Popping
 

Can someone kindly explain to me what causes and how the popping sounds are created when an aftermarket exaust is installed on rotary engine cars?

Thanks

When the engine is running heat is generated. When the hot exhaust gases passes through the exhaust the pipes hold the heat. When metal gets hot it expands and when it cools contracts. So what you hear is the exhaust pipes contracting while that cool. You stock exhaust probly did this too, alond with every car that is made.

But it sounds like a combustion or explosion if you will...

doesnt sound like a metal pipe contracting?

personally I think its back fire ... from the car running too rich .. I had a motorcycle like that , it was a thumper single cylinder 2002 suzuki savage. .. miss that bike like crazy ... anyways ... backfired like crazy ... ran too rich .... I think its the same for the rx-8 , way too rich from the factory ? but I am told backfire occurs when its too lean also ? I an't a engineer nor a mechanic, but I am guessing its backfire from unburnt gas ?

hey tit grey... ive just noticed you have a lightning yellow why is your handle titanium grey ?

It happens. Not just rotaries, pistons do it, and old carburated cars do it best.

Downshifting an mgb I had with abarth pipes into a corner would sound almost like a machinegun fusilade.

The miata I have does it too, just lower and much less frequent, say, one or two pops every 3 gears down or so. :D

I like it! Brrrrmm*POP* :D

That or it could be, as I hear when it starts up, residual gasses and fuel popping off

UHHHHH.....
Beavis, I think we have a problem.

My FD backfires all the time, but that is because it is tuned to run rich. My 8 never does, but perhaps yours is running richer than most of ours for some reason. I think Haze had an issue with his car backfiring at one point. I don't know if it still does or not. The backfiring doesn't seem to be a common issue for the 8, but as people start to mod and it is more important to run rich, I bet it will become an issue.

I'd think it does it with the stock exhaust too, just that the pulse is broken up enough by the muffler that it's not as noticeable. But if you sit at idle and quickly rev to 3500 or so and let it fall right away, you'll hear a kind of "boom" or "thud" out the exhaust as the revs fall, I'm assuming that's a backfire after going through the muffler.

I never noticed it at all with the stock muffler. The second I ran the car with the Borla, the sound was apparent. Same car, same settings.

I can hear it with my stock exhaust but it was very faint. After I got my HKS, the sound is more noticeable, especially if I leave it in neutral and step on it,

How do you like your HKS?!

Tone? noise level? droning?

the HKS is a very quiet exhaust until WOT. Riding on the freeway, you can hear it a tiny bit but the radio will drown it out. So far I am very satisfied with it. I will post up a video when I have time.

I also never heard it with the stock exhaust. Installed the Borla and I hear it all the time.
Installed CZ stage 1 (which leans out the fuel mixture) and I still hear it.
I have the M flash also.

it would be awesome if you could post up a video from the startup...to low speed crusing..... then WOT

Please please please :D

Haha, I'll see what I can do

My friends black rx8 pops when he revs and as the revs come down...2 or 3 pops follow....kind of annoying.

So im still unclear about this...

can someone just say it in one sentence...?

WHAT causes it?

Thanks

sorry about the late response , I got 2 rx-8's :) , 1 titanium thats basically stock base model and 1 lightning yellow fully loaded and basically gonna be a show car. Probably gonna make the titanium into a track beast once I blow the motor ... I mean if I blow the motor :cool: and convert to 3 rotars , lol , anyways , I see you have a lightning yellow too , great choice, we gonna be the few lightning yellows out there since they are discontinuing our color ! yay *retarded voice lol :D

My guess , running too rich , or too lean and its backfire. probably 100% right because ... slap a borla on there and what do you see? flames .... yep its definitely back fire ... now moving on ...

The real question is , is it running too lean or too rich ? Maybe canzoomer or one of the ecu master's that worked the greddy e-manage can answer that question ... they shoulda tuned it out and maybe theres no more backfire after the piggy back ecu's ?

Dunno ... as I stated before I an't a engineer or a mechanic , just some 17 year old that loves speed :)


did a quick search on backfrire , err heres a sort of summary in a forum - http://forums.nasioc.com/forums/show.../t-556866.html

What causes it?

Unburnt gas making it out from the combustion chamber to the hot exhaust, which in turn ignites it.. That's all. Some things may make it more frequent: Advanced timing will pop on lift, retarded timing will pop just about when it feels like it.

Loud pipes make it louder, quiet pipes may mask it as a 'burble'.

Nothing to be worried about, it's actually the mark of a hi-strung engine. Carburated hi-compression motors with BIG valves, or multiple valves for the exhaust do it really really nicely.

Today is LeMans. Watch the tailpipes, particularly of the bigger P-type cars. You'll see fire when they lift. Tha's the same thing, except them boys run open exhaust, so not only you get the 'pop' (BANG! is more like it in those cars!) *plus* you get a light show at the tailpipes.

:D

missinmahseven you still got that mgb you talked about?

Thanks,
Jamie