Here are a couple of T3 maps. Ironically a bigger compressor might help (I
think).
A turbo tachometer would help us match the turbo.

Paul Lamar

Bulent Aliev wrote:

Paul, I was thinking the same thing. Can we fit a bigger compressor on our
turbos? I see on ebay T4 compressors for sale, but my practical turbo
knowledge is nill?
Bulent

Yes I think we can. As I recall from a message about a year ago there is
someone in Australia doing just that. I don't know if a T4 compressor
will fit on a stock 1991 turbo however. We could also just put a muffler
on the turbo to slow things down with back pressure.

According the Hugh MacInnes book Turbochargers as a rule of thumb a
turbocharger
picks up speed at the rate of 2% per 1000 feet. At 10,000 feet it is 20%
higher RPM.

Since centrifugal force is proportional to the square of RPM the stress on
the blades is 44% higher at 10,000 feet all other things being equal.

At 15,000 feet it is 225% higher. This is mitigated somewhat by the colder
temperature at higher altitude but your turbo is more likely to explode
in the warmer climates :)  We must design for this.


To follow along on this you will need Hugh MacInnes book "Turbochargers".

Page 37 Sea level.

150 cu in/ 1728 = .0868 cu foot

0.0858 X 7000/2  = 303 cubic feet per minute.

Hugh is assuming 100% volumetric eff. here. We may be higher.

He assumes most engines are 80% VE so he adjust for that. We won't and
will stick with 100% in this case.

For 10 psi boost and 65% compressor efficiency.

(10 X 2.03 +29)/29 = 1.7 pressure ratio.

from table 1 page 16 Y = 0.162

0.162 X (70F + 460F) = temp rise in degrees Rankin or 202F

Density ratio is 1.36 actual compressor inlet flow is therefore
1.36 times 303  or 412 cubic feet per minute.

Converted to pounds per minute that equals 28.42

You plot this number along with the pressure ratio on a
turbo map. This looks like it won't fit well on any of the
T3 maps. This is probably our problem.  In fact this point
falls off to the right of almost all the T3 maps. We could
easily be getting 150,000 RPM at altitude.

Given this the right map is T04E "54" trim at 80,000 RPM.
Max RPM on this turbo is 115,000 RPM. Perhaps a TO4 "50"
trim might be safer also at 80,000 with max RPM 126,000.

Dave, what trim is that TO4 turbo you have?

This needs to be redone for altitude. In fact we need to do a spread
sheet or a QB program to calculate this for all altitudes and inlet
temperatures. Anybody want to take on this job?

I think Dave's inlet temperature is around 140 F as I recall.


Paul Lamar

John Slade had his turbo reconfigured by Leon Promet in AUS,
http://www.turbonetics.com.au/
but have not flown it yet. The web site explains what he does. I wander if
somebody can do that here?
Bulent

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