Quote:
Originally Posted by 95 imp
I doubt the air in the intake manifold/intake port is there long enough to raise its temp. At 1000 rpm each valve is opening every 8 seconds. At 6k, 50/sec
Every time the valve opens you suck in 13.5 CFM (per cylinder @ 1K rpm @ 100% efficiency.) That jumps to 163 CFM @6K.
So, 163 CFM 50X per second @ 6K.
Under hood air... different story. Very inefficient because, as Cmitchell said, hot air is less dense. That means less oxygen per CF. It also leads into what you said, more prone to knock.
As far as drag racing, They do that to prevent heat soak and usually those engines have VERY small cooling capacity to save on weight. Half filled blocks (or solid blocks with no water jackets). You're running the engine for 20 seconds (burnout, stage and run) and the engine gets shut off at the top of the track until the next round.
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Just about every carb performance intake has the heat crossover eliminated and the intakes are raised so there is air space between the intake and the valley to keep the plenum of the intake manifold as cool as possible. Heat can be a enemy in the wrong place at the wrong time. Hot cylinder heads, combustion chambers and blocks raise the need for higher octane to reduce detonation or one needs to back off timing which lowers horsepower.