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Discussion Starter #1
I just put my car on a dyno for the second time. It is a BB Chevy, gen7 dfi, twin GT40's and 2-40mm Tial wastegates. First time on the dyno it only made 9psi. So,I put an AMS-500 on and try it again a few months later. I left the solenoids unplugged and the thing made 14psi. Then I took the lines off the top of the wastegates and it would make 13 psi every time. I made no other changes and I know it's making more boost because it picked up 200 hp.
 

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Are you just passing on some information or is there a well hidden questions here?
 

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Discussion Starter #8
Well, I thought it was obvious. I am trying to figure out why it is making more boost than the waste gates should allow. Several previous dyno pulls it only made 9psi. Which is what the springs in the waste gates should allow. Now with no changes, it makes 4 more psi.
 

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40mm are a little small for a bbc.
What turbo and how many cid?
 

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It is a 468. The turbos are gt 40's with the compressor side having a 82mm exducer.

The first time I dynoed it, it was about 110 degrees and this time it was in the 50's.
 

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If it really is a Tial(thought they only made 38mm), then I'm in the same boat you are. I had the same problem on my car, and 3 others with Tial gates. Made the right amount, then suddenly a year later all of them over boosting. Dunno if the gas changed or wtf. Ditched them for JGS 40's, problem solved. This was all street. Yours, is it possible the dyno was just loaded more and your seeing a problem that was covered before ?
 

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How are the solenoids plumbed. By unplugging them you may have caused a boost leak to the bottom of the gate sorta like a manual controler. If you are using a three way solenoid and they are not switching it may cause the valve to bleed off some of the boost that is supposed to go on the bottom of the gate.
 

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could the diaphragm be broken causing it to need more boost to compress the spring?
 

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If the solenoids are normally closed when no electricity is applied, the atmospheric conditions could have been different when you plumbed it vs when you dynoed, causing a small amount of positive with respect to ambient pressure to be stored on the top of the waste gate, causing the slightly higher boost pressure.
 

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It is a 468. The turbos are gt 40's with the compressor side having a 82mm exducer.

The first time I dynoed it, it was about 110 degrees and this time it was in the 50's.
I think you found your problem:pmy kenworth will do that every winter.....normally it will make 25lbs all day but when it gets cold out, up it goes.....it will make about 28 to 30,just cuz of cold air
 
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