So I've had my 2006 Cobalt SS/SC for over 2 years now, (Bought it used completely stock) and was normally boosting about 13-15psi since I had the ZZP stage 2 kit installed until just recently I've only been able to boost 3 PSI!!!!!

This barely started happening after my alternator went out (which doesnt make sense at all) I got the Alternator replaced with a brand new one and ever since then, it hasnt been boosting right.
I had the 3.1 pulley on it (since its my daily driver) but today, i swapped it out and tried the 2.9pulley on it and even after switching and trying both pulleys out, I'VE STILL ONLY BEEN ABLE TO HIT 3PSI!!!

I'm pretty sure it's not a boost leak since it doesnt hit full boost (15psi) and drop down. It strictly hits 3psi everytime i punch it, and no more boost than that. Bosst stayed the same even after switching both pulleys

I can only think of it being the alternator pulley but i'm not sure if they come in smaller sizes since they look completely identical.
Any info will help out. Thanks.

 

I kno alternator pulleys do come in different sizes for other car alternators ive never changed a cobalt alternator pulley but im sure u can find a smaller pulley for it, there a bitxh to get off someti,es

 

Yea that's what I'm hoping it is. Because even if i swap out from my 3.1 to my 2.9 pulley it still only boosts 3psi which makes driving this car boring now =/
Yea and I haven't heard of anywhere to find an alternator pulley either. I need HELP!!

 

sounds like a bad Supercharger bypass valve tbh. The pulley that connects the alternator runs with the supercharger also iirc. do you have any belt slack?

 

Its not the alternator. It sounds like you either need a new bypass valve solenoid or a new bypass valve.

Solenoid: Ecotec LSJ Supercharger Bypass Valve Solenoid 1997244 - Crate Engine Depot

Valve: Cobalt & Ion ---> ZZ Performance

 

i want to put a 2.8 pulley on my stock car for more boost. how much more power will this produce? and do i need to do any upgrades to make the car hold up to the extra boost? (the car produces 17 psi right now) thanks

 

People have gone down to 2.5in pulley with stock internals just fine, you just need to reduce the heat if you want it to be reliable. Plus i believe you will need a retune.

 

how do i reduce heat?

 

Maybe when the alternator went out, it caused the belt to slide on the alternator pulley or crankshaft weakening/damaging the belt, and now the belt is slideing on the supercharger pulley? Or crankshaft? Hows your AC?

 

1. you wont boost nothing over 12.5 on a stock tune, doesn't matter if you put on a 2.6 pulley or 2.9. you should go back to the main LSJ page and use the search button because your asking questions that have been answered a billion times. dont thread jack its not kind

to the OP its probably your bpv, just replace it and youll be good imo

 

The belt seems fine. I checked it out when we swapped pulleys and it didn't seem to have any damage on it.
The A/C works perfect.
It's just weird how it started happening til after the alternator was changed.
I want to look into the BPV but is there a certain way to check if there's anything wrong with it? As in any certain signs that I'd be able to tell if there is something wrong with it?

 

Bypass solenoid guaranteed!

 

Unless theres a problem with your car. If there is the BBV will blow off all the pressure to save the car.

3800s do this with their superchargers too.

Any codes?

 

You should seriously up the boost. I run 23psi...

 

Dang I am dealing with this problem right now! OP did you figure this out? I also started to experience this after an alternator change.

 

lol this thread is def winning

Edit: and ppl wonder why they blow their motors