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Discussion Starter #1
Ok, so I am slowly turning up the wick on my car and getting the bugs worked out.

This thread has the basic specs on the car
http://www.yellowbullet.com/forum/showthread.php?t=808818&highlight=xr4x4ti

Since then I swapped out the cam for the 226/226 114 +3 cam, totally new exhaust and I ditched the EEC-IV for a Holley HP EFI.

I went to the Dyno a few weeks back and it put down about 558 all wheel HP at 15psi boost. I thought that was ok, but I am always looking for more. I measured the back pressure pre-turbo and at 15psi of boost I measured 37psi back pressure for a PR of about 2.5:1.

What are people thoughts on that? I know the rule of thumb is keep it under 2:1. The car is a stick and I like the throttle response, but I was thinking of swapping out the turbine housing to a .96AR from the current .81.

How much do people think it will drop the back pressure? How much will it increase my spool RPM? Right now I pretty much have full boost by 3000rpm.

I want to try and run 20+psi and I know the back pressure will only get worse.
 

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Discussion Starter #6
Did you get the bigger down pipe?
Yes, I did end up putting in the new down pipe and improving the exhaust in general. It worked so well and reduced the back pressure after the turbo that I had to install a second waste gate to control boost.

How long is the down pipe?
The car has full exhaust. The down pipe directly after the turbo is 3.5in. It then expands to 4.0in under the car, goes through a 4in magnaflow muffler and then splits into twin 3.0in tailpipes that each have a Dynomax bullet muffler on them.

That small turbine is about done.
Are you referring to the size of the turbine itself or just the turbine housing?

Do the .96
Simple enough, I am going to order up the housing and see what happens, it will be a good experiment.
 

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Discussion Starter #8
Yes the turbine itself is about done.....
Well, I ordered the new housing.

What would you recommend? Remember that it is a manual transmission car. I am ok loosing some low end, I already have with the new cam, but it can't be a total turd.
 

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Something in the BW lineup with a turbine that won't choke.
 

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I have that turbo on a 347sbf .96 A/R 3.5 inch down pipe to the bell housing then to 4 inch, I have not checked back pressure yet but I am sure it is high. I run it at 23 psi it made 800+ but is tapped out, it works great on the street.
 
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