View Full Version : Twin supercharging a 5.0

03-02-2003, 08:45 PM
Ok, I want to get some input on this idea I have been messing around with for a while.

I have a 91 cougar 5.0L. I was thinking of doing a twin supercharged setup using the eaton M90 blowers, and a custom upper intake manifold. The idea would be to replace the upper intake with a structure that will serve as a plenum accepting the boost from both blowers as well as have a frame that holds the blowers in place. Here is the catch. If I build this, I can not afford to have a second car. Nor do I want to have 2 blowers running at all times as that would quickly kill my engine, not to mention my gas mileage. I was thinking about running the blowers by an electric motor, and having an electric linear actuator set up so that one switch would simultaneously start the blowers spinning and seal off an intake hole that would be used to bypass them whenever I have them switched off. I know I would have to have a custom hood with probably at least a 4" rise to clear all the plumbing and everything, but I just want to know if anyone sees any problems. I will post a sketch of the design at this address.


Let me know what you think. Thanks.

fast Ed
03-02-2003, 09:12 PM
Take a look HERE (http://www.toohighpsi.com/SCTC/sctc.htm) , this guy has been running a twin Eaton blown 351W powered Turbo Coupe for a few years.

Ed Nicholson

03-02-2003, 10:11 PM
I wouldnt know of any problems but i like that idea of having to switch themoff whenever you want, kind of like there will be 4 turbos on your car at once,, sounds awesome, good luck-

03-02-2003, 10:31 PM
One m90 would be just fine :O)

03-02-2003, 10:59 PM
with regards to the twin eaton blown 351, I know of that car and I have asked that guy several questions as I was designing it. I am basically taking the main structure of his design for my car. But his car is running a speed density system, not a mass air. Also he doesn't have any kind of bypass valve at all. His car is under boost all the time, making it thorougly impractical as an everyday driver. With regards to thinking one blower would be enough, I doubt it, and it certainly wouldn't be as cool.

03-02-2003, 11:01 PM
If i were you, buy a junker car to drive. pretty much any way you set it up it will hog the gas and break down just because of the performance factor.

03-02-2003, 11:28 PM
Getting the actual vehicle isn't the problem. I still have both my 89SC and a 79 firebird formula. The problem is I can't afford to put both cars on my insurance, and what's the point of building this thing if I can't drive it.

Rob Noth
03-03-2003, 09:32 PM
When you say "running the blowers by an electric motor" do you mean you would do this instead of the accessory belt off the crank pulley? Seems like you'd need a very powerful electric motor to do that, in fact I would have thought it wasn't possible. Maybe I misunderstood what you said.

03-03-2003, 10:19 PM
That is what I meant. I didn't think it would need to be that powerful of a motor. Like I said, I want to be able to turn them on and off, and running them off the crank would not let me do that. I thought an electric motor would be an easy enough way to do that. I was thinking maybe something like a modified starter. My figuring was if it is powerful enough to crank an engine over, then turning 2 90ci blowers would be no problem. But I don't know much about it so I could be wrong. If I am, let me know. Also if anyone knows of another way that I could turn them on or off without using an electric motor, let me know. Thanks.

03-03-2003, 11:25 PM
Mad running them off an electrical motor is completely impractical...A strong enough electrical motor to spin a blower at high rpm woul dnot only be large and heavy, youd need to plug into a house to use them..However if you used an electric clutch setup at the blower such as that found on an AC compressor that would work..Why youd want to do that I have no idea...I still believe one blower would be enough:O)..Unless of course your looking for mega HP..Then Id say go turbo:O)..And not running a bypas would not make the car impractical..However it would increase blower life..I dont mean to knock your idea but what is it yoru exactly looking to do with the car

03-04-2003, 12:03 AM
Electric powered SC's just wouldn't work. They suck 50-70 hp when at speed pumping air. Try pricing and figuring out how to wire up a 70hp electric motor from a 12 volt system. Uh, yeah, right.

Same problem with electric clutches on the front of them. It would have to be quite an electric clutch when you consider the impact that they would have to absorb if engauged when the engine is turning 2800 rpm and the SC tries to come up to speed in the blink of an eye. I can see the pieces flying already.

The MR2 from Toyota had a electro-mechanical clutch on their SC but it was very unique and the SC was just a tiny thing. A computer was used to gradually engauge the clutch so it wasn't just an instant on/off type of design.

03-04-2003, 12:23 AM
I am looking for mega power, but I absolutely despise turbo lag, and I am also a big fan of low end torque, which turbos don't help at all. The other thing is I want this car to be a daily driver that can be made killer without opening the hood. Basically I don't intend to use the blowers all the time, just when someone challenges me at a light, or once in a while on the highway at night. With regards to the clutch blowing up trying to get the blowers up to 2800rpm, would that work if I only turned the blowers on at idle? That would work just fine for my purposes. Also why would not having a bypass valve increase blower life and not decrease engine life? I don't understand that. Thanks for your input.

03-04-2003, 12:38 AM

Here is what you would have to do in theory. But if you think I can help you with the practical application of the theory, you're mistaken. I can't imagine the engineering that would have to go into makeing something like this work.

