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.

The pipe was cut back along the cut line marked with marker.

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.

He has the high compression rotors. Porting the waste gate may help

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.

He has a manual waste gate. You can read the details at the bottom of this
page:
http://www.canardaviation.com/cozy/chap29.htm#diagnostics

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

He is going to have to use a modest amount of boost indeed with high 
compression rotors. Looks like extensive porting of the waste gate is called
for and a new rear cover for the turbo with a straight shot waste gate
pipe.

Paul Lamar
 
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