noshibby

Okay so yesterday I got my first rotary car. a 1988 13b n/a rx7



my one problem im having it that when im at say 4k or above rpm it will make on loud pop when im shifting or letting off the accelerator fast. any idea what this would be. the exhaust does not appear stock and thats the only mod done to it if its not.

phinsup

Does it have cats in it?

noshibby

it appears as if its a resonator and not a cat.

defprun

They tend to do that if they are running rich, I'm pretty sure mine is and at pretty much any RPM if I let off it'll pop.

phinsup

If you are running rich without cats you'll definitely get some backfire, or technically "afterfire", if you are hearing a 'pop" when you let off the gas and shift and you don't have cats, that's normal, limited back pressure will do that with the rotary.

katkaroto

anywho, you wouldnt be the first guy who thought something was wrong. i have a 1988 rx7 GTU, i thought it was odd saying some weird test pipe later found as a resonator too. :P and yea, the whole thing was like custom fittings and flex pipe with no tip on but in the car. so i put the tip on to avoid trouble.



everytime i drove the car it was like pop pop pop on 5 gear cruise, and bang, after revving the thing up. but i learned how to avoid its popping and bangs, i would let off the gas all the way and then clutch, shift, and then balance clutch and gas. i shift in and out smoothly without having to worry about attracting the wrong crowd. also, i heard the FC's are running rich aka too much fuel.

noshibby

is there an easy and cheap way to fix my problem that is not put back in a cat.

katkaroto

anything cheaper than not getting a cat is going to still resolve in back firing. like we all said, the FC runs rich. rich means a lot of fuel, lean means not enough, stoich means good. if you want it to stop back firing, get a SAFC to lean the fuel injection down. just dont do it too much... too lean damages the car.