Why doesn't someone develop an exhaust that has a type of valve that opens and closes at different RPMs to allow either more or less back-pressure. That would allow for more torque at lower RPMs and more HP at higher RPMS.

 

I will get right on that!
Just kidding seriously, but I like the idea of this, its sort of like the hot rod turn down pipes, that allow the exhaust the option of no restriction or full exhaust flow. The variable back preasure would be a good concept, but I am wondering where the optimal place in the system to put such a device. This is pretty thought provoking.

 

I want some royalties if this goes anywhere :smile:

 

Bmw actually had these on some of the older 96-98 3 series cars.Problem is, these are all true dual exhaust cars, 2 pipes from the cat back. Minis are single all the way back to the muffler, or mufflers in the case of the cooper s.

 

>>Why doesn't someone develop an exhaust that has a type of valve that opens and closes at different RPMs to allow either more or less back-pressure. That would allow for more torque at lower RPMs and more HP at higher RPMS.
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You mean like the new/updated for '03 Buell XB series bikes? Someone's already on it....

 

Taken from the Buell Website

"To keep the torque band fat, the new XB1200 engine is equipped with Buell InterActive Exhaust. An electronic actuator activates a butterfly valve housed in the muffler to adjust back pressure by alternating between two gas flow paths. The engine ECM monitors engine speed and throttle position while activating the valve to optimize torque and horsepower for the riding condition. At wide-open throttle, for example, the valve is opened at low rpm to reduce back pressure so the engine can gain rpm quickly. The valve closes in the mid-range to increase acceleration torque, and then opens again at high rpm to maximise horsepower. Buell InterActive Exhaust enhances the rich, throaty rumble of the Lightning exhaust tone. As part of the system, header pipe diameter is increased from 37.5mm to 43.75mm."

I probably broke some copyright and/or trademark laws by cutting and pasting, so all credit to Buell motorcycle copmany, the Buell website, etc. All content property of them, blah blah blah...

 

ahh thanks for ruining my fun so my "original" idea has been used before. However I still believe that it has some potential for the mini?

 

While not nearly as refined as that, SuperTrapp does allow one to tune for back-pressure. I'll be getting one soon (a 2.5" 24" long unit) as I begin make a new exhasut system for my MCS. They've been around for a long time and DO work exceptionally well, and also shave much weight... Until such an interactive systems comes along...

 

Yamaha did this on their early 1990's 1000cc 5 valve motor. The guys that replaced their stock exhaust with an aftermarket one lost mid range power.

 

here is a crude diagram I was thinking about using a rotating disc like in the throttle body. except with better reinforcement. Also I was think that a simple spring could control the amount of opening.

 

peter from M7 has one on his car

where the valve opens and closes depending on sound and other stuff

u should contact him