What parameters determine how much boost my engine can run on 92 octane?
Good question. One of the top 3 most commonly asked. Variables include the following. 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 3psi. 3psi 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 require an intercooler. Others, such as the Kenne Bell, 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 (+2psi to overcome inlet and outlet losses). Consider two 8 psi superchargers: 8×10=80, 8×20=160. The 160 supercharger should use an intercooler. An air to water inter
