Joejoe3769

i got a 85 rx and i just put a brand new 3a racing muffler on it and i dont got the sound i want from it. it sounds ok but quit what i want. plus on top of that evertime i shift it bak fires anyone know what the could be it back fires really bad and it sounds like crap if you can let me know what i can do about that as soon as possible that would b cool

RX7Rox

I'm assuming it didn't backfire before??
If it didn't, I'm guessing you created a exhaust leak installing the muffler.

Joejoe3769

it did back fire before. and there shouldnt be an exhaust leak we got it professionally installed. when it gets over 3000 rpms and i shift it back fires it dose it more now that me pipes are wide open. some one told me that it might be my carberator and that i should think about rebuilding it.

Rogue_Wulff

A carbed rotary with no cats, and a free-flowing exhaust will almost always have a "pop" when you let off the throttle. It's just unburned fuel in the exhaust. The stock cats would burn it off, without causing the poping exhaust.
My 83 does it anytime I shift at higher than 3500.............

twigg

every shift i do or when i let off the throttle it burns off all the extra fuel and pops many many times, if u watch it at night u get a nice fireworks show.

Kentetsu

It might be worth the effort to check your timing if you haven't recently.

boyee

iTrader: (3)

same here.. i believe that my cats are shot which is causing my exhaust to pop many many times.. not so sure about the nighttime fire show though.. one time i reved my 12a to just a little before redline and it made a super loud pop! i wonder if flames shot out..

carlweitzel

My 85 12a with strait pipes did the same thing: it would pop numerous times when you let off the trottle after revving it up. also it would backfire really loud sometimes when I really revved it up. I rebuilt the carb, and it fixed the big backfires, and it hardly ever does the little ones.

carlweitzel

My problem was exactly like that

boyee

iTrader: (3)

so i should tune/rebuild my carb? would it be my cats because i smell gas all the time when the car is running? would it also be good to replace my cats/muffler since the backfires burn up the packaging inside the cats and muffler?

OtakuRX

iTrader: (1)

If you weren't in cali I would say to just ditch the cats, but you can't (unless your sneaky about it) but ya a good carb tune should do it, mine did the same and I patched the exhaust up and got a new carb and that fixed it, and made it faster.

LokiRx7.1

iTrader: (1)

If your timing your engine and you have any performance mods even timing it to spec will have backfiring you will need to time the engine by ear, my timing is about 4 degrees out of spec and I have no backfiring at all. The backfire happens because if you are no longer stock your intake exhaust characteristics will change. The reason it is dumping that fuel into the exhaust guys is your spark is happening to late you are not making your full potential HP/Mileage. adjusting your timing can advance/retard when spark occurs and can burn the fuel entirely. If you dont believe me I am uploading a video on streetfire.net and in the video I shift between 4-5 the entire time. stock timing is for stock parts unfortunately there is no book that will tell you how many degrees according to how many mods, you will have to adjust it, listen to your idle, and when you think you've got it drive it. If it still pops then adjust again, well that my 2 cents later