would u recommend this combo??? If not what would be doable??

 

I do it, it's bad. I'm not going to change what my pulley size though, I'll run the risk of maxing my injectors out for the tiny bit of time that im at 6k plus rpms.

 

ya some1 told me about u. how much? i was leaning towards a 2.9. Now the one thats on the car now is the intense one. I just bought this car and i should be getting this car this week. But would like to replace the pulley. Intense sells the 2.9 for $60

 

Hey Nate, do your pulley's have any markings on them? I'm looking for something that can be easily mistaken for a GM stg 2 pulley.

 

The Cobalt Addiction pulley is 2.79" and says on the front 77.9mm. It is made to look very much like the stage two pulley

 

but the whole point is not to run lower than a 2.85, so the CA 2.79 won't work.

 

^^^ exactly. If they made a 2.9 with the right markings I'd be all over it like stink on Oprah.

 

Had my 2.9" that I got from you installed yesterday, Nate. Looks great and no problems with the install. Getting the stage reflash today.

To the original poster, I would stick with a 2.9" to be on the safe side.

 

in my opinion, a 2.8" pulley with 42.5lb injectors should be perfectly fine. just make sure you have some way to get it tuned properly. otherwise you will run like crap. i had a 2.85" pulley with those injectors and ran fine with room to improve.

 

now when i replace the pulley, i have no need to retune my car, right? just want to make sure

 

I talked to CA today and they said its perfectly fine to run their 2.79 pulley on the stage 2 as long as your not going to run the **** out of it. They said 60# injectors was overkill especially if its a daily driver.

 

did u get my email???

 

please don't swap pulleys and just expect it to run....especially with a 2.8" pulley. you WILL need to retune.

 

I've been running Nate's 2.9 for a while now. And i just got HPtuned by BCP now it runs even better.

 

ya well some1 told me that i do not need to retune car if i replace the pulley. that i only need to retune it if i replace injectors. U dont need to criticize my question, since im new with all this!!!!!

 

Ok....point taken. My apologies. Let me explain it a little better. If you replace the pulley with a smaller one, this means essentially your supercharger is forcing more air into your motor per revolution. To compensate for this added air, your PCM will increase the duty cycle of the injector so the AFR (air to fuel ratio) inside the combustion chamber matches what GM specifies. Theoretically (I have not seen or heard any definate information), but theoretically the stock injectors can accomodate enough fuel to accomplish this. However, this will most likely max out the injectors. I personally don't think the stock injectors can handle this type of abuse unless you drive it like a grandma. Any hard acceleration would cause some issues I'm sure. I also believe that since the PCM will be compensating A LOT for the added air, the car will run in limp mode. I am not 100% sure on that though. The reason you heard that you don't have to retune when you replace the pulley is because when running slightly smaller pulleys (like maybe a 3.0" or 3.1"), the PCM can compensate and the injectors are not maxed out.

However, when you change injectors, this is why you need to retune. The PCM still thinks you have the stock injectors which flow at a certain rate. Your new injectors flow at a higher rate. The PCM uses percentages. If, say, at WOT (these are just made up numbers) your injectors are running at 50% and flow say 550 cc's, then approx 275 cc would go through. Say now your new injectors are 750 cc and your PCM sets your injectors at 50% again at WOT, you are not at 375 cc. This is an extra 100 cc of fuel! This is why you need to retune.

In summary, if you swap your stock pulley for a 2.8", then your car may run, but chances are it will run like poop and perhaps go into limp mode, or reduced engine power, whatever its called. With a proper retune, you may be able to run your stock injectors, but I would advise against it. You definately want to get the 2.8" pulley with 42.5lb/hr injectors and the new plug'n'play harness for them. If you want to tune yourself, just pick up a MAF-T and a Wideband. Otherwise, find someone who can tune it for you. Good luck and happy modding.

 

what was your IDC?

 

IDC???

 

let me clarify this 1st, right now i currently have a 2.8 with 42.5 injectors. Its been tuned by INTENSE. Im thinking about putting a 2.9 pulley in, instead of the 2.8 to be on the safe side, since ive been hearing lots of probs with the 2.8 with 42.5 injectors. So since my cars been tuned already with the 2.8 if i put on the 2.9 do i haveta retune it?

 

Sure a 2.8 and a 42# is a fine combo. I am running it now with no problems.

 

really? ive been hearing that i either need to get 60lb injectors or downgrade to the 2.9 pulley. so all that is a bunch of hocus pocus??

 

It's not just about 2.8 / 42.5 # injectors, but also what other mods are on the car.

Someone with just 2.8 and injectors will probably run fine without any problems. Take someone else with that plus, intake, gutted exhaust, ported blower, etc. and you'll be more likely to run into problems. Also, air density (affected by temperature, elevation, etc) will play a large part as well. If you're really worried, either stick with the 3.0 and 42.5, or find a way to datalog your car and see exactly how much you're stressing your injectors.

 

Yah thats what I thought, your car seemed like it ran fine but you dont really know. IDC is injector duty cycle which is expressed in a percentage. This is the reason why most guys are upgrading to 60#ers because the 42.5#ers are to stressed with smaller pullies.

 

my IDC is typically high 90's at the top end, but my AFR is in low 12's. I depends on how you have your PCM setup to control the fueling, typically with Piston Protection and Cat Over temp *ON* your PCM will command 10.8 AFR and so 42# are WIDE open and your IDC is 100+

Sure you can go for 60's but IMO you don't need to if you plan to stick to a 2.8.

BTW I have a header back 3 inch exhaust and K&N filter.

 

As far as i was told by the intense guys was the 2.8 would work with the 42.5 from the stage kit but they recommended reducing the 7000 redline back to 6500 rpm to be safe... that was with the GM stage 1 tune.... Now if you run a custom HP tune thats a different story.

I went with there advise and got the 2.9 but i am retuning soon and will switch to a 2.8 and keep my 7k redline