ok so i'm about to tear my hair out. I have been running on the stock supercharger with a 2.6 and 2.7 switching it on and off. Thats not the point though. With the 2.7 on my boost starts to drop off around 6000rpm's (i redline at 7250). It spike about 16.5 psi then if i take it to redline goes to around 9 psi. It sounds like the belts slipping. So long story short i got a belt tensioner, the didnt work, replace the gaskets, got a new stage 2 belt, that didn't work. Took apart the supercharger, everything was fine. It was still slipping or sounding like it was over spinning. The whining at high rpm's was like not a costant whine, you could hear it slipping. SO, i buy an entirely new supercharger and put that on with a 2.7 pulley today. guess what? not it barely builds boost at all, spiking at only 14 psi. i dont hit 10 psi untlil like 4300 rpms now and its slow as ****. With the first supercharger on the 2.7 pulley i hit way more psi much quicker. so knowing all that what could it be? also my car is throwing no codes and im tuned for a 2.7 by area47.

 

Other then the SC pulley are all the other pulleys stock?

GM tensioner, or some knock off tensioner?

a 2.7 with a stage 2 belt and everything else stock should be fine with no slipping.

Kevin

 

Are you on a Stage 2 Belt? Just curious.

I was going to say it was tune related since it was loosing boost, but then you mentioned who you were tuned by and my guess is its not that..

It may be MAF related?

Someone else should chime in as well

 

Sounds like an issue with the bypass valve actually

 

is your intercooler pump running? parameters are set to reduce boost if your IAT2's get too high..it will cut boost to 60-80% if your IATs are above 200*.

 

yea bypass valve check for any leak in the vaccum lines or just put a vacumm pump on it and test it or replace it.... also try removing the vacumm line from the the valve and plug it with a bolt so it wont open and see how much booooooost u get

 

What are your mods..

Take a can of Carb Cleaner that you can get for 5 bucks at Auto Zone.. Start your car.. Start Spraying it on your vacuum/boost lines and on gaskets.. See if you have a leak!

 

Yea it is either a bad bypass valve or your intercooler pump is dead.

 

Just unplug the vacume line connecting the plastic wastegate to the boost bypass valve and place a vacume cap on the port that the vacume line was attached to on the bypass valve leave the plastic waste gate open to atmosphere. Take it for a spin you'll be very happy!!!!!! https://www.cobaltss.net/forums/problems-service-maintenance-69/boost-flutter-4000rpms-above-100299/

 

my intercooler pump is fine. the supercharger makes a terrible noise that isn't constant when im at high rpms. ill try the boost bypass valve mod but it did this with both superchargers remember.
also remember that the first supercharger built boost fine then just dropped off, the new supercharger is not building enough boost.
my mods:
60lb injectors
meth kit
full vibrant header back exhaust
k&n intake
my tensioner is zzp's old one they came out with, its on the middle of 3 settings.

 

Talk to your tuner about it?

 

it was just uploaded on my car via hpt

 

boost bypass mod!

 

do you guys really think its the boost bypass valve thats the problem? how is it actually not functioning properly? can someone explain that to me? i dont think my IC pump is dead bc it bubbles when the car is on and if i take off the cap it almost overflows. what would taking the vacuum line off to though?

 

rofl im having almost the exact same issue... only my supercharger also sounds like a tin can with pebbles in it. im sure you cant hear that over your exhaust if you are have the same issue.

i am reverting back to stock and taking it in to get serviced. GM warranty ftw if they come through

my boost wont go over 10psi and i have that same fluttering blower whine you are speaking of at WOT but at light throttle and 5psi is makes this racket thats hard to explain. does some one know what this is o was thinking coupler, gears or bearing.

swappin pulleys tonight, do you think i should put the stock injectors back on and reflash... or press my luck and leave the 60's in? i am tuned for meth too so hopefully the bigger pulley will make WOT rich enough so i can safely take off the meth without having them blow the motor as soon as they step on it.

 

the noise is a non-issue here.

what i'm not seeing is what are you running for a tune here?

if the allowed and S/S map tables are not done correctly, you'll run into a boost wall at 16.2 psi, the computer will then bleed of the boost.

 

its not the blower in my case i dont think. ive used 2 different superchargers. the first one builds boost fine and then sounds like **** and loses boost above 6 grand and the second one doesn't build it fast enough. why does it sound like my s/c belt is slipping?

ok i cant remember the guys name in maryland but he is the OP of the thread MARYLANDERS IM CALLING YOU OUT. he sold hit cobalt and got a g35. his cobalt was blue and had full exhaust and a 2.7. area47 sent him a basic tune for a 2.7 to upload on his car. he just did the same for me. ever since then though i havent been able to see full boost. im really not sure if my IC pump is shot, im nervous now that it may be bc i cant think of anything else.

 

Try the boost bypass mod and see what happens. It's a old mod that isnt needed anymore but it will tell you if you are having boost bypass issues. Thats my best guess. I'd put the old SC back on aswell.

Maybe it's all in the tune? Talk to your tuner

 

ok, so if this boost bypass mod works then what does that mean? should i leave it like that? what does it mean if it doesnt work?

 

once again, if the SC MAP tables are not done correctly, you'll have this issue.

if it works, its your tune causing the issue.

 

^what should i do next if it isn't the tune? and if it works is it ok to drive around on?

 

What does the boost bypass mod do and why is it outdated?

 

the boost bypass mod WORKED! so does that mean its my tune then? can i drive around with the boost bypass mod?

 

I wouldn't but you can i guess. Get your tune tables fixed!

It's a really old mod that helped SC's drop pullies and use a MAF-T to help"Tune" for the added boost. It's not needed because we can tune the LSJ now for real with HPT.

 

Got it but I am on a Stage II tune and I have noticed that I do not hold boost either. In first or second gear after a certain rpm it just drops off. Thought a supercharger was supposed to given continuous boost.