Ram induction

[JHertzman@domain.elided]

After Dave Johnson mentioned "very long runners from the centrally located 
carb to each cylinder bank, presumably increasing the torque and reducing 
top-end power versus the Ti," Tom Callahan wrote "Hmmm, educate me, please. 
How does the length of the intake manifold affect the torque and power? I can 
understand if there is significant variation between one cylinder and the 
next, but length? Bends, twists, turns, all that I can understand, too. It 
affects flow. But length? I'm at a loss on this one (and no expert, either). 
Anyone?"

As Greg Hermann replied, "The math to explain it all gets VERY complex, very 
quickly, and there are a variety of fluid dynamic effects involved", but I 
would nominate one good place to start getting educated. There is a superb 
discussion of ram induction (along with many, many other things) in Colin 
Campbell's "The Sports Car: Its Design And Performance", one of the classics. 
There is an even longer and more thorough discussion in the second edition 
(1959) than in the fourth edition, the other one which I have.

I use the term "classic" advisedly. The first edition (1954) was reprinted 
four times in 1955 and 1956; the second edition (1959) was reprinted in 
1960,61,62, and '65; third edition (revised) in 1969; fourth edition, 
substantially rewritten, in 1978; and probably more since. I don't know if it 
is in print currently, or in which edition, but in my opinion it is one of 
those books which should never go out of print, and which is worth the search 
if you can't get a current edition. It is also one of those books (like the 
1911 edition of the Encyclopedia Britannica) which I would never let go of 
one edition just because I had a later, (New! Improved!) one.

John H. 
Raleigh, N.C.

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