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+--- Thread: Rotrex Superchargers... Opinions (/showthread.php?tid=7457)
Rotrex Superchargers... Opinions - matfield - 10-08-2016
Gents,
Whats the opinion on these? and this model specifically C38-61.
http://www.tts-performance.co.uk/rotrex-c38-supercharger
Given that you could have zero back pressure, and very limited lag.
It does say they're for gasoline engines, but I'm guessing that would just be a case of getting the right pulley to give the correct RPM to the charger.
Pros, Cons, Experiences all welcome, or if it's been discussed before let me know.
Mat
RE: Rotrex Superchargers... Opinions - R-3350 - 10-08-2016
i wouldn't recommend a centrifugal type for twin-charging. they don't quite have the immediate response of a roots or lysholm type unless you run a big overdrive pulley then you run the risk of over revving the blower. at high rpm its better to use a turbo as it doesn't take as much power to drive so you get more usable power.
RE: Rotrex Superchargers... Opinions - matfield - 10-08-2016
Makes sense. So they can't physically push enough air, or create enough pressure for STD?
RE: Rotrex Superchargers... Opinions - R-3350 - 10-08-2016
they generate plenty of pressure the issue is in the higher rpm needed to do so. Rotrex and any other centrifugal blower like a pro-charger are not positive displacement pumps they have a minimum rpm the rotor must spin in order to produce a positive pressure. with a turbo this is delayed by the mass of the rotor and the ability of the turbine to extract energy from the exhaust flow. with a centrifugal supercharger the delay has to do with the gearing ratio between the impeller and the crankshaft. you could run an overdrive pulley such that the impeller would be spinning fast enough to make useful boost right off idle however the issue there is that you would over rev the impeller at higher engine rpm. this would mean you would have to install a clutch like the one in an AC compressor to switch it off above some rpm. with a roots blower or lysholm type supercharger you have a positive displacement pump which means they move a fixed volume of air per revolution. a common blower used for super turbo set ups is an Eaton m90 it moves 90 cubic inches of air per turn. so to get positive boost from that all you would need to do is gear it to turn fast enough to displace slightly more than 1/2 of the engine displacement per rev (a 4 stroke engine consumes its displacement in air every two revolutions). this would let you build boost even at idle which helps to cover the gap before the turbo is spooled. the reason you don't want to only run a super is they are significantly less efficient at compressing air than a turbo. this means much higher intake temps along with energy lost from the crank to turn the supercharger that ends up being wasted as heat out of your inter-cooler.
RE: Rotrex Superchargers... Opinions - NZScott - 10-08-2016
Pretty well explained, centrifugal superchargers combine the worst attributes of blowers and turbos IMO
RE: Rotrex Superchargers... Opinions - matfield - 10-09-2016
End of conversation then! Thanks.