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Low boost on a 3.4 setup

GTP2188

GTP2188

New member
I am having a problem with my supercharger just recently only boosting up to a max of 5psi. I have the 3.4 setup. I have checked the BBV and the boost bypass solenoid and they seem to be working fine. I have replaced all vacuum connectors and checked the lines. A little while ago i found the vacuum line coming from the a/c control burned in half and spliced it into the accessory line that run between the BBV output line and the brake booster line. Do not think that has anything to do with it. It gets about -18 vacuum at idle. What could be wrong?
 


First off, what all mods do you have??? If you have headers, that will drop quite a bit of boost, along with a ported blower/LIM/heads. Also rocker/a cam will drop boost.
 
Hrm....you should have higher boost than 5PSI then. Do you have a new downpipe in?? because if not, then you're probably knocking, and the computer is having to retard the timing, and not letting you achieve full boost.
 
no new downpipe but it has been fine for the 2 1/2 years that i have been running it and it would get about 7-9psi, then at shift it would hit 11psi it just recently started doing this
 


Hmm....have you ever scanned your car for knock?? because the U-bend in the downpipe is a major restriction....

It may sound silly, but if your air filter is clogged, or the cat is starting to crap out, that could do it.

For the longest I couldnt figure out why my car was acting up under boost, and not reaching full boost. I knocked the filter out and about 2 pounds of sand came out, solved my boost problem.

Also, listen to FFDP, headers rock, and scanning your car is the smartest thing you can do.
 
I do not have a place to scan for knock around here or the program, i know its not the air filter, and i'm also on college kid budget so no money for stuff like the headers right now, idk about the cat it could be that but idk, the car also has 198K could the rotors be going bad in the supercharger and not letting full boost be acheived
 
really only 2 ways for the rotors to go bad. Either the coating will flake off, and your motor will ingest it, or catastrophically, in which case, you'll know. If the Cat. is stock, that could very well be it, or you can check to see if the throttle body is sealed well against the S/C.
 
So the cat could have gotten stopped up and yes its factory and original if not that any other ideas
 
Just checked the throttle body and its tight the air filter a little dirty but not enough to stop it up.
 


Yeah, thats a lot of miles for a stock catalytic, does the car bog down under hard acceleration? or does it just not simply create the boost it used to. Also, how are you measuring the boost?
 
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Probably has the stock U-Bend too. Way to go L67killer...read the link in my signature. Take off the pulley now, OR...put more mods on it...seriously.
 
it does not bog down just lost the boost i used to have i will get to the other mods but for right now all i am trying to do is get to the boost back and i will worry about the other stuff later i will probably go do the u-bend delete this weekend and then could give a look inside the cat. just needing ideas!
 
Yeah, hes not kidding, I was really weary of putting my 3.4 pulley on, and only did it after headers....
Is the car handling different? Because loosing that much boost, it should feel like a totally different animal.

However you're reading your boost levels could be the problem. If its a boost gauge, there might be a crimp in a line, or something minor like that if it's still running the same.
 


I am using a autometer gauge and i have checked the line and yes i know the factory one only uses blocks but it will not fill up on about 6 to 7 blocks. It does not handle any different just kinda has factory or worse acceleration
 
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Yeah Yeah blue i get it but i'm not looking for your comments of what im doing wrong i get it and i know so you are not helping the issue whatsoever!!!
 
Oh I'm not? Ok...telling you putting on a stock pulley isn't helping? Telling you you probably need to address your spark plugs because they might be smashed isn't helping? I've toasted plenty of motors jeeves...and if you don't like my comments...tough sh1t? Its the internet...hate me I don't care...but I bet 20 to 1 I'll figure out your problem before you do...could be a clogged converter too...and probably because you still have the ENTIRE stock exhaust...is childish.
 
no those first two are not helping the issue of not getting enough boost. I have been planning on it, but I am a full time student and do not a job right now to get these things. i am going to do the ubend delete this weekend, then i can look in the cat and see how it looks. Well maybe you will figure it out and i hope you do but you do not have to be rude about it, and its lasted for 80k like this so it can go a few more miles w/o it, so i will do it just not this immediate second. but back to the issue at hand of not getting enough boost need more ideas
 
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