ratboy

iTrader: (1)

I just recently installed a racing beat street exhaust on my 85 gsl-se (headers--> muffler) and it runs sooo much better now but I have one question. At 5000 + rpm if I let off the gas and let the engine slow down the car I get some popping and sometimes a pretty loud backfire sound. Is this normal?? I know my car idles a bit high (~1500 rpm) and I will be working through the nice FAQ to get that back to normal this weekend.

-Erik

Tom

^ I don't know about the SE's, but my 12A will do that if the idle runs that high and I shut her off. The popping is normal for me under deacceleration too, especially with gutted emmissions. No AAV and stuff like that.

I love giving her a good rev before I shut her down, especially at the food store- Scares the living **** out of people!

ratboy

iTrader: (1)

"I love giving her a good rev before I shut her down, especially at the food store- Scares the living **** out of people!"

Yea Im starting to see the usefullness of this feature!
thanks...

Kentetsu

I also have that same exhaust. I wouldn't be too worried about it, but if you really want to fix it I would recommend checking your timing. If that is not the problem, then check your mixture at the carb. The high idle could also be a symptom of either of those. Good luck.

MosesX605

Did you get the O2 sensor installed in the header or did you leave it out? If it's left out, the car could run too rich and cause afterburn (popping in the exhaust.) Of course you should check the idle as well, but be sure and get an O2 sensor installed, for no other reason than you will get better mileage. A header system on a decently tuned RX shouldn't produce any popping at all, or at least it hasn't in my case or on Manntis's car, which was meticulously maintained. In fact the popping that was present on my SA's stock system was eliminated by the header system. According to those in the know, the SA model RX-7's afterburned from the showroom.

Tom

Hmm.. I usually get a very light 'pop-pop' when I decel, and I know I'm not running too rich.. I always thought it was a normal phenom after removing the Anti Afterburn Valve and other emmissions equipment?

MosesX605

Mine never pops with the header installed, but my old '82 GS with a manifold back exhaust did pop all the freaking time, so maybe it's a quirk of the SA models.

cdrad51

My 85 will pop as well on deaccel, especially if its from high rpms and I let go of the pedal suddenly.

MosesX605

Maybe it's because I don't have a dashpot? I took it off because it made getting carburator off easier, and then never put it back on again.

cdrad51

Sterling carbs don't have dashpot either.

MosesX605

Well from the pissing match that you and Sterling regularly get into about your tuning of his carb, who the heck knows what you've done to it?
(j/k)

At any rate, I would still say that the dude should fix his idle so that it's at a proper RPM and look into getting an O2 hooked up, if he hasn't already.

ratboy

iTrader: (1)

I did install a new O2 sensor when I installed the exhaust but like I saw several in several posts the car is running a bit rich. Im going to address that this weekend and see if that helps. Im just glad to know im not going to blow my engine up or anything! I'll post after I do that and let everyone know if that helped. thanks everyone!

-Erik

Siraniko

iTrader: (13)

Carlos=

Rx-7Doctor

iTrader: (13)

I'm just curious, you have been a member since 2003 and you have 8 posts? Did they get removed or have you been in a coma,lol. Jk.
As far as the o'2 sensor goes. the computer only gets a signal when you are in 5th gear.
Popping under deacceleration is part of the emmision adjusts. Could be the tps is off adjustment. idle at 1500 means that when you shut it down the computer is not seeing it at rest. Which means it is still giving it fuel. You need to cure the idle problem first.
Whatever you do, do not mess with the adjustment of the afm or the mixture adjustment. I am pretty sure when you get it to come down to idle properly the
popping will go away. rx7doctor

eViLjAy

I have heard that a small exhaust leak can cause the backfire too. Ya know... unburnt fuel(a bit rich) plus air(leak) and heat=pop. might want to check that out.
I have a carbed 12a that backfires every time i shift above 4 grand. It may annoy people but its not going to hurt your engine.

DAVID GRIMES

It's common. Some of the guys on this forum find it desirable and would pay to have your problem.

rwatson5651

iTrader: (5)

I have a streetported 13b 4port with a RB exhausts and a mikuni siddraft and mine has a very nice rumble upon decel with occasional "pops".

Through tuning my carb I have found that it is very much affected by the richness, "Popping"being more prevelent at richer settings.

diabolical1

iTrader: (3)

as long as it's not an O2-sensor issue, i'd say check the joints of the exhaust system. mine gives a pop on serious engine braking (highway speeds) and even then, it's only on fairly rare occasions and my Dell is still pretty rich.

Rx-7Doctor

iTrader: (13)

check previous post on o'2. Forgot to ask him if he is running the stock FI ir carb.
If it is carbed. It will be a differnt story. If it is stock Fi, seec uring of idle. also did you use the block off plate for the acv and remove the air pump. The acv plate has a tendency to leak it not sealed correctly and will cause vacuum leak. rx7doctor