DIY_EFI Digest V5 #88

[Greg Hermann]

>>The speed of sound (Mach 1) varies with the square root of the absolute
>>temperature of a gas, NOT with its pressure. So--if it is NOT intercooled,
>>you need somewhat longer runners to get the same effect. The pulses will be
>>pretty well proportional to the density, thus stronger.
>>
>>You might also want somewhat larger runners--because the friction loss in a
>>tube is also proportional to the density of the gas--but friction loss
>>would be the same % pressure loss if boosted with the same size runners.
>>
>>Greg
>
>>
>*Thanks Greg!* My Encyclopedia Britannica said that too:) I just wondered
>if there was more to it than that. I appreciate the input! The car is
>intercooled, soon to be water to air intercooled. This is in a drag only
>car that will be using dry ice in the resevoir to supercool the intake
>charge. I have heard of people with similar setups actually getting below
>ambient temp at full boost the whole 1/4mile. I guess this would then
>negate the variables caused from the increase in air temp. Being an engine
>that will never see lower than 3500rpm, I am leaning towards shorter
>runners, something like 6 inches from valve to plenum is convenient, and a
>plenum that is 90% of displacement. Sound good?

Plenum volume sounds good, runners sound rather short. I would think more
like nine or ten inches---

Greg


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