FI and RPM question
01-01-2008, 05:12 PM
#11
2nd Gear Member
Join Date: Dec 2006
Location:
Posts: 261
RE: FI and RPM question
i understand that part. But the supercharger works only as hard as the input is spinning, in this case the input being the pully system. So if it only has one speed the amount of boost made at 3000 RPM does not change from one situation to another (varies slightly due to ambient surroundings i guess). The throttle position then must be what determines that psi-a in the manifold right?
I thought that was the pitfall to a supercharger, where as the amount of boost a turbo creates is a function of engine load and boost controls which is a plus to the turbo.
This is just how i understood it, i may be wrong.
I thought that was the pitfall to a supercharger, where as the amount of boost a turbo creates is a function of engine load and boost controls which is a plus to the turbo.
This is just how i understood it, i may be wrong.
01-01-2008, 05:49 PM
#12
6th Gear Member
Join Date: Sep 2006
Location: Gainesville, FL
Posts: 11,278
RE: FI and RPM question
ORIGINAL: Gene K
On a Roots (Like Roush, Magnuson) it takes like 1/3 bhp to spin the rotors when bypassed.
On a Screw Type like a Kenne Bell, Saleen, or Whipple I think it takes slightly more but still not much.
On a Roots (Like Roush, Magnuson) it takes like 1/3 bhp to spin the rotors when bypassed.
On a Screw Type like a Kenne Bell, Saleen, or Whipple I think it takes slightly more but still not much.
01-01-2008, 05:56 PM
#13
6th Gear Member
Join Date: Sep 2006
Location: Gainesville, FL
Posts: 11,278
RE: FI and RPM question
ORIGINAL: slySTANGguy
Can a supercharger produce vacuum and boost at the same RPM under different conditions?
Can a supercharger produce vacuum and boost at the same RPM under different conditions?
So to answer your question, yes you can have vacuum and boost at the same rpms under different conditions. Starting from a stop at 1/4 throttle i'd have vacuum, starting at full throttle i'd have an instant 8lbs of boost with the whipple HO and with street tires i'd have the rev limiter shortly after that.
01-02-2008, 01:01 PM
#16
4th Gear Member
Join Date: Nov 2007
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Posts: 1,699
RE: FI and RPM question
ORIGINAL: moosestang
As hammeron said, the supercharger doesn't produce vacuum. When cruising in 3rd gear at say 4,000 rpms you will still have a vacuum in the intake manifold. Not much vacuum, but still a vacuum. When you push the throttle past a certain % and go from vacuum to no vacuum the bypass valve will close and boost will fill the intake manifold and be pushed into the combustion chamber when the intake valves open. The twin screw blowers do not rely on engine rpm to make boost, the centris and turbos do.
So to answer your question, yes you can have vacuum and boost at the same rpms under different conditions. Starting from a stop at 1/4 throttle i'd have vacuum, starting at full throttle i'd have an instant 8lbs of boost with the whipple HO and with street tires i'd have the rev limiter shortly after that.
ORIGINAL: slySTANGguy
Can a supercharger produce vacuum and boost at the same RPM under different conditions?
Can a supercharger produce vacuum and boost at the same RPM under different conditions?
So to answer your question, yes you can have vacuum and boost at the same rpms under different conditions. Starting from a stop at 1/4 throttle i'd have vacuum, starting at full throttle i'd have an instant 8lbs of boost with the whipple HO and with street tires i'd have the rev limiter shortly after that.
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