Hey guys,

This is my first supercharged vehicle. I understand the boost gauge should read 0 at idle when you start the engine. Mine is -9.5PSI. It also feels no more powerful than my PoS 2.0l jetta, naturally asperated. When i punch it to redline, it goes JUST over 0 PSI

Bypass valve actuator moves freely. What else could this be?

 

At idle it should read around -18 to -20 for vac.

 

1.) Welcome to the site.

2.) Boost at Idle should be in Vacuum ... roughly -20

3.) What boost gauge to you have ?

4.) check out your vacuum lines, you probably have a hole in one of them.

 

Sounds like a massive leak somewhere. If I had to guess, air is getting in after the throttle body causing the less than expected vacuum at idle, and getting out at the same place causing your lack of boost.

 

Vac leak, or the solenoid for the BPV could be shot too.

 

If its actually reading -9.5psi then he's at -19inHg, but if he's reading the gauge in vacuum its listed as -inHg not -psi

 

At idle an engine is pulling negative pressure because the throttle body is closed and the engine is still sucking in air.

 

Yes the - is normal at idle, should be about -20, the other issue? I agree with the leak or vac line hole so ur gauge not reading right. Ss sc doesn't really feel very powerful stock, iv driven one, wasn't impressed, but that was coming from my sstc on tune lol

 

stock isnt anything impressive, pulley down, bad ass tune, 7k redline and a 40 roll .. now thats whats up lol ... add some e85 to the mix then its just pure sex .. instant powwaaaa!!!

 

Its stock, but its not actually in PSI, its in kPa (im canadian) so its reading -65 kPa. The manual for the car says it should be 0 at idle... Maybe i misunderstood that.

Thanks for all the quick replies by the way. Glad i signed up.

 

At -65kPa you're right where you should be for idle, idk why they would list it as 0kPa for idle. How much kPa are you getting when you WOT first or second gear? (Have a passenger watch the gauge, also the gauge is electronic not mechanical)

 

when the car is "off" the gauge should go to "0" ... as soon as you start it should be in the vacuum (negative).

-65kPa = -19hg ... aka your golden Pony Boy.

What is the boost at WOT ?

are you reading my mind ???? lmao

im typing and then i see your post right after i hit enter lmao

 

At WOT it goesJUST over 0 kPa, maybe 10 kPa MAX

 

So if -65 kPa is normal for idle, how high should it go at around 4500 rpm?


Also, what could cause vacuum to be normal, but boost to be nill?

If there were a leak, i would imagine the vac reading would be less too? I dont actually hear a leak, but its hard to say. Any troubleshooting steps i can try?

Thanks again for your help with this!

 

Hmmm a leaky supercharger gasket possibly .


You may want tondo some searching around the forum and see what others have done. At wot on the stock pulley i think u shild b at 12.5 psi

 

Are you just looking at it in first gear?

 

Nope, in 2nd and 3rd too. I floor it, and it stops steady at 20 kPs (2.9 PSI) and won't go any further.

I've been driving a vw gti VR6 for the past couple years, and this cobalt is supposed to beat it from 0-60 by about 2 seconds, but at this rate a friggin camry could beat me.

 

would u like to buy my 30 psi boost gauge i have? kpa is gay, im from canada its the lnf one, idk if it plugs into the lsj though. i changed out for a defi, so i got this sitting around.

 

what would be the best way to identify this? i think i might have a leaking gasket. besides pulling the blower off cause i got no shop space atm