Hi guys. Ive got a fair bit of a problem since i had my engine replaced a couple of months ago. When i floor the accelerator from standstill, the 1st turbo will boost to about 11psi, but as soon as it gets to around 4000 revs when number 2 should come into play, the boost just drops down to about 5psi. It will do the same thing on kickdown too. The thing is, if i accelerate slowly up to 4000revs, the 2nd turbo will come online and boost up to about 14psi. I cant find any boost leaks, but it sure feels like one. Its been in and out of garage ever since and he still hasn't traced the problem. The mechanic has tested all the Vsv's, actuators and vacuum pipes. Anyone on here got any ideas?????? Its made my car crap for racing and just embarrasing.

Hey SupraTrev,
The exact same thing happened to me a couple of years ago before I went single. It turned out to be a bad actuator on the midpipe that controls the butterfly to turn on the 2nd turbo.
Instead of replacing the actuator (there are actually a couple that it could have been) I just went ahead and hard-wired the actuators open (TTC mode.) This causes both turbos to come on at the same time, all of the time. It is a little more laggy, but once the turbos come online it is nutz!
Here is a link on how to "hard-wire" the actuators open:
www.mkiv.com/techarticles/ttc/ttc.html
You will actually want to skip down to the section "How to wire teh actuators open" and start from there. (The section above that assumes that your VSV's and actuators are working properly..)

I was VERY happy that I performed this mod, and it only cost a few dollars to do. You will stop loosing to everything you race!!
If you have any questions just let me know.
Good Luck,

ShaneW

Cheers. Have you got the manual or autobox though? Ive heard its too laggy with the auto and makes driving at lower speeds hell. Which actuator do you mean exactly? Do u mean the Exhaust gas control valve at the top of the exhaust, or the Intake Air control valve at the back of the turbo set-up on the top? I did suspect an actuator cos of the symptoms, but didnt know which one. Is there a way to check them at all? Cheers for info though. Got a good idea now.

I do have a 6-speed, so the lag wasn't really that big of a deal to me...
I too have heard that TTC mode on autos is pretty laggy, but a little lag is better than NO boost!

I was refering to both of those actuators actually (Exhaust gas control valve AND Intake Air Contol valve.) If either of those valves is not opening, then the 2nd turbo will never come online...

One thought (although I have never tried it myself, but I dont see why it wouldn't work) would be to wire one of the valves open (ie Exhaust Gas control valve open), and leave the other valve (ie, Intake Air Control valve) hooked up normally. This "should" allow the normal sequential operation of the turbos (assuming the Exhaust valve is the broken valve.)
If your 2nd turbo still does not come online, then swap the valves:
Exhaust Gas Control Valve=normal
Intake Air Control Valve=hard-wired)

If I had to guess which valve is failing, I would guess the Exhaust Gas Control Valve ( it is subjected to MUCH harsher conditions (extreme heat, weather, etc.)

Hope this helps. Let me know if anything I said is unclear.
Good luck,


ShaneW

hey whats up
this is just a real wuick question about the TTC mod....if i do this i can turn it back to sequential easuly right??? and the second question is if i do this will the boost change at all or will it not be in increments..it will most likely be all at once basically right?? also does the boost controller work the same as before and can i boost higher or anything like that...these sound like noobie questions but i havent tried this mod and i wanted to know the facts about it ..i read the article on it but they ddint say anything about using a boost controller..say a profec b or something

ok thanx
icedsupra

Red 1994 Supra Twin Turbo 6 Speed
BPU

"You know you can't keep up"

check your turbo pressure sensor thats bolted on the side of the intake manifold. make sure its connected good. also try doing the
bleeder-t mod.