rs4jg

Do i need to be concerned? I was driving on a "closed Circuit" late last night being followed by a buddy who is a big fan of his new mazda 6. I am only at 700 miles so used shift points of 6500rpm and 80% throttle all the way to 13.0 mph. He obvously had the perfect view to see that during deceleration i had major sparks coming from the left exhaust tip. What does this mean? and wow was the car stable at 13.0mph

Parikh1234

No clue on the sparks issue.

RI A6

I'm glad to hear it's stable at 20 mph. Whew!

McGyver

pullin' out of the garage?

RI A6

Damn, must have been the hump between the driveway and the street, my bad!

RI A6

I assume he could not see "sparks" from the other tip because of the angle. Normally on deceleration the ECU will enrich the A.F mixture to keep from going lean (known as the overrun mode). This will cause some backfiring. It should be visible in both exhaust tip.

If it's sparks due to something metal being abraded, you've got serious problems. Your choices are pistons, rings or valves.

Parikh1234

you need to stop laying dead bodies there. You are supposed to burry them.

rs4jg

Lets hope its related to back-pressure. Service soon so i will have them look into it.

ELEVENS

My experience with ECU programming (admittedly dated, 1985-1991 Corvettes) was the exact opposite. Called DECEL mode, the map would go waaay lean to save fuel and PREVENT backfiring (unburned fuel igniting in the exhaust).

About the sparklers: A suggested workaround would be to travel at 13.1mph There's no way chunks of pistons/rings are getting past the cats and out the tailpipe. Now if you manage to get the exhaust ridiculously hot and there's lots of carbon in there, you might get a very minor pyrotechnic show. Certainly not normal IMO! Marketing idea: Some guys would gladly spend hard-earned ebay paypal money for automotive fireworks!

daveak05

primitive decel valves used to prevent over rich mixture to avoid backfiring, IIRC.