Has anyone ever tried twin M90's?

moore89

Registered User
I was just bored and thinking about the supercoupe, then my mind drifted to the spare parts I have at my disposal (which includes a pair of home ported M90's). Anyway I saw a long time ago that a guy with a fox bird put 2 M90's on a 351. Has anyone ever tinkered with the idea of putting two on a 3.8 or is it just a waist of time? I've done some sketches and drawings with layouts and measurements, which I think I could fab up. My idea is to take two M90's and mount them on a custom bracket that angles them side by side on top of the intake manifold (with a custom inlet setup that uses one large TB), from there the outlets would run back merge to a 3" or 3.5" pipe and then run to the front twards a custom FMIC which would feed back running under the previous pipe and into the stock intake manifold inlet. Naturally this would not fit under a stock hood and may not even fit under a cobra R hood. I wold just like any oppinions on this and to know if it's been tinkered with before. My dream is an autorotor but that is out of my current budget.
 
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i saw the thread recently, it looked evil as hell!!!
Now, nobody has actually done it on an SC and I imagine that it would equate to some serious fab work although if successful you would have absolute bragging rights for 'coolest thing done to an sc'.

anyhow, as far as I know, nobody has done twin superchargers-- everyone is always focused on maximizing the one they have. I am not sure exactly how much power would be had using twin M90's or how many PSI of boost it would generate. The M90 flows a given amount of air no matter what depending on how many RPM it is turning, now assuming that you cut the volume of the engine in half but keep the RPM the same, then theoretically that would make like 26 psi of boost? I am sure my logic is wayyy off but I imagine it would generate significantly more boost than stock given that it would have a compressor powering each bank of cylinders, and then making sure the m90's are matched exactly to ensure even power delivery comes into play etc etc, I am sure there is someone far more knowledgable than me about this and probably actually halfway knows what they are talking about.

as far as hoods go, just cut a BIG hole in the top of it and glue a small dinghy (a rowboat) upside down on the hood, make some louvers in it and voila, one of a kind heat extraction 12" cowl hood!

if you think you can do it, power to you and you get a + for encouragement.

-Ghost
 
ive wanted to do that too .. i do tha same thing lol dream about making my car faster them it is and pulling both front wheels off the ground
 
ive wanted to do that too .. i do tha same thing lol dream about making my car faster them it is and pulling both front wheels off the ground
LOL, I don't think mine will ever pull the front wheels off the ground. I just daydream alot. And with the sc's being matched, my plan was to feed them both into one pipe ( I know they're close to the same but nothings perfect).
 
one thing to consider is the incredible power needed to run TWO of these blowers. Just imagine the strain placed on the crank by doing this.
 
one thing to consider is the incredible power needed to run TWO of these blowers. Just imagine the strain placed on the crank by doing this.

As long as I still run off the jackshaft setup would the strain be that much more on the crankshaft? I did consider the amount of power it would take to run two, but I was also thinking about the gobs of torque it would probably put out.
 
Yup, there would be more linear stress on the crank and jackshaft.....

Uhm, think of it this way, and it was the reason I was saying the other day about the bracket that goes between the power steering pump and the water pump should be put back in when its removed.

By looking at the diagram I posted, you can see that not only do you have a rotational stress on the pullies, but a linear stress... ie the pullies are getting pulled closer together. This happens because the crankshaft has to "pull" the belt on the top side to overcome the friction and load thats on the other pully. So the more load you put on that other pully, the more effort has to be used to "pull" the belt down to the crank pully, causing the pullies to try to pull each other closer. Of course the belt has only so much coefficient of friction so you will get to the point where the belt lets loose and things start slipping.

I mentioned the PS one because of the high load the PS can put on the system, and the accesory bracket is only held on at the head...
 

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Yup, there would be more linear stress on the crank and jackshaft.....

Uhm, think of it this way, and it was the reason I was saying the other day about the bracket that goes between the power steering pump and the water pump should be put back in when its removed.

