Paul,
By the springs in the wastegate diaphragm, I would say there is at least 5
psi. no hard data, but I thing high strung diesel systems and race turbo's
are even more.
Larry


That is a great idea. I have some of those 2nd gen waste gate servos up at
the hangar.
All you need do is pull on the waste gate flap with a small spring scale
and then calculate  the area of the flap.

I just have a TO4 here in the office.
--
Paul Lamar ...No rotor no motor.

Larry,
What is 5 PSI in bar, is 2 bar 5 psi?
George (down under)

1bar (barometric pressure) = 14.5psi.  bar is actually a useful unit
of pressure for certain things.

5psi is 0.34bar.


Matt-

Larry,
Tests at Mistral of Turbo charger backpressure, show an average of 2 bar, so
that must be 29 psi.
George ( down under).

I don't believe it. Something wrong. That would be about 40 psi boost
Or 55 psi absolute 110 inches of Hg. A two rotor would be putting out 800 HP or more
and I don't think Mistral is interested in building engines like that.

If it were intake manifold pressure it would be somewhat more believable at 2 bar or
15 psi boost.  Able Ibarra gets 800 HP on alcohol, 18 psi boost and NOS.

You have a decimal point off there somewhere.

Paul Lamar ...No rotor no motor.

Paul,
I was asking about pressure in the combustion chamber just before exhaust.
Gordon mentioned the back pressure on the Turbo they were testing, as
backpressure affects exhaust flow. If atmosphere is 14.71 psi 29 (2 bar) is
only double that at full power.
If that doesn't make sense, I'm sorry I said anything!!!
I'm afraid I'm out of my depth with turbo's.
George (down under)


You did not say absolute. Maybe Europeans assume it is absolute when they
use the term "bar".

Still 15 psi gage in the exhaust manifold is a lot. The boost must
then have been around 25 psi. That is still a lot of boost.

Well it could also have been Gordon's mistake on how he was measuring it.
He may have been measuring  total pressure in the exhaust manifold.
If the pressure sensor was facing the flow it will read dynamic pressure
as well as static pressure. In that case I can believe it was two bar absolute
as the flow is near supersonic at times.