Procharger & gears....
- Thread starter inkjunkie
- Start date
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As in, the rear end, sure, it's pressurized, the engine. Turbo or supercharger, the same idea holds.
CUUDAK
Well-Known Member
If the idea is pressure they are the same. A turbo works specifically from exhaust flow. Gear driven turbos work on the same theory as a blower. You only get as much boost as the drive gear allows.
Turbos like load i.e., higher gear ratio(2.90-3.23) in the diff. and weight.
Prochargers are spun by the crank same as a blower so imo a lower n/a gear(3.73-4.10) would be used.
Jus my 2 cents.
Turbos like load i.e., higher gear ratio(2.90-3.23) in the diff. and weight.
Prochargers are spun by the crank same as a blower so imo a lower n/a gear(3.73-4.10) would be used.
Jus my 2 cents.
Sorry, thought pressure is pressure.
forced 340
Well-Known Member
your going to want to go with a higher gear with a supercharger. a supercharged engine is basicly a high comp engine that gets rpm and hp with the crack of the throttle. turbos need "load" to really work well. thats why you need a lower gear ratio with turbos. they create a lot of load. i have a 3:23 w/ a 28'' tall tire on my turbo dart and gets to the chip(7000) faster than when it was n/a running 4:10 gears!
Under full throttle starting at say 3000 rpm you will make less boost than say at 6000 rpm and it will build gradually through the mid range and until you shift. I like to gear them like you would a high spinning big block that's kind of how they act ( Good tourqe and the power keeps coming until redline, 3.55 to 4:10 It will depend on how and where ( rpm ) you will drive it most of the time.
Joe
Joe
I don't want to beat a dead horse here, but I have a little experience with belt-driven centrifugal superchargers (Vortec on a 360 Magnum) and have access to information about what are probably two of the very fastest turbocharged /6's on FABO (Tom Wolfe's '70 Dart and Ryan Peterson's '66 Valiant,) both of which make about 500 HP from 234 cubic inches.
My V-8 car, with the belt-driven supercharger, LIKES to spin RPM's to make power. I have it geared 4.10:1 in the rear, and that keeps the rpm's up, finishing the race at over 5,000 rpm, with maximum boost (10psi) at that engine speed. More rpm = more boost, up to a point.
The /6 turbo cars I referred to, act more like the motor in a fuel dragster, making outrageous amounts of torque when held back at medium rpm's, which is what happens with the 2.76:1 ratios they use in the differentials.
Even their 60-foot times seem to benefit from these "hiway" gears.
I know that seems very strange, but I think it has to do with the amount of exhaust gas that spins the turbo impeller.
With our similar (copy-cat) /6 car, we are going to start out with a 3.55 gear , but are putting a spool in a 2.76 center section to use, down the road.
Our local drag strip is only 1,000-feet, so quarter-mile gearing would be a little different (1,000-feet is only 75% of 1,320.)
3.55X .75 = 2.69. Not far from 2.76...
Cut and try... LOL!
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