[Wolf1]

Does the supercharger decrease my fuel mileage? Not under normal driving conditions. However, if you use the boost it will, of course, use more fuel. You can't make power without fuel.

What kind of performance increase can I expect A Supercharger Kit? Approximately 30-50%.

Why is a supercharger better than other performance modifications? A Supercharger is by far the best performance value of all. You can spend more money on exhaust, headers, cool air, chip, cam etc. and not get anywhere near the performance you would from the supercharger kit. You also can benefit from a lot of these in conjunction with your supercharger. A Supercharger is a power adder. So with the exception of higher compression, you can benefit from other performance modifications, especially anything that increases volumetric efficiency of your engine.

What parameters determine how much boost my engine can run on 92 octane?.
COMPRESSION RATIO - Lowering the compression ratio allows the engine to run more boost with the same octane.
For example, 8.0:1 vs 9.5:1 can tolerate another 3 psi. 3 psi gives 38HP. The 1.5 lower CR loses 3% (2% per point) or around 9HP in a 300HP engine. That nets 29HP (38-9=29). Now you know why OEM's use low compression ratios on supercharged engines.

AIR CHARGE TEMP - The supercharger itself determines how much boost the engine will accept. Some superchargers can require an intercooler. Others, don't need intercoolers because the discharge air temp is cooler.
1 psi boost increases supercharger air discharge temperature 10°-20°, depending on supercharger type. A 6 psi "rated" kit usually requires 8 psi "total" boost (+2 psi to overcome inlet and outlet losses). Consider two 8 psi superchargers: 8x10=80°, 8x20°=160°. The 160° supercharger should use an intercooler. An air to water intercooler will lower that 160° to around 80° (160°-80°=80°) or the 80° temperature of a more efficient supercharger without an intercooler.

BOOST - Both higher compression ratios and boost increase cylinder pressure and demand higher octane fuels to eliminate detonation. Fuel octane determines the amount of boost an engine will accept. One octane will support one psi of boost.
Example: If fuel octane is 94 or you add a can of NOS Octane Booster you can typically run 8 psi.

IGNITION TIMING - Retarding ignition timing will allow the engine to run more boost but not without a penalty. 4° retard=16HP.

AIR FUEL RATIO - You can't make horsepower without fuel. Richer air fuel ratios reduce power but permit higher boost levels on a given fuel octane. Leaner ratios make more power but need lower boost so a lean mixture with high octane makes the most HP. Supercharger kit tuning demands ignition timing, air fuel ratio, fuel octane, boost, compression ratio, discharge temperature and supercharger parasitic losses all be carefully considered in the design.
What causes detonation? 1. Lean fuel mixture, 2. low octane fuel, 3. excess boost, 4. lack of fuel, 5. advanced ignition timing, 6. vacuum leak, 7. "hot" spark plugs, 8. overheated engine, 9. excessive inlet temperature (underhood filter).

What is the most ridiculous aftermarket product?
Hands down, it's the "little intake fans" and the "throttle body spacers" with the bore grooves.

Right there on the list has to be those "underhood exposed filters" that suck in 200° underhood air instead of ambient (70°-100° air from the fenderwell).

10° air temp rise is -1% HP.

That's how dynos are calibrated for temperature changes. Does anyone really believe that all those OEM manufacturers designed expensive plastic inlet systems - for the last 20 years - that pull cool air from the fenderwell, hood or grill because they didn't have anything else to spend their money on?

Then there's those "factory calibrated" mass air meters that do not use a chip or re-calibrated processor with oversize injectors. They unwittingly reduce the voltage signal to the mass air meter to compensate for the larger injectors at WOT but they neglect all the driveability issues. The result is over advancing timing, lean mixtures, detonation, surging, bucking etc.

So if converting to a MAF, the idea is that it is sending a signal your ECU can read and use at all temps and RPM range. AFM can be tricked as can the stock ECU on the 944. With a 924, well CIS is a different animal, but principals are the same.

Why is knock protection so important? Knock (detonation) can destroy your engine if it is not negated. Suppose your wife or a friend unknowingly fills your tank with 87, or you get a "bad batch" of gas, the engine overheats, someone installs a pulley that raises supercharger boost, the wrong spark plug heat range is installed (too hot) or a vacuum leak develops and the engine leans out. That's when an engine needs knock protection.