Automotive and Theory > Aero and Fluid Theory

iIs this the proper thread? superchargers

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With the stock pulley on the Eaton M62 off a Mercedes, the flow differences are @ 1.1% improvement over the SC12. Even though the displacement of the M62 is 1000cc as opposed to the 1200cc of the SC12. the pulley is smaller the than the SC12's and it spins faster. All I rwsally have to go off is a rough measurment, the SC12 has a circumference of @14", and the M62 has @11.5". The M62 should be very close to the SC12 with a more efficient flow and lower exit temp than the standard roots type supercharger. Not sure if I have the USDM or JDM version though.  OK, the measurements I have are loose at best. i measured the pulleys on the outside of the grooves with a seamstress's tape. The stock crank pulley is @ 18". The pulley on the SC12 is @ 14". The pulley on the M62 is running 11.5". The difference in the RPM of the Supercharger driven at an engine RPM of 7000RPM is the SC12 at 8,960RPM anbd the M62 at10,960. At this rate the M62 flows a little over 1% more air than the SC12.  The SC 12 has a displacement of 1200cc per revelution, the M62 is actually 1016cc. The SC12 is limited to an RPM of 12,500 RPM the M62 is limited to 15,500 RPM. The M62 is more efficient! It has a lower high side temp than a standard roots type supercharger, and has a lower drag on the parasitic drag on the engine. For S&G, the M90 has a displacement of 1472cc. So I still want to try the M62 on a 4AGE.

62 and 90 cubic inches = 1.016 liters and 1.475 liters.

Why not just start with the M90 from the get go? People are turning the SC12 to get 12 or 13 PSI of boost on the stock 2" intake and intercooler piping size. 14 PSI on the GZE is not a realistic number yet you see many places claiming to get 14 PSI. The Cusco pulley will only get you 13 PSI on a very hot day. Really, the only "true" way to get 14 PSI out of the SC12 is with the Non Stop Tuning multi-pulley setup, which over-revs the SC12.

I am assuming your SC12 clutch measurements are with the stock USA pulley, correct? The M90 is 22.9% larger than the SC12, so just turn it 22.9% slower for the same boost & much lower exit temps.


Take into consideration the aftermarket for the M90/M62/M45. First the stock pulley is only about 2 1/2" to 3" in diameter. Probably be able to use the N/A pulley to drive it to a decent boost level. Now the aftermarket. Pulleys are available to about a 2" diameter. Advantages would be a lighter crank pulley and a shorter lever on the crank snout. A couple of pounds saved on the crank snout wouldn't Seem like much, but would make a difference. Shorter lever on the crank snout would possibly lower main bearing loads. Now just need to compare parasitic losses related to boost and mass. Loss to boost ratio,  and compare boost maps.

M90 with short snout from a 1995-97 Jaguar XJR or X300 4-liter AJ16 engine. Only downside is the non-clutch pulley...

I'm good with clutchless. Maybe use the stock N/A crank pulley with that pulley. 20lbs off the bat!


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