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Building boost on line??

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Old Jun 14, 2011 | 12:45 PM
  #21  
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Originally Posted by Phil99vette
Do you run an AMS-500/1000?
What RPM are you trying to leave @?
Are you flat on the floor when staging?
Do you have dual rear brakes?
Motor is a 390...what size turbine/turbine housing?

You need a box with a 2-3 step. 2 limiters down low.
Have an AMS-500 however it was not being used because we couldn't get it to hold the gate closed using boost because of the backpressure.

Will stall to about 4000 rpm on the brake so leaving there.

I stage, engage the brake and put it on the floor.

Stock rear brakes

Turbo is a GT-91 with a 91mm turbine and the housing that was on it was a 1.08, am being told that was too small which was causing the backpressure to be high.
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Old Jun 14, 2011 | 12:48 PM
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Originally Posted by Fireball
lots of bad info in here...

two step/three step for an auto car only control rpm/total boost...not the ability to build boost

if you can't build on the brake against the converter, you aren't building any on a 2-step either

potential problems:
wrong cam
exhaust leak
boost leak
wrong converter
wrong turbo size
too much fuel
not enough timing
not enough compression
etc
Well thats why I am here to try and diagnose this thing, will see if the exhaust housing remedies the issue.
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Old Jun 14, 2011 | 12:48 PM
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Originally Posted by tording99Z28
Have an AMS-500 however it was not being used because we couldn't get it to hold the gate closed using boost because of the backpressure.

Will stall to about 4000 rpm on the brake so leaving there.

I stage, engage the brake and put it on the floor.

Stock rear brakes

Turbo is a GT-91 with a 91mm turbine and the housing that was on it was a 1.08, am being told that was too small which was causing the backpressure to be high.
Its cheap and easy to plumb in a mechanical backpressure guage....I'd add one instead of guessing...
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Old Jun 14, 2011 | 12:52 PM
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My tuner put one on the car and they said it had 15 psi of back pressure. It was a gauge that looked like it went where the wastegate goes so that it measures the backpressure where the wastegate sees it. Would this be considered a lot?
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Old Jun 14, 2011 | 01:04 PM
  #25  
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Originally Posted by tording99Z28
My tuner put one on the car and they said it had 15 psi of back pressure. It was a gauge that looked like it went where the wastegate goes so that it measures the backpressure where the wastegate sees it. Would this be considered a lot?

It needs to measure the pressure in the crossover between the headers and turbo. It had 15psi of backpressure when? idle, staging, down track? What was the boost pressure it measured 15psi?
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Old Jun 14, 2011 | 01:20 PM
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Well that is in the crossover tube but its after the Y. I believe that 15 psi was at idle but I could be wrong on that as I didn't ask that exact question. The highest boost we can get it to boost to is 8 psi before the wastegate opens, and thats with a big wastegate spring, like a 15 psi spring.
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Old Jun 14, 2011 | 01:21 PM
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If it had 15psi of backpressure at 8psi of boost, the turbine housing is probably too small. 2:1 back pressure at that low of boost will kill any motor. Its a problem I'm seeing more and more of with the cheap ebay turbos. Seems like the turbine housing/wheels are not efficient.
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Old Jun 14, 2011 | 01:22 PM
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Originally Posted by tording99Z28
Well that is in the crossover tube but its after the Y. I believe that 15 psi was at idle but I could be wrong on that as I didn't ask that exact question. The highest boost we can get it to boost to is 8 psi before the wastegate opens, and thats with a big wastegate spring, like a 15 psi spring.
Do you have any log files of it coming up on boost?
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Old Jun 14, 2011 | 01:24 PM
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Well thats what they are saying too so thats why we are puting a bigger housing on it. This isn't a cheap ebay turbo though, its a Garrett, it is considered to be one of their "budget" turbos but its not some chinese garbage company that nobody has ever heard of. We got it here. http://www.forcedinductions.com/productsgarrett.htm
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Old Jun 14, 2011 | 01:26 PM
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Originally Posted by Phil99vette
Do you have any log files of it coming up on boost?
No I do not, I am sure the tuning shop does though, I will once its back together as I do have HPtuners but only drove the car enough to make a couple of shakedown runs.

So whats a good ratio of boost to backpressure thats acceptable?
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Old Jun 14, 2011 | 01:45 PM
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i build about 12psi on the line on a foot brake... no 2step or Tbrake....
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Old Jun 14, 2011 | 01:48 PM
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Originally Posted by tording99Z28
No I do not, I am sure the tuning shop does though, I will once its back together as I do have HPtuners but only drove the car enough to make a couple of shakedown runs.

So whats a good ratio of boost to backpressure thats acceptable?
1:1 up to 20psi and slowly gaining from there.

Is your turbo a T4 or T6 turbine housing?
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Old Jun 14, 2011 | 01:49 PM
  #33  
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T6 housing
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