I just put a 75mm on my car from a 77.9mm. But however when I gas it I don't see a increase in boost. It still boosts as a 77.9mm pulley. I'm on 42llbs injectors stock cooling mods and gm tune. why am I not seeing more boost?

 

I see you have a gutted cat but are you still with stock cat back and every car is different there is someone on here with a answer

 

O n yea I got a gutted cat. And yes I still have stock cat back

 

Come on somebody. Its a huge lsj community here. I know somebody knows somethin

 

Belt slip? What belt are you running, stage2? Does the car feel any stronger ? You could do the boost bypass mod just to check that it's not something in the bypass solenoid.

 

Yea I'm running the stage 2 belt. Belt slip? I don't think so. I'd feel that right. Belt slip would feel like I wasn't goin anyway right or like the car was in neutral. I don't know if the car feels faster or not. It does but the gauge doesn't read more boost. And what's the boost bypass mod? What does the bypass soleinold have to do with boost?

 

How much boost is it reading?

 

14.5-15psi

 

I'm running a 77.9, Stage 2 and getting 16.

I'd always heard of being careful dropping pulleys on 42's. Bout all I can tell you.

 

But I have a huge thread out talkin about it and everyone told me I'd be ok with the pulley size I dropped to

 

either gm tuned it lower cuz of the injector size or its defenitly the gutted cat..if u gutted the cat after dropping pullies then u freed up backpressure. so really ur running a more efficient 15 psi then someone running same 17 psi on a stock exhaust sysem...boost doensnt equal power...the more boost the more pressure the more pressure equals more heat in the system. i put on the ott stage 1 with 2.8 and was hitting 20 psi so i cut out the cat ran a straight pipe and but a v2 header on to relive pressure now i run 17 psi and its much more powerful. gutting the cat is ur reason im almost 100 percent sure. iwouldnt worry about saying i have 22 lbs of boost on race day when its as efficent as 18 on a good exhaust setup.. ur 15 psi is probably equal to 17 but safer. plus its cooler smoking another cobalt running more boost. there like damn son how did u beat me.

 

I totally understand what you are talkin about. I gutted my cat when i had only a intake because on my bros speed3 at the time. He clogged his cat and i said i wasnt goin thru that so i gutted mine. That was way before i went stage 2 and way before i dropped to a 75mm. I mean the car feels faster but that could be my mind is playing tricks on me since i know i got a smaller pulley. But it boosts the same as stage2 did

 

Seen this post and i am having the same.."problem" i guess you could call it. Was running a 2.9 with intake, vibrant header/dp/exhaust and hi flow cat. 15-16psi

I recently swapped another member my stock sc with his (its mildly ported) and i changed to a 2.8 pulley. So now i have 2.8 and ported sc with my previous intake/exhaust set up. Car feels slighly more powerful but i get about the same boost readings 15.5-16psi

Could this be my problem as well?

 

if you gutted the cat at the same time you switched pulley's thats why you're not seeing an increase

 

I gutted my cat before I swapped pulleys. I gutted my cat only while I had a intake before I went stage 2

This most likely is your problem as well. Listen we gonna help eachother out. Ok do you have any cooling mods? (Meth front mount etc) I think we boosting lower becuase of heat soak maybe? Get on it before you car gets near reg temps. Like almost as soon as you start your car ans see if you boost higher! I did that yesterday and I was at like 16.5 psi but once my car got hot it went back down normal to the 14.5 and felt much slower also. So I'm thinking its heatv soak. Do that and post what happens

 

If you do the Boost bypass mod, it basically takes away all computer control over boost, it keeps the bypass closed no matter what. The reason i suggested it was to help diagnose if it's the computer bleeding off boost for some reason....... or rule it out as not the culprit.

Gutting you cat can drop boost PSI too, but the car should feel stronger , not slower.

 

O ok well I'm goin to do that soon haven't done it yet. So questions what to do if the bypass works? Then what. What to do if the bypass doesn't work?

 

ported blower lowers boost levels. remember boost is only a measure of pressure, not airflow

 

It does feel stronger but idk but as stated I gutted the cat way before I swapped pulleys

 

I have 2.8, ported sc, injen intake, vibrant header, downpipe with hi flow cat, and exhaust, h/e, stu mod.

I think i was boosting slightly lower due to warmer weather round my area lately (i.e. heat soak in 98* weather) and also due to the fact that i have a ported sc now. I guess i havent gotten used to it yet, im a believer now more psi doesnt always equal more power. Thank you Blazin.

On a side note just for reassurance on my part i went out round midnight the other night and made a few passes, it was much cooler last nite in my area, i saw .5 to almost 1 full psi of more boost. Didnt do nuttin just ran at night. 17psi

I also tried the boost bypass mod, didnt do nuttin for me.
i also tried moving the hose on the other side (front side) of the boost bypass solenoid to the bottom male fitting instead of the top. I actually saw less boost when i did this. Just seen it and figured id try it.

 

Ok this isn't ur prob. U good

 

I hope so..thanks

Was wondering have you or anyone else here tried to move the hose on the top front side of the bypass valve to the bottom fitting instead of it being on the top and what exactly does it or is it supposed to do? I know the bottom fitting on mine had like this little foam crap just barely pushed in and around it, kinda covering it and 2 hooks on either side of it. what is the bottom fitting for and why it it just left open like that?

I figured this was the bleeder fitting for the "excess" boost pressure above 15psi but not sure.

 

Do you have HP T? if so I can help

 

No i dont..sadly enough. I have bin considerin gettin a tune tho and some 60s just need the dough and good local tuner but i can wait.

 

Ok so I did the boost bypass and no increase in boost. So what's next?