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Turbocharger Engineer
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He guys I'm helping a buddy of mine with his 95 Supra TT, for some reason we can not keep the boost up. He can launch and in 1st gear it will hit ~15-16psi, then hit 2nd and it will go to 19psi where it should stay, but by 5K rpms the boost drops back down to 13-14psi? It continues this in the next 2 gear......will go to 19-20psi, then fall to 13-14psi. Why is the boost creeping back down? Does he need a stronger spring in the wastegate? Or does he just need a boost controller? Thanks for any help.


Jose
 

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JZ 97 SS 1500 said:
All he has is downpipe, cat back exhaust, K&N drop in filter in stock airbox, and the boost is rigged for 19-20psi, not sure how he has the vacuum lines routed. Thats about it.....

Jose
Sounds like he may be using the Bleeder 'T' to raise boost, I had that mod for a bit and it did the same thing, it's a bad way to control boost IMO and doesn't hold the boost well.
 
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Try using the TTC mode setup.
sometimes the sequence is really mass up.
 

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JZ 97 SS 1500 said:
The stock twins I thought were enough to sustain 18-19psi with the stock motor. At least thats what I've understood...

Jose
They can, but usually thay are unable to hold that much boost to redline in the higher gears, they just can't flow enough air.
Again, what method is he using to raise the boost??
 

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Ok, Ok , I’m the mysterious guy with the boost problem. Jose is a good friend helping me out but the answers we have received so far are the same I received over a year ago. So let me give a few more details. I had talked to many people then until I decided it was up to me to figure out the problem. Boost leaks, no… BOV, no the only solutions I could come up with is wasted gate was too weak. No one would accept that possibility so I had to prove it. Well the problem came about after Majestic Turbo in FL rebuilt my turbos, I would only make 14PSI :( with the hoses to waste gate unplugged where before I made 17-20psi, 21psi in od. I have heard over and over the turbos will only flow 17-20psi. Well maybe, but I took the simplest fix I could think of. Which was to take a one way air valve to pull a vacuum on the waste gate at idle and hold it there under boost. The boost spiked to 24psi. Well after seeing 24psi and hearing a few pings and had visions of engine parts laying on the road. I quickly unhook the vacuum line and found a spring to hook to the waste gate. The results varied but kept the boost up around 17-20psi but would roll back to 14 psi at the top of each gear. Well it was close enough to drive and only slowed me by a tenth or two. With the vacuum line hooked up it would hold 20psi but would spike way too high and 20 was a tad more then i wanted on pump gas.

With just the spring the boost dropping off in each gear also killed the top end charge that the supra is known for and after having a stock LS1 camaro stay with me it’s time to get back what was taken.
(note: This LS1 runs 8.4 in 1/8, my best was 8.1 and now i run 8.3 on a good night)

So guys, I know if I find the right spring and put a BC on the car that my problem would be solved but then it would be rigged. I don’t want it rigged anymore then it already is, I just want to work on it once and be done with it. I want to hold 18 or 19 psi all the way. I need to know if you can replace the spring or replace the waste gate on the car without pulling everything apart. If so, what do I need and how much do I have to pull apart to get it done.

Thanks for all your help :D
Jimmy
1994 Auto
[email protected]


http://hiwaay.net/~dimos


 
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