Centrifugals and Screws, CompRatio vs. Boost and Detonation?????
01-10-2003, 09:13 AM
#23
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Hello, Guys,
The posts I am reading here are very correct, especially on the centrifugal blowers. Consider also that the Whipple makes much less heat than a roots-in fact, about the same as a centrifugal. The roots makes a lot of heat. The big thing about the Whipple is the low end power. If your outdrive can stand it, two boats that are identical in every way except the blower, one Whipple, one centrifugal, and both bang the throtle at about 3,000rpm, the Whipple will destroy the centrifugal. Timing curves are very different for each type of blower and would require a book (or several) to cover. Some type of boost referencing the timing curve is always best.
The posts I am reading here are very correct, especially on the centrifugal blowers. Consider also that the Whipple makes much less heat than a roots-in fact, about the same as a centrifugal. The roots makes a lot of heat. The big thing about the Whipple is the low end power. If your outdrive can stand it, two boats that are identical in every way except the blower, one Whipple, one centrifugal, and both bang the throtle at about 3,000rpm, the Whipple will destroy the centrifugal. Timing curves are very different for each type of blower and would require a book (or several) to cover. Some type of boost referencing the timing curve is always best.
01-10-2003, 10:01 AM
#24
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Blown- I will disagree on your comparison between whipple & procharger in a race. I would say if both boats were coming from off plane (1000rpm) then the whipple will kick butt on the procharger (That is if the drive on the whipple holds together) I would have to say from a 3000rpm stomp the procharger is going to be right there with the whipple. I know that when the throttle is wide open the intake manifold presure for the whipple will be at or close to the max boost at high RPM's & the procharger boost increases as the RPM's increase thus the whipple will have more low end torque. In reality when I stomp it at 3g the motor raps to 4500 right away & then keeps on climbing. At 4500 rpms my boost will be close to max.
03-07-2004, 10:07 AM
#27
1975 X-18 Donzi, Arneson
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Tom Cat, Turbo Jack,
Good guess,,
I lowered the CR to 8.5 did one pull, with the old 324IC set up, lost 20hp do to the lower CR.
Then switched to a 504IC, cleaned up the piping a little, (Quickly just for dyno work), and gained 131hp @ 6400rpm's and gained 4.5 psi of boost (3.8lbs vs. 8.3lbs) with the same 5" pulley.
Good guess,,
I lowered the CR to 8.5 did one pull, with the old 324IC set up, lost 20hp do to the lower CR.
Then switched to a 504IC, cleaned up the piping a little, (Quickly just for dyno work), and gained 131hp @ 6400rpm's and gained 4.5 psi of boost (3.8lbs vs. 8.3lbs) with the same 5" pulley.
Last edited by GEOO; 03-07-2004 at 10:18 AM.
03-08-2004, 11:03 AM
#29
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TurboJack I will back you up on that. The fuel injection having cleaned the cylinders up at lower RPM's, bringing the air fuel ratio up to a reasonable level that it no longer is puking raw fuel, I can do a full throttle roll at 65-70 with my M-4 and blow the prop completely out. That was a pretty broad statement to make, not true in every case.
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