Create an intake system that allows you to route incoming air into the supercharger and back into the intake manifold, or directly into the intake manifold bypassing the supercharger. This is because if they are not spinning, they won't allow any air to flow through them.

Second, create some sort of clutched drive system you can turn on and off and whim. This would likely need to be either a hydraulic type of clutch, or electro-magentic. Either system would need to have some way of gradually engauging or dis-engauging to prevent shock to the input shaft of the SC, or the crankshaft of the engine.

David Neibert
03-04-2003, 12:56 AM
Just use bypass valves similar to what comes on them stock. When the bypass valve is open (anytime there is vacuum) it only takes 1/2 HP to spin the supercharger.

Hitting the throttle quickly, drops vacuum to zero and the bypass valve closes forcing the air into the engine instead of allowing a portion of it to recirculate.


03-04-2003, 01:25 AM
Old paxtons used electromagnetic clutches to engage and disengage the supercharger....

03-04-2003, 01:33 AM
In theory, the clutch problem would be solved if you just shut the car off before engaging the clutches. However, the amount of money that you would spend to TRY to develop this would easily pay for the insurance on another vehicle. It would be easier to just make a "quick on/quick off" belt that you can put on to turn the superchargers when you want to run them. It would mean getting out of the car and spending a few mins under the hood, but these ideas of electric motors, etc, just seem completely impractical. Just my opinions, it's your car.

03-04-2003, 01:41 AM
Like I said, that really doesn't work for what I want from the car. I might end up just doing that, but if there is any way in the world that I can switch them on and off instead, I am going to do that. If using a vacuum operated bypass valve is the only way it can be done, then building it is just a matter of time and money.

03-04-2003, 04:34 AM
Celeb DV is a major prick. Just thought I'd share...

Anywho, wouldn't you be better off going with a single M112? (isn't that the next size up??) I realize that that isn't going switch on switch off able... but you know... what about picking up a junkyard turbo and going with one of the supercharger/turbo setups that I've heard about? That way you'd get the immediate response of the supercharger and then the turbo would kick in like a bat out of hell... and I think with the turbo you can you some variable electronic blow off valve or something??? This way at least you would be able to disable the turbo part of the car? Also, I thought that sometimes with twin turbos they had them set up so one kicked in at very low rpm and then the other would pick it up at higher RPM?

03-04-2003, 05:03 AM
There are some new superchargers that use a clutch pulley like an thermal clutch, they spin freely and then engage and lock up and make the supercharger spin. I forget what models are using this set up though.

David Neibert
03-04-2003, 09:32 AM
If you shut the superchargers off, you will still need a bypass valve or the engine wouldn't run in normally aspirated mode.


XR7 Dave
03-04-2003, 10:12 AM
Um, guys, both the m112 and the m90 used on the GTP's have INTERNAL bypass valves. No need to fab anything up there.

That being said, I agree with Damon, there is no problem with running the supercharger all the time. It runs all the time on our cars anyhow! The only difference is that that pressure is equalized on both sides of the system while under normal cruise. It only costs a couple of HP to run the SC under vaccum, and on a v-8 you will never even notice.

The lack of a bypass valve is NOT what makes Mikes twin SC'd bird impractical to drive. Think about it, the Vortec crowd doesn't have bypass valves. The only reason Ford had Eaton design the bypass system is to meet CAFE fuel requirements and also somewhat to help compensate for the low HP levels of the 3.8 when not under boost.

It is simply NOT an issue unless you make it into one.

03-04-2003, 07:01 PM
Here's just a thought that hasn't been mentioned yet. Why not go with 1 supercharger (either an M90 or M112, or even a cetrifigal one) and then have a Nitrous system hooked up. That would give you good low end with "punch of the button" hp like you want. I'm not sure what the CR is on a 5.0, but if you run say, 6-8 lbs of boost you should see pretty significant hp gains and with a nitrous system on top of that, you'd kick some @$$ in a 5.0. Also, I think that it would be much cheaper and much more practicle for the application you are looking for. I don't know how you feel about nitrous, but it is something that will get you what you want for a lot less than you are looking at right now. And another thought, just remove the 5.0 from the insurance and put one of your other cars on it while you are doing your mods. I realize that it would cost you a couple or three months up front for the other car, but better than having no car to drive or paying for insurance on 2 cars when you are only driving one anyway.

