m90 on 4 banger

eightvalver

Registered User
Hello. I am here because no one else has good info on the m90. I am planning on mounting a m90 to be used on my 4 cylinder car just as a challenge and project.

The crank pulley doesnt have as many grooves as the supercharger pulley...it has like 3-4 grooves. It is also 4 7/8" in diameter. The supercharger pulley I am planning on getting is like a 2.5" diameter...to compensate for the smaller crankshaft diameter.
4 7/8 X 3.14 = 15.3075 (crank dia.)
2.5 x 3.14 = 7.85 (supercharger dia.)
15.3075/7.85 = 1.95

7000rpm X 1.95 = 13650

I have been reading on here and it looks like the smaller pulleys like to slip. I plan on compensating by having the pulley sandblasted and possible having crosscuts by a machinist perpendicular to the grooves.

I have a megasquirt for fuel and timing management that was previously on the car or might use the stock computer with a msd boost timing master and a fuel pressure riser.

Any thoughts on how this blower will perform on my 1.6???? Is this too much blower for the motor?
 
I don't have my analysis software in front of me, but off hand I'd say that your 2:1 drive ratio is going to be way too much for the motor. You could probably go down to a 3" pulley and still make 15-18psi.

I think a 4 rib belt will probably get eaten up. Slip won't be the problem, but if the belt has too much load it will just get torn up. I think 6 ribs would be ideal.

How much boost do you hope to run?
 
what's the compression ratio on the 4 cyl.? or maybe some actual pressure numbers. That will start to get us an idea on how much boost it can handle.
 
wow you guys have really good info to share...many thanks....

I am just trying to see if I can mount the supercharger in the tight confines of the engine bay and get it to work.....its a stock motor, cast pistons 9.8 - 1 compression... so I have to limit the amount of boost for now (really low)....but the end goal is to run high boost with a built motor with forged pistons

I rechecked the crank pulley...it allows for a 6 ribbed belt...so thats good....as far as the 2:1 drive ratio...thanks for the advice....I'm glad it from your tip dave that I wont have to get a smaller pulley
 
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