Originally Posted by TehMonkay (Post 61504)

Last i checked they made a couple of one offs for the right price.

Originally Posted by need RX7 (Post 61506)

Anyone know anything about what design elements (pipe diameter, length, bends, etc) make for best torque/horsepower, and optimizing powerband and stuff like that? Like for someone who was going to fabricate their own?

Originally Posted by fidelity101 (Post 8588709)

okay you want to get use of scavenging in your exhaust system, primarly the header by a low pressure area created in the exhaust system that can be used to "draw" the exhaust out the chamber. I know how to explain how reversion works on a piston engine but I'd have to look into it further for a rotary. BUT if you reduce reversion you increase volumetric effeciency and power so you basicaly build your header for RPM range.

now you want low power? then you need to utilize equal length tubing with a maximum variation of +/- .5" the bends (as long as they aren't crush bent or 90 degree bends) won't affect the flow, the length and tubing size will. By going from a 2.5" (outer diameter) primary pipe to a 2.0" (outer diameter) primary pipe you increase the exhaust velocity speed providing more low end power since you want the smaller tubing to maintain a high enough velocity when there is less exhaust volume at lower RPMS.

have you considered thermal coatings or wraps? With thermal coatings you can use those to retain heat in the exhaust system since as the gases cool they loose velocity, velocity increases scavenging at high speeds and reduces reversion (reverse flow at low RPM) and not to mention reduce underhood temp so you can get cooler air into your intake for MORE POWA! Thermal wraps do a better job but I wouldn't recommend them for a street vehicle since they tend to retain moisture and will rot your pipes alot faster.

smaller pipes better low-mid range power, so basically from going to a larger pipe to a smaller pipe you move your power curve more over to the left hand side of the graph (X axis is RPM, Y axis is exh velocity or power) steeper slope.

you generally want to keep around 240-260 feet per second when an engine is operating at peak torque.

to calculate the pipe size you need there is a formula

1. desired RPM at which max tq is to be produced
2. multiply CID of one cylinder (or rotor)
3. divide by 88200
the result is cross sectional area of the pipe required

4. now divide that by 3.1412
5. take the square root
6. multiply by 2
the result is the necessary inside pipe diameter.

by changing the pipe size you shift the torque curve around by going from a larger pipe to a smaller pipe your causing the engine to take away torque from one RPM and add it to another.

increasw the length, adds tq below to engines tq peak, and vice versa.

the lower RPM range the header is required to work the longer the pipes need to be.

you can also use a collector to produce more tq below the peak but will decrease tq after the torque peak, typically you want your collector to be 3/4" bigger than your primary pipe diameter.

hope this helps!

Originally Posted by Flooder (Post 61512)

Racing beat. Nuff said.

Originally Posted by Flooder (Post 61536)

Most people who buy the header are putting it on stock cars/daily drivers. If anyone builds a serious track car, where every horse power matters, it's usually a turbo setup.

Originally Posted by Roen (Post 62995)

There's a guy on the other forum called pirsq. He says he's got a new exhaust system, similar to the ISC, with some promising results, though none verified.