Hey any of you supercharger guys know how fast you can safely spin an Eaton M90? I have one I am going to use on a 300 6Cyl, but just realized I will have to spin the living shit out of it. I am looking at blower speeds around 12,000 RPM at 4000 crank RPM. Will this thing self destruct or do other people spin them faster? 12k sounds really fast. Thanks!
M90 Blower Question
- Thread starter 84FordVan
- Start date
Blower maps here:
http://www.eaton.com/EatonCom/ProductsS ... /index.htm
Click on the tabs for M90 and M112 and look at the maps.
Both are happiest at 6000 RPM and get rapidly less happy as you get above 8000 and are making almost as much heat as boost when you get above 12,000
A 300 will likely be a better match for an M112.
Looking at the M112 graph: a 300 at 4500 RPM consumes about 442 M^3 per hour at zero boost (14.7 PSIA) and 100% volumetric efficiency. If you want 7 PSI of boost, that gives a pressure ratio of 1.47:1 and requires a theoretical 651 M^3 per hour. That just catches the corner of the highest efficiency area of the M112 graph and requires that the blower be spun at about 1.47 times the crank speed or 6600 RPM at 4500 engine RPM. You run right through the middle of the efficiency island from about 2500 RPM up. I'm guessing that a set of 1.5:1 blower drive pulleys are readily available.
That's as close to perfect as you're going to get
http://www.eaton.com/EatonCom/ProductsS ... /index.htm
Click on the tabs for M90 and M112 and look at the maps.
Both are happiest at 6000 RPM and get rapidly less happy as you get above 8000 and are making almost as much heat as boost when you get above 12,000
A 300 will likely be a better match for an M112.
Looking at the M112 graph: a 300 at 4500 RPM consumes about 442 M^3 per hour at zero boost (14.7 PSIA) and 100% volumetric efficiency. If you want 7 PSI of boost, that gives a pressure ratio of 1.47:1 and requires a theoretical 651 M^3 per hour. That just catches the corner of the highest efficiency area of the M112 graph and requires that the blower be spun at about 1.47 times the crank speed or 6600 RPM at 4500 engine RPM. You run right through the middle of the efficiency island from about 2500 RPM up. I'm guessing that a set of 1.5:1 blower drive pulleys are readily available.
That's as close to perfect as you're going to get
I was thinking tonight, and realized I did my math for the M90 wrong, man do I feel dumb. I figured in a 100% efficient situation, the Eaton moves 90 cubic inches of air per revolution, where the 300 moves 300 c.i. per revolution. I thought I would be spinning the blower 3.33 times the speed of the crank just to keep up with the engine's flow. My mistake being the 300 moves 300 c.i. of air every 2 revolutions, not one revolution. It takes 720 degrees of the crank to complete an entire engine cycle in a 4 stroke. Totally forgot that. This now cuts my blower speed in half, making the M90 a feasible option for boost production. Anybody have any thoughts on this? Thanks!
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