6G Celicas Forums

Ok so before my car died my boost gauge at the most i ever noticed read about .9 bars. calculated thats about 13 psi. i bought an upgraded ct26 with a larger compressor wheel from brashboy on ebay. im not sure what the wastegate is set at but this seems really high. i dont want to wreck anything internal and only want to run about 8 or 9 psi. also i have a custom 3 inch exhaust that i personally built with a high flow xlerator muffler with a single 3" inlet and dual 3" outlets. i know im running some major boost creep and am wondering how best to stop that and add some backpreassure to the turbo to slow freewheel.

The smaller the exhaust, the less creep youll have.
However, 8-9psi is less then stock boost on a 3sgte. Ive been running mine at 1.05bar for a few years now without any problems.

Isn't factory boost around 11 ~ 12 psi on the 2nd Gen ? and 13 ~ 14 psi on the 3rd ?

Depends on where they were sold. US 2nd gen is only 7-8PSI.

No its not. If your only getting 7-8psi, you either have a very restrictive exhaust, or the ecu is keeping you in low boost mode.
All stock 2nd gens should hit about 10-11psi stock.

ok i was under the impression that 13 was way more than stock. plus with the fresh turbo and larger compressor wheel 13 should be fine then. i know the smaller the exhaust the more back pressure but does anyone think that a three inch turbo back through that muffler is to free flowing.

Is there such a thing as too free flowing for a Turbo?

Yes, in a way it is...
The stock wg setup on the ct turbo's has a hard time dealing with boost creep on a free flowing exhaust. A few people remedy this by going with a 2.5in downpipe or keeping the stock one, but then you also loose a few hp from the smaller exhaust.

On a cold day, even with the boost controller off, I'll probably hit about 14psi. This really isn't an issue though, as 14-15psi is were your going to want to keep the boost at anyway.

7psi = Crazy slow
10psi = ok but still slow
13psi = Nice
15psi = Ah yes, this is why I did a swap.

USDM MR2's included? The MR2's I know around here were limited to 7-8PSI until they added an MBC.
Admittedly I have almost no experience with alltrac/GT4's but I know that the MR2's I know have this "problem".

Please help me out if you can cause I can barely hit 6PSI and I have no codes other than the speed sensor one we discussed caused by my not yet having fixed my speedo/speed sensor/ecu issue.

This post has been edited by DEATH: Jun 5, 2008 - 3:15 PM

All 3sgte's should hit 10psi stock. If yours isn't (i feel bad for you ) then its probably because of...

1. boost leak
2. Ecu code
3. old cap/rotor/plugs/wires
4. restrictive exhaust/cat
5. tvsv system damaged or not connected properly.
6. incorrect ignition timing or mechanical timing (timing belt)

This post has been edited by lagos: Jun 5, 2008 - 3:23 PM

I wish there was someone in this area who knew the 3S better than me besides Chris K who I couldn't even afford to have look at the hood of my car much less diagnose anything.
No boost leaks
the only code I have is the speedo one
Ignition system is new
Even when I was running open downpipe I had this problem
Wouldn't have a clue about the Tvsv system
Timing and Tbelt is correct and double checked by Toyota dealership I trust and know me well

Wait, you mean to tell me I typed out that whole speedo how to, and you never did it? come on, man!

I just got done with my other little Gremlins and had a few pop up last night. trust me - I'm a perfectionist I can't have these little BS things giving me trouble all time. It's very high on the list now. And your help was and still is greatly appreciated. It'll come back to you in time - i have 3S parts laying around and I'm very generous to those who've helped me
Just gotta prioritize you know? You should see the massive amounts of little issues this car had.

your only hitting 6psi
thats scary haha
is your knock sensor hooked up??
did you do that red/green LED knock sensor?
even if you have a speed sensor code, if should only throw the ecu light after a few minutes of driving.

How's the turbo look? Fins Okay? No Play? Could the waste gate be stuck open a little? It HAS to be some kind exhaust side bugaboo keeping your boost way down....

That's exactly how it does. It won't throw a code at all either driving or just letting it idle for a long while and then checking the codes [or on the gauges obviously]. If I get up to 55-60mph [judging by RPM] it'll throw that one code.
I haven't been freaking about this issue cause I've been busy tracking down other issues [Ooh I've got a horror story I'll share with you via PM - I about fell out when I found this one]. I've been systematically attacking large portions of the car, disassembling them and putting them back together the way Toyota intended. Once I've got everything 100% then I'll worry about turning up the boost - when I know it's safe. My AEM Wideband should be here today or Mon - that'll help with my peice of mind and I wasn't about to turn up the boost before I installed that and knew it was working well.


It's on the list. Got the parts and the write up in the garage already.



Beautiful. I looked at it and then had it looked at to double check when I had the engine apart for the rebuild. It's not leaking, very little play, the wastegate is shut nice and tight.
*Knock on every single peice of wood surface in this office*
I would think perhaps the Tvsv is probably still disabled from when it had a MBC installed before? That was my thinking last night as I was mulling some of this over.


This post has been edited by DEATH: Jun 6, 2008 - 9:20 AM

put a restrictor plate at the bottom of the downpipe inbetween the dp and front pipes, maybe a 2.25" or 2.5" , that should cure it slightly, in saying that i get no more boost creep after fitting a fmic..

if you have the wastegate ported on a CT series turbo it helps keep the boost creeping in check.
i have a CT-27 with the wastegate ported along with a 2.5" KO DP + 3" MP + stock catback <---will replace soon.
i've only hit fuel cut a handful of times on cool nights & in the winter with a JDM ECU which is around 15psi.
any other time boost stays around 10psi in 90+ degree weather, 12psi in 75+ degree weather and 14psi in temps lower than 65 degrees.
just by having the wastegate ported i haven't had to worry about buying or making a boost controller as the boost stays where i want it & fuel cut is still enabled to keep me from killing the motor.

Death, it sounds to me like you are having problems with the TVSV, b/c you should be making at least 8psi in 3rd gear on a bone stock motor.
ECU limits the boost in 1st & 2nd gear to only 5psi & after you hit fuel cut it will go into limp mode allowing only 5psi until the car is shut off & turned back on again.
If someone had a MBC installed then they disabled/bypassed TVSV.
you may also have a vacuum and/or boost leak somewhere.
do you hear any hissing in & around the engine?
what is your vacuum reading at idle?