[quote=spdrun]Yecch. I’d sooner take a turbo-4 than a gorilla V8.[/quote]
Really? I guess you are not too much into the real ‘specs’. The Miata cylinder block is cast iron and is generally a two bolt main cap on the crank bearing. The corvette engine is a LS block, which is an aluminum block with 4 to 6 bolt mains, two of them being cross bolts for each main cap. Because the LS engine is an aluminum block is why there is very little weight difference between the two.
Because of the two bolt main, there is a limit to how much you can boost the original 4 cyl before having crank/main problems, not to mention head gasket problems because of aluminum head vs cast iron block while under boost(different coefficients of thermal expansion). To even get close to an LS3, you will be over-stressing the Miata block and will sacrifice reliability.
–BTW, turbo Miatas come at around 170hp (nearly 250 if you want to risk parts), the LS blocks start above 300hp and run into the high 400s.
If you are doing autocross, it is better to have instant horsepower instead of time delayed as in a turbo engine (boost has to build up).
BTW: The actual gas mileage on the newer Vettes, is around 28mpg on the highway. The T56 trans has a double overdrive which drops the rotation speed of the engine to just above idle at highway speeds (approx 1700 at 75mph – depending upon rear axle ratio).
