danhaggis

iTrader: (3)

well im not sure but i was just wondering if the rotary motor did need back pressure??? i know lower back pressure higher torque in the high rpm range and more (well i mean balanced ) to the low end torque is this true??

J-Rat

iTrader: (2)

backpressure is dependent on if you are N/A or not.

Roen

iTrader: (2)

there are a lot of threads on backpressure and exhaust size.

please search.

Formerly known as jgrewe

Look for posts by rotorygod in your searches. No engine needs backpressure to run better but the RX uses some to open 5-6 ports on some years. Anybody that tells you that you need a 'certain amount of backpressure' doesn't know what they are talking about. Engines respond to exhaust tuning which is dependent on pipe length, dia., rpm, exhaust temp and some other variables I can't remember because they have an ever decreasing effect the more you try to cover every possible combo.

J-Rat

iTrader: (2)

By reducing the backpressure, some amounts of raw fuel (and fresh air) will be "scavenged" into the exhaust system. So by reducing the amount of air and fuel in the cylinder at the time of combustion.

* A degree of cylinder pressure will be lost (a decrease in available torque)
* Effective air/fuel mixtures will be leaner (possibly leading to parts damage).
* Ignition spark requirements will change.
* The exhaust system's temperature will rise (owing to the burning of air/fuel mixtures in the exhaust manifolding and pipes).
* Exhaust gas temperatures will increase (particularly notable during engine dynamometer tests).
* There will be a tendency of back-fire (or popping) during deceleration of the engine.

And while other conditions may arise (depending upon how a given engine is configured), the ones listed here are probably the most common.

Roen

iTrader: (2)

I think the point was that it's not the backpressure, but the increase of flow of the exhaust system that causes the things you mentioned. Lower backpressure is just a side effect or by-product of a decreased restriction exhaust, and shouldn't be pointed to as the cause of the effects listed.