has any one ever heard of flycutting the tops of the vitara pistons to lower the compression ratio of a boosted d16 to be able to make 400-500hp and still run on 93 pump gas and not have any pre det problems ?? this is done alot in the diesel drag racing world to reduce the pressure on the rotating assembly therfore increasing engine life... just wondering if anyone had ever done this in conjunction with a ported and posished head 3 angle valve job and a thicker head gasket to run the same boost and timing as with race fuel but still be running on pump gas... any input would be appreciated....

 

I'd worry about weakening the pistons..

 

thought about that but i think if you only took like 10 thousands off the pistons and mabe ran a 10 or 20 thousands over head gasket....

 

Yeah I see what you mean.. dunno pretty risky. If you don't care about it blowing, I would try it just to see how well it works out. You might start something new.

 

They are already stupid low compression. If you really think you need lower it more than 7.5-8.0, then just run a slackable head spacer gasket. People have made 415+ on PUMP with vitara's as-is.

 

I thought there was a 500+ version, albeit with spray. Anyways the problem isn't really the compression. The problems include the head (porting), displacement, sleeves, and bore size.

You'd need some good headwork to make 500whp on it. You also need to rev the **** out of it to spool a large enough turbo, which goes back to headwork. Concerning bore size, the Z6 has a really narrow bore for it's stroke, thus does not like timing. "Race" motors are usually designed with a short stoke, while this motor is derived from Honda's 1980's initiative where they wanted high-HP motors that still had decent low-end. Thus we got motors with decent heads vs other brands, but with a long stroke for torque. Finally, you have thin sleeves to deal with. It would be very risky above 400whp to use stock sleeves.