boost presser and power gain

[Tom Sharpe]

More later Sergey........  Tom Sharpe

Tom's Turbo Tips:

These are the results of my experience with a T04B V2 trim on a 350 SBC
with adapters from Accel. It was quite a while ago so and my memory is
not as good as it used to be. The math is for us ten finger users, if you
need a calculator, you need better formulas.... As always, your results
may vary..........

My 350 example engine is capable of 350 HP @ 5250 rpm, if yours is not
capable of 1 hp/Cu.In. then adjust accordingly.
Horsepower = Torque @ 5250 RPM.  Start thinking torque.
........Compressor maps.........
Calculate air flow @ 2000, 3000, 4000, 5000, 6000 RPM. Assume a VE of ??
(I used 95%)
350*5000/12/12/12/2*.95=CFM=481   @4500 at 13lbs boost = 850CFM
Calculate the same @ 1 1/3, 1 2/3, 2, 2 1/3 PR. (5, 10, 15, 20 lbs. boost
(gauge)).
(Multiply by 1.3333, 1.6667 etc.) As pressure goes up, VE goes down, but
only a few %.
You should now have 25 points.
An engine capable of 1 Hp/CuIn will deliver approximately 1.333 Hp/CuIn @
1.333 PR, 1.666 Hp/CuIn @ 1.667 PR, etc.
An engine capable of X torque will produce 1.333 X torque @ 5 lbs. boost
................ .is the light on yet??
How much Torque do you want to produce???? At what RPM ????? Will the
short block stand it?? Will the heads stand the airflow??

Plot and connect the rpm points @ 1.3 PR on the compressor map.
You should have a line from the bottom center to the middle right (or
there abouts)
Repeat for the 1.67, 2, and 2.3 PR lines. You should be adding lines up
and down, left of the first.
The idea is for the line to go through the center of the compressor
efficiency island. Stall is generally to the left and above the island
(compressor too small).
You should now know if you have chosen the correct compressor. Indy car
compressors are most efficient at high boost 30-45 lbs. gauge or 3-4 PR.
Others are lower.
Turbochargers are just air pumps... just like an piston pump (engine) and
the compressor map describes it's capacity which can be expressed in
Lbs./min. CFM, or horsepower. A T04B is capable of 450-500 HP, on a 302
Ford, that’s 13 lbs. Boost @ 5250 rpm, more at lower rpm (Think Torque).
On a 122 CI Pinto (2L), it is 30 lbs. boost @ 8000 RPM. On a 502 BBC,
it's a soda straw in the intake and a cork in the exhaust.
The turbine housing ratio can be thought of as Blower pulleys. Smaller
numbers cause the compressor to spin faster and produce more boost and
torque at lower RPM (until it runs out of capacity). Larger numbers lower
boost and raise RPM potential (and Horsepower) (again until it runs out
of capacity).
Turbochargers have a "range", usually from X RPM to 2X RPM..... any more
requires a wastegate.

The vehicle was a 2800 LB Jeep CJ5 w/ 350 SBC and 350 Turbohydro w/ a
HoleShot Converter. The short block was stock w/ 8.5 CR. & cast pistons
and crankshaft. I used an Accel suck through setup with a 650 Holley and
no intercooler with 3.5" exhaust to twin 2.5" turbo mufflers. The Turbo
was an Air Research T04B V2 trim with .96 Turbine housing. I was slightly
restricted on both the intake and exhaust sides to control Boost. No
other boost control was used. From a standing start, I could not get
boost in low gear (turbo 350) because of the relatively stock 12"
converter and poor brakes to load the motor. Second gear was like low all
over again. With the exhaust open, the 15 lb. boost gauge would slap the
stop (chipped the red paint on the needle) with the shift, then drift
back to 13 lbs.

Once rolling, it was like the boost gauge was connected to the gas pedal,
instant response. It had a tremendous amount of torque. You never had to
downshift. Roll into the throttle at 50 MPH in high and 80 was a blink
away. Just a whoosh like a small jet aircraft taking off. No fuss, just
pushes you back in the seat. At 4000 RPM, it started to tail off, 4500
was time to shift, and 5000 RPM was ALL DONE, like a potato in the
exhaust, boy did it wheeze.

I went through two crankshafts before I learned to control DETONATION.
Keep spark @ 30-32 deg over 3000 RPM, retard spark from 2000-3000 a lot.
Added water injection, (a pressurized tank and windshield washer tubing
and squirter into the turbine inlet--- .080 hole) which helped a lot.
Most engines will not detonate over 3000 rpm, but less advance is needed
because of the increased fuel density. The short block was a stock 8.5 CR
w/ cast pistons and crankshaft.