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Selecting the right turbo is not simple. Some would think the bigger
the better, but that’s totally wrong. You also might think that the
Turbo must have ball bearing to start quickly, but that is not the
key issue either. It depends mostly on which driving dynamics you want.
You may go for either dynamic street performance or fastest on the ¼
mile strip.
I now have tried out 4 different configurations, from Garrett T25 and
up to bigger ball bearings ones.
All configurations were calculated and tried out on dyno runs. Every
time welding of new flange and down pipe. It gave a lot of experiences.
My very short conclusion: Go for dynamic street performance with a lot of
mid band torque and lowest turbo lag.
I know, it's not an easy decision. Most want as
much top power as possible.
Select the compressor side, just big enough to deliver the amount of
air at the pressure needed for the wanted power. Select the turbine
side not bigger than a compromise between backpressure and max
power, lean to the high backpressure side to get lowest turbo lag and
quickest spool-up.
Gas flow and heat into the turbine will generate power, so isolate the
manifold.
 Cold air into the engine is a very important issue. Cold air has
more oxygen mass and will burn more fuel and thereby generate more power.
Compressed air will increase in temperature: See 'Engine theory'. If
the inlet temperature increases from 25deg C to 50deg C, you will
loose almost 8% in power.
Turbo key issues
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Is about heat management in the engine room. Turbo
and power generates lots of heat
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Isolate the exhaust manifold and shield inlet parts from
exhaust side
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Cold air into the intake and the engine. Use as big as
possible intercooler
Turbo
manifold before and after external Waste-gate
 
Oil temperature and manifold pressure |
