Twobit

Im new with compression...can anyone explain what each of the numbers mean?
Ex. 9:4:1 I think thats what I saw in someone elses post. Anyone who can have a detailed explaination it will be very helpful.

Turbonut

iTrader: (1)

Hope this helps. Naturally in the RX7 it will be a rotor in place of a piston, but compression numbers the same.
The compression stroke is the upwards movement of the piston in the cylinder with the valves closed following the intake stroke. This upwards motion compresses the fuel air mixture inside the combustion chamber raising the pressure. The difference between the initial volume of the cylinder and the final volume at the top of the compression stroke is known as the compression ratio. Typically this is approximately 9:1 in spark ignition engines and 15:1 for diesel engines. The compression ratio is particularly important in compression fired engines such as diesel engines. The fuel-air mix and compression ratio is critical to avoid pre-ignition which is the abnormal ignition of fuel in the combustion chamber before the combustion stroke. In diesel engines the fuel is injected under high pressure towards the top of the compression stroke. The distribution of fuel before combustion is also of interest because it effects the efficiency of combustion.