Supercharger PSI

[Jetson8294]

Hey, I was just wondering how much PSI are you supercharged 3.0 guys are running safely? i was wondering if 10psi would be safe.

[mwinkle353]

13 psi is the normal with a Ford Thunderbird M90 and the stock crank pulley.


Wink

[Ondonti]

You cant just pick and choose your boost unless you have the right pulley combination.

I personally would love to see someone running the 12-13psi setup spray some alky into the rotors. boost would increase a little and detonation would be gone. I think that would be a monster. I dont know why Dad never sprayed alky.

[Jetson8294]

i have a interchangeable nose cone on the m90 i have. i was wondering because i dont want to put over 15psi into the motor.

[Boogieman142]

what about the gm 3800 one?

[big_P]

the GM 3800 is the Eaton M-90. It is also the same as the one used on Ford Super Coupes.

I've got one waiting to be thrown onto my LeBaron.

[Boogieman142]

yeah i figured that but i wanted to know how much boost it will have.

[Ondonti]

12-13 psi.

If you put an underdrive pulley on it will be more like 6-8 psi depending on the size of the pulley.

[Boogieman142]

ts about all i wanted to run anyway.

[Boogieman142]

so, doesanyone have the specs on it, like how much flow at what rpm, pulley size etc...

[Boogieman142]

ok, ifound out that while on the 3.8 it is supposte make about 7-9lbs of boost

[Harvii]

Quote:

Originally Posted by Boogieman142 ok, ifound out that while on the 3.8 it is supposte make about 7-9lbs of boost

3.8 has a much smaller crank pulley than the 3L does =)

[Boogieman142]

hats what i was thinking except that i will be running a nick boers udp too so it will prolly be much less.

[Avenger]

My brother's 95 Bonneville would make 10lbs on the stock pulley all the time. And that's with the smaller M62 SC. When he got his current 98 Buick, it would hit 13lbs on the stock Series II pulley, and gets up around 15-16 now.

The Ford version of the M90 is SLIGHTLY better, the shape of the inlet into the supercharger is larger and better, allowing slightly more flow.

As far as CFM, I dunno. But if you chuck a socket into a Makita drill, and use it to drive an M62 in reverse at 600rpm at the pulley (blowing air OUT the inlet), it makes a jim-dandy little leaf-blower!

[Shel-Game]

Quote:

Originally Posted by Boogieman142 so, doesanyone have the specs on it, like how much flow at what rpm, pulley size etc...

That's easy - the Eaton M90 displaces 90cuin of air every revolution. They lose only a slight bit of flow at higher manifold presures. If you spin the S/C at 10krpm, that's ~520cfm. That should be good for 400hp, minus the 50 or so it will take to spin the S/C, gives a net HP of ~350. Pulley size depends on how much power you want, and therefore how fast you want to spin the S/C. If you want to make 400 hp using an M90, then choose the pullies so that the crank to S/C ratio is ~2:1.

Likewise, the Eaton M45 displaces 45cuin, the M62 - 62cuin, and the M112 - 112cuin...

When it comes to a positive displacement, screw-type S/C, you don't care about boost pressure. You care about flow rate. More airflow = more HP. So, just spin it as fast as you want (or whatever is required for your desired HP level), the manifold pressure is completely secondary. In fact, manifold pressure is, technically, bad with a screw-type S/C. Again, they lose flow (albeit only slightly) at higher manifold pressures.