Bulent Aliev wrote:

Hi Paul, over the last couple of months I noticed that people with
turbochargers like the one you are going to use are having problems with
over boosting. John Slade is flying with the waste gate fully open and air
bleed at the intercooler. Still he can not apply full power for being afraid
of detonation. Looks like someone has to specialize in cutting down the
blades on the hot side of the turbo? Bleeding more air on the cold side will
only over speed the wheels. I just had mine rebuilt, but looks like have to
do something about this problem.
Bulent

What year turbo does he have? There is a big difference in the waste gates
from 89 to 90. The 91 is+ on the left. If you have an 88 you can port the
waste gate
and or run a separate exhaust pipe for the waste gate instead of making the
gas
turn right angles. Also what size exhaust pipe after the turbo is he running?

Paul Lamar

He has the same turbo like yours and mine 89-90. His exhaust pipe is only
about 4" 2.25 diameter straight out without any bends.
Bulent

The exhaust pipe may be too small. Should be three or more inches in diameter.
Probably restricting the air coming out of the waste gate. There is also
a remote  possibility that the prop is sucking air out of the exhaust pipe.
Try a two inch long pipe. Come to think of it the existing exhaust pipe
is more like six inches long rather than four by looking at the pictures.

He could fab a bolt on  box so the waste gate can go wide open at 90 degrees 
and add a 2.5 inch dia. straight pipe inline with the waste gate. Also use 
a die grinder to smooth and enlarge the waste gate passages.
Are you sure he has low compression rotors? Also is he using a detonation
sensor and audio amp so he can hear detonation? How much boost is he seeing?
If he has had detonation and it cracked an apex seal he would know it.

Another possibility is the waste gate pneumatic servo is leaking air and not 
opening the waste gate fully. Use an air pump with a pressure gage to check
the functioning of the waste gate servo. It should be fully open at about
8 PSI.

Use a water manometer and check the pressure 
around the exhaust pipe opening. The pipe is too long anyway to act as
a cooling air ejector. In other words it is not positioned properly
relative to the large diameter ejector. It needs to be positioned
near the beginning of the ejector.

Kind of hard to believe all this as the stock 90-91 engine only generates about 
5 or 8 psi max. This is pretty much identical to what Francois is running 
with no apparent problems. Francois what is the diameter of your exhaust 
pipe after the turbine?
  
Paul Lamar
 
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