Slaping a spare m90 on my Subaru Forester

Yep, A 2.5 liter engine with a 1.5 liter SC. Still getting some machine shop work done to get the block ready to accept forged parts. I've seen too many sc setups where the sc is mounted off the side of the head or in some other strange area; also limited psi obtained. If this works out right I should be seeing 25psi boost on a 2:1 ratio. Wondering if it will be eaiser to just swap in a sti computer to work with the boost.
Here a link to a subaru forum where it all started
http://www.rs25.com/forums/showthread.php?t=98949

verry kool! i am rolling the thought of doing something somewhat similar to my 85 bmw 635csi. the 3.5L inline 6 should really scream with one. i'm just unsure of if i'll use the m90 or the m122. i know it'll be easier plumbing wise and the wife already loves the power band in the S/C.

that looks cool as hell, bro... cant wait to see it done!

If i folllowed the supercharger calculator right, at 1.5 liters per rotation at a drive ratio of 2:1 would give me 23psi. Is this number realistic or would the higher psi creep back through the rotor gaps?

A 635csi w/ an m90, SWEET! I will take one!

Stephen

23 psi non intercooled..you crazy? Id stay under 10

For simple fabbing yes its easier without an intercooler, and for hood clearances to, but if I have to go with a hood with a scoop on it then I'll add in the intercooler too. If i run 10psi I'll end up with a large sc pulley or small crankside one

If a 2.5L is a 153 cubic inch engine
if you doing a 6500 rpm limit on the engine
then the engine will require 287 CFM of air (153*6500)/3464
Anything over this will be boost
with a 2:1 ratio the SC will turn at 13000 rpm producing 677 CFM, ideally

with a VE of 75% to calculate boost:
boost= [(677*.75)-287]/287 CFM *14.7psia
boost=11.3 psi

Can't recall if the volumetric efficiency is overall or just for the SC, overall would be as follows
[(677-287)*.75]/287 CFM *14.7psia
boost=15psi

Well, either way its not 25psi, somewhere between 12-15psi, some guys are running the M90 up to about 16k but thats the limit, definately have to be charge cooled, i'm running water-to-air in mine, with estimates on outlet temp well near 400F, its a heat pump!

I cant wait to see the hood on this thing!

You will definately need something to cool the air if you think you are going to get 20psi out of it with no problems. Up to about 8psi is good with the M90. More than that and you will run the IATs way up...obviously higher with higher boost.

SWS

Very nice! That would also go well with a subaru SVX (starting to like those cars...awd too!)

cmill95 said:

verry kool! i am rolling the thought of doing something somewhat similar to my 85 bmw 635csi. the 3.5L inline 6 should really scream with one. i'm just unsure of if i'll use the m90 or the m122. i know it'll be easier plumbing wise and the wife already loves the power band in the S/C.

Click to expand...

NICE! love those e24's....id love to see that ...i want a e24 m6...and that with an m90...yummy!

shorter nose options

I'm going to need a shorter nose to make this possible. What are ny options? Are there other m90 noses that are shorter or do i need to have a machine shop shorten it for me?

>I'm going to need a shorter nose to make this possible.

Sorry if I missed it...how much shorter?

in the range of 2-4 inches, i'll know more when I start the mounting plates and measure clearance from rear wishbone link and clutch slave cylinder. For the crank pulley 4 rib belt wont drive the sc, thinking of having a machine shop turn some extra ribs on it; then find a set of same size pulleys with more ribs at a junkyard

seems I need it to be 3.5 to 3.75 inches shorter unless i incorporate a jackshaft setup but i doubt that will shift it that much

project will get a nudge toward actual work when the short jag nose gets here from shipping; like a m62 short one but m90 bolts up.

washing my hands clean of the SC

I do however plan on building up my 96 lx, but not supercharging it.
I'm going to grab the following parts from the 94 sc. Speedo, rear 90 posi, spare 03 stang 4r70w, new torque converter, from seats, maybe rears too, 4 sc rims, key fobs, v8 moded exhaust,dual rear exhaust, auto climate control, one rear trunk light, the 97 headlights and turns that i grabbed from the bone yard. Extra tranny cooler, injectors for a second try at alcohol/ 60% nitro fuel again. maybe some others i missed. But everything else should be posted for sale soon.

I got that rare jag m90 never used and now I have a short nose to work with. Magnacharger likes my project and planning for the supercharged ej25 Subaru motors. When I have a completed setup and a few people show serious interest i can have a few custom lenght noses made. I could but not sure what positive effect using a mpx will do on this as I'll see 14K blower rpms at 25-30 lbs boost already. High boost, lower than usual rpms.
Going with a six rib setup as the GM aftermarket pullies are insane= 3.4 to 1.9 in .1 increments, decent prices.
So if this works out well and I end up making 4-6 supercharger units I think I'll end my ownership of anymore Thunderbird SC's. Theres something more to seeing a AWD car just shoot off the line and then drive that same car in 1 foot of snow with ease
Link to my work so far
http://www.subaruforester.org/vbulletin/f145/universal-eaton-m90-supercharger-setups-63326/

Picked up a used and upgraded mig 220v mig welder. Looks like this project will be getting some life shortly

"Yep, A 2.5 liter engine with a 1.5 liter SC."

I think its a great idea...
I don't see any progress on your link yet, you getting it together at all?
I will likely try this on my minivan for giggles...

paul

stalled due to a job loss

Not being at work gives me all sorts to time to fool around with stuff, the harder part is keeping the funds up. For that I'm selling as much of the SC stuff as I can and still keep around a supercharger or two for this.

The other problem is getting my spare block exchanged for one with excellent bore diameters instead of my well worn one. I got a Subaru guru with a large subie graveyard that gets new short blocks and sends the old core in for $. He said if I bring him my old engine, swap my crank n bearings into a "good" core he'll send mine instead. Cant just sell me a core as he needs to keep the exchange chain going. Just gotta make time for that.

Next question is what are the pro's and con's of turning a m90 at a slower pace yielding higher boost in smaller engines? Don't really care to downsize to a m62.