so.....Ive been driving my 8 for a few days now, LOVE it. I have about 250 miled on the odo.
I am a little concerned with the exhaust note. When I start the car when cold, there is a small flutter and pop from the exhaust. Also, if you just tap the throttle on a warmed engine, enough to tic the needle up a few hunded RPM, you can hear another "flutter pop" as the needle settles. The car sounds sweet going throught the gears.
This may all be normal....I am one of those people that listens for the least little thing, BUT a Nissan Mechanic heard it an said it was alittle odd, the 350Z doesnt do that, however he was fairly unfamiliar with rotaries and said it could be normal.
When reving the engine in neutral-it pops a couple times when you let of the gas also.......
Anyone with a new 8 heard any of these things?

 

Welcome to the rotary club my friend. When my RX-7 is cold, I can shoot flames a foot long. I nearly took my dad's leg off when we were looking to buy the car last year. When any IC motor is cold, it requires a richer mixture to run. Because rotaries burn more gas than their piston counterparts, when a rotary runs rich, it REALLY runs rich. The pops you hear is unburned gas igniting in the exhaust piping. It's nothing to worry about.

You may also find that if you ever take your 8 out on the AutoX course, that when you've been hard on the throttle for a while and let up, you may get some backfiring. My 7 sounds like a rifle sometimes, when the temperature outside is just right.

KA-POW! :D

 

Definately sounds like backfiring as SA22C said. Nothing huge to worry about.


I can't wait to get my midpipe to start flinging the flames.

 

OMG I can't wait for my RX8!

 

Doesn't backfiring destroy the catalytic converter???

 

um, the cats?? it doesn't really happen if you have cats 'cause the cats are what burns up that excess gas before it gets to the hot tail pipe and the air outside... if you have a straightpipe and muffler, there is no cat to destroy, but yes, it'll blow out a LOT of mufflers rather easily :D

 

If it shouldn't be noticable w/a cat, then why is Gyro's 8 doing it as reported? Would little pops be enough to cause worry about the exhaust system as a whole?

 

It can happen with a cat too. The exhaust setup makes a difference in how the backfire reacts too.

Notice that Gyro is commenting on some rather small noises, not the normal "bang" that is associated with backfires.

---jps

 

I hear the same thing when I start my car cold. In the morning, it will flutter and pop a bit...the RPM's rise for a second....drop a little......then jump up for a few seconds and then drop to idle after about 30 seconds or less. All is well after that.

I also have noticed that when idling warm, such as at a stoplight, the exhaust flutters and pops very slightly though no change in RPM is noticed.

I guess it's like they said..."Welcome to the rotary club."

Thanks, it's great to be here!!!!!!

1500 miles and counting.................

 

[QUOTE]Originally posted by rotary_it_up
[B]

I hear the same thing when I start my car cold. In the morning, it will flutter and pop a bit...the RPM's rise for a second....drop a little......then jump up for a few seconds and then drop to idle after about 30 seconds or less. All is well after that.

I also have noticed that when idling warm, such as at a stoplight, the exhaust flutters and pops very slightly though no change in RPM is noticed.

I guess it's like they said..."Welcome to the rotary club."

Thanks, it's great to be here!!!!!!

1500 miles and counting.................

I have noticed all of the same things.....the rev up....then down...then up again when cold. Must be in the design.

 

Rotaries have a tendency to "burble" a bit - a lot of it is due to the shape of the combustion chamber, and a little incomplete combustion. As the engine breaks in more, some of that will likely go away, but not all.

It's definitely nothing to worry about - RX-7's have done it for years with no detrimental effects to the exhuast or cats.

I still wish Mazda would open up the exhaust note a bit more - I've driven VERY low mileage stock RX-7's (2nd gen and 3rd gen) and they're VERY quiet, as I imagine the RX-8 to be from sound clips and videos I've seen. The rotary really has a beautiful, unique exhaust note, especially with a turbo on it . I'm interested to hear how the side exhaust port engine sounds when it's cracked open!

Also, if you don't know, rotaries are historically DEAFENINGLY loud when you open up the exhaust. Mazda went through a lot of work to get them as quiet as they are. With no exhaust valves in the way of the exhaust ports, there's little to muffle the sound. Turbos do help a little, but a rotary needs such a free-flowing turbo for its size that it still doesn't dampen it much.

This is not to scare someone from modding their exhaust - this is moreso on extreme cases with FULL open pipes with minimal muffling. The cats muffle a LOT of the sound - a well-made cat back will have a nice tone without being overly loud. Once the cats go bye-bye, that's where the noise starts to come on.

Dale

 

i think i had a video of a bridge ported fd rx7.......... DAMN that thing was loud, and sounded wierd as hell........ the sound steped up in pitch like it was someone going thru keys on a piano

definately need to get a free flow intake on that engine, then you can hear your sweet song

 

My 1974 RX-4 would backfire so loud at times that it actually sounded like a 12 guage shotgun going off.

That is 100% true. CATs absolutely muffle a lot of any engine's noise. I had a 94 T-bird that I put straight pipe on from the cat back. It was just a bit louder, but passed State inspections all the time. The result of reving it was a whine sound like a Ferrari. It was a nice car, but no RX-8.

I would not however recommend putting straight pipe from the cat back on a rotary and expect to pass State inspection. Just toooooo loud.