backfire on rapid decel
 

Sometimes when I idle down quickly on my 91 N/A I get a few minor backfires. I have a HKS intake and exhaust and an aluminum flywheel so cycle down times are pretty quick. Is it and EGR prblem or do I finally need an AFC? If the electodes on my spark plugs are any indication I'm running a little rich.

I always thought that this was part of the dashpot/ACV's job list?

I could have sworn that there is an after burn valve in the ACV that connects with the plenum (S4/NA) in wich it injects air on deceleration or something...
Wasn't there a valve in the ACV that gets gummed up over time and doesn't open properly, resulting in this problem?
meh.. im not sure, sorry.

should be dashpot/ACV

I alwayts backfired and shot fire on decel. My dsahpot wasnt even touching though

i always thought that the tps needed an adjustment when that was happening

probably all three im sure.

Most people love the 'rotary popping' as they call it...when I was on the dyno and he let off the gas and it started back firing they all started clapping and screaming...I felt so good at that point lol...even though it only put down 111hp they still were screaming and hooting.

I love backpops. Their fun if you can control them and scare other drivers hehe.

good pops
 

As long as its not indicative of a problem the I'm cool with them. I've notice they can be sustained indefinitely into a satisfying rumble at certain rpms.

I like it when it does that (but that's just me).

one more thing
 

I forgot to mention that there is a slight exhaust leak. The nuts that hold the cat to the header were frozen so when I tried to unbolt the cat to drop the drive shaft for my flywheel/clutch install I backed the studs out. Now I can't tighten them enough to seal it up. I have new studs but haven't gotten them on yet. The extra back pressure that creates should help to moderate the decel a little.

That is probably causing a lot of your problems... an unsealed exhaust will create a situation more along the lines of backfiring, as opposed to what most RX-7's do - have popping and shoot flames out of the tailpipe.

HELP Backfire on S4 TII
 

I have a 1988 Turbo II, with an HKS F-con, full 2.5" exhaust, with a 2.5" Resinator(sp), intake, and Greddy blow off valve, it's also backfiring under rapid decel. is this because of a lack of backpressure, or is this a serious problem, it didn't do it too bad when the TPS was fried, but now I've installed a new TPS, just hadn't had time to adjust it, so it idles kinda high, steady, but high... the car runs smooth, just have to watch for boost creep, (hadn't had time to port out my wastegate). all I know is it's loud crap when it shoots the flame, but doesn't really pop before that at all. someone help me understand why

What's happening is that when you close the throttle suddenly at high rpm there's a sudden cutoff of air into the motor, and the fuel that's being injected isn't combusted, it then proceeds out the exhaust system and when it hits the air once it exits the pipe it combusts, causing flames and a loud bang. With cats the fuel gets combusted there, where the airpump is pumping air into the cats, this eliminates the backfiring. It is my understanding that it's more or less a given that a rotory with no cats will backfire, at least a little bit. My car does this with a full RB exhaust (no airpump connection), and a cone filter intake. I've been told that it's made 5 ft flames. It runs very rich at high rpms due to the stock computers calibration. A piggyback fuel computer can lean it out and I understand that this will help minimize backfiring.

fox... normal for your setup listed above... not to worry my friend.

Josh

Backfires as far as I know will happen in any FC. My stock 91NA backfired (after high revving gear changes/decel. :) Totally normal!