This car is my daily driver, not a track car, so I certainly wouldn't be doing back to back pulls.

I am more concerned about A/F ratio and running lean and going boom. I would likely keep the stage 2: 3.067 inch pulley and run it in the winter and colder months and use the slightly smaller pulley in the summer and warmer months, unless it would be safe to keep the smaller pulley on all year long.

That being said, I want as much performance enhancement as possible from the small decrease in pulley size without endangering my combustion chambers from dangerously lean conditions.

So. How low can I go? I would be comfortable with a 2.9 or maybe even a 2.85 from the research that I have done. I feel like a 2.8 is not out of the question but I feel it's very close to dangerous.

What do you all think?

 

I wouldnt run anything past 2.99 im running a custom tune with gm stage 2 pulley (3.06) and stage 2 injectors(42s) and im already maxing them.

 

Yes & no....

The 76mm pulley will give you a decent bump in power (nothing crazy) over the 77.9mm pulley, but it is noticeable, and recommended to be ok straight from GM. I've tested pulleys from 77.9mm-70mm with my current GMR setup, and I never felt a huge bump between any of them (just a little more low end torque). I can't really compare my car though, because my blower was the biggest differece in power change, and pulley swaps seemed minimal to me, haha. I currently run the 76mm GMR S3 pulley, and make nice power and torque with it (while maintaining cool IAT2's).

 

Are there any vendors that sell the GM stage 3 pulley (2.99") other than CED who charges $115?

I see smoothflow let's you specify the size for $55, or ZZP has a 2.9" GM stage pulley upgrade, but I think ZZP is a 2.90" pulley?

 

Yeah zzp is 2.90, either order smoothflow or check part section for a used stage 3 pully

 

Yes.

Nate at Smoothflow will make you any pulley size you can think of.

 

Look, I'm no tuner either. Whatever you guys decide to do, though, here is something I've been saying for years:

There is what can be done to a motor, and what SHOULD be done.

Whatever you all decide to do, make sure you get it looked at by a GOOD tuner who knows what they are looking at and what they are doing. If they tell you your injectors are over duty cycle, I don't care what any knuckle head on here tells you; you should probably get bigger injectors. If they tell you your IAT's are high, you should probably get some cooling modification done.

Another way to look at it is this: A cell phone may work for a little while after getting water on it, but it's only a matter of time until it soaks in and the thing shuts down.

Your car might still pull like a frieght train without proper cooling. It may run problem free without the correct size injectors or a proper tune and running lean as hell...

...but for how long?

In the end, going cheap gets very expensive.

 

Post your logs where you rev'd it out to 7,000 rpms.

Back to back pulls really doesn't have anything to do with it. Its all about maxing the injectors at high RPMS and running lean.

Good advise. I did the same thing.

GM 42# injectors, stock GMS2 Pulley, custom tune.


99% IDC at 7k.

 

If you don't have sufficient cooling mods, even the stock pulley can give heat soak running at the track. With the proper cooling mods, you can run the 3 inch pulley from GM stage 3 safely. Exhaust flow becomes important with smaller pullies. The GM stage 3 tune and pulley is aggressive enough that it pulls timing if you don't have at least 93 octane fuel. Look at the dyno thread for the modifications necessary to put down your desired power. Also realize that dyno queens only need to do one pull, and high numbers don't always mean reproducible performance during long runs at a road course. Millions of dollars of GM money tell us what works best, so follow their build book for the most reliable performance. Watch my dyno video on YouTube where my car put down nearly 260 hp to the wheels 3 pulls in a row with no rest to cool between pulls. My car runs strong, fast, and reliably because I followed the recommendations of GM's research.

 

Same here.

 

Yup. Good old GM. They know best!

lol

 

Never said they know best.... but some of the info/parts they do provide actually work. Imagine that!

 

They did a good job on the GMS3 PCM. There is no reason why all LSJ PCM shouldn't be like that.

 

Agreed!

 

Now that you have the GMS3 PCM, are you still using the GMS2 pulley?

 

No. But I would if I was running GMS2 42# injectors.

Right now I am running a TVS with a 2.7" pulley and E85.

Last spring I did some injector/pulley testing just for fun. Its a good read if you got a few minuets.

Stock Injectors Stock Pulley Stock Tune and all the bolt-ons - Saturn ION RedLine Forums

 

I am likely ordering a pulley from Nate @ Smoothflow Pulleys.

Any reason I would want a polished finish over the machine finish? Is it specifically for appearance?

Just not sure if I want to order a 76mm (2.992 in) or a 75mm (2.953 in) pulley.. I am hesitating now because I feel like my injectors are already working quite hard with the stage 2 pulley.

What do you all think?

 

You will notice hardly any (if at all) difference between the two....

Go with the 76mm.

The finish is just your choice polished or machined. Has no affect on performance.

 

revival!!!! i have zzp stage 2 3.1 pully 42 ib injectors... looks like 2.9 is really the safest you can go with what i have (+ a tune)... correct? i have a custom tune and am running super rich (zzp cai is next on the list)... any input greatly appreciated

 

This thread is redic old.

Research people!!! All the answers about pulley size and injectors has been discussed on this site many times over.