03-04-2003, 11:23 PM
I'm thinking your aspirations for this project are off. To try and balance between moderate daily driver and highway dominator is rough. I'd stick with one or the other. Usually cars that try to be both end up being too expensive, breaking too often, using too much gas, etc.
To try and run something with two superchargers is twice as complicated and twice as expensive of a system to design as a single supercharger. So if your looking to keep it charged, I'd definately go with a single one.
But, my personal preference for your situation would be a turbo. I don't know what experience you have with turbos, but turbo Buick 6's easily dominate some of the standard hi-po V8s, and from what I've seen in the way of turbo fords, a custom intercooled turbo system would be a lot more applicable to your daily driver idea (figuring that you'll be able to electronically change boost levels, etc. with a proper turbo system). Plus, I bet you've never matched up against anything Callaway has put a turbo on. Educate yourseld about turbos!
Turbo lag on a modern, mid-level race tubo isn't much longer than it takes for your s/c to spin to max boost. If you spend enough money and match the size of turbo to your engine correctly, you can get one that'll actually spool as fast as an s/c. I'd defiantely recommend both of Corky Bell's books to you, if I remember correctly they are Maximum Boost and Supercharged!, if you read through both they'll point out the pros and cons of each set up. I'd head turbo, the intake will be way easier to manufacture and the turbo seems to fit your intentios. I'm not exactly sure how serious you are about the project, but any research beforehand will more than likely help you in the long run.

Originally posted by MadMikeyL
I am looking for mega power, but I absolutely despise turbo lag, and I am also a big fan of low end torque, which turbos don't help at all. The other thing is I want this car to be a daily driver that can be made killer without opening the hood. Basically I don't intend to use the blowers all the time, just when someone challenges me at a light, or once in a while on the highway at night. Mike

03-05-2003, 01:54 AM
Well my intake design DOES have a bypass valve; an electronically controlled one. As for the nitrous idea, once I have the money, I intend to use that too. But for now, I simply can't afford to buy a motor that is capable of withstanding that much abuse. At first, I would be building the twin supercharged setup on a stock shortblock, and even that might be pushing it. Just a thought, if the blowers were running all the time, and the bypass valve were operated electronically, would that cause any problems in normally aspirated mode? I was told that the car might run lean, but the guy who told me that doesn't know that much about roots blowers. He mostly deals with novi2000's. As far as turbos go, I thought it would be easier and more suited to what I want out of the car to do a supercharged design, especially considering how cramped the exhaust is in these cars to begin with. Anyway, let me know what people think will happen if they are running all the time with an electronic bypass valve. Thanks.

03-05-2003, 02:18 AM
Not sure how far you have thought about this or who you have consulted about this. You mention a "stock shortblock" is your base for the twin supercharger idea. I am assuming that you are not rebuilding it? And if so, what are you doing about the compression ratio? I know that the CR is higher in the 5.0. I'm guessing about 9.0:1 or so. You can do enough with 1 supercharger to cause detonation and blowing holes through your "stock" pistons. I think that if you get a M90 package for your 5.0 (I think that they make something like that, or is it just for the 4.6?) and have the supercharger ported as well as a high flow inlet, you will see significant boost. But with stock pistons, your asking for trouble going with anything over 9 lbs of boost. And I'm sure an M90 ported is capable of that, even on a V8. Then you'd have a setup that will get you some significant power with everyday drivability. Then save your $$ for a 150 shot of nitrous. You will have plenty. You can bolt on virtually any performance part for the 5.0 to increase your power as well. Go with GT40P heads. Those are excellent heads. Not the best as far as performance, but nearly the best and a vast improvement over stock. Simply put, the $$ you will spend trying to develope an intake (even copying another's design) will be as much if not more than some serious performance parts that can benefit you far more that twin superchargers. And you will keep you everyday drivability (you will loose fuel economy any way you go). I've looked into a 351 supercharged on my T-bird before. Entirely possible, but a second supecharger would cause a lot of headsche. I know where you want to go with this though. I'm right there with you. Do a lot of research before you commit to one thing though. That is the best advice I can give you. I did and ended up with a SC over my LX. I'm happy with it for now. But I'd still like to put that supercharged 5.8 into a T-bird sometime. That would be a car to drive...

03-05-2003, 03:07 AM
That M-90 kit is only for 4.6's. I hadn't thought about the compression. That is a major problem for the turn on/off idea regardless of how I drive the blowers. DAMN! Anyway, I already have a set of GT-40P heads in my garage. I guess this idea is going to have to go away for a while.

Anyway, about the 5.8 supercharged car, you would save yourself a lot of headache using a 347 stroker instead of a 351. I actually talked about swapping the 5.8 into my cougar with the only guy who has done it, and he had to do stuff like make custom motor mounts, get a raised hood, dent in his oil pan, cut into the cowl panel, bend his headers, and I don't even remember what else, but he was still cutting it really close, and that was a normally aspirated motor. With the stroked 5.0, you would probably have a little more room to work. You can see the 5.8 cougar here.

03-05-2003, 09:16 AM
That's why I have the SC now. :) But seriously, I think that you are well on your way to a well performing 5.0. There are two things you have to consider: how to mount the supercharger with a custom made lower intake and how to drive it. Those two things are going to be enough with 1 supercharger, let alone 2 of them. I know the roots supercharger looks great in an engine compartment, but a whipple would be more efficient and getting more efficient is the centrifigal superchargers, and they are much easier to mount. If I were you, I'd go for a centrifigal and mount a horizontal supercharger under/infront of the AC condensor. You'll be making some really good power. But it'll cost you too. Turbos I think are more expensive, but a twin turbo setup on a 5.0 would be really cool. Just thoughts...