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Originally Posted by TrinaBabe
I see someone already tried to make a manifold that is extremely similair to this test one  |
From what I've seen, the intake manifold for the Saab Viggen hillclimb car is almost identical. Same cone/plenum/runner setup. I haven't had a close enough look to be sure, but it looks pretty dang similar. The exception is that the injectors are mounted on the plenum and shoot the streams of fuel straight down the runners. Pretty neat.
Still not sure why you're worried about the length of the runners in relation to flow. The length of the runners serves primarily to pulse-tune the intake setup. There's a good formula on this borrowed from the book I mentioned previously:
Runner length (from valve to plenum) = (90 * 1,100)/RPM
The value of 1,100 will be loosely dependant on intake temperature. (IE: speed of sound) The RPM is the approximate RPM at which peak pulsetuning effect should result. There will also be a significant change in the effect when different camshafts are used; a longer duration cam will require a longer runner tube to create the same pulsetuning effect. (Though the "same effect" may not be desirable.)
For an engine running peak torque at saaay
6,000 RPM, you get a value of
about ~16.5 inches, give or take a couple.
Sometimes people tune to the second pulsewave, which reduces the requisite length by quite a bit. (Not exactly half, IIRC, but somewhere in the vicinity.) In either case, it's worth thinking about.
