What causes these awesome exhaust pops when shifting?

[L4ces]

I once heard an e46 do this on the street and it sounded like a shogun.

What results in these beautiful pops?

I tried set the link to start at 53 seconds and it doesn't seem to work so slide up 53 seconds in the video.

[nycplumber]

https://en.m.wikipedia.org/wiki/Back-fire

A back-fire or backfire is combustion or an explosion produced by a running internal combustion engine that occurs in the air intake or exhaust system rather than inside the combustion chamber. Unburned fuel or hydrocarbons that are ignited in the exhaust system can produce loud sounds even if flames are not present at the tailpipe. A visible flame may momentarily shoot out of the exhaust pipe where the exhaust system is shortened. Fire may also travel into the air intake piping. Either condition may cause a loud popping noise, together with possible loss of power and forward motion. A back-fire is a separate phenomenon from the fire produced by Top Fuel dragsters.

If a backfire does occur in the exhaust, that is called an after-fire. The term backfire is when unburned fuel moves back into the intake, and combusts, whereas an after-fire combusts unburned fuel in the exhaust side of the combustion cycle. A likely cause of this is from running rich, which in certain cases could be from the combustion not achieving high enough temperatures to correctly burn the fuel. Meaning a foul spark plug, coil, or plug wire could be the cause. In most cases, after-fires are bad due to the combustion, or fire within the muffler or exhaust system. This will over time cause damage to the mufflers and piping of the exhaust—eventually leading to an exhaust leak, and a burned out muffler/catalytic converter. Also there will be performance lost due to a weaker combustion.

[brplatz]

Well the fun answer is exhaust overrun. My old corvette did it all the time, so did my pops. It was almost effortless. Seems like the German v8s it might be harder to do?

[Mikeystone]

Originally Posted by brplatz

Well the fun answer is exhaust overrun. My old corvette did it all the time, so did my pops. It was almost effortless. Seems like the German v8s it might be harder to do?

That sounds great, my car with gintani race exhaust and catless x pipe and DCT has nice pops on downshift. Not to the level of your zo6 though

[Mikeystone]

Originally Posted by L4ces

I once heard an e46 do this on the street and it sounded like a shogun.

What results in these beautiful pops?

I tried set the link to start at 53 seconds and it doesn't seem to work so slide up 53 seconds in the video.

Also sounds like that car has a dog box transmission or some variation which I'm sure helps with that popping sound on full throttle upshifts

[L4ces]

Thanks for the responses... ??
I am more familiar with pops while decelerating than I am with those caused by upshifts as heard in the videos.

I'll look up dog box.

[jcolley]

True sequential gearbox is the first reason, that's the whine you hear. Second is the engine management. On gear shift it uses an ignition cut until the next gear is engaged allowing no-lift (throttle) shifting. The combination allows for quick gear changes (often pneumatic) and the fuel delivery to the cylinders is never interrupted, only the ignition.