RogueSTi

iTrader: (14)

Having just finished reading Maximum Boost by Corky Bell (which is an outstanding and highly recommended read), I am intrigued by intake manifold design.

What I took from Corky's book is:

1) Intake port runner length: Higher speed engines benefit from short runners. Low-speed and mid-range torque generally shows gains from longer runners. Turbo applications generally findbest results with long runners, which provide a broad, flat torque curve at low speeds, while the turbo keeps the top end strong.

Question--> Is there a formula used to determine intake runner length?

2) Intake port runner diameter (section area): ?

Question--> How do you determine the intake port runner diameter?

3) Intake port runner rate of taper: In all applications it is desirable to accelerate air toward the combustion chamber. This is accomplished by gradually reducing the section area (diameter) of the runner as it nears the chamber.

Question--> Again, how does one determine the rate of taper?

4) Plenum size: Plenum volume should be a function of engine displacement-in general 50-70%. One of the most critical design points is the plenum-to-runner intersection. Ideal plenum-to-runner intersection (air inlet) shape is shown in the following diagram:



Comment--> The book doesn't go into any more detail as to plenum volume, shape, position, etc. I am now searching for another book that goes into much more detail on intake manifold design. Obviously, it needs to be current, as carburated intake panifolds are a completely different animal due to the fact that an EFI equipped intake only has air flowing through it. A carburated intake has fuel and air.

5) Fuel Injector Location: Only 2 basic rules apply to the location of an injector. First, it must be aimed as straight down the center of theport as possible. Second, it should discharge at a point where air velocity is at or near its highest. The primary injector should be positioned no more than 20 degrees off-axis from airflow in the port. In cases where airflow dictates the use of a secondary injector, it's position is not as critical as the primary. Street applications benefit from the secondary injector being aimed downstream (like the primary), however; Race applications sometimes benefit from aiming the secondary injector upstream as this may offer slightly better atomization.

Question--> Mounting the injector at the point of highest air velocity would put it at or near the very end of the port runner, near the mounting flange. This is also the hottest part of the intake manifold as it is in direct contact (via a gasket) with the cylinder head. Wouldn't the heat from the cylinder head damage the injector seals and O-rings?


The book goes on to discuss throttle bodies, however I am more interested in the manifold at this point.

Please discuss, however I ask that you guys not bog down the thread with mindless technobabble and statements like "My brand X intake manifold is the shizzle" My intention with this thread is to discuss intake manifold design theory and application.

Disclaimer" about 90% of what I typed above was directly copied from the book Maximum Boost Corky Bell. Let it not be said that I plagiarized.

RogueSTi

iTrader: (14)

http://www.newcovenant.com/speedcraf...ors/intake.htm

http://www.popularhotrodding.com/eng.../0601em_intake


I found these links that have intake runner calculators, etc.