Low Boost HELP!!!

[1toofastlt1]

I have a 97 z28 with a vortech v1. I just Did a base line tune on my car and I took it out to finaly kick in some boost. I punch it down and I get 1 maybe 1.5 psi. I double checked everything and i think i have it right but any ideas on what might be happening please let me know. http://images.ibsrv.net/ibsrv/res/src:www.ls1tech.com/get/forums/images/smilies/LS1Tech/gr_banghead.gifhttp://images.ibsrv.net/ibsrv/res/src:www.ls1tech.com/get/forums/images/smilies2/icon_confused.gif

[BLOWNDFIZ]

One thing I can think of is severe belt slippage. Check around the pulleys for belt dust. Your idler/tensioner should have really really tight tension applied to the blower belt.

Make sure your bypass valve is installed correctly, make sure all the hose connections are over the discharge tube on the blower. I have heard of the inlet ducting colapsing and in turn not allowing air to enter the blower but I doubt that is the case.

[1toofastlt1]

OK I had my dad in the passanger seat holding the lap top and he said he thought he could hear the belt slipping. Also im using proscan for my logging and my MAP says at idle I have 5.5 psi. i know thats not right. The car runs really good. just no boost

[BLOWNDFIZ]

OK I had my dad in the passanger seat holding the lap top and he said he thought he could hear the belt slipping. Also im using proscan for my logging and my MAP says at idle I have 5.5 psi. i know thats not right. The car runs really good. just no boost

I'd hook up a good ole mechanical boost gauge and really see if you are getting boost. I would not trust the scan tool if it's showing boost at idle.

Also, are you sure the MAP value is in psi? I believe most scan tools read %MAP and even then at idle I believe that is should be 0 and 100 at WOT. Someone else jump in here if I'm wrong.

[1toofastlt1]

i'm using a mechanical boost guage right now. at hot idle it shows -15 vac

[BLOWNDFIZ]

OK cool, I was confused by the dad with a loptop statement...:D

[1toofastlt1]

o sorry ha ha.

[1toofastlt1]

I will check the belt asap. I bet thats it

[1toofastlt1]

the tentioner was messed up so i replaced that and it doesn't sound like the belt is slipping anymore but i still only get 2 psi. do you think i just need a smaller pulley on the blower?

[Z28pr0jekt]

possibly you're bleeding off boost somewhere? check for vacuum leaks

[Nasty93]

I dont think they even have a 2psi pulley, gotta be going somewhere

[BLOWNDFIZ]

Check the bypass valve again. Make sure the vacuum line is connected to it. Make sure all the hose connections are actually connected. If the boost is not escaping then I'd say the head unit needs inspected. Time to trade it in on a T or YSi...:metal:

[1toofastlt1]

i have a 6 inch crank pulley i think that was the problem. 3.33 was making me 2 psi so i got a 2.95 and im making about 4 psi. WTF! do i need a smaller supercharger pulley or do i get a bigger crank pulley?

[popo8]

Out of curiosity, what heads do you have on your car, and do you have any work done to them?

I lost 2 pounds of boost when I had head work done before. It was explained to me like this:

If you blow through a straw you will build more pressure than if you blow through a garden hose.....

[BLOWNDFIZ]

i have a 6 inch crank pulley i think that was the problem. 3.33 was making me 2 psi so i got a 2.95 and im making about 4 psi. WTF! do i need a smaller supercharger pulley or do i get a bigger crank pulley?

You should be making 8-10 with a 6", 2.95" combo.

You make more boost going with a bigger crank and/or smaller blower. The problem is the 6" is the only Vortech pulley available unless you go with a custom pulley from ASP or something. That is what I did.

[1toofastlt1]

my heads are stock, I guess i will just run the 4 psi and be happy with it till i can build the motor. It fast enough i guess, i got a ticket for speeding today :(

[popo8]

Doh!!! tickets SUCK! I hardly ever write any....

[1toofastlt1]

Doh!!! tickets SUCK! I hardly ever write any....
i was going with the flow of traffic too. its not like i was zooming around. he also got me for no from plate.