Thursday, March 7, 2013

FMF Q4 Mod tested

Somewhere on the web I bumped into a great idea to modify the Q4 spark arrestor to reduce the sound.
So I bought an extra spark arrestor for $35 and tried it out.
The idea is that you cut some slots in the end of the arrestor and bend the tabs over the block the pipe a bit. I used duct tape to mark where I was going to cut:

Here are a few shots of the modified spark arrestor next to an unmodified one:

FMF Q4 with Spark Arrestor
RPM            Original          Modified
2000             87 dB                87 dB
6000             102 dB               102 dB (whistle sound noticed on modified)
8000             106 dB               106 dB

No improvement! Wow, I really expected this to work.  I guess I could bend the tabs down some more, but I don't want to crudely block the exhaust too much. I guess the lesson is that you need actual baffling, not just some blockage.

Another note is that these measurements with the original spark arrestor are different from the ones in my last post a couple days back. Just shows how variable this testing is.

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