pros and cons to locking up an E55 supercharger clutch
 

Can anyone help me out with this? I'm thinking about locking up the supercharger clutch on my E55 essentially making it direct drive. What would be the down side of doing this. MPG and supercharger servicing are some things that I can see, but you could do different size supercharger pulleys, and I would think you would have a much better feeling power curve.

Does anyone know the operating characteristics on the bypass valve on these? Is it the same as a conventional vacuum operated bypass valve?

From what I have seen, the bypass on our motors looks to be more of a throttle body just under the inlet of the supercharger that is electronically controlled. If you were to go direct drive, I'm sure there may be a bit of a programming hassle as going to a vac operated BPV would probably be a good option.

I would be interested to see what you decide to do. If you could imagine a way to also remove the giant rotating magnet the clutch grabs to when our cars switch to boost, you would free up some significant rotating mass.

Edit: Looking at the pics of the Weistec 3.0l kit, it seems they favor the electric BPV over vac opperated. it must be too difficult engineering wise and programing wise to do differently.

The Weistec uses the stock bypass valve.

I am sure you can spin the supercharger all the time and the bypass valve would not care. This is how most other supercharger systems work.

One point of concern is over spinning the supercharger all the time. Keep in mind my supercharger had a bearing failure in less that 1000 miles with the 180 pulley on it. Of course I was hammering on it pretty good.

There is a step up gear set inside the nose drive so the impellers are being spun faster than the input shaft is. With a larger than stock crank pulley I am sure those impellers are signing at a pretty high speed. If you run them all the time it might accelerate the wear on the whole system, but the elimination of the sudden shock load would likely be a very good thing.

G

The supercharger spins constantly on our cars regardless of the clutch being engaged or not. engine vacuum is enough to get the rotors moving on their own. There are many other manufacturers out there that have used direct drive eaton based blowers for decades. I have owned a car that used such a set up. I don't think its too unfair to ask if we can achieve the same with our factory blowers. If someone wanted to do the R&D to fab up a complete replacement snout for the factory supercharger, that may open up a wide range of pulley options for those leary of bolting on a larger crank pulley.

I don't think this can be done....If the ECU detects boost when the clutch is supposed to be disengaged the car may go into limp mode...meaning the ECU will open the bypass all the time and set the CEL, and you'll have no boost. Just a theory though.

What about the weistec kit. Their kit has a plug for the supercharger. maybe something similar can be done

Not sure how their system works.
1. Is it a plug that tells ECU that charger/clutch is there. Which is what I believe it does.
and if used in a factory Clutch set up
2. Does the supercharger need constant voltage to maintain clutch lock. I.E leave it unplugged

Maybe Gadget can get a pic of his plug or describe it..

Boost is ultimately controlled by the throttle valve. Generally, supercharger systems start producing boost at around 30% throttle.

All the other supercharger systems run the impellers all the time. When the throttle approaches 30% the vacuum in the manifold goes away the vacuum controlled bypass valve will close. When the throttle is pushed past 30% the manifold pressure will began to exceed ambient pressure, boost. They will also still make boost if the bypass valve sticks open as well, just a lot less and the CDT will be much higher as the compressed air gets run through the impeller more than once.

Now the E55 bypass valve is much larger than on most systems. I wonder how much boost the Weistec can make with that thing stuck full open.

The Weistec kit includes a jumper that you splice into the clutch harness that has a resistor that simulates the load of the clutch coil. I do know that if you leave that clutch unplugged the ECU will know it. I remember getting that dash warning a while back when I forgot to plug it back in when I did the EC Stage 3 upgrade.

http://i239.photobucket.com/albums/f...DA81D16C75.jpg

You can see the jumper in the above picture. It is the black wire in a U packed in the plastic container with the two blue T Taps.

G

You'll have to have the car retuned to work with it locked up all the time. I'd say that'll be the largest hurdle.

Maybe not. If the ECU engages the clutch before the bypass valve closes, which has to be the case, it may work just like normal.

I am sure he will find out soon.

G

Thanks for all the responses, I guess I'll just have to try it and see what happens. I would assume that Mb is closing/opening the bypass just as they engage/disengage the clutch. If that was the case it should function ok with a direct drive as long as I can tap in a resistor on the clutch wire leds as Gadget stated.

Gadget, what kind of power are you putting down with your Weistec kit. I remeber reading your build a the other day (white, lost part of the rotor lobe when your SC bearing went) and its gotta be one of the baddest 55's I've seen.

Weistec says my combination should be close to 600 RWHP. It would be cool to break 600, but I am just happy to be able to drive the car again. It was in the garage for 6 months with a seized up stock supercharger.

I can tell you this, I have to be very easy on the throttle in the lower gears or it will break traction. The car definitely has some power.

G

Man thats awesome. Can you tell a big differance from you stock charger? I think you had about every possible bolt on... 82mm tb, crank pulley, headers. Was that enough to get you into the 500's WHP?

You'll run lean at idle and under low throttle conditions with it permanently engaged. I've had mine lock up when it's not supposed to and stayed locked.

Seems like tuning would be the only problem. Someone needs to try it and let me know what happens before I do ;)

I'm trying to beat you to it Steve:)

It would be real easy to try.

Just cut a disc out the same size as the clutch plate and thick enough to take up the space between the disc and the driven plate and when you crank the bolt down it will lock things right up.

You can crank this out on a water jet, CNC Plasma or a hand held plasma with the circle cutting attachment.

G

That's the easy part, it's the tuning I'm concerned with. Plus I want to eliminate the entire clutch assembly altogether. I always say if you can do something you should overdo it:)

It would be a quick cheap test to see if it is worth making real hard parts.

It will also answer the tuning question. I cannot see how it would make a difference there, but could be wrong.

G

I don't want to be the guniea pig but if you could loose all the weight it would help for sure.

Besides the weight savings , what Is the benefit??

Sure but the ecu would care. So it doesn't really matter about the valve since it's a slave(output).

Just ask Weistec to tune the car. The do offer tuning right?

Do they offer remote tuning? It's going to take some work to get my car dialed in after the build so it looks like i'll be taking the car down to Jerry in Texas after its finished for him to get the tune dialed in.

before you guys melt your motors spinning the blower all the time think of this,our ecus basically are NA and Bossted ecus,we run very high timing when the blower is off and once on load the ecu pulls timing big time and dumps a **** load of fuel.

now lets say you are crusing at 40mph in 4th gear with 4 people in the car and you have your blower making full boost and you give the car 10% throttle,guess what? you just ran 35D timing with almost zero fuel and put massive load on your engine with max boost!!!

do NOT run the blower all the time without a proper off boost tune

Boost is still controlled by the throttle.

Just because you have the rotors spinning does not mean you are making boost.

G