dan just stick with open headers, i never heard a bad set yet. 
Drone and a Possible Cure
- Thread starter BigBlueLB756
- Start date
dan just stick with open headers, i never heard a bad set yet.
The O2 sensors read too much ambient air and dump shitloads of fuel in.
BigBlueLB756
Cheap But Not Inexpensive
Possibly overkill, but I'd rather give too much information than not enough. It's a long thread, but there's a lot of good stuff in there.
http://www.g8board.com/forums/showthread.php?t=16077
http://www.g8board.com/forums/showthread.php?t=16077
BigBlueLB756
Cheap But Not Inexpensive
Simply put, the formula for determining the length of a Helmholtz chamber used to knock out a drone frequency is:
1100 feet/second (roughly the speed of sound) divided by the target frequency you're trying to eliminate (in cycles/second) gives a full wavelength in feet per cycle. Divide this number by 4 to get a quarter wavelength (a much more convenient length to work with). Finally, multiply this wavelength by 12 to get the chamber length in inches.
Tap this length of pipe into the exhaust tube, making sure the other end of the pipe is capped off, and you have a Helmholtz chamber that takes the annoying frequency and bounces it back into the flow 180 degrees out of phase, knocking it out. The results: no more drone.
(See the above cited forum thread).
1100 feet/second (roughly the speed of sound) divided by the target frequency you're trying to eliminate (in cycles/second) gives a full wavelength in feet per cycle. Divide this number by 4 to get a quarter wavelength (a much more convenient length to work with). Finally, multiply this wavelength by 12 to get the chamber length in inches.
Tap this length of pipe into the exhaust tube, making sure the other end of the pipe is capped off, and you have a Helmholtz chamber that takes the annoying frequency and bounces it back into the flow 180 degrees out of phase, knocking it out. The results: no more drone.
(See the above cited forum thread).
Interesting solution.... I'm sure it's been done before like this, but I've never seen it....
BigBlueLB756
Cheap But Not Inexpensive
The door on this exhaust technology is slowly creaking open, thanks to the introduction of AFM/DOD engines by GM and Chrysler and the accompanying "drone" when these engines shift into 4-cylinder operation. Check out Solo Performance and what they're doing with it.
Yeah I saw that yesterday.
Just to be a bit more needy, what technique did you use to figure out the frequency of your drone? The only way I know to do it involves bringing a guitar into my truck, getting up to 70mph, and matching the drone to a note.
azmidget91
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for a simpler solution sound deaden your back wall, it seems the back wall on the f150's at least not sure on others resonates at about the same frequency as the exhaust
BigBlueLB756
Cheap But Not Inexpensive
Several apps are available for spectrum analyzers on cell phones that work well and are covered in the G8 Board forum thread cited above. The drone I was after was approx. 115 hZ, which worked out to be 27.5 inches, or so. Someone will use this theory to deal with unpleasant aftermarket truck exhausts. I just threw the idea out there to get the party started.
A solution is always better than a band-aid.
A solution is always better than a band-aid.
