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501 Posts
Greetings list,
I was thinking of ways to possibly/slightly improve performance of my 33 16v boxer motor that I have recently rebuilt as the engine by its nature doesn't have a great deal of torque at low rpm. I thought about ways to improve this a little, and exhaust back pressure seems to be one way of acheiving slightly more torque sub- 3500rpm. The flipside is that it is too restrictive at higher rpm - so here's my idea:
I wish to either find or construct a heavy duty butterfly valve which is operated by a servo or stepper motor, much like a throttle body. The butterfly will of course not completely shut off the exhaust but let exhaust through holes in the buttlerfly plate. My plan is to utilise a small microcontroller to variably open/close the valve depending on RPM (as my background is computer science, this will be the fun part!). I know that Ferrari have done something similar on the 360 Modena, so I would be interested to know how their system works.
Another aspect of the project is to simply have the car "quiet" below 4000rpm, but make a bit more noise when I push it a bit harder - so I only annoy the neighbours when I want to
I don't really know where the valve should be located - in between the engine headers and the resonator? between the resonator and the muffler?
And before I start hassling someone to use their mill, does anyone know where I can find a suitable 2" or 2.5" butterfly valve?
Your comments + criticisms welcomed
~Benjamin
I was thinking of ways to possibly/slightly improve performance of my 33 16v boxer motor that I have recently rebuilt as the engine by its nature doesn't have a great deal of torque at low rpm. I thought about ways to improve this a little, and exhaust back pressure seems to be one way of acheiving slightly more torque sub- 3500rpm. The flipside is that it is too restrictive at higher rpm - so here's my idea:
I wish to either find or construct a heavy duty butterfly valve which is operated by a servo or stepper motor, much like a throttle body. The butterfly will of course not completely shut off the exhaust but let exhaust through holes in the buttlerfly plate. My plan is to utilise a small microcontroller to variably open/close the valve depending on RPM (as my background is computer science, this will be the fun part!). I know that Ferrari have done something similar on the 360 Modena, so I would be interested to know how their system works.
Another aspect of the project is to simply have the car "quiet" below 4000rpm, but make a bit more noise when I push it a bit harder - so I only annoy the neighbours when I want to
I don't really know where the valve should be located - in between the engine headers and the resonator? between the resonator and the muffler?
And before I start hassling someone to use their mill, does anyone know where I can find a suitable 2" or 2.5" butterfly valve?
Your comments + criticisms welcomed
~Benjamin