Eaton M90 supercharger Question

[SHOguy 92]

If your going to run an M90, make sure to get a Gen V, they flow a lot better than any of the previous generations, but like said, I would shoot for a 112 or a 122. If your going to be doing fab work, go to the biggest cheapest one you can get.

 

[Off Road SHO]

The nice thing about the GM M-90 is that the throttle body is integrated into the housing. Of course it was made for a 3.8 pushrod motor that reved all the way to 5000 rpm's, but it is one less thing to have to fabricate.

Tom

 

[SHOguy 92]

The nice thing about the GM M-90 is that the throttle body is integrated into the housing. Of course it was made for a 3.8 pushrod motor that reved all the way to 5000 rpm's, but it is one less thing to have to fabricate.

Tom

Thats a myth, my cars cammed and I run the sucker to about 6400, if I had beefier valve springs my cam would be good to about 6600rpms, very close to stock SHO neighborhood. Just like GM's pushrod V8's, these motors can get some real nice top end also. And once my cars up and running again I'll be running a 2.6" pulley and pushing to 6400, that'll just about be maxing out the M90 though, but hopefully be good for 360whp.

 

[CplPflummUSMC]

Ok so both are viable options with the nod going to the M-112 style. My next question would be either of these require that the injectors be changed? i know that the fuel pump will need to be switched out. Also what is the odds of over spinning these blowers and grenadeing them? I have no intentions of revving over the 7K RL, but i don't want to overspin them. Alos is there any good books one can recommend on the subject? thank you all again this is a real help. Semper Fi!

 

[SHOguy 92]

You won't grenade them, they will just out of of efficiency range. With a Gen 5 M90 you should be able to pulley down from the stock pulley and still maintain efficency, if you use an older Gen then there really is no point. And if you move up to the MP112 you should be good.

 

[AREA 91]

why no tune yet?

No TwEECer lessons.

 

[SHO U UP]

The m112 is quite a bit bigger and I believe weighs 50% more than the M-90 from Ford ( the M90 in GM cars are a bit different). The bigger the gulp per revolution of the blower the slower you have to spin it to get a certain amount of air. Forget about boost psi. Boost is a description of how restrictive the path is to the flow of air. Concern yourself with air volume.

The SHO motor gulps about 100 cu inches of air per revolution of the crank. If you turned a 112 at a 1:1 ratio it would be almost the same as the engine struggling to suck in atmospheric air. That is why they turn the blowers (positive displacement Roots style, not screw type) at a 2:1 ratio. When engaged the blower will then move 224 cubic inches of air for every 100 cubic inches that the engine needs. Actually the 3.0 uses 91 cu in and the 3.2 uses 97.5 cu inches, but that's not important in this discussion.

To figure out the ratio; divide the circumference of the driving pulley by the circumference of the driven pulley on the blower. On The Other Woman I just used the accessory belt and the stock crank dampener pulley with the stock 6 rib belt.

My opinion: use an M-90 with a 2.78" diameter driven pulley, run an air-to-air intercooler and methanol injection. Try and get a 94-95 SuperCoupe blower because the lobes are teflon coated. Use two or more 1" bypass valves and make sure their outlets are pointed in the direction of the air flow like a "Y" and not a straight "T".

Tom

This pic here is with an M90 next to my Whipple.



Here is my M112 next to my Whipple.



I was unable to get the M112 & M90 together side by side as I was working on my Lighting and SHO at two different times. Of course the Lightning and Cobra M112s are different as theirs intakes are on the top for the L and on the back side on the Cobra. There is a substantial size different though in the M90s and M112s.

And as for the teflon coating on the rotors, strip that crap off before you install the blower. It chips off and clogs up inside the intake/intercooler and blocks air flow. Here is how they look once they are all stripped down.

