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SolaraGuy.com • View topic - Did you loose some boost with headers?
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Did you loose some boost with headers?

PostPosted: Tue May 18, 2010 1:56 pm
by usoff89
Ok, so the headers and full 3inch exhaust are on the car. The guage read 4psi on the dot before, and now only reads 3psi. I do feel a jump in performance, even with lower boost. Anybody else have the samething happen (hopefully)?

Also I saw on the pullyboys web site, they have a 4.5psi pully. Could the stock fuel system handle that pully? I would think it could, just beacuse it ran at 4psi before. I'm not ready to raise the boost to much just yet, and thought maybe that pully would ge me back round 4-4.5psi safley.

So what do you guys think?

Re: Did you loose some boost with headers?

PostPosted: Tue May 18, 2010 2:33 pm
by PASolara
usoff89 wrote:Ok, so the headers and full 3inch exhaust are on the car. The guage read 4psi on the dot before, and now only reads 3psi. I do feel a jump in performance, even with lower boost. Anybody else have the samething happen (hopefully)?

Also I saw on the pullyboys web site, they have a 4.5psi pully. Could the stock fuel system handle that pully? I would think it could, just beacuse it ran at 4psi before. I'm not ready to raise the boost to much just yet, and thought maybe that pully would ge me back round 4-4.5psi safley.

So what do you guys think?



Did you have the 3inch exhaust before the headers? Or did you do it all at once?

Re: Did you loose some boost with headers?

PostPosted: Tue May 18, 2010 2:37 pm
by 1gSE
Not that I have any experience with the s/c, but i have seen on other forums that when you open up the intake (after the sc) or exhaust side, you'll lose some boost. Not to say you actually lose any amount of air its flowing, there's just less resistance

Re: Did you loose some boost with headers?

PostPosted: Tue May 18, 2010 6:14 pm
by usoff89
Yes, I did the headers and the 3inch exhaust at once.

Anybody have any comments on the smaller pully idea? I still want to stay in the safe range for the stock fuel system.

Re: Did you loose some boost with headers?

PostPosted: Tue May 18, 2010 8:05 pm
by ToyoSolV6
the stock fuel system would hold up fine with 4.5psi of boost. its when you raise it higher than 5psi is where you need fuel mods.

Re: Did you loose some boost with headers?

PostPosted: Wed May 19, 2010 4:58 pm
by usoff89
ok, thanks.

Re: Did you loose some boost with headers?

PostPosted: Thu Jun 03, 2010 9:05 am
by PASolara
usoff89 wrote:Ok, so the headers and full 3inch exhaust are on the car. The guage read 4psi on the dot before, and now only reads 3psi. I do feel a jump in performance, even with lower boost. Anybody else have the samething happen (hopefully)?

Also I saw on the pullyboys web site, they have a 4.5psi pully. Could the stock fuel system handle that pully? I would think it could, just beacuse it ran at 4psi before. I'm not ready to raise the boost to much just yet, and thought maybe that pully would ge me back round 4-4.5psi safley.

So what do you guys think?


As far as loosing boost from headers that is common. I have modified a lot of Grand Prix's (GTP’s) and some other L67 and L32 cars. When adding headers to those cars you lose anywhere from 2-5 PSI depending on other mods.

Re: Did you loose some boost with headers?

PostPosted: Thu Jun 03, 2010 9:39 am
by usoff89
The 4.5psi pulley is on the car, and running great. I took it to the track last night and I ran a 14.8-14.9 all night. The car ran a constant 15-15.1 with the stock pulley at 3psi.

mods so far:
headers and 3inch exhaust
ingen intake
TB spacer
lite weight crank pulley
4.5psi pulley
GM knock sensors

mods to come:
walbro 255
supra injectors
jims fuel upgrade
6psi pulley
afc and y-band

I hope with these mods I could get the car in the high 13's, but we'll see. :wink:

Re: Did you loose some boost with headers?

PostPosted: Fri Jun 11, 2010 11:44 pm
by bbq bob
#1, if you go to 51/2lb pully or above you need to run 94.2 octane or better, or you'll blow it up, go read all of jetbtkng's forced induction posts, im at 296whp doing what he did, frank's solara is over 304whp and 302lbft at 7lbs, also franks going to put an 8 pounder pully on, he thinks he can get 310 whp, with no problem...

Re: Did you loose some boost with headers?

PostPosted: Sat Jun 12, 2010 8:49 am
by usoff89
I do plan on running a higher octane, I'd also like to look into meth.

Re: Did you loose some boost with headers?

PostPosted: Mon Aug 30, 2010 9:33 pm
by SirThomas88
usoff89 wrote:I do plan on running a higher octane, I'd also like to look into meth.


Meth is great. You really can feel the gain. Seriously, there have been a couple times where I stupidly let myself run so low on meth that the force of accelerating pushed the remaining boost juice away from the bottom of the reservoir where the port to the pump is. A moment later and the liquid would move back down and through the pump. I could easily feel that short delay in meth delivery.

Someone is selling a new meth kit on the forums if you can nab it.

Edit: Wow just realized how old that post was. Oops.

Re: Did you loose some boost with headers?

PostPosted: Fri Sep 10, 2010 6:43 am
by Eye8Pussies
^ you should really avoid doing that....that lack of power before the "power boost " when your meth finally hits is your engine knocking since it was tuned to run with meth, and the knock sensors retarding the timing until the meth comes in to cool down the intake charge....someday the knock sensors may not do their jobs and your motor's going to pop



and as everybody's been saying- that loss of boost is from less backpressure from the exhaust, and theoretically, boost will build a bit slower as well