Muffler Data
07-21-2002, 11:33 AM
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Muffler Data
Finally got around to getting out the sound meter to see how loud the new exhaust/muffler setup is (my wife is an acoustic engineer, so we keep a sound meter in the closet 
). The setup is a pair of Lightning headers with extra long collectors and water entering just ahead of the transom. Since I have TRS drives with transmissions my collectors are about 2 feet longer than a typical Bravo setup and I have no sign of reversion with 245 at 0.050 duration 110 centerline cams. I have Gil full-time clamp-on mufflers attached to Stainless Marine transom tips with no flappers.
Measuring roughly according to the noise spec of 4 feet behind and 4 feet to the side of the transom I have 85 dBa at idle (900 RPM out of gear) and 90 dBa at 2000 RPM.
For comparison, the same mufflers when used on my old completely dry tailpipe Gil exhaust measured 106 dB at about 3 feet directly behind the transom between the two engines (sorry, not quite the same measurement point).
The headers with wet pipes and mufflers are maybe 50 RPM lower than the Gil dry pipes with the same mufflers, so there is possibly a 1-2 mph loss, but MUCH quieter (legal this time).
Later - Greg
). The setup is a pair of Lightning headers with extra long collectors and water entering just ahead of the transom. Since I have TRS drives with transmissions my collectors are about 2 feet longer than a typical Bravo setup and I have no sign of reversion with 245 at 0.050 duration 110 centerline cams. I have Gil full-time clamp-on mufflers attached to Stainless Marine transom tips with no flappers.Measuring roughly according to the noise spec of 4 feet behind and 4 feet to the side of the transom I have 85 dBa at idle (900 RPM out of gear) and 90 dBa at 2000 RPM.
For comparison, the same mufflers when used on my old completely dry tailpipe Gil exhaust measured 106 dB at about 3 feet directly behind the transom between the two engines (sorry, not quite the same measurement point).
The headers with wet pipes and mufflers are maybe 50 RPM lower than the Gil dry pipes with the same mufflers, so there is possibly a 1-2 mph loss, but MUCH quieter (legal this time).
Later - Greg
