Copy of my other susbequent post over at mbworld.
I've had a look at the two supercharger gearings.
I've often read about the 2.3L lysholm doing 23,000rpm.
Well that's partly correct - half of it is - on stock pulleys SL55 of 155/91mm and at 6200rpm x 2 internal gears of 1.35 x 1.66 = 23,813 - that's for the 3 lobe rotor.
What I've termed the "cavity" rotor, is ony doing 3/5ths of that = 14,288rpm.
Suprisingly what I've worked out (
apologies to those who already knew)
The 1.6L is doing similar speeds.
In stock format - 155/74m pulleys @6,200rpm the cavity rotor is the pulley driven rotor is doing 12,986rpm and the 3 lobe rotor is doing 5/3rds of that = 21,644rpm.
Of course in Guran's case for a 185/65mm = 17,646/29,410 rpm.
Although it is purely a relative term - that's some
serious rpm!
The other thing I'm still trying to work out is the relative differences in the dimensions. I suspect the 2 compressors use the same rotors - but the 1.6L rotors are cut shorter to suit the shorter V6 blocks.
(
If anyone has some info on this, much appreciated)
I currently working on the assumption the LYS2300 isentorpic chart floating around the web refers to pulley'd rpm and some sort of base m3/min - either STP or NTP.
If you drive the 1.6L at 10,000rpm, the cavity rotor is turning at 10,000rpm - its directly driven by the pulley drive.
Now the LYS1600 doesnt directly have rpm on it. I'm only infering it is the line that goes through ~16m3/min (564cfm) at PR1.0 which at 10,000rpm = 1.6L/rev. Alterntate/additional information appreciated.
If you drive the 2.3L at 10,000rpm, based on the chart and extrapolating down to Pressure ratio of 1.0 you get 22.5m3/min or 794cfm or....2.25L/pulley rev at 100% Volumetric Eff..That's the deisgn specified volumetric capacity.
However, the "cavity" rotor is actually turning at 13,544. If you actually divide it by the cavity rotor's rpm - this points to 22,500Litres/min at 13,544 rpm or, 1.66L/rev of the rotor.
hmmm....this is only 4% more than the 1.6L unit.
...not exactly what I was looking for. If the rotors are the same profile (assumption only) then the 2.3L rotors must be about 4% longer.
What I was hoping for was.....
Coming at it from another angle -
Well I've never pulled one apart - but measuring the cases, the 1.6L casing on my car is 220mm and if you look at the attached dimensional comparison,
compliments of RobertAMG, and scale up by pixles - the 2.3L is 278mm or 26% longer.
Someone with an actual measurement appreciated.
So I guess you can say - work in progress....but some interesting revelations just the same (
against other things I've read out there).
PS - also note the teflon coated rotor is on different sides for each application.