Looking for some opinions on my turbo trouble.

I have a 2008 Mustang GT with a 4.6 stroked to 5.0. I purchased a turbo kit from a vendor who went belly up about 2 months after I bought, which is probably a clue in itself. The turbo is a COMP CT-4 6765 oil-less with ceramic ball bearings .96 A/R.

I replaced the hopelessly small kit intercooler with a Mishimoto 4" intercooler.

Just trying to get a 91 base tune before going to E85 and having horrible trouble. With a 7 pound BOV spring and the boost controller set at 10, the car boosts to 10, but will not hold it. The boost tails off to 7-8 pounds. 7 pound springs in the waste gate.

After a LOT of trouble shooting, the shop doing the install believes the up pipe to the turbo is the issue. It is 2.5" running from each shorty header to one 2.5" pipe to the turbo. He believes the exhaust is stacking due to the small 2.5" up pipe and the wastegates are bleeding off.

Thoughts?

 

I doubt the 2.5" up pipe is causing you problems at this power level. What boost controller are you using? What wastegates? Where is the boost controller referenced and how is it connected? (plugged into intake or charge tube, before or after intercooler?)

 

2.5" should be plenty, guys have made close to 1k hp on more cid with a 2.5" log. What do you have for a down pipe, and what exhaust? Have you checked back pressure? what style of boost controller? You could try bypassing intercooler just to eliminate that. It sounds like you're out of compressor, or pre turbine pressures are high. If you run it just on wg spring does it fall off?

 

My twin setup has 2 1/2" going to the turbos and 3" downpipes and it can make 1000rwhp , mines around 800 but seen the same kit make 1080rwhp so I don't think your problem is the size, bad waste gate placement could be a problem also and boost controller. Who's kit is it.

 

if your boost controller gets its signal from the turbo itself this is a good indication of your intercooler pressure drop. if you plumb the controller to the intake side of things your boost(in the intake) will be more solid

 

Not trying to bust your balls Charles, but I don't think you can compare twin 2.5's to feeding one turbo with a single 2.5", and bad gate placement typically causes creep not boost falling off.

 

I'm trying get a better grasp on pressure drop.... does the pressure drop go up with air density? Or is it a flow restriction... or both?
Sorry to the op for hijack.

 

What boost controller?
It could be one of two things. The 2.5 tubing is not your problem. We've done very close to 1200rwhp on 2.5 after a 2.125 merge. The back pressure is pushing the gate open which is possible w a comp turbine, but not at that boost level. Or a combination of a very good wg placement and or a spring in the gate with not enough spring rate.
We stuck ours in a damn goo spot w direct flow. So much so at wel under 2-1 back presure the gate gets pushed open. -CPRsm

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flow restriction. generally most intercoolers, plumbing, throttle body etc make for a bit of restriction. if the dudes pressure gauge is in the intake manifold and his boost controller is getting signal from the compressor(how most diagrams are) and his cold side drops 2psi of pressure at peak power that would explain the difference.

for example i broke in a new motor without the turbo, just put an air filter where the turbo would have been. at 6000rpm i had only 80kpa inside the intake at wot. that is about a 2.5 psi pressure drop without the turbo

 

I'll post some pic's of the setup. The kit intercooler was so small, with in and out on same side. I had to have the entire cold side refabricated for the bigger intercooler. the routing picked was the least bad solution. Some pi's will show how it was mocked before the tubing was welded up The wastegates and BOV are TIAL. The wastegates are vented direct to atmosphere. I went to dual wastgates because the stock single location was about 1/32" from the crank pulley and not acceptable. Since a shop is installing, I am not sure how the vacumn line is being run at this time. The boost controler ia 2 stage turbosmart. Trying to isolate what was going on, they bypassed and went with a single manual controller trying trying to figure out the issue.

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LOL sure you can. on the twins isn't one 2 1/2" feeding A turbo.

 

well if its the turbosmart dual stage like mine it says in the directions to remove the ball and spring from the boost "T" if boost is spiking.

page 4 http://www.turbosmartusa.com/wp-content/uploads/2011/11/TS-0105-1001-DSBC-JUL-12-rev-2.pdf

 

How do you like the Turbosmart Dual Stage boost controller. Im in the market for a simple one and I like the 2 knobs, the Greedy P S 2 I have you need to be a Chinese engineer to program and just to completed for what I want, I like the remote switching part of it but hate the controller it's self.

 

They removed the ball and spring, and it did help, but not stop the issue. They then put a true single manual controler, and it helped a little more, but did not stop the boost from bleeding down.

 

Haven't had a chance to use it yet, took it to the dyno and on gate pressure alone it was pushing through the converter so we didn't even get a chance to turn it up

 

If I can get by the current issue, I am pulling the turbosmart 2 stage controller off the car.

Additional info on car. Both wastegates are referenced to the intake. The BOV was checked for damage and a hand held over during a pull. It was not venting. They are gonna rig a port just before the hotside flange on the turbo, try and measure how much pressure. Also gonna get some 10# springs.

 

do they do a boost leak check?

 

Yes, they have checked that multiple times.

 

Need to get the shop on the forum so they can tell us what they've tried and how everything is hooked up.

 

The shop does not do any forums. There dyno was booked 6 weeks out this summer. They have gone from insanely busy to merely crazy busy now.

I am using the suggestions from here and S197Forum to crack the problem.