M90 Questions

Fbod383

Registered User
Hello, I'm new here.. obviously. I am currently undergoing a project using an M90 from a T-bird. I figured this would be he best place for info.

OK, are there other places who make smaller pulleys than March?

I here the stock pulley makes about 10-12 PSI (depending on app), is this correct? And how much of a temp increase can I expect from a 2-4psi increase. I have fabricated an Air to water intercooler to help drop the heat and will also be using water/alcohol injection. Also what is the max output of this S/C? Is belt slippage a big problem? This motor will spin near 8000 rpm
 
Fbod383 said:
Hello, I'm new here.. obviously. I am currently undergoing a project using an M90 from a T-bird. I figured this would be he best place for info.

OK, are there other places who make smaller pulleys than March?

I here the stock pulley makes about 10-12 PSI (depending on app), is this correct? And how much of a temp increase can I expect from a 2-4psi increase. I have fabricated an Air to water intercooler to help drop the heat and will also be using water/alcohol injection. Also what is the max output of this S/C? Is belt slippage a big problem? This motor will spin near 8000 rpm

Check www.supercoupeperformance.com for smaller pullies. You can also check other such as BTM Motorsports, SCI and there's a few more out there who make them as well.

The PSI that is made with the M90 is very dependent on many variables. Measuring boost is nothing more than measuring back pressure. With better flowing heads, open exhaust, opened up intake, you can easily make 13 psi, but be making close to 100 rwhp more than the stock 10-12 psi that is produced from the factory. Simply asking how much PSI the blower can make is not a measure of performance.

With a small pulley, belt slippage can be an issue. The SC uses a jackshaft pulley to drive the supercharger. Do you have one of those? And if you are using both a air/water/air IC, and alcohol injection, then you shouldn't have to worry at all about the intake temps. Just me advised that the M90 is generally a heat pump. You can get porting done that will help reduce that, but it is still a heat pump.
 
Let's start off with some specifics about your project such as the displacement and compression ratio of your engine before we throw pulley sizes around.

Paul
 
Boost pressures are based on drive ratio, blower displacement, engine CID.

Roots blowers increase temp about 18-20* per PSI.

Jeff
 
Well, I'm hardly new a forced induction. I know quite a bit about the 4th gen M90 used on GMs. But it seems this 2nd gen M90 is a whole different bird. I asked about max PSI because no matter the restrictions on the engine, the S/C will only make so much boost before cavitation begins and all eeficiency is gone out the winda. on GM S/C it is around 18PSI, but they are more efficient. I found a 94 S/C on ebay I may spring for.

Some backround on me. My first real project was my 91 Z28 with a 383 and a Novi2000. I've since gone 4 banger :eek: But at least i'm keeping it domestic. I'm building a Quad4, its got a forged steel crank, Eagle H-beams, and ross forged 8.5:1 slugs.. thats for the bottoem end. The head is very aggressivly ported running Si stainless valves.. very very good flowing heads. My other side project is my roomates 93/97-LX/Cobra... uhh go here and it will eplain it www.modfox.com We just finsihed the motor rebuild on this and are putting it back in this weekend.
 
18 psi, is that with an intercooler? If you pick up an m90 from a 94 bird, putting in late 90's teflon rotors from the gtp is an excellent upgrade, and may cure belt slippage. I got a set from Ed, excellent deal.
 
Tickler said:
18 psi, is that with an intercooler? If you pick up an m90 from a 94 bird, putting in late 90's teflon rotors from the gtp is an excellent upgrade, and may cure belt slippage. I got a set from Ed, excellent deal.
The rotors are NOT coated with teflon, they have an epoxy based coating which is different than what is used on the latest gen of Eaton blowers which also does not use teflon on the rotors.

You will see a higher psi reading with your 4 banger due to reduced displacement, than the SC engine displays when turning the blower at the same speed (all other things besides displacement being equal).

Paul
 
Thats what I figured with the smaller motor, thats why I havent gone out a spent the money on a pulley, until I see how much this thing will boost to.
 
Fbod383 said:
Thats what I figured with the smaller motor, thats why I havent gone out a spent the money on a pulley, until I see how much this thing will boost to.
I have the Racer Walsh pulley on my early M90. I thought it was a 10% but I've heard it's actually more like a 12% overdrive. I bought mine used but I think they're available through Ford Racing.
 
Fbod383 said:
Well, I'm hardly new a forced induction. I know quite a bit about the 4th gen M90 used on GMs. But it seems this 2nd gen M90 is a whole different bird. I asked about max PSI because no matter the restrictions on the engine, the S/C will only make so much boost before cavitation begins and all eeficiency is gone out the winda. on GM S/C it is around 18PSI, but they are more efficient. I found a 94 S/C on ebay I may spring for.

So what you are really asking for is the CFM capacity of the blower at different drive ratios?

I've got a buddy who's got a slightly modded '94. He's seeing over 20lbs of boost with a slightly ported blower. My blower is ported a bit more and I only see about 16 lbs at most. Our mods are pretty close to the same. His exhaust is opened up just like mine is, but he sees 4 lbs of boost more. Something makes my engine a bit more efficient than his. I'm not sure what it is, but there's something. So right there shows you that what you are really looking for is CFM capacity. There are people here overdriving their sc by nearly 30%. Mine is only overdriven about 8%.
 
That other Quad4 guy is Phil, he's a freind of mine. The reason we, and a few others have chosen the T-bird S/C is mainly because its a more compact package than the GM setup, although that integrated bypass valve is nice, i'm sure I'll find a way to rig one up on this. I should have pics of it bolted to the engine in a week or so, whats this "jackshaft pulley"? I know the ford uses an 8 rib pulley whereas GM uses a 4.. or whatever
 
Basically it's a idler, only you have the crank drive a smaller pulley then a larger pulley that actually drives the SC. This gives you a nice step up as you mutliply the first ratio X the second ratio for the overall drive ratio.

GM uses a 6 rib and a huge pulley and it's a press fit. The Ford is a keyed pulley and is 8 rib as you said.

For a Bypass you could use a Bosch type, Saab 900 and 9000's use them for their turbo systems. Forge (sp) makes a metal version that is supposed to seal very well. Although they all leak a lot.

Jeff

How is your friend's setup running?

Jeff
 
Phil doesnt have his running yet, he's waiting on my version of an intake manifold, so he can copy it :rolleyes: :D
 
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