Quote:
Originally Posted by Wolf
Yes I know that but too much psi and the gas will self-ignite... so what's the psi range of gasoline engine before self-ignition
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What are you talking about gasoline engine? I'm not sure exactly what your question is?
Self detonation,as was said, is not only about manifold air pressure. You can have self-ignition in a naturally-aspirated engine. It's all about the heat of the fuel, and the fuel igniting from temperature vs. spark. Temperature can change with increased intake air temp, increased fuel-air ratio, changes in compression ratio, changes in manifold pressure, etc. There is just too much going on to look at one component - otherwise anyone could tune an engine.
Take this gross oversimplification with a grain of salt, but it will help you to unerstand: the engine is a pump. The greater volume of fuel/air mix it can pump through at a given rate, the more power it can make. Now, you can increase that pumping rate several ways:
1. Speed up the pump.
2. Increase density of fuel / air mix (i.e. more fuel / air per given work cycle of the pump).
3. Increase the physical capacity of the pump.
#1 is accomplished by simply adding more RPM. Obviously there is a limit to how fast all the whirly bits can spin around without coming apart.
#2 is accomplished by forced induction. Supercharging and turbocharging (really exhaust-driven supercharger to be correct) increase the density of the fuel / air mix in a given volume of intake gas by compressing it. Therefore as the engine moves it's fixed volume of gas per cycle, more fuel / air mix is passed through.
#3 is a fancy way of saying increasing displacement of the engine.
Now, there are a lot of factors that influence design decisions. One example is bore vs. stroke, which will dictate the usable RPM range and the torque characteristics coming off the engine. That's why a ship diesel has connecting rods the length of a broom handle and an F1 car's is the length of a toothpick. There are literally hundreds of other parameters that will influence the design and the outcome. '
Hope this helps!