jd93

I have a 2016 is350. I just took off my is250 exhaust and installed it onto the 350. It is an invidia axelback paired with a tsudo midpipe. Since I have made the switch I have noticed several times after braking and coming to a complete stop within a couple seconds the exhaust "pops" usually 1 time and it is fairly loud. This did not happen on the 250. What is concerning to me is that it doesn't sound like normal exhaust popping/gurgling when slowing down or downshifting it is more of a sudden loud single pop after coming to a stop. Anyone have any idea what this is? Or if this is considered normal? Also why it would happen on the 350 but not the 250?
Thanks

Swacer

Search Tool is your friend.

jd93

Thanks for the super informative answer, very helpful.

Swacer

It was, if you use the Search, you will find this has been discussed plenty of times before, in which you will find your answers.

dnasians

iTrader: (4)

freeing up flow means more fuel can potentially get through the exhaust, espes with no cats (or high flow cats). when the appropriate combustion mix is met with hot metal, a little bang can go off. no biggy.

jd93

Thanks for the help!

DEMONX

i have noticed how helpful some are in here... Lol

abenjack

I have that too on my 350 with a muffler delete. I think its just the back pressure escaping. Mine happens after medium to hard acceleration when I'm coming to a stop.

Viktimize

Backfires are from unburnt fuel in the exhaust igniting off hot exhaust gas. This happens generally from removing a catalytic converter, which is used to get rid of those hydrocarbons still left in the exhaust gas. The only way a simple muffler delete should allow this to happen, is due to decreased back pressure that lets the exhaust gas pass through the cats fast enough that the catalyst doesn't finish it's job and let's some hydrocarbon pass through.

It always happens most on deceleration because when you let off the throttle the spark plugs stop firing. So you have a lot more unburnt fuel that was already in the cylinders being pushed into the exhaust instead of being ignited by the plugs.

anthonys2r

iTrader: (1)

I've had this happen also with an aftermarket axleback on this car (with stock midpipes), I'm not sure how to explain that though since it doesn't touch the cats

dnasians

iTrader: (4)

an aftermarket axleback will free up flow compared to stock mufflers. as explained above, with higher flow, more fuel is allowed to escape, and therefore is more likely to ignite in the exhaust.