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Discussion Starter #1
how much boost can i run before the comp ratio needs changing? and where can i get pistons etc to change the comp ratio, what other stuff would be needed?

i'm on 7PSI at the moment but was gonna get the bigger crank pulley (from CFM) and maybe a smaller SC pulley to take it to about 10-12psi.

and will water injection be needed when it gets to that level of boost.
 

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how much boost can i run before the comp ratio needs changing? and where can i get pistons etc to change the comp ratio, what other stuff would be needed?

i'm on 7PSI at the moment but was gonna get the bigger crank pulley (from CFM) and maybe a smaller SC pulley to take it to about 10-12psi.

and will water injection be needed when it gets to that level of boost.
Percy,

First of all, do not lower your compression ratio. Superchargers like compression. You lower compression ratios when you are going to be using high boost levels with a turbo. When turbo's spool they spool really well and they go to full boost. But it is usually in the 3-4K rpm range. At this period of time at 3-4K rpm, the intake valves are open for a lot longer period than they are at 7K rpm. This long intake valve opening period combined with the thrust of boost that a spooled turbo produces creates high spike loads on pistons and rods. It is also the thing that makes turbos feel so good. But it is very hard on engines. So that is the reason that turbo cars lower their compression. But superchargers raise their boost levels in a linear fashion. The higher the boost the lower the time that the intake valve is open. Thus reducing shock load to the internal engine components. Plus, you aren't going to be able to produce the high level of boost with a supercharger that would require lowering your CR. Your supercharger will work fine without any cooling as long as you stay at 10 psi. Above that you are working in an area where the supercharger isn't efficient. And there is no sense going there. If you want more power from a supercharger you might "raise" your compression a point and then tune it for the additional compression. Horsepower is all about cylinder pressure and air molecules. If you are running 10 psi and you have 300cfm of air molecules that you know you can't go above, why not raise the cylinder pressure a bit. Install a big valve FR head with the cylinder surface machined a little and you will have more CFM reaching the cylinders and more compression to make it go bang!
 

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I ran a 2.3 pully with a stock crank and ran 9.5psi with no cooling for about a year and have had no problems. I just added a larger crank pully and now making 11 psi. I also added Snow's MAF controller ontop of my custom water injection setup. So far I like how the controller works.
 

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Discussion Starter #4
cheers for the info guys, very helpful as ever
 

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Phil, get that head ported and polished mate, you know it makes sense, especially after I showed you mine !!!Ooooeerr matron !
 

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Discussion Starter #6
might do eventually if i get better pistons to cope with a [censored] load of nitrous on top of the supercharger - for now i just wanna have a cheap minor boost upgrade lol! not desperate for extra boost but might as well get the wheels in motion.

your head is so nice its almost a shame to put it on the car
 
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