 

[CplPflummUSMC]

I am currently reading Pat Ganahal's book on street supercharging and learning some good stuff from it. It has confirmed that despite myself going for an eaton based on price these blowers make more usuable street power. They fit my goals better than a centrifugal blower. So with that babbleing out of the way my question to you is will a M112 fit under the hood of a Gen II SHO? Were would it even mount as I have seen that it cannot go where the AC compessor mounts due to its size? Also does the lighting M112 use the integrated intercooler like the mustang one? Assuming this is the difference between the two. Thanks for all the great info.

 

[Off Road SHO]

You could mount it where the AC compressor normally sits but you would have to do like I did on The Other Woman; new engine mount, lose the AC compressor, and a new exhaust manifold on that side.

PM me your cell and we can talk about it. I have other ways of making one fit.

Tom

 

[somedude_001]

You could mount it where the AC compressor normally sits but you would have to do like I did on The Other Woman; new engine mount, lose the AC compressor, and a new exhaust manifold on that side.

PM me your cell and we can talk about it. I have other ways of making one fit.

Tom

hey tom that M80 I got from you for my 1990 car. I am really considering throwing that on and keeping the boost 6-8psi. think that unit will hold up all day on a road course without a problem? I was thinking of not running charge cooling because of the low boost to keep the front lighter and since i'm not chasing big hp numbers with this car. I would like to get it to the low to mid 200whp #s thoughts?

reliability reliability reliability reliability is imperative for this car. in aug I am racing at 4 roadcourses in one week and I would like to not have to do much wrenching if any at all.

 

[RonPorter]

I know that everyone loves their beloved "snakes" intake, but if I considered it, I would have a nice Wipple in the V with a new intake. This is what we were considering for a V8 SHO many years ago. Looks a lot more impressive than the snakes, which have become common since 1989.

IMO, for a DD, not having a/c is not an option.

 

[SHO U UP]

I am currently reading Pat Ganahal's book on street supercharging and learning some good stuff from it. It has confirmed that despite myself going for an eaton based on price these blowers make more usuable street power. They fit my goals better than a centrifugal blower. So with that babbleing out of the way my question to you is will a M112 fit under the hood of a Gen II SHO? Were would it even mount as I have seen that it cannot go where the AC compessor mounts due to its size? Also does the lighting M112 use the integrated intercooler like the mustang one? Assuming this is the difference between the two. Thanks for all the great info.

Yes, the Lightnings and Cobras use intercoolers between them and the intake. It's a special intake that is not found on the n/a 5.4s/4.6. The intercooler itself mounts under the intake and sits in the valley of the block. The two lines enter behind the upper plenum and run to the intercooler degasser tank on the shroud and then to the lower heat exhanger.

 

[SHO U UP]

I know that everyone loves their beloved "snakes" intake, but if I considered it, I would have a nice Wipple in the V with a new intake. This is what we were considering for a V8 SHO many years ago. Looks a lot more impressive than the snakes, which have become common since 1989.

IMO, for a DD, not having a/c is not an option.

I don't know Ron. I sure am missing my "snakes" on my Gen 3 partner. Don't get me wrong, my intake is unique now with a blower sitting near it, but the runners I think are simply bad ass looking! And I can agree 100% with ya on needing the a/c. AMEN!

 

[SHOguy 92]

I am currently reading Pat Ganahal's book on street supercharging and learning some good stuff from it. It has confirmed that despite myself going for an eaton based on price these blowers make more usuable street power. They fit my goals better than a centrifugal blower. So with that babbleing out of the way my question to you is will a M112 fit under the hood of a Gen II SHO? Were would it even mount as I have seen that it cannot go where the AC compessor mounts due to its size? Also does the lighting M112 use the integrated intercooler like the mustang one? Assuming this is the difference between the two. Thanks for all the great info.

The M90 or M112 do make great street power... on a motor that makes great street power. Like on my 3800, it makes power just about anywhere, but SHO's like to live above 4000. In general they don't like making street power and adding this kind of blower isn't really going to change that, it's just how the intake is setup. And no matter what route you take, you will need to find a place to hide the thing, won't ever fit directly on top. I always wondered if an M90 could sit upside down on top of the front valve cover. Would be very easy to run piping off it then for an air/air intercooler rather that liquid/air like most of them run.

