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Of course a B20F head is a good way of dropping compression a bit... but it's not necessary with the basic kit's 5-6 lbs of boost, and 155 bhp with corresponding torque increases completely transforms the car (so I'm told -- I certainly have not driven one). There should be no detonation problems using a vacuum advance distributor and premium gas at this level, although the working pressure is roughly equivalent to having 13:1 compression in a normally aspirated motor.
The current solution to higher boost than that is detonation-sensing ignition; the solution under development is a full EMS system, both adding substantially to the cost of the project. Then there's a "wall" at which the stock exhaust ports will simply not flow more regardless of the boost level, so you're into a porting job. After that point, you'll want forged pistons.
I think it's a terrific system, but 200+ bhp seems to come out to much the same price no matter how you go about it.
Regarding the KGT heads, current thinking is that lowering CR by much in order to run more boost is counterproductive. That's how it was done back when people were first playing around with turbos, but check out the specs on late-model turbo cars and you'll see quite respectable CR and relatively low boost -- remember that horsepower has nothing to do with acceleration (nothing, really nothing); it's the area under the torque curve that matters.
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