512 BB Exhaust Noise

Boxer · 06-10-2004, 09:38 AM

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 · 06-10-2004, 10:41 AM

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 · 06-11-2004, 11:02 AM

Here's a better example.

Boxer · 06-11-2004, 10:03 PM

Great picture and thanks for the advice. Boxer42

Stradale · 06-12-2004, 04:16 AM

Thanks Senna.

06-10-2004, 09:38 AM	#1
Boxer Owner Elite Member Join Date: Apr 2004 Location: UK Ferrari Life Posts: 12,773	512 BB Exhaust Noise 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 Boxer Current: F40, F50, 612, 430 Scuderia Past: 360 Modena, 360 Challenge, 550, 575, 365BB, 512BB, 456 GT, F355 GTS, 365 GTB/4 Daytona, 308 GTB

06-10-2004, 10:41 AM	#2
senna21 Join Date: May 2004 Location: Los Angeles, CA Ferrari Life Posts: 476	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.... Charles Wells (aka senna21)

06-11-2004, 11:02 AM	#3
senna21 Join Date: May 2004 Location: Los Angeles, CA Ferrari Life Posts: 476	Here's a better example. Charles Wells (aka senna21)

06-11-2004, 10:03 PM	#4
Boxer Owner Elite Member Join Date: Apr 2004 Location: UK Ferrari Life Posts: 12,773	Great picture and thanks for the advice. Boxer42 Boxer Current: F40, F50, 612, 430 Scuderia Past: 360 Modena, 360 Challenge, 550, 575, 365BB, 512BB, 456 GT, F355 GTS, 365 GTB/4 Daytona, 308 GTB

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06-12-2004, 04:16 AM	#5
Stradale Owner Join Date: Sep 2003 Ferrari Life Posts: 1,685	Thanks Senna.