Okay, looked up the real regs.
For Open Category cars with turbos (Open class and Group 5 class), you need an adjusted displacement of under 5100cc. For rotaries, your displacement multiplier is 1.8, for turbo/supercharged the multiplier is 1.7, and pushrod the multiplier is 0.8. So, the SRT-4 in stock configuration is 2400cc x 1.7 = 4080cc adjusted displacement. The 2.0L Subaru motor has 2000cc x 1.7 = 3400cc.
Now, the next reg on restrictor plates is if your adjusted displacement is at or under 4000cc, you use a 34mm restrictor. If it is greater then 4001cc, you use a 30.7mm restrictor.
If I were an SRT-4 driver, I'd mod the motor to only have 2350cc of actual displacement, so that the modified one was just under 4000cc. I don't know what competitors actually do though.
These are the Rally America/ex-SCCA rules. This doesn't necessiarly apply to WRC or other rallies. In WRC, I believe the displacement limit is 2000cc w/ a 34mm restrictor with no option for a larger displacement motor and smaller restrictor.
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While a standard engine is powered by a belt connected to the crankshaft, a turbo engine runs on its own exhaust steam, making it more energy efficient. -- CNN
Last edited by Nick Koan; 2006-02-03 at 12:00 PM.
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