Clutched M90

CaifanSC

SCCoA Member
Has anybody done this before? Does anybody know who might make a clutched pulley the size of the stock supercharger pulley? I havent found a clutched pulley from an AC compressor small enough, and the only superchargers with a clutched pulley are too small. Just wondering if anybody here has any info or experience on the matter. THanx in advance
 
& the reason for this, is............................

CaifanSC said:
Does anybody know who might make a clutched pulley the size of the stock supercharger pulley?
I think that everybody who reads this, is thinking, "Why in the world........"?

68COUGAR
 
do the inquiring minds want to know? heh....well, among other things it might be an option for better gas milage...like its used on the little brothers of the m90 (m60 & m45 i think) on some mercedes benz cars. But like I said, that would be among OTHER things.
 
The bypass valve used on the Eaton superchargers effectively does what a clutched SC pulley would gain you. There may be some slight additional load from the SC rotors being turned, but the difference would be minimal.

When in bypass, the SC is basically just idling using almost zero Torque/HP from the crankshaft and simply letting air flow through it without building any pressure.

That is one of the reasons the Eaton SC was the first supercharger that went into wide use across many product lines. It's a fairly efficient pump as used in generic street cars.
 
SC clutch

I can appreciate the sentiment, but I think the cons outweigh the pros....
that SC is high rpm shaft and adding extra mass (inertia) to it will definately hinder performance. JMHO
Bill
 
Mike, if we're talking about idle rpm's, then most certainly i see your point, but if, per se (lets just think hypothetically here), you wanted to disengage the blower at higher rmps...say 4500, then the difference must me greater. Besides, i dont know if the bypass valve would work just as good tring to let out that much presurized air and at such rpm's. At that point the blower is, or is just about, to peak its efficiency.

Crazy couper, definatelly adding mass to a rotational shaft will eat up more force...essentially hp...but in reality...i dont think that the weight difference cant be that much between a regular steel/aluminum sc pulley and a clutched pulley of the same size (please correct me if Im wrong). I'd like to hear what you guys consider as cons for clutching the sc. Just so I can educate my self...thanx guys!
 
Two things.

#1 - RPM have little if nothing to do with the power sucked by the Supercharger when it's in bypass mode. Bypass mode isn't driven by engine RPM, it's driven by load/vacuum. Remember the parasitic drag of the shafts spinning is minimal due to the types of bearings and cut of the gears within the supercharger. It's designed to be efficient up through 14,000rpm.

#2 - An electro-magnetic clutch with sufficient clamping force to grip and hold the SC shaft from dis-engaged to engaged at 40mph would be large and heavy.

It's not that it couldn't be done. It's just that doing it would provide little benefit other than the unique factor of saying you did it. Sometimes that's all the benefit a person is looking for.
 
If we could only put a clutch on the main pully to cut power to the large
Belt during WOT? You would lose all drag from water pump, alt, ps. pump just for the brief blast off. I thought about having a lever with a cable to relese the main belt tensioner to let the belt slip just like a tractor mower but would not want to risk loseing a belt, but there I go thinking again. :rolleyes:
 
Mark-
Nice idea, But i think you got too much time on your hands hehe :cool: . Maybe you should invest in another SC :D.

-Trey
 
if he has too much time on his hands maybe he should come to LA and fix my SC up, put the ABS back in and so forth, i got a list of stuff that needs to be accomplished.
 
No problem, I used to work on boats :D Send me a ticket cause im freezing
my a$$ of here in Chicago. I have looked at a few SC`s but I like to find them in pristine condition with mecanical needs but all im finding is turds.
Trey you need to wait till the auto rotor is availabe. Then were talking performance. All I can tell you is it all works together. Put one small pipe in and now you have a restriciton. all big pipes like maf, intake tube,75mm throttle body,mp inlet plenum,bigger blower,raised top, ported intake manifold, ported heads, larger exhaust and more fuel + tune and now your rollin :D Some of this has been done to your car but the rest will be up to you and just how fast you want to go+ $10,000.00 dollars maybe a little less if your thrifty.
 
Mike, im going to abuse of your knowledge a bit here. Can you elaborate abit on this you say: "RPM have little if nothing to do with the power sucked by the Supercharger when it's in bypass mode. Bypass mode isn't driven by engine RPM, it's driven by load/vacuum. "

I tried imagining this in my head and im not sure if im thinking the right way. As far as I understand the amount of air sucked in by the supercharger IS directly dependant on rmps as its turned by teh crank pulley...but im trying to see what you mean by 'when in bypass mode'. Im thinking that by this you mean when the bypass valve is open....i took my spare plenum out and the hole for the bypass duct is not that big. Thats why i thought that if the valve is opened at like 4500 rpm's when the supercharger is packing tons of air into the engine simply opening the bypass valve wouldnt be enough to stop the supercharger from spinning...plus i think it would take longer than if the thing is clutched ..then it would (i think) stop spinning right away.

as far as the pulley its self, when you say " An electro-magnetic clutch with sufficient clamping force to grip and hold the SC shaft from dis-engaged to engaged at 40mph would be large and heavy" do you know of any wbsites where i can read up on this?

also, im sill hoping that somebody here knows a place taht may possibly make custom clutched pulleys. :D
 
I tried imagining this in my head and im not sure if im thinking the right way. As far as I understand the amount of air sucked in by the supercharger IS directly dependant on rmps as its turned by teh crank pulley.
True.

...but im trying to see what you mean by 'when in bypass mode'. Im thinking that by this you mean when the bypass valve is open..Yes thats what he means.

