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Old 01-24-2010, 03:26 PM   #1
SuperX
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Default 1990 Supra Turbo

Hi Just got a 1990 Supra Turbo.
I have a question about the boost gauge. It seems to always read -4 on the boost, when driving. I can run down the interstate at 80 and it still reads -4. Now if I jump on the gas it will show boost up to 3 or 4. I haven't driven it hard I just got it and had to bring it home in the middle of the night 250 miles so I was kinda easy. If I get on the gas (hard acceleration) the boost will go up and stay there until I let off the gas and then back down to -4.
Is this normal.
Thanks SupraX
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Old 01-24-2010, 06:07 PM   #2
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-4 Should be the bottom of the stock turbo gauge if you aren't on the gas on a decent accel it should'nt boost too much, so staying at -4 while cruising is ok. When you do hard accel does it reach what looks like 6.7 lbs of boost? Any shuttering as you let off the gas from hard boost? Basically need more info, but from what I hear there shouldn't be any problems.
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Old 01-24-2010, 06:25 PM   #3
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It seems to accelerate pretty fast, with out the boost pressure rising. If I get on it with 3/4 throttle then the pressure comes up to 2 to 4 but I get over the speed limit and back off. I don't have the car registered yet so I not pushing it.
Getting on the interstate with quick acceleration, not hard the boost gauge movers only lightly off the bottom. It runs great just didn't know cruising at 80 if it should be carrying boost.

This is my first turbo import and not real familiar with it. My F250 carry boost on the gauge all the time except at a stand still it seems.

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Old 01-24-2010, 09:24 PM   #4
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-4 to 0 is common when cruising but at about half peddle on accel you should be getting a decent amount of boost, even cruising at 80 if you hit an uphill and have to press the gas slightly harder it should boost to 0-2lbs in my driving experience. Get someone to ride with you in the car and take pictures of the boost gauge and rpm's while you drive it, while you do that make sure to modulate the way you hit the gas as much as possible.
Hmm if you're giving it 3/4th it should be hitting 6.7lbs of boost, check all your hoses and intercooler piping for leaks, specially the vacuum hosing running off the turbo.
Quick easy way to see if your turbo will boost to full potential, go out to the street and floor it to 40 mph boost should reach 6.7 before you hit 40 if not there is something wrong

Last edited by 916MKIIIx2; 01-24-2010 at 09:27 PM.
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Old 01-25-2010, 08:50 PM   #5
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I found a vacuum hose that was unhooked. I put it back, and drove it today. I floored it and the boost hit around 6.7 ( hard to tell with no marks between 4 and 8).
The boost seem to come on a little more today and stayed up while on the gas.
Thanks for your help.
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Old 01-25-2010, 10:01 PM   #6
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IIRC, 6 to 8psi is spec for a stock GTE... the amount you'll see depends on a couple things.
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