Cruising and higher speeds when the engine is in the 4K RPM range, if I let off the gass and begin to coast I may get a couple of pops that can easily be heard. If I then apply just a little gas to lightly accelarate it happens again. It only occurs during the transition from no gas to gas or vice versa.

Dont think its loose valves or manifolds cause it did it with the stock valves too.

Is it just the Borla not blocking the sounds or maybe somthing else.

This does not happen all the time but it is easy to reproduce.
The engine runs super strong.

Thanks all

 

my car used to do that alot.... i wnet with new ngk iridium spark plugs and wires and it seemed to ease up and not be so loud. i would tey a basic tune up and it will help it alot.

 

I have the NGK iridium plugs already.
What exactl constitutes a tuneup in an engine like this?
Plugs are new
Plug wires are new
O2's new

 

I thought those pops were caused by an exhaust leak, my car does the same thing and so does my buddies. I have an m6 and if I rev it in neutral and let off the gas it makes LOUD pops all the way back to idle RPMS's. Also when lettig off the gas while cruising in gear, when I hit the gas again but only slightly it makes a puttering sound for half a second.

 

I am pretty confident I dont have an exhaust leak. I just did a header and gasket install and this problem ocurred with the stock manifolds.

 

The popping is caused by the exaust valve not closing fast enough on the decelleration.. pretty common i think.. does not take that to be open to far to cause it.. I have the same problem in my 84 z28 with the manual transmission..

 

The unburnt fuel and no cats will make it pop.

 

Based on this is it safe to say its harmless?

 

mine does it all the time

 

Word, don't listen to all the other crap.

 

yeah a decent tune will also help eliminate some of this popping, so i hear

 

yeah it eliminated some of mine.... but not all of it. of course my car doesnt have any cats. i feel its safe to say its safe. i didnt worry on mine and i have the engine out and i do not have any burnt valves or anything of the sort. its basically unspent fuel burning from hot exhaust. you might notice it only does it after the engine is good and warm. no need to worry about it.

 

Yeah, word to the no cats.

I had this EXACT same thing on my old drag car..a 87 RX7 with only 78 c.i.d. (1.3 liters of N/A fun running 14.1)

It had a header on it with y pipe, to straight through duals.

It would pop...and then blow 3 feet of blue flames out the back. It was tuned to run sloppy rich and had two tune modes: Street/strip was no as rich, and would only slightly pop. Full Race mode would basically have gas coming out the tailpipes in liquid form....yeah...it was kinda like that for me...

Oh yeah, it didn't have any valves to be blowing by....