 

[CplPflummUSMC]

That is what I thought about the M112 that it had the heat exchanger between it and the intake. THis probally means it will be to tall for anything, but radical mount as it will be significantly taller than other choices. If I am wrong please tell me. As far as my remark about street power I mean that a roots blower makes power from start to finish. It doesn't need to spool like a centrifigual. Now I don't really take my SHO above 6500rpm so would a ported Gen III M90 be suitable? On a Pontiac Grand Prix forum I saw that a ported Gen III will flow just about as well as a Gen V. Also I plan on running a FMIC to keep charge temps down. Will this help keep the SC inside its VE range? From what I have read and understand I will be spinning the M90 faster than normal at those RPMs which will heat the air more than intended thus bringing down the VE of the unit. Is this right? Trying to get all my ducks in a row before i start spending money. thanks for the steady flow on good info. Semper Fi!!

 

[SHOguy 92]

If your going for a blower it's for going fast, and if your going fast you might as well take it to 7000. Around town the boost won't help, so it will only matter when you get on it. Also a Gen 3 M90 flows good, but even fully ported a Gen V unported will outflow it by quite a bit. In the GP world the guys running fully ported Gen 3's who then switch to a Gen 5 usually pick up around 20whp.

Also an IC is a necessity if your going to make any power on the SHO platform with any M90. Once they get spun fast they become massive heaters, it's a pretty old design, think the first M90's were in 89, so a 21 year old design basically. I'm not sure about a Gen 3, but a Gen 5 you aren't going to want to push more than 15psi, that will put it out of the VE, but up until that point you should be fine, but you'll need an IC for anything over 10 really.

 

[rubydist]

the Roots design will build boost all through the rpm range, but that doesn't mean the SHO motor will suddenly have tons of torque at 2k rpm, 'cause it won't.

the good ve range on the blower has to do only with pressure ratios, not whether you have an intercooler or not. the Roots design is really good for pressure ratios of about 1.5 - that is to say around 7 psi boost, which is not that much. my experience is that above 7-8 psi boost you better be running some kind of charge cooling or you will be taking out so much timing to prevent knock that your hp gains will be disappointingly small.

 

[CplPflummUSMC]

I understand that a roots isn't going to make the SHO motor be a fire breather from 0 rpm to redline. I just like that from what i have read their positive displacement style means that they will boost through out an rpm range unlike a centrifugal which is more peaky, but does give much better top end boost. The reason for an intercooler is that as the roots comes out of the VE range they turn into heat pumps. So by chargecooling I was hoping to stave that off and prevent knock as you stated. From what I have read (I'm still very much learning here) is that as the air heats knock becomes likely to happen and there are only two real ways to stop it. First by keeping the charge temps down or by running a fuel that is more knock resistant. I also understand, even if I haven't stated it, that the any blower really only works under WOT. I also know that an eaton, any style, has an internal bypass valve that is opened when there is vacuum in the manifold so it isn't really being used unless you are at WOT. Thanks again for all the good info. You gentlemen are greatly helping me out here.

Edit: I see where in my prior post that I was wrong in my understanding of what an intercooler will do. So is the intercooler better at preventing knock? Thanks again for the clarification rubydist.

 

[Off Road SHO]

Tuning is what prevents knock. An intercooler is very much advised or your tune software will have to back out timing, and/or you will need better gas. You might also look into alcohol water injection.

I have the start of a project that puts a Roots or screw type PD blower on the SHO heads. I'll post a pis or two of what I have so far.

Tom

 

[somedude_001]

Tuning is what prevents knock. An intercooler is very much advised or your tune software will have to back out timing, and/or you will need better gas. You might also look into alcohol water injection.

I have the start of a project that puts a Roots or screw type PD blower on the SHO heads. I'll post a pis or two of what I have so far.

Tom

I still maintain my stance that I would buy this if you build it. I'm dont trying to set records but I do want a little more go in my sho