sn cog set up

**vibrant_93** · 02-22-2011, 05:59 PM

do they make a cog setup for a sn2000 blower? and if they do is it smart to run the setup? any help is greatly appreciated

**Michael** · 02-22-2011, 11:54 PM

I've never seen a cog setup for an SN blower. But that's doesn't mean one doesn't exist.

If you're using the car on the street, then the answer is 'no', it's not smart to run a cog drive. If it's a dedicated track-car, then a cog setup is fine.

However, I have to ask: how much boost are you running that you're considering cog-drive for your SN?

**vibrant_93** · 02-24-2011, 12:56 AM

It is strictly street use with a little track ttime on the side, I was just interested in the cog setup but not something im going to do now, im seeing about 8-9lbs of boost

**Michael** · 02-24-2011, 01:05 AM

It's not worth going to a cog drive setup if what your seeing is 8psi-9psi. You could move to a blower which produces double that boost and still not need to go to a cog drive setup.

But as I said, cog drive has it's place and that place is primarily the track. If it's a street-driven car (or even just a show car) with less than 10psi boost, then a cog drive system is overkill.

**Joo** · 02-24-2011, 01:40 PM

cog belts are not very common in conjunction with street superchargers. The advantage of a cog belt is the lesser tension (depending on application). The synchronous drive of a colt belt in this case is a disadvantage because due to hard acceleration of the engine the whole mass of the internals of the chargers are accelerated and this means a very high load on the gear or ball drive. The slippage of the v-belt is there used to prevent the internal drive from damage and the ball drive from internal slip in case of the Paxton SN (I assume).

Regarding a VR4 @ 14 psi I really don't know if the v-belt drive can transfer the forces.

**suede57ford** · 02-25-2011, 12:00 PM

I used factory style thin dual V-Belts on '57 Ford with the SN converted VR57 Blower with the VR4 impeller and did not notice any slippage issues at all. Seemed to work very well and the belt were the Napa 7525's with the original ford supercharger pulleys and tensioner.

**suede57ford** · 02-25-2011, 12:05 PM

I feel that cog belts on a ball driven street driven blower would be a bad idea.

When you drop RPMs during a gear change the belt slips just a little to help the blower transition its speed change. You also need the belt to slip slightly when you let off the gas, so it does not shock the blower.

**JPJP** · 02-25-2011, 01:08 PM

I am not sure about the statement of desiring slight belt slippage when letting off the gas. If that is the case how does one prevent the belt from slipping at the higher RPM's and then allow it to "slip slightly" during shifts and letting off the gas?

**suede57ford** · 02-25-2011, 01:31 PM

Slippage is the reason a ball-driven blower was so reliable on the street.

Because of the instant, in comparison to the acceleration curve, change in engine speed during a shift or closing of the throttle blades the internal slippage of the ball system prevents heavy shock blower components.

The reason they did not have gear driven centrifical blowers in the early days is the changes in engine and blower speeds, would sheer off the internal gear teeth. Until modern day technology enabled stronger gears to be made, gear driven blowers like the Vortecs would not have lasted on the street.

The slippage of the balls and belt is what gives the blower reliability on the street.

A properly set up belt set-up will not slip under acceleration, as that is a slower curve than the instant(shock) speed changes that occur durring a gear change.