Stock Boost?

toayoztan

Moderator
I always thought it was 6-8psi. Depending on the weather, I hit anywhere around there. Mods such as DP, etc can increase your boost to an extent too w/o any boost controller.

Bryan
 

-==L=a=N=c=E==-

New member
Thanks guys. Reason i ask, is that i've had problems with a boost leak. And i think i've finally tracked it down. And i never had a boost gauge on the car before the boost leak happened. So hence why i ask.

Mods wise, i have a 3inch exhaust, with no stock CAT and the stock downpipe. So im guessing 7PSI is good. I get around 6-8PSI all the time now.

All good, thanks for the replies guys.
 

SuperWhite92

New member
I hear 9 for most people, but for some reason, mine always ran 14psi when it was stock. No boost controller, Bone Stock. And I still haven't found fuel cut, which has not been disabled as far as i can tell.
Ignoring the fact my car is freakish.... I'd say about 9psi is right.
 

Gary

Moderator
OK guys, according to the BGB,
7.1-11.8 psi while driving with the engine running at 2800 rpm or more with the WOT in the 2nd gear.
 

toayoztan

Moderator
SuperWhite92":1hpqwnk9 said:
I hear 9 for most people, but for some reason, mine always ran 14psi when it was stock. No boost controller, Bone Stock. And I still haven't found fuel cut, which has not been disabled as far as i can tell.
Ignoring the fact my car is freakish.... I'd say about 9psi is right.

I had the exact same problem you did. I hit around 12-13psi all the time w/o any fuel cut when i bought my 93 alltrac. I couldn't find the problem, so i decided to change out my WG actuator from my 92 alltrac. However, while removing the 93 actuator, i found a rip in actuator hose leading to the VSV. You might want to inspect the hoses around there. It might have to do with the fact that since air does leak through that hose, it takes just a bit more psi for the VSV to "see" stock psi. That's just my theory.

Bryan
 

Gary

Moderator
Sound right Bryan. The leak will act like a bleeder valve and the actuator will keep the wastegate shut due to there is not enough pressure.
 

-==L=a=N=c=E==-

New member
Okay, just quicly help me.

Reason i asked what ths stock boost levels are, is that i 'think' i have a leak somewhere.

My vaccum is at 20hg/in but when i go onto boost, my gauge is at anywhere from 5-9psi at the moment. So the leak would be somewhere between by turbo and inlet yes? a loose coupling perhaps?

Would this also explain then when i turn up the boost, the spiking and settling affect? or is this more MBC related?
 

Gary

Moderator
Your vacuum reading sounds healthy to me.
I think it's more of the MBC setting. Do you have one?
Have you disconnected and capped hose from the wastgate actuator to t-vsv?
 

-==L=a=N=c=E==-

New member
Gary":3hkq5z22 said:
Your vacuum reading sounds healthy to me.
I think it's more of the MBC setting. Do you have one?
Have you disconnected and capped hose from the wastgate actuator to t-vsv?

Tvis is pulled and plugged. I think its the MBC that i have installed.

Ill retighten my clamps again. I have an unmodified intercooler that im gonna install tommorrow and see how that goes.

Cheers
 

Gary

Moderator
Richard,
Someone on Celica.net have problem with his MBC. It turns out he didn't drill a small hole to bleed air out.
BTW, I guess you meant t-vsv, not the t-vis
 

-==L=a=N=c=E==-

New member
Gary":16ejy3ty said:
Richard,
Someone on Celica.net have problem with his MBC. It turns out he didn't drill a small hole to bleed air out.
BTW, I guess you meant t-vsv, not the t-vis

T-vsv, tahts right. Im pulling the MBC today. Just going to go back to the stock controller.
 

Griffin

New member
The stock controller is very restrictive. Mine can only make about 10 PSI with my cams and echaus and all, but I made over 24 PSI with the wastegate actuator shimmed out to keep it shut. I'm looking into a better quality VSV to control pressure bleedoff.
 

-==L=a=N=c=E==-

New member
okay, this boost leak is realy frustrating. Soemtimes it'll boost 9psi, soemthing 6psi, sometimes 7psi, sometimes 8psi.... Sometimes it'll boost up, and then slowly drop down. Sometimes it'll hold it. Playing with the bleed valve sees it boosting higher, but then dropping. or it will hold boost. Its all over the place.

Ive tracked down every vaccum leak. Ive sealed upa ll the hoses on the intercooler run. The only thing left is a tired wastegate. Or something else. Maybe one of the vaccum lines is leaking under boost or something.
 

Gary

Moderator
If your vacuum reading is stable, I don't think you have any leak.
It sounds like your MBC or wastegate problem, not the vacuum leak.
 

alltracman78

Active member
Did you have these problems before you got the mbc? Even if your wg actuator is shot, it won't see any boost 'till the mbc opens.....
 

toayoztan

Moderator
I haven't been keeping up with this thread much, but does your MBC have a bleeder valve? I've heard from somewhere that unless you're boosting a pretty good amount of boost, the bleeder valve will cause spiking.

To me, it looks like your MBC is messing everything up. Make your own WITHOUT a bleeder valve (basically, don't drill that stupid hole ;))

Bryan
 

-==L=a=N=c=E==-

New member
toayoztan":2sw1cdxa said:
I haven't been keeping up with this thread much, but does your MBC have a bleeder valve? I've heard from somewhere that unless you're boosting a pretty good amount of boost, the bleeder valve will cause spiking.

To me, it looks like your MBC is messing everything up. Make your own WITHOUT a bleeder valve (basically, don't drill that stupid hole ;))

Bryan

Yup, i traced it back to my Boost controller. Im in the process of snatching up an electronic one.

Thanks for the advice guys...

BTW, my wastegate has been modified to take 7psi at stock boost. Which is fair enough, since it used to run in a JDM, and then came here with all the controller pulled. No sweat though.
 
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