Contour Enthusiasts Group Archives Forums Modifications General Mods Rifle the intake?

Same rule applies as you are still talking about air flow; e.g. exhaust gasses vs. intake gasses (ambient air).

Scavenging of exhaust gasses is a theory that has resulted in several different design philosophies that include primarily tubing configurations of the exhaust system itself, starting at the cylinder heads & continuing onto the tail pipes.
Such considerations as the diameter or varying diameters (stepped headers), length, bends, location of cross-over (H or Y pipes), internal baffling of mufflers & other similar areas have all been addressed in different ways to improve the efficiency of a particular engine's ability to effectively rid itself of exhaust gasses.

Once again this involves the balancing of laminar vs. turbulent flow which brucer touched on in his original reply.

Perhaps the most extreme example I can think of off the top of my head regarding exhaust system theory application is the elaborately overlapping "bundle of snakes" utilized by Ford on the GT-40 & early Lotus IndyCar programs in the 1960's.
Similar systems continue to be utilized by prototype endurance sports cars & F1 machines to this day.

That "bundle of snakes" as you call it, is/are called 180 degree headers. Sounds like crap, a pain in the arss to do, but there's extra power in 'em. Truly only feasible in mid/rear engine cars.

This place http://www.airborncoatings.com/customer/index3.html has a coating (xylan) that is supposed to decrease the volume of air slowed by being near the manifold wall...just some food for thought.

Have you seen this?
www.tornadofuelsaver.com

Some people are so gullible...

sigh....
:rolleyes:

Regarding the "bundle of snakes" exhaust Ford used in the 60's. This is an effort to get equal timing between the exhaust pulses in the header. W/ 90 degree crank on a V8, thehe firing pulses are not equal on each bank. (IIRC each bank has 180, 180 90, 270 between firings.)

Now to the simple solution: use a 180 degree "flat" crank. Essentially it turns the engine into two 4cyl engines joined at the crank. It does vibrate more, but according to Ferrari (the only maunfacturer who uses a flat crank on a street engine) it is worth about 5% horsepower, gained through better exhaust scavenging. And the engine sounds better! This is why a CART/IRL engine sounds so different from a "regular" V8. The initial IRL engines were 90 degree cranks and they sounded likes high speed trucks.

This has little to do with the initial question, just a bit of near useless trivia.

As to the original question, go to Amazon and buy this book (you will then know more than 99.9 of enthusiasts about intake and exhaust design):
http://www.amazon.com/exec/obidos/ASIN/0...5205160-6460128


My $.02

Richard