Turbo Stockers

[Mark Yacavone]

Originally Posted by Rob Lloyd

I'm not to worried about the compressor side. It's the turbine I'm worried about. I have a good turbine housing, but all of my turbines measure at least 0.04 smaller than the housing at the exducer. I think maybe my turbines are worn down pretty far. My guess is it should only have 0.01" clearance, but I don't know for sure what the turbine is supposed to be. I found some specs that say it should be 1.88" - mine measure more like 1.84". Ouch! But, again, the housing bore measures close to 1.88" So, I don't know if that spec is for the housing or the turbine.

You definitely do NOT want 2mm clearance around the compressor. It will cause a very slow boost rise. You want as small a clearance as you can run on the compressor side.

Related question - Art, did you have trouble seizing the wastegate arms? I seem to seize one up every single season. The 'good' turbine housing I mentioned above I shelved because it seized the WG arm. I took it apart and reamed it out, but I'm concerned it will just seize up again. I reamed it with a 5/16" drill (the arm measured 8mm, so there's alot of clearance now). Just gotta get the arm welded back up and put my 'good' turbine in there for Indy...

And what would be the reason for having movement in the waste gate arm?
Is that what they call "bracket mode" ?

[Rob Lloyd]

Originally Posted by Mark Yacavone

And what would be the reason for having movement in the waste gate arm?
Is that what they call "bracket mode" ?

Well, yeah. If the arm doesn't move, the boost is uncontrolled. I've gone fast that way, but consistency is non-existent.

[art leong]

Originally Posted by Mark Yacavone

And what would be the reason for having movement in the waste gate arm?
Is that what they call "bracket mode" ?

We delay the waste gate opening but not stop it. With the waste gate closed you melt the motor, but go fast.
Bracket mode would be lowering the total boost. Or running it rich. I've done both sucessfully
Bracket mode on my N/A car is just shift it 1000 rpms early.