By looking at the diagram I posted, you can see that not only do you have a rotational stress on the pullies, but a linear stress... ie the pullies are getting pulled closer together. This happens because the crankshaft has to "pull" the belt on the top side to overcome the friction and load thats on the other pully. So the more load you put on that other pully, the more effort has to be used to "pull" the belt down to the crank pully, causing the pullies to try to pull each other closer. Of course the belt has only so much coefficient of friction so you will get to the point where the belt lets loose and things start slipping.

I mentioned the PS one because of the high load the PS can put on the system, and the accesory bracket is only held on at the head...

Do it like this and you could practically eliminate all linear stress. :eek:
 

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hey, thats a really good idea, then you also won't have to worry about running 2 blowers off of one jackshaft, and would effectively minimize the slippage problems that would otherwise result from jackshaft to crankshaft. the only drawback would be the incease in stress on the jackshaft pulleys since i assume the blowers owuld be mounted on the top of the motor, but replacing bearings in the jackshaft would be better than breaking cranks...you're one fart smeller
 
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But you'd still have the torsional stress, which seems to me the be the higher of the two forces on the crank. especially if running two Sc's
 
I also don't think there is enough wrap around of the belt on the crank to grip...there would be massive belt slip.

unless you used a crank pulley with 3 belt slots, and ran one belt to each side for the sc's then the other slot for your accesories.

The two Sc forces on the crank should be in opposite direction and about the same, and cancel each other.
 
Still takes a lot HP and room to run two blowers. Just go with a bigger blower than the M90. Even if you fabricated a dual blower set up, it wouldnt do much good as the rest of the engine from heads, cam, bottom end would have to be able to handle the extra boost or it is just a waste. I think Randy said it in another tread. Its about a complete system working together not just a lot of boost. Two blowers is just a novelity idea as far as I can see just my two cents
 
well it certainly isn't the most economical, reasonable or efficient way of going about making power. But it sure as hell would be cool, give you a great topic of conversation, and give you some sort of bragging rights.

As for the torsional stress. Now that i think about it the limiting stress factor is almost certainly the torsional stress, not the normal stress in the shaft caused by the bending moment of the belt. Considering i am taking strengths of materials right now i'm surprised that i didn't think of that myself

As for the belt contact. Using one belt hasn't even crossed my mind. (i'm just thinking conceptually here, i wasn't thinking about actually doing it) I had just figured that the setup would use two different belts, and i'm sure that was XR7dave's idea too.
 
i saw the thread recently, it looked evil as hell!!!
Now, nobody has actually done it on an SC and I imagine that it would equate to some serious fab work although if successful you would have absolute bragging rights for 'coolest thing done to an sc'.

anyhow, as far as I know, nobody has done twin superchargers-- everyone is always focused on maximizing the one they have. I am not sure exactly how much power would be had using twin M90's or how many PSI of boost it would generate. The M90 flows a given amount of air no matter what depending on how many RPM it is turning, now assuming that you cut the volume of the engine in half but keep the RPM the same, then theoretically that would make like 26 psi of boost? I am sure my logic is wayyy off but I imagine it would generate significantly more boost than stock given that it would have a compressor powering each bank of cylinders, and then making sure the m90's are matched exactly to ensure even power delivery comes into play etc etc, I am sure there is someone far more knowledgable than me about this and probably actually halfway knows what they are talking about.

as far as hoods go, just cut a BIG hole in the top of it and glue a small dinghy (a rowboat) upside down on the hood, make some louvers in it and voila, one of a kind heat extraction 12" cowl hood!

if you think you can do it, power to you and you get a + for encouragement.

-Ghost

Jesus...... Is there anything you don't know about these cars. Lets see you've been here since June. And you average over 3 posts a day.
before you give anybody tips on how to run two superchargers on there car why don't you figure if your crank is in two pieces or not.

Christ .....what a bag of wind you are.
how can you possibly give anybody any advise when you don't know crap about these cars. I suspect your mouth moves faster than your brain does.
You couldn't even figure if it was a HB or not.... you posted wanting to know how to fix your car before you even looked under the hood.

Hopefully your crank will be snapped. You can't fix it, you don't know how.... so you will just fade away......
Hey Have A nice Day

Tony
 
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damn must be bad blood between them

i thought of duals m90s yrs ago but it didnt work out
 

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