AntonL

iTrader: (2)

I know GSL-SE's use back pressure for the 6 port and all but not too sure how all that works, do i really need the airpump? does it make a difference if i take it off? is there a way to run a straight pipe on a GSL-SE? theres just so many questions idk what to ask and what to say... also can i use custom made headers with the 6 port? i know RB has separate headers for GSL-SE's so just curious. any and all help is appreciated

thunkrd

iTrader: (1)

i use the GSL SE testpipe from RB. it works well, inexpensive, compared to full exhaust. pretty good hp gain, pretty good sound without adding anything else. It's louder than the full exhaust from RB, but not that loud. havn't taken the airpump off.

74RX4

iTrader: (10)

Welcome. Start here. Its the third sticky at the top of the page.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/1st-gen-rx-7-faq-page-237777/
If you can't find what you want there, try the "search this forum" on the right side of the grey bar just above those stickies. You can also do the same search in the 1st gen Archive forum.
Air pump is for emissions. Aux ports are activated by back pressure from the exhaust.

slow5oh

i removed mine from my car. ive got the aux port sleeves and actuators removed completely, air pump removed, ect. ect. I read alot about how these motors fall on their *** at low rpms after this mod, but i was pelasantly surprised. with all that removed, a racing beat road race header, and readjusting the idle the car runs fantastic. plenty of torque on the low end and it screams on the big end.

AntonL

iTrader: (2)

idk what for the fuel injected ones and whats not.... mines the fuel injected one. would it hurt me to take off the air pump? and if i took off the first two cats would that make the 6 port not work?

74RX4

iTrader: (10)

Been a while since I looked at a stock exhaust, but I believe the back pressure pipe for the aux actuators is connected to the first pre-cat. If you remove your air pump, air will no longer be sent to the main (3rd) cat. This will cause it to overheat and eventually stop working or maybe even clog.

If you don't have to pass a pollution test, I recommend removing the air pump and the Air Control valve. Get a block off plate for the ACV and replace your exhaust manifold and the three cats with a Racing Beat header and pre-silencer. You can drill and tap a hole into the header and attach a line to supply back pressure for the actuators.

AntonL

iTrader: (2)

i live in salem oregon and we have no kind of emissions control cuz all of our smog gets blown off to portland =P

there is nothing connected to the first cat, its just a plain old cat, theres a tube going to the third cat, the only one that isnt hollowed out or cut out. could i really just replace it with a pipe and cut a hole in it and attach the tupe to that pipe?

slow5oh

its not going to hurt your motor, but i cant remember if it will affect the actuation of the aux ports or not. as far as the cats go, the aux ports run off exhaust backpressure. theoretically if you have enuogh back pressure in the piping, you wouldnt need any cats or mufflers to make it work. I dont know how much is actually needed though so youll probably want to do a search. i know this topic has been covered, ive seen it in another thread somewhere on here.

AntonL

iTrader: (2)

ok so pretty much mine is an S4 right? as far as im understanding, so due to that i theoretically dont need the air pump and can get rid of all of that as long as can get a hole and some tube positioned to where i can get about 3 psi to open the 5th and 6th port i'll be just fine? i read through some other posts and thats the basic idea im getting from them. i just want to be sure before i start tearing into my 7.

slow5oh

if my understanding of the system is correct (which i think it is) then yes, that is the idea. fyi, the gsl-se's are s3's not s4's. the s4's started in 86, BUT the gsl-se's benefit a good bit from an s4 intake swap.

AntonL

iTrader: (2)

ok i see, and iv seen people swap in different intake manifolds but i have no idea where to find them, iv only seen ones for carbed 13b's. and then do i need the mass airflow sensor? or can i get rid of that and just put a cone filter? right now im having an adapter fab'd up so i can get rid of the airbox and just have a cone.

AntonL

iTrader: (2)

so is an S3 basically the same as S4 or no?

thunkrd

iTrader: (1)

the engine is more or less the same... the housings are slight different, the rotors are lighter, intake system is enhanced, 4 injectors instead of 2 really large injectors. etc... but its all very similar, just improved

slow5oh

the intake bolt pattern is the same, hence the reason the swap is so popular. s3 has 1 large injector per rotor. s4 has two that kick in sequentially (this is where the notorious mid rpm studder in second gens comes from). the s4 intake also flows alot more (30% or more IIRC). I THINK the s3 center housing has a tab sticking out under the exhaust outlet that the s4 does not. I bought a used header for my car which i think was from a second gen, and it would not bolt up without modification because it wouldnt clear the tab, but i cant be 100% sure that my housings are s3 housings either. just an FYI since your the owner of another GSL-SE. The vacuum control system can be a PITA if its not in good shape. when it works, it works GREAT, but when you have a problem, it can be hard to find because there are so many places for vacuum leaks, be prepared.

thunkrd

iTrader: (1)

lol vacuum leaks suck, just replace every hose with silicon ones... they look great, i'm thinking about them soon.

AntonL

iTrader: (2)

so iv doing more reading and i guess its just S5 rx7 that really need the airpump, S4 down dont necessarily, i have heard that the pully on my water pump can break though if i take it off, how true is that? has anyone had it happen?
and if i do run the straight pipe and the tube all hooked up right, what will be my noise level with a full cat delete and no muffler at the end? right now iv got 2 cats deleted and a home made canister at the end, no muffler. it sounds real nice right now.

Also how can i know if an intake manifold is an S4 or not? is there an easy to see difference? can someone post pix that show what to look for?

AntonL

iTrader: (2)

My current cat set up


my tailpipe, not sure if that really affects back pressure


The inside, just a hollow canister, has a great tone though

AntonL

iTrader: (2)

^^ and i didnt take any pix up there but the third cat is 100% original, i was gonna cut it off when we did the other ones but didnt have a pipe long enough at the time, the first one is hollow because we couldnt bend the pipe the way the first cat is bent and the welder sucked so we left it hollow.
im going to draw up the plan iv got to hopefully make it work and have back pressure, all around im hearing it needs from about 2-4 psi, thats not very much at all.

AntonL

iTrader: (2)

heres one of my designs for a cat delete idea that would in theory get back pressure, free up flow, and in this one hopefully muffle the sound a little to keep my noise levels legal.


this is another design i had, this one is more of straight pipe but as you can see my idea is to have a tube angled against airflow to hopefully pick up enough pressure to open up the ports. it has some airflow restriction but probably alot less than the cat.

AntonL

iTrader: (2)

so any and all feed back on those is greatly appreciated, and i know i spelled exhaust wrong...

slow5oh

personally, I think with that muffler you have, you will have enough back pressure to open the ports. I dont think a cat delete setup like your drawings would be needed, however, I very much like the idea of the first one if it turns out you DO need something to create more backpressure.

AntonL

iTrader: (2)

the second one was kind of a longshot, im liking the first one better too. im really curious on the sound it'll give me too. i want to put a header on too, most likely the RB one because i hear it beats the pacesetter one every which way so with all that changing the exhaust tone i hope it stays good