2.8 pulley question ???????????
 

I had a 2.8 pulley given to me and was wondering if anyone has ran that on the stage 2 set up and if they have had any problems.

I ran a 2.85 with the GM S2 tune with no issues until the weather turned cold and then went back up to a 3.0

what made you switch back to the 3.0 in the cold?

if you are talking about GM Stage 2, do not run a 2.8 pulley on it. you will max out the injectors which can potentially cause other serious problems. anything under a 2.9 is not smart to run on a GM Stage 2 tune. Hell, I wouldnt even run anything under a 2.95 on GM Stage 2, but people have, and will cont. to tell you it's safe, when in all reality its not.

If you did run the 2.8, and by some chance nothing bad happens, your car will prob actually be slower then a GM Stage 2 car running the 3.06" pulley. This will be due to the Stage tune pulling massive amounts of timing in the upper rpms from running too small of a pulley. Not to mention the increased amount of heat the 2.8 will produce.

read a couple horror stories so just took the more cautious approach

those would be some old threads so I wouldn't know where to look exactly

Injectors.....






























will hate you.

It is safe. Yes the injectors will be maxxed out but the gms2 tune is also on the rich side. So technically u are safe until u start to go lean. Now if u are running around in freezing weather then u may get a lean condition. Cooling mods are highly recommended.

I am running gms2 with timing bumped to 20deg, 2.8, intake, header, dp, ls4 tb and I definitely noticed a difference when the 2.8 was added. I drive my car hard and redline it every day. I live in the heat of fl with no cooling mods which is not recommened.

You are obviously running a modified GM Stg2 tune. Putting a 2.8" pulley on a GM Stg 2 tune (no modifications) is a very bad idea. 42 lb/hr injectors can safely support a 2.8" pulley on a good custom tune, but on the GM 42's & GM Stg 2 tune you will max the injectors and run into unsafe lean conditions up top.

OP if you want to run a 2.8" pulley get a custom tune, or a tune from ZZP/OTTP. Don't cheap out, and put that pulley on just because you have it.

I'm running 2.85" with 42# injectors (Same size as GM stage 2) without any problems. I'm still a little rich too. If my injectors were maxed out, my dyno would show a major lean out at high power but it doesn't. But ya, I have a custom tune though too.

check out post #8 ;)

Even on a custom tune IDC's are through the roof.

Not safe.

while it's rare, I've seen some peoples pulse widths on a "good" custom tune while running a 2.8. They were close to being maxed, but no worse then how close the injector pulse widths are to being maxed while running the GM Stg 2 tune & 3.06 pulley.

but you are right, it really isn't a good idea. I wouldn't try it, and I hope the OP is smart enough not to try it either.

^^ I agree with this guy (G85). I put a 2.8 on mine and scanned it just to check it out. IDC's were hit 90 at approx 5500 rpms at WOT. I didn't even run it up to 7 grand because I was scared. So I ran the 2.8 for a while, no problems just didn't run it up over 5500-6000.

all i did to the GMS2 tune was highlight the cells and change them till it ramped up to 20 deg. No fueling was ever touched just the timing in the upper rpms. I do not have a wide band. Anyone with hpt could do what I did without ever starting the car. I did have it at 23 deg with the 3" but bumped it down for the 2.8.

My IDC's were 122% with GM Stage 2 and 2.9 at 7 grand. I would rev to 7300 so I could only imagine what the other 300 rpms did.

Injectors are technically 'maxed' out at 80% IDC's IIRC. But in any event, I'll definitely not work my injectors as hard as I used to.

And I would not recommend going to a 2.8 on GM Stage 2. 2.9 is even scary. Custom tunes reduce the stress on the injectors because the car isn't commanding a pig rich tune. But if you ever scan your car with HPT with 2.8 on GM Stage 2, you'll see.

It is not "safe" to run a 2.8 on stage 2 tune.

I have a 2.95" pulley running 11.4 AFR. In the summer I hit 90% IDC, in the winter I am maxing the injectors at 110% IDC.

Yes the stage 2 tune is rich. Just because it is rich does not mean it is a good idea to max out the injectors.

Discussion pretty much has solidly said, no 2.8" on the GMS2 tune!

.......................but looking for more solid opinions on the 2.85"/GM 42's/custom tune.

my car has had the 71.9mm (2.8) pully on gm stage 2 for 98k miles...

mine had a 2.85" pulley on a stage 2 tune for 6 years before i went with 60lb injectors and a 2.7. never an issue.

Lol guys thread from 2009. Don't think any of the original posters are around to continue the discussion.

yeah but i found this searching so someone else might.

My car with a 2.8 on 42's is at 90% IDC commanding 11.8 AFR. This is at about 80F degrees ambient. This winter it will run out of injector just like it did on the stock pulley last year when temps dropped below 50*, so I'll be switching to 60's or 80's soon

what does it do in the winter back timing down when it leans out?

Colder, denser air increases the oxygen content for a given volume of air so it needs more fuel. That and intake temps are low so it should allow full ignition timing which will also lean it out.

i get that.

my question was if the knock sensor pulls a bunch of timing. i was under the impression you were watching it since you knew what your injector % was