Quote:
Originally Posted by toohighpsi
Screws and Roots cannot be grouped - Screws SCs have internal compression, Roots SC do not.
When a roots device is at cruise - the SC is under manifold vacuum (lower air density to spin the rotors in) and it is simply recirculating the from the SC outlet to the SC inlet, input power to the device is very low and heating is minimal. While there is some temp increase, it is due to the recirculation of the low density air and lack of fresh inlet air. Once the throttle is opened there is a rapid drop in temp due to fresh air induction followed by a gradual rise as manifold compression occurs.
A screw device is under the same manifold vacuum except the device is compressing and releasing within the rotor mesh during cruise even though the compression is not needed. The bypass valve routes the excess outlet air back to the inlet, but it cannot turn off the internal compression. This results in increased supercharger input power at idle/cruise, increased manifold temps, and reduces fuel economy compared to the roots.
A centrifugal supercharger is always operating at atmospheric pressure since it located before the throttle body. This allows it the benefit of not having to recirculate the air back to the inlet of the SC providing a continual flow of fresh air. While this keeps temps down it also costs in the form of SC input power at cruise conditions the due to pumping full atmospheric pressure air through the device and higher mechanical losses compared to a roots or screw from the gear drive system to achieve the necessary RPM to make a centrifugal compressor operate.
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You basically just wrote exactly what I was saying in my original post...
Though I didn't want to add a bunch of tech stuff and confuse people
Cliff notes on BOTH of our posts.
Roots = Temp increase when not in boost.
Screw = Temp increase when not in boost.
Centri = no temp increase when not in boost
Turbo = no temp increase when not in boost
Which makes the quote below incorrect, by now THREE people.
- You, that works for a Roots blower manufacture.
- KenneBells own website that builds screws.
- Myself that works for ProCharger a centirfugal.
Quote:
Originally Posted by JANNETTYRACING
Please understand the blower only makes heat when making boost.
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Again, just as I stated in my post... all of this isn't the end of the world.
And really isn't a big deal. However, its not factual to say things like that.
Thats all I was trying to say.
Members of this forum want to hear FACTS, not opinions.
I appreciate your posts always, since they are always solid.
