Hope this question makes sense...I have an HKS exhaust with the Berk hi-flow cat.

I noticed that when I'm decelerating without gas, my exhaust makes that "putt putt putt" sound instead of a clean and even deceleration sound like the oem exhaust. This seems to happen on most aftermarket exhausts I've heard.

What actually causes the "putt putt putt" sound during deceleration?

Thanks!

 

I always thought it was backfiring or something. My old car used to do it with the aftermarket exhaust. I think its cause of the fact the new exhaust flows freer. I'm not an expert though, lol.

Does sound cool though

 

typically unburned gasoline igniting in your hot exhaust.

 

does that mean my car's running too rich with the hfc and exhaust?

 

It's not backfiring or unburnt gas igniting. It's just back pressure