Blow through vrs draw through screw supercharger
Blow through vrs draw through screw supercharger
(OP)
I was wondering if it would be possible to run a blow through screw supercharger. It seems throttle response would be greatly enhanced by going to blow through ITB`s where positive pressure is waiting on the throttle plates to open. If not this a couple of large throttle plates on a sealed pre plenum opening up into a plenum for the runners to keep losses down in the runners.
The engine is designed for race, fabrication and cost are not a factor.
I was also considering an electronically controled throttle plate before the supercharger to keep pressure down so that it would be drivable at a cruise without over responding to the constant positive pressure.. Or an alternative might be a boost drain off valve. It seems mounting the supercharger like this would result in terrible part throttle efficiency. Continously venting pressure into the atmosphere. Although there must be drag associated with reducing the blower`s adiabatic efficiency as well. Im unaware of the nessasary tools to figure the difference in efficiency loss when compared to part throttle blow through vrs draw through.
Im primarily concerned with optimal throttle response, and top end power.
-Thanks-
Travis
The engine is designed for race, fabrication and cost are not a factor.
I was also considering an electronically controled throttle plate before the supercharger to keep pressure down so that it would be drivable at a cruise without over responding to the constant positive pressure.. Or an alternative might be a boost drain off valve. It seems mounting the supercharger like this would result in terrible part throttle efficiency. Continously venting pressure into the atmosphere. Although there must be drag associated with reducing the blower`s adiabatic efficiency as well. Im unaware of the nessasary tools to figure the difference in efficiency loss when compared to part throttle blow through vrs draw through.
Im primarily concerned with optimal throttle response, and top end power.
-Thanks-
Travis





RE: Blow through vrs draw through screw supercharger
RE: Blow through vrs draw through screw supercharger
Im not sure the itb`s will work yet though. I certainly dont want to put together something that isnt going to work.... properly.
Any idea on what camshaft specs would lead towards producing the snapiest positive displacement throttle response?
RE: Blow through vrs draw through screw supercharger
RE: Blow through vrs draw through screw supercharger
The engine has a serious problem with short circuiting or overscavaging n/a so itll probably be worse witha blower. I can custom make the throttle bodies to any size nessasary and then im probably going to position a set of light injectors like 19lb`s up front spraying down on the valve with a set of 50`s upstream behind the plates. Current cams are stock. Probably running the whipple 3000 cc per revolution blower. Intended redline is arounnddd 7300 even though piston speed is VERY sane at that rpm because of the short stroke I could go as high as 7700 but thats the upperlimit without going dry sump. Bottem end will be built to handle what it needs to. This is more of a theoretical question then an engine specific one. But thats what im gathering information for. I can build pretty much anything that needs to be built so thats not a problem either.
RE: Blow through vrs draw through screw supercharger
RE: Blow through vrs draw through screw supercharger
I agree theoretically you'd get better response from the system you are considering. But if the blower can pump 3000cc (one displacement) per revolution how much clock time will you be saving?
If you keep it standard, with a throttle body in front of the blower your life will be much easier. Those flow numbers are awesome, the car should really fly!
RE: Blow through vrs draw through screw supercharger
I agree theoretically you'd get better response from the system you are considering. But if the blower can pump 3000cc (one displacement) per revolution how much clock time will you be saving?
If you keep it standard, with a throttle body in front of the blower your life will be much easier. If you need to do something trick, then add an intercooler. Those flow numbers are awesome, the car should really fly!
RE: Blow through vrs draw through screw supercharger
Lag is not an issue with positive displacement blowers, in fact even with a convectional setup, the response is amazing, even alarming if you are not prepared for it.
Throttle plates downstream of the blower are more prone to shaft deflection. Even when the throttles are in front of the blower, throttle shaft deflection can cause an unstable or rolling idle.
Regards
pat pprimmer@acay.com.au
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RE: Blow through vrs draw through screw supercharger