Hey everybody, I'm new to the forum. I have a 93 rx-7 with 54k miles. At WOT in third gear, the acceleration feels a bit hesitant; almost like it is choking. I figured it was time to get a downpipe because the pre-cat might be cloged. I'm worried about emissions though. I failed before and had to replace the O2 sensors. I'm still failed so I don't know if that worked. I thought I would just drive the 2 months rejected. If I replace the pre-cat with a straight pipe, will I still be able to pass emissions in MA? Which downpipe is the best? I need to replace the muffler too. Which cat-back is best? I don't want too much noise, but I want huge hp increases. Can I have both or are they connected? Will just the downpipe and the catback make my mixture too lean? Do I have to buy a Fuel controler to handle the rise in boost? I'm sorry I'm so ignorant. Can anybody help me?

 

installing a downpipe will only affect emissions when the car is not warmed up all the way. as long as you have a working main cat you can still pass emissions(NJ). my car has a bonez dp and stock cat with 90k and racing beat catback it passed emissions with flying colors about 1/4 of maximums. all the downpipes are about the same just try to get a stainless steel. if you want a quiet hiflowing catback get the racing beat www.racingbeat.com . if you want a loud one get an apexi N1 or apexi GT. if you have downpipe and catback it would be VERY wise to get either an ecu upgrade or apexi power fc. i think that answers all the questions

 

I know of stock 3rd gens that don't pass emissions. good luck though. I barely passed with just my DP and Catback.

 

moved to tech support

 

I have a 93 with 57000. It has a stainless down from Pettit and catback from turbo tuff (rather quiet). I was told not to worry about running lean because they put a holley jet in my orfice that keeps the boost around 11psi. They also gave me a variety of jets to vary the boost. Hopefully you have a boost gauge. It will tell you if your boost is creeping with the new mods. The secondary turbo should not fully spool all the way at full load if boost is over 11psi with stock ecu. (Another so-called safty tool or overboost prevention.) Don't worry about running lean unless you toy with a midpipe and/or larger intercooler. Then it is time for an ECU upgrade/fuel computer. Oh yea... Make sure you look for carbon build-up in the main cat when swapping exhaust. That is crucial for extending engine life.Good luck...G....

 

Is the signal from the O2 sensor indicating a lean or rich condition when the power goes away? Which exhaust emissions are out of range on your test? If we're talkin' about HC, a partally restricted exhaust could be the problem. Is the problem worse when the engine is hot or cold? A fuel delivery problem could be the cause, but I'm more inclined to think you're problem is more fundamental. A compression test and a good visual examination are in order. How's the secondary circut? Got wonder plugs in it? An ignition coil that's a little light in the *** will cause the hesitation you're describing too.