08-22-2005, 09:16 PM #1
Why does the SC have to have the Clutch???
I understand that it has to slip so that you do not build unwanted pressure, but why can we not machine a new shaft with no clutch and not have the clutch at all? You would have to have the blow off valve as a must; so can someone explain this??
Everyone is waiting on the belt drive SC and it is going to do the same thing, eliminate the clutch and replace the SC with a drive gear of some sort. This in turn will rotate a SC with no clutch so why can we not do the same thing with the stock housing???
08-22-2005, 10:05 PM #2
I often ask myself the same thing since the clutch is meant to do the same thing a blow of valve does just not as good. I have a riva BOV and you can hear that baby workin.
08-22-2005, 10:13 PM #3
I think the main goal of the clutch is to disengage the blower when the pump unhooks, so it doesn't reach crazy RPM and the stress that comes with it when this happens.
On a turbocharged motor the B.O.V. just releases the pressure and that slows the turbo down, but with direct drive the B.O.V will release the pressure but the shaft will still spin the blower over the limit.
Hopefully the aftermarket belt driven units will be strong enough for that treatment, the stock obviously can't.
08-22-2005, 11:36 PM #4
The clutch and bov serve two different purposes.
The primary reason for the clutch is to protect the the SC shaft/gear from the extreme inertial forces involved when engine rpms change rapidly. The crankshaft may only spin up to 8100 rpms, but the SC spins up to around 40,000 rpms. If you eliminate the clutch on this particular design, you can almost garantee a broken SC shaft, and it won't take long to happen.
The BOV's ONLY purpose is to releive overboost between the throttle plate and the supercharger when the throttle is cut suddenly.
08-23-2005, 12:00 AM #5
Well Thomas we're basically saying the same thing, but BOVs will also slow a turbo down because it's gas driven, on a mechanically driven SC no way.
08-23-2005, 08:54 AM #6
with a belt driven setup you will still have a small amount of slippage, which is normal, not as much though so a belt driven setup would be the way to go,
08-23-2005, 09:51 AM #7
But explain if I am wrong, the motor can only reach it's revlimiter and it is not asking the SC to do anything that it does not do under normal surcumstances.
You are running at 6500 rpm's and the pump comes unhooked and bangs the limiter at say 8200 rpm's what is the differance of just running at 8200 rpm's?
You could possibly build to much pressure that the motor can not use since it is not loaded so with the motor coming unhooked will it see vacuum and open the BOV?
What is the differance with the no clutch option and the belt driven unit?
Just imagine moving our existing unit with no clutch up on a bracket and driving it with a belt. I still do not see the differance of where the unit is driven from either a shaft or a belt??
08-23-2005, 09:56 AM #8
I think it's a matter of avoiding brutal acceleration/deceleration during unhook/re-hook.
08-23-2005, 09:58 AM #9
So you do not think the BOV will work??
08-23-2005, 10:07 AM #10
Superchargers were originally designed for autos, where there were no "unhook" problems as in boats. I think a clutch of some type is needed to have slippage in a system where the motor (and SC) can spin up to high RPM's in a fraction of a second...as when you become unhooked. This situation puts sudden stress on the SC. I really wonder how long the SC will last in a belt driven application on PWC....fine for a few races maybe, but in really rough water or in wave jumping, I doubt it is going to be problem free. Makes me think..how do the super charged off shore race boats do it ??
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