Hey Guys,

Just got my GM Stage 2 Installed like 2-3 weeks ago and Noticed that I'm only Boosting Like a MAX of 13psi, Now I can remember back when I put my AEM Intake Air Box MOD on Instead of Boosting at the Normal Stock 12psi I was then MAXING out at like 10psi, So for some reason the Intake Reduced my Boost by a little Bit and hence now it's only at 13psi after I installed my GM Stage 2 Kit, I read on this Site that I should be Boosting at 15psi After the Stage 2 installation, Should I be Concerned? Thanks in Advance...

 

Wait, Hold on...I Cant Focus with Everyone Posting at the same Time! PLEASE Dont Everyone Answer all at once! Lol. Does ANY ONE have ANY Input on this Issue or is it a NON-ISSUE and thats why No Ones Posting Anything? Thanks

 

Please search around, this topic has been covered many, many times before...

 

The stage 2 tune is what gives you the 15 psi,not the smaller pulley or the injectors.they are needed because of the 15 psi.
So maybe you didnt get the tune or your boost gauge is inaccurate!

 

Yeah, gm stg 2 is something like a 3.06 pulley and 42.5lb injectors fyi,,(sig)

 

Uhh, there is no set psi for a stage kit...so...the tune is what increases the boost and the pulley is needed because of it? explain that..

 

I'm barely hitting 15psi at the top of third on a 2.9 pulley. The stage 2 kit didn't give me much boost over stock. If you want more boost use a smaller pulley. A better tune is a good idea with a smaller pulley

^ lol I wanna hear this explanation too!

 

I saw 14psi on GM S2, 16psi on a 2.8. So many factors determine boost from your exhaust to where you live to the temperature.

 

What he said. The tune has nothing to do with psi. Only the boost reduction in first gear limits boost but only in first gear

 

This is not a turbo car....

The pulley is what increases the boost!

This.

 

Don't people normally see lower boost in summer anyways, due to higher temps?

 

YEp .... I used to lose 1 psi when it was hot and humind




There are a bunch of things that could lower the boost on GMS2 ...... but the pulley is what controls how many PSI the blower is capable of producing .....not the tune . The pulley ups the RPM of the blower there by raising the PSI.

The pcm and injectors are there to supply the extra fuel to keep the AFR's in check after adding more PSI .....so it doesn't go lean . Full exhaust (good thing) .... humid hot air , a shitty boost guage and elevation can all drop boost to some degree . Or not buying the stage 2 belt can cause belt slip so it wont boost as high either .

 

Yeah, Thats what I thought, But basically what I'm gathering is its Not an Issue and just because I have the same GM Stage 2 that others have because of a Variety of other factors it may vary Greatly, Thanks for Everyones Help!

 

get a 2.9 pulley if you want a bit more boost. I'm running one on the stage 2 tune and it's been fine. some people say it's a bad idea, some people say it's perfectly fine. it's all up to the person

 

Actually now that I think about it, I was running 13 psi with the stage 2 kit before I bought the 2.9 so I'd say it's normal

 

Don't worry so much about "boost" man....

Worry about efficiency, and making safe power.

It's good that you noticed changes in your boost levels, but like others said many factors will alter the reading.

 

I just wanted to make sure that I didnt have a Problem with the Supercharger, But Now I Understand how much the Boost Levels can Vary, So Thanks for all your Help!

 

how do you even know what your full boosting anyway? what i consider full boost is like 5krpm in 2nd
and at that point it would be too unsafe to look at the boost gauge

 

Only if your not a good driver would looking at the boost gauge be bad. Plus you should be able to see it in your pereferals. Lol

 

To clarify the above post:
Stock tune gives you 12 psi correct me if Im wrong.
Stage 2 tune give you a increase to 15 psi
If you were to run a stock tune on stage 2 pulley you will only see 12 psi as well because the tune is limited to it and the rest would be dead headed into recirc.
Im pretty sure you guys are mixing up volume and pressure as well
If the tune doesnt allow it you wont get more just ask the guy when he has a 2.9 pulley and only gets 5 psi because of a bad Maf sensor (psi restricted to save the motor from damage with limp mode)even though by your theories the guy should be getting 18 or more!!!

 

the GM Stage 1 kit is only a tune and new injectors. it doesn't up the boost at all.

GM Stage 2 is a pulley, Belt, Injectors and a tune.

The tune does not control how much boost you get after first gear. First gear has a boost reduction parameter in the tune to keep torque low as to not put as much stress on first gear as the others.

the theories we have put out there are that with a smaller pulley comes more boost due to the fact that you are spinning the supercharger faster thus compressing and forcing more air at the engine.

So in your theory I should only be running 12 psi on my gm stage 2 even with my 2.9 pulley?

 

And just another little piece of info, The bypass actuator valve is a vacuum reference type controller. if it sees increased vacuum due to the throttle body being closed it will open and recirculate the air so that there isn't a chance of a lean mixture in the combustion chambers.

I'm pretty sure I'm not entirely wrong here but I have been fooled before! lol

( The above posts were not intended to come across as being a a$$ or anything)

 

Yes the stock tune will open the bypass at 12.5 psi ..... but even if you do the boost bypass mod and take the control of the bypass away from the PCM ...... it wont boost any higher on the stock pulley.

The stage 1 and stage 2 tune are the same ..... so when someone goes stage 1 .....in your theory they should see 15 psi ..... they dont. The stage 1 to stage 2 upgrade is a 3.06" pulley and smaller belt ..... thats when you see 15 psi.