Well i have a 86 gxl thats going to get its cat gutted out on friday, i have a few questions. I have an rb header and rb mufflers, thats my exhaust set-up. So far it is very loud. I know by gutting or hollowing out you cat will give you more power, but at what price? By gutting out my cat with my loud exhaust set-up is it going to be so loud that cops are going to be pulling me over left to right? Has anybody done this to their fc's yet? What do you think about it? Is it loud and nasty sounding on your car? Im still stumped because i had a sunfire with its cat gutted and it sounded like crap! My freinds fc has the dual apexi exhaust with a straight pipe and its more quiet than my exhaust set up! So any comments about this before i go ahead and gut it out on friday?

o btw, i also wanted to do this because i heard you can shoot big flames out!!

 

There is next to no power gain in the cat, unless it's clogged.

And yes your car will become louder. The stock setup used the manifold/cats combination as a large percentage of the muffling.

 

it will be loud. yes, i have been pulled over before. although i had a 3" pipe from teh stock mani to a 2.5 Y to glasspacks. sounds powerful tho. That exhaust setup made a huge power difference vs stock.

DONT FORGET THE AUX PORTS!!!! they probably wont work with a gutted cat, so you better have some other way to actuate them.

pat

 

Don't forget that a new cat is a couple thousand bucks, and aftermarket cats DO NOT LAST, so if you sell your car to someone in an emissions area you're pretty much ensuring that there will be one less RX-7 on the road.

 

what are aux ports? Well since guuting the cat is going to make it loud, but better performance should i just go straight pipe? O btw does the straight pipe make more flames?

 

straight pipe is better than gutted cat. full custom exhaust is better than that. i always just do the full custom thing. eds up being 200-300 bucks, and fits perfectly, and about the most power you cna get.

AUX PORTS are important. if you disable them, you will lose twice as much power as you gain from the freer exhaust. read the 2nd gen FAQ for an explanation.

pat

 

i read the faq for 2nd gen. Said nothing about "AUX" ports. Can somebody plz tell me what these are?

 

aux ports, aka 5th and 6th ports, are the secondary set of intake ports on second gen NA rx7s. they open at ~3800 RPM, and allow for a lot more flow and different timing. basically the rotary version of Vtec. all aux ports are operated stock by pneumatic actuators which pen when they get 2-3 psi of pressure. on s4, this comes from exhaust backpressure before the main cat, on s5 it comes from the airpump. without the aux ports opening, you can expect about a 50% decrease in performance above 4k rpms.

there are several ways to male the aux ports work in a non-stock configuration, most involve a RPM switch that uses one method or another to open them at the right time.

you should be able to search and find info on all these things. in fact, i just posted some in another thread, if you search my name and look for stuff about 5/6 ports, you'll find it.
if not, post up and i'll explain.

if you decide you need an RPM switch, PM me, i have one i want to get rid of.

pat

 

how much do you want for it?

 

35 bucks shipped. sells for 45 + shipping at summit. and i think that is on sale too.

i think i still have the instructions and everything, wires have never even been cut or stripped.

adjustable from 1500? to 9800 rpm by internal switches. by 100 RPM increments.

pat

 

im going to check my bank account and see if i can spare some dough, btw what does this rpm thing do anywayz? lol

 

haha...figure out what it does before you decide to buy it.

http://www.fc3s.org/how_tos/electrical/6_ports.html

 

so its like a v-tech controller if you have 5 or 6 ports?

 

sorta.

the RPM switch is just a switch. you set it to a RPM and it turns on when you get there.
after that you have to figure out some way to actually open the ports...usually either a airpump hooked up to the actuators or a solenoid hooked directly to the rods.

pat

 

did you do this to yours? Im steel new to rotary's when if comes down to the little tricks and stuff like opening ports ect.

 

i never did do it. i was going to, but ended up selling it and buying a turbo II.

thats what this forum is good for is finding out all the little tricks. i was new to rotaries once too.

pat