Supercharger pressure?

Does anyone know a safe operating pressure to run a belt fed supercharger into a KZ650 rebuilt all stock?

sorry i dont know . if now 1 can help here, u can try dragbike.com Good luckB)

if you are running cast pistons id say to underdrive it.might i also suggest a good set of main studs and center cap support;)

Ball park estimate...

Atmospheric pressure is about 14.7PSI at sea level and 70 degrees. Your stock compression ratio is about 9:1.
You can go to about 11.5:1 on pump gas with carbs and care with ignition timing. Approx 11.5/9 increase in ambient pressure will give you the same internal pressure as you'd get with 4lb boost.

You can increase boost with a more knock resistant fuel.
IMO 6lb would be it without careful(computerized) fuel and ignition management.

No practical experience to share. I'm still looking for a steal on an M45

Set it up and see. You can use an adjustable pop off valve to vary boost while you tune. When done, you can select you final pulley size to give that pressure by using the SC manufacturers or your own RPM vs boost curves.

-Duck

What's stock compression ratio, 9.0:1??

Atmospheric pressure is 14.7 psi, so 5 psi would be close to 1/3 additional atmosphere, and 1/3 of 9 is 3, so it seems to me that it would be like having a 12:1 compression ratio.

Seems like that to me anyhow, but I have never bolted a supercharger on anything (at least not yet, would really like to get a M45 though)

I type entirely to slow, Duck done beat me to it!!!
But at least great minds think alike, eh :evil:

My excuse is I had to answer a phone call while in the middle of typing my post, and I can't type and talk at the same time

Post edited by: steell, at: 2008/02/29 23:58

i think stock is 9.5. but it wouldnt be hard to drop compression to run more boost. do some work to the combustion chamber to increase flow at low lift and that should also drop compression. its way better than going with a baseplate spacer as that would just make the quench huge when used in this application

6-7psi should be ok.

OK, so I have a belt driven *blower* that is rated for 38psi @ 8000rpms. So if I drive the pulley ratio down to 6:1 engine:blower, I should end up with 6.333psi. Does anyone have any opinions about running this on a stock carbeurated 650?

The pressure the blower makes will depend, among other factors, on the engine you intend you use it on. It might make 38psi flat out against a sealed box but whether it makes that on a motorcycle engine is another matter. It's not unusual to run a blower at half engine speed or thereabouts though.

If I was going to do it on a stock carbed 650, which I wouldn't, but if I was, I'd blow through the carbs by balancing the float bowls to boost. I'd also fit a lockup clutch as the stock one has no chance, even with heavy springs. Other than that I'd just err...ummm...save my money and buy a GPz750 turbo :evil:

I like your style. Crazy for horsepower. If you really want to make this supercharger work right do what everyone is saying too and then work the cams if you can get more overlap and duration it will lower the actual compression ratio even though the static compression ratio will stay the same. Also my suggestion would be to ditch the carbs and find a way to adapt a FI system to work. It may seem like alot of work but in my opinion it will make it much more worth it in the end. If anyone disagrees please voice your opinions.

Longer duration cams are a bad idea as increased overlap results in more of the fresh charge being pushed straight out the open exhaust valve. This is why the GPz750 turbo uses KZ650 cams instead of GPz750 cams, the 650 cams are about 30 degrees less duration and work better in a turbo/supercharged application.

If you want to lower the compression on the cheap use a 2mm base spacer.

Go buy a book on the subject...

Motorcycle Turbocharging, Supercharging, & Nitrous Oxide by Joe Haile will give you a base education on turbos and superchargers. You can pick this up on ebay or Amazon for about $15.00

Generally you don't want to use a supercharger on the street - they are very harsh on drivetrain components.