Electronic Exhaust Cutout
03-29-03, 11:39 PM
#1
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Electronic Exhaust Cutout
My buddy with his '03 SS just added an electronic exhaust cutout right before his muffler. After riding in it before and after and feeling the difference, I got to thinking hard. Would this be possible for an FD? The only concern I could concieve would be running rich and mabe a lb or 2 more of boost, which is not necessarily bad, especially with a programable ecu. I searched for this and all I could come up with were people that had the idea but no follow-throughs. Could this be possible considering the layout and ground clearance of our cars? (since the tubes usually dump down at an angle?)
-Taylor
-Taylor
03-30-03, 12:20 AM
#2
Rotary Freak
I've never seen it done on an FD, but I'm sure it could be done with no problem. You shoud have plenty of ground clearence as long as your FD isn't slammed ot the ground. Reprogrammed ECU could handle everything with the cut out open or closed, and if you have an EBC you could keep boost at wutever you want.
IF you ahve a ported wastegate, perhaps the cutout can be before the cat. just open it up before u go raceing or whatever.
IF you ahve a ported wastegate, perhaps the cutout can be before the cat. just open it up before u go raceing or whatever.
03-30-03, 01:57 AM
#3
I have seen an electronic cutout on an FD. If you do install one, be sure to discharge the exhaust away from the undercarriage or you might burn it up with the hot rotary exhaust.
Opening the cutout would cause the car to run leaner than it would with the cutout closed, assuming that you keep the fuel map the same. Since you have less backpressure at the exhaust port, you will get more fresh air into the chamber for a given boost level. The speed density fuel injection system just measures pressure (& RPM, temp, etc. but not flow), so it will be completely unaware of the flow increase you get from opening the cutout. However, the difference might be small enough that the car could run fine with the same map both ways. It would just be richer with the cutout closed.
I was thinking about a midpipe with two pipes, where one of them would have a cutout installed inline to open or close the second pipe. The idea would be to use smaller-than-3" tubing that would have good velocity at low speed for better torque, and then open the second pipe when you need more flow, perhaps with an RPM switch after dyno testing to see what the right RPM would be. However, there seems to be a general rule of thumb that a huge pipe after the turbo is always better. That might be just for maximum peak power, but if it means better power at any RPM, this dual midpipe thing would be pointless from a performance perspective. I am not sure what the truth is.
One other advantage to this setup is that you could perhaps use it for noise abatement at low RPM. Send the primary though a muffler with the secondary (valved) pipe unmuffled in the midpipe section. I would want to join them both at the rear of the midpipe section to send all the exhaust through the cat-back, perhaps with a y-pipe before the connection to the cat-back. Alternately, it could be done using a dual input / single output muffler, which would muffle both of the pipes rather than having the secondary unmuffled.
-Max
Opening the cutout would cause the car to run leaner than it would with the cutout closed, assuming that you keep the fuel map the same. Since you have less backpressure at the exhaust port, you will get more fresh air into the chamber for a given boost level. The speed density fuel injection system just measures pressure (& RPM, temp, etc. but not flow), so it will be completely unaware of the flow increase you get from opening the cutout. However, the difference might be small enough that the car could run fine with the same map both ways. It would just be richer with the cutout closed.
I was thinking about a midpipe with two pipes, where one of them would have a cutout installed inline to open or close the second pipe. The idea would be to use smaller-than-3" tubing that would have good velocity at low speed for better torque, and then open the second pipe when you need more flow, perhaps with an RPM switch after dyno testing to see what the right RPM would be. However, there seems to be a general rule of thumb that a huge pipe after the turbo is always better. That might be just for maximum peak power, but if it means better power at any RPM, this dual midpipe thing would be pointless from a performance perspective. I am not sure what the truth is.
One other advantage to this setup is that you could perhaps use it for noise abatement at low RPM. Send the primary though a muffler with the secondary (valved) pipe unmuffled in the midpipe section. I would want to join them both at the rear of the midpipe section to send all the exhaust through the cat-back, perhaps with a y-pipe before the connection to the cat-back. Alternately, it could be done using a dual input / single output muffler, which would muffle both of the pipes rather than having the secondary unmuffled.
-Max
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