I have a 90 na, it doesn't have the cats, and when i'm driving it, and release the gas pedal, i hear a loud pop in the exhaust, i think it is backfiring, also i think it is running rich. anyone knows why this happends??? Thanks for any help that you may give me!!

 

You answered your own question. It backfires because you have no cats and you might also have a hole(or holes) in your exhaust.

The running rich thing...what makes you think that? Smell gas? If so you might want to check/change the pulsation damper.

 

If you have no cats and it's always backfiring, is there a way to make it not backfire, or do you just have to live with it?

 

Its really the stock port design that leads to backfiring ( So yes...youre pretty much gonna have to live with it ).

Sure you could lean it out some and possibly make the backfiring less....But leaning out a rotary is something I wouldnt exactly be willing to do

 

How old is your exhaust? If you have any leaks it will make it alot worse.

 

Using a downpipe to replace the 1st catalytic converter and using a performance cat in place of the OEM 2nd catalytic converter will cure most of this.

Mine only burns off the ritch fumes in the exhaust & pops when reving past 6000 rpms with this setup.

Plug it passes emissions with flying colors, has a good exhaust note, good exhaust sell, and impresses friends with high revving.

 

the car has a bonez race pipe and a N1 Dual Apexi, and both of them are a couple of months old.

 

Running w/o a cat will always smell like gas. Put a cat on

 

I guess, not really gas but I different smell to me. Just making sure he has no gas leaks. I thought my car was just running rich for a while until I noticed some gas leaking on the concrete one time.

 

My friends probe runs w/o a cat, all you can smell is gas and its not running rich at all. My car.. well lets leave it out of this, it has a blown motor so it doesnt count

 

I basically have the same setup execpt I bought the RP cat-back because it was pretty cheap. Mine only back fires if I get on the acclerator and rev it pass 5500rpm then just let go of the acclerator, it won't back fire as bad if you control the rpm by letting go of the gas slowly.

 

Running full duals all the way will also reduce backfires.
I only get a small pop, only after backing down from really high revs.
I'm not sure why - maybe the extra surface area of pipe cools the exhaust more?

 

Thanks for all the help guys, but i have another question, the car still has the smog pump in there, but the cats are gone, and i know that the pump is good for nothing if the cats are gone, but is it going to do any harm to the engine if i keep it there??? since i know that i would have to get another pulley, and some plates to block the hole where the pump is. or anyone knows where i can get that pulley and the plates??

Thanks again guys!

 

sure shot, maybe its becuase each pipe only has 1/2 the mount of fuel in it because only 1 rotor is spitting fuel into rather than both.

 

sureshot, maybe its becuase each pipe only has 1/2 the mount of fuel in it because only 1 rotor is spitting fuel into rather than both.