I put a 2.9 and now I am going for 60lb injectors. My car never ran good when I put my 2.9 and vibrant header so one of the two made my car slower than before.

 

 

when i had the 2.9 my idc was at 98 at6800 rpms

 

80% is the standard capacity for most injectors. Your pid for idc's could be off to

 

with the 2.8 my idc was at 109 %

 

this useless post has been brought to you in part by.... a typical cobaltss member

does anyone have solid information like logs from hpt that show a 2.9 is not good on stage 2? i'm tired of seeing these posts and people saying "yes" or "no" without backing it up.

 

alot depends on where you live

 

see this is an example of a helpful post where he has posted his idc with a 2.8 pulley without trying to make anyone look stupid

 

depends on your elevation for the question to be answered but at sea level you are screwed



your beloved stage 2 and a 2.9" pulley 115% idc's and is that 5* of knock i see oh my.

 

yea with the 2.8 i have 6 degree's of knock with stock plugs hehe

 

i have multiple logs from different cars that prove the 42# injectors were overworked with just the stage 2 pulley and gm tune. nothing else done except the stage 2 and i was seeing 20msec pulsewidths, 110% idc. with a 2.9" i was in the 130% range and 22msec pw. it would likely be the death of my car had i kept running it.

high altitudes and low air density places are the only times people can get away with smaller pulleys on stage 2.

 

yea but i drive my car like a girl..i maybe take jump on it 2 times a month and when i do i shift at 6k,,,i never get any races its weak around where i live

 

well that spoils my fun.... i have my 2.9 on the way but now i'm having second thoughts... althought i'm at 800 feet above sea level that doesn't make me feel much beter

although from other posts people have said you can safely lean out the rich gm tune and you will no longer be maxing out the idc's.. i don't know how true that is.. but if it is true....

then who is flying to winnipeg to tune me?

 

if your injectors are maxed, a smaller pulley will only work them even harder. the leaner afr resulting from smaller pulleys is a result of the injectors not being able to supply the demanded fuel. my afr was dangerously lean with the 2.9". i saw no gains in my 1/4 mile times or trap speeds.

 

so basically i would be better off with at 3" pulley with 42# injectors? rather than a 2.9

 

This is good info

What about compared to the gm stage 3 pulley sized at 76mm or 2.99? I realize it's not a big size difference from the gm stage 2 pulley but was curious since I have all three.

 

on a side note... what, if anything, (besides hp tuners) can measure injector duty cycle? can an interceptor?

 

damn, so i bought the pulley for nothing lol

 

the gm stage 3 pulley is basically a 3" pulley that you are paying over $100 for. .01" isnt going to do a thing.

the interceptor will not display your IDC%. an interceptor will display injector pulsewidth, which is actually a better indicator than IDC in most cases for measuring injector performance. dont concern yourself too much with the IDC%. all it does is provide a calculation based on pulsewidth, engine load, rpm, etc. HPTuners isnt the most accurate calculation of IDC. 19msec - 20msec is the pulsewidth where an injector is completely static (lost control of itself, cannot provide any more fuel, packing up its **** and going home)

yes.

 

Thanks Bika

 

thanks!, i appreciate your help. I've been thinking of getting an interceptor and thats one more reason in favour of it.

everybodies car is different so it's probably best if i get one and see what my own pulse widths are before i put on the 2.9 i already bought lol.

 

Hey guys, I found this post that contains a formula for converting the injector pulsewidth into IDC. This should be useful for those with the interceptor and wanting to figure out IDC's.

https://www.cobaltss.net/forums/show...dth#post644739

Edit: even easier.. more searching revealed this website: http://www.stealth316.com/2-calc-idc.htm
just plug in the rpm and ipw in ms and it spits out your injector duty cycle %. I'm definitely going to try this out with my different sized pulleys. Thanks again for the good info!