....i took my spare plenum out and the hole for the bypass duct is not that big.Does'nt matter because with an open hole of that size you cannot build any boost pressure and that releases the pressure on the rotors so that they can turn with same ease as using your hand to turn them.

Thats why i thought that if the valve is opened at like 4500 rpm's when the supercharger is packing tons of air into the engine simply opening the bypass valve wouldnt be enough to stop the supercharger from spinning...plus i think it would take longer than if the thing is clutched ..then it would (i think) stop spinning right away.
Where did you get the idea that the blowers rotors ever stop while the engine is running? When the engine is running the rotors are turning it does'nt matter if your making boost or not. The bypass valve does away with having to put any kind of a clutch on the blower drive. Those few cars that do have blower clutch's probably do not have bypass valves otherwise theres no need for a clutch. I mean yeah it looked cool on Mad Max's blower but theres nothing practical or usefull about it on an SC's setup.
 
Mike, thanx for the clarification....at least i know im not that retarded when it comes to teh operation of the supercharger. As far as the rotors turning....you are correct..they never stop turning if they have a pulley like ours.....the boost just gets vented out by the bypass valve...but they do completely stop if the pulley gets clutched correct? Yeah, in the stock super coupe set up, its pretty much pointless to think of clutchign the m90...but we're thinking hypothetically here arent we?

oh, and its funny....b/c you are the second person that talks about the mad max blower...i saw the movie eons ago..i dont even remember it, but i might have to watch it again to know what you guys are talking about!
 
Oh yea mad max was one of the first movies that have a nitros setup on a truck. Its a must see for freaky race fans. I would just like to add one thing. The clutch would need to hold about 70 hp @ WOT. I dont think ac compressors would hold that much without slipage. I was led to beleave that the supercharger added to fuel economy@ modest boost levels. Maybe someone with a disconnected supercharger belt can chime in here about their fuel economy.
 
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Mike, thanx for the clarification....at least i know im not that retarded when it comes to teh operation of the supercharger.I did'nt mean to imply that you were retarded, I really hope you did'nt take it that way.

As far as the rotors turning....you are correct..they never stop turning if they have a pulley like ours.....the boost just gets vented out by the bypass valve...but they do completely stop if the pulley gets clutched correct?Yes they would stop then, but on the otherhand they just might spin slowly simply because of the manifold vac pulling on them if allowed to freewheel by completely disengageing the blower drive from the belt.

oh, and its funny....b/c you are the second person that talks about the mad max blower...i saw the movie eons ago..i dont even remember it, but i might have to watch it again to know what you guys are talking about!Yeah I about fell out of my chair when I first saw that years ago. Thats the first and only time I've ever seen a blower drive do that. Can you imagine the turbulance those stopped rotors would be causing in the intake tract not to mention the restriction since air still has to pass through the blower housing for the engine to even run. LOL!!!
 
scbird1 said:
Oh yea mad max was one of the first movies that have a nitros setup on a truck. Its a must see for freaky race fans. I would just like to add one thing. The clutch would need to hold about 70 hp @ WOT. I dont think ac compressors would hold that much without slipage. I was led to beleave that the supercharger added to fuel economy@ modest boost levels. Maybe someone with a disconnected supercharger belt can chime in here about their fuel economy.

Boosted engines do get better gas mileage than the exact same engine running NA as long as you drive with some sense. A boosted engine has a much higher volumetric efficency which will make the engine not work as hard to do the same job. The key is keeping your foot off the floorboard. ;)
 
MIke not to worry...you didnt imply anything, i just said that.

I guess in order to see how the car feels if the sc is clutched and the rotors stop turning one must have to disconnect the sc belt. I 've read it sux! no power, no nothing....but it works!

AS far as the turbulance if the rotors are stopped....couldnt this be solved by somehow adding a conduit that brings meatered air directly from the TB into the lower intake plenum..sort of like skipping the supercharger? Maybe somehow modifly the supercharger's inlet plenum for that........i duno, right now im talking out my @ss just thinking outloud.

BTW...still hoping to hear from anbody with regards of a place that sells clutched pulleys! OH, and yeah....thanx for a very educative conversation
 
Note that the engine in Mad Maxes vehicle never did have a functional supercharger on it. That was a hollow cavity with electric motors in it that gave the appearance that it actually did something.

I think where some of the confusion here comes from the idea that the Supercharger itself is compressing air. In point of fact, the M90 Eaton supercharger doesn't compress the air as it moves through the supercharger. The M90 is a roots style positive displacement air pump.

For each revolution of the rotor pack, a fixed volume of air is forced through it. As long as there is nothing preventing this air from moving, the air doesn't become compressed. As long as the air isn't being compressed, it doesn't impart any negative force against the rotors.

Thus the bypass valve allows any excess air (air not being pulled into the engine) moved by the supercharger to be recycled into the input side of the supercharger. Thus when in bypass, the supercharger will effectively just rotate the same air out, then in, then out, then in and so on until the engine uses it up.

When the bypass closes, then air moved by the SC has no where to go but along the path through the IC piping and into the intake manifold. Once in the intake manifold it can either enter the engine through the valves during combustion, or stack up there. Because the Supercharger moves a greater volume of air through the intake tract than the engine can consume it, positive pressure is developed which you see as "boost".

It is this positive pressure in the intake tract that fights the further rotation of the rotor pack as the rotor pack attempts to insert more air into the intake tract. This is what causes the supercharger to consume engine energy from the crankshaft as it fights this pressure that develops in the intake tract.
 
I did'nt know that about Mad Max's blower Mike, thats a cool bit of Hollywood trivea. The rest of what you said was spoken like a true scholar. ;)
 
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