I was recently reading up on those popping exhaust sounds upon releasing the throttle. As mentioned in the previous posts, it's attributed to unburnt fuel making it through the exhaust like mini backfires. I suppose if you really lay your foot down to induce the excess fuel, you may get some burble, but it seems our cars run efficiently enough that it's still hard to achieve. Perhaps get a tune and have it programmed to run extra rich. With this condition and the absence of cats, you might even get some exhaust flames.

 

Here's how Jaguar does it for their F-types.
http://articles.sae.org/12441/

 

(In regards to Jag's tricks) Crackles/pops from unburnt fuel, what is known in the old days as overrun, from lift throttle, especially in the power band with revs is different than 'burbles'.

Burble is more attributed to pulses bouncing around a chamber that is larger and unbaffled and less 'flowy'. Exhaust pulses bounce around before exiting, as opposed to a chamber that just guides them straight out.

Short exhaust length, limited space and a Flat 6 engine note, and said engine note sits on top of the exhaust system mixing the sounds to be more mechanical and less 'exhausty', makes it very hard to get burble, especially with regular cats.
.

 

No burbles or crackles from my PSE-equipped 997.2 GTS. I'm in the camp that doesn't like the popping/burbling sound on the 991/981 Porsches.

 

This is fascinating - the "controlled misfire."

 

Given their source (small explosions of unburnt fuel), what damage might burbles be causing?

 

Carbon build up on your exhaust tips but that's it if we are talking about unspent fuel igniting when it reaches oxygenated air.

 

If the exhaust system from the exhaust port to the tailpipe is of proper material and strength, it's almost a non issue.

 

The same concept is used for those exhaust flame kits. The control module momentarily disrupts the ignition to allow fuel to pass through unburnt, then a spark plug which is screwed into the tail pipe ignites it giving you exhaust flames.

 

I don't think that Jaguar would engineer it into their car if it an occasional misfire blip would cause any problems. Interesting article, thanks for the post JCD.

I did find out what would happen once if way too many misfires occur though: They will fuse the pellets in the catalysts. This happened in a Corvette I had. The coil started failing in the middle of the desert and I decided to try to limp to the closest town on the map. Yes, way back when there was a single coil on a car. That was a pricy lesson.