Exhaust POP! topic
 

Is this common on early first gens? I used the search but I can't find many people talking about it besides a few people joking about the bang. Is it failing emissions or something like bad carb tuning, or do they just all do this?

Let me know if any of you have experiences with this.

better description of symptom please

are we talking about the popping noise they make at fast idle and no load, that every rotary does because of the way the engine is

or the pop it makes when you get off the gas @ high rpm full throttle, that would point to an exhaust leak somewhere

or something else?

My 84 SE used to pop/backfire LOUDLY when I was coasting/let off the gas. I could get flames out the tailpipe!! It was the TPS (Throttle Position sensor). I adjusted it properly and the backfire went away. There are threads on how to adjust the TPS (quite simple).

Steve
84 GSL-SE

It can be caused by many Things. As stated above it can be due to an exhaust leak, Its commonly caused by running too rich, Also the addition of a better exhaust and carb/intake manifold can help induce poping. Its mostly beacuse rotarys dont burn all the fuel that gets sent into the combustion chamber so it ends up in the exhaust were it collects until it "pops" this is why u get the flames, and also why it tends to do it more at decel after being at wot.

I'm talking about the post-WOT pop. I have it pretty bad, and I can't find any exhaust leaks. (1980) I think I need to mess with my carb some more :-/

My 80 does it when its COLD and/ or running the choke, but shouldn't do it once warmed up...
Presume yours is stock? If not we'll need to know mods.
Stu Aull
80GS
Alaska

The popping on 79-80 RX-7s when cold is the thermo reactor getting ready to "light off". Choke + warming reactor + closing throttle + reactor not up to self sustaining burning conditions = explosion in heat exchanger or exhaust system. Probably the reason why most TR systems eventually fail.

RXDad

Yeah, mine does it a lot less when really warmed up but it still does it. My TR is bad?

Mine does a small pop when i decelerate but then again i am running rich right now

This has been a sure-fire sign for me over the years that my AAB valve inside the air control valve has given up, if it continues after warmup. Has happened twice in 20 years, both times, same cause.

Good ACV's for 80's are sort of hard to come by now. Least I found them so.

Could you explain the operation of the ACV, or send me a link to where I can read more on it? I'll do some digging myself as well.

Not finding a whole lot. Does it just make sure there is enough air for a clean burn when there is liftoff?

Also - would removing emissions/stripping down the carb help? What about removing the TR and putting on a header?

Thanks for the information so far guys, we're getting there :D

if you don't need smog, i'd suggest getting a header and some other parts :)

Awesome. I'm guessing I'm going to have to remove and plug some emissions stuff? If I do this I want to make this as clean an operation as possible!

j9fd3s mentioned a popping at high idle that is supposedly common to all rotarys. Mine does this between 2000 and 3000 rpm, warm or cold, all the time, especially when driving, but also just sitting in the driveway. It acts more like a misfire or something like that. Could it be rich, timing, or something else? It also pops when I shut it off and start to get out it lets out a little pop.

Mine was bad. I replaced the exhaust system with a Racing Beat System and the backfire completely went away. Runs/sounds a lot better too.

Inefficiancy of the rotary combined with no emissions crap = lots of decel popping. AKA unburnt fuel igniting in the exhaust system.

Oh always wondered what that was.

Can a missing gasket between the cat and the connecting pipe be the cause of an exhaust leak?

this is a good thing!
it means your getting plenty of fuel and the exhaust system is free flowing more power and better for the engine.