[Boxer]

When I was out running the Boxer today, a couple of times when I took my foot off the gas it sounded like I had a short misfire (almost a "cough" coming out of the tailpipe). Any idea what might be causing this ? It is not something I have noticed in the past. Thanks, Boxer42

 

[senna21]

This is normal. Most silencers will cover a "trailing throttle" and you'll never hear it. How old is you muffler? It may be getting old and the packing might be deteriorating to a point where it is no longer absorbing as much sound. Most mufflers are packed with fiberglass, stainless steel wool, etc... When you come off the throttle the engine takes a load and the valves end up opening just a bit earlier. This dumps still burning fuel into the exaust. This is why you see some race cars (with open exhaust- and some without) shooting flames out the exhaust while under hard braking.

Like this Morgan at LeMans....

 

[senna21]

Here's a better example.

 

[Boxer]

Great picture and thanks for the advice. Boxer42

 

[Stradale]

Thanks Senna.