I'm a new owner of the fabled RX-7 and love it...The 1985 GSL-SE was sold to me buy a neighbour who needed some cash...it is a great machine but needs some engine work. Since I plan on building up another motor before this one goes i have soem questions. I have a question about the 13B 6 port configuration. I was told by a shop that its possible to take my engine apart find some 12A cast housings with the 4 ports on them, use my 13B rotor housing and get some 1990 rotors, e-shaft, front balancer etc...or even 93 but then id need a thrust bearing assembly...anyways I wanted to ask this for a couple reasons cause i dont doubt the shop i called they no there rex's but will this satisfy my porting needs cause the 6 ports arent as good street ported are they? Also with the 12A casts is it possible to hook up the 2 injector per rotor system from the 2nd gens or is it even worth the effort is the single system from the 85 GSL-SE fine...another thing I've read alot on this sight but im having trouble finding a thread to tell me major differences between bridge and street ports...and the difference both will make on my future 13B 4 port configuration...please need some help before i go about this task.

Thanks, new member

Curtis

 

ok i can help u out a little bit but not alot.. i think ur getting ur ports mixed up... the 4 and 6 port basicly means how many holes go into the engine from the intake manifold. i aint to sure why the 4 is better but everyone say so, so will i.
the street and bridge ports are inside the engine. on the side walls. the large u make the holes the more fule and air get in, a street port is slightly bigger and longer than a stock port and with be good for everyday driving with a bit more power and bridge port is biger and longer agian and will give u alot more power but make it not as good as an every day driver as it doesnt like to idle..

thats all i can hep u with. now over to the people that know

 

Welcome to the forum. If you need any help locally, which shops are reputable and such, or find people to come over and give you a hand, be sure to check out www.bcrx7.com

Don't you have to worry about Aircare in Vancouver still?

 

Yeah we have aircare here but I'm using parents insurance from small town until my insurance goes down...so if i insure it there then i dont have to worry about aircare...but anyways thanks for the bridge port and street port info...what your saying is that bridge porting is better than street porting more air and fuel will go into the combustion chambers....okay i dont really care about rough idel and such it doesnt bother me. But other wise i need to know if 4 port and 6 port intakes can be ported with the same gains in hp from what i read a 12A can gain waaaay more hp from the same type of port cause theres more metal to gut out.

Someone help me with these problems please, i need to know before i go ahead and start looking for parts.

 

Here's some links that might help you visualize the porting process.

http://www.mazdarotary.net/porting.htm

http://www.mazdatrix.com/faq/porting.htm

you can also see the diffrences between the 4 and 6 port motors.

I had another site the other day that showed how the rotor over laps each port, but i can seem to find it now.

 

Ok couple things.. yes the 4 port is better for porting.. a 6 port is not very portable.. Yes you can mix and match 12a & some 13B housings.

As for injectors, no the 12A does not have a place for injectors in the center housing. But you should be able to use your current center housing. .Only the outer irons have the 5th and 6th port.

I would suggest dumping the GSL-SE intake and ECU anyway. It sucks.


hope that gets you started.

 

what intake and ecu should i upgrade to...I'm not made of money but if it wont work then i need something that will...can you help

 

Well, for NA, the stock intake might be ok.. not nearly as good as an aftermarket one.. but it isn't worth the money when looking at the options.

As for ECU, you could go with whatever you are comfortable with. I would suggest if you dont know much about them, to go to a local tuner and see what they are familair with..


The reason i say it is not worth buying an intake, is cause you could pick up a TII block, and a haltech and almost drop it into your car..

You would just have to change the front cover and oil pan from your old engine over.


Hell that could be an option, get a jspec TII and have it rebuild with high compression rotors and ported. (it is a 4 port)

then just run it NA.. and sell off the turbo and intercooler and stuff.. or leave the rotors as the normal compression and go turbo


-Zach

 

Carburate it!

 

I didnt know that the turbo 2nd gens have 4 ports...i thought they had 6.....hrmmmm......so the turbo 4 port 2nd gens have the same ports as a 12A and the same porting capabilities? Then why wouldnt i just use 2nd gen cast housings instead of the 12A ones...would this confuse things with my setup...and if i use the gsl-se centre housing i still have the 4 ports?

 

watch for the coolant seals.on the 86 the coolant groove are on the side housing while the gsl-se are in the rotor housing.becareful with that.

 

Yes, the water seal grooves are on the GSL-SE rotor housings, while the later 13Bs had the water seal grooves on the side housings. Also, try to make sure you get the later 12A side housings as they are gas-nitrided, unlike the pre-RX7 12A side housings which wear faster. I'd go with a carb, myself. Either a Dellorto, Weber or Holley will work for you, though I prefer the Dellorto for it's choke. Going with a carb means that there are NO engine control electronics to mess with, other than the ignition system. That's a huge plus in my book. I'm not sure how the 12A turbo port size compares to a stock or street port, but I would assume that it's larger than a stock N/A 12A's ports.

 

hrmmm....looks like go carbs all the way in this thread...there kinda expensive though...but i guess id make up for it with fuel injectors and ecu managment systems etc.

 

I have a streetported 6-port GSL-SE and I like it. The car is much faster. Of course the 2nd gen intake manifold and a full exhaust help too. The ports in the early 4 port motors vs. the T-II 4 port motors are not the same. You can port out the early ones really huge on both the primary and secondary ports. Bigger isn't always better though. What good is a port that makes peak power up above 8000 rpm when your induction system only flows enough air for power up to 7000 rpm? On the T-II housings the secondary ports can go as large but the primaries can't. They can still get bigger than stock though. The port runners on the T-II housings are larger as well. What good is a larger port opening if the runners can't flow as much? A streetported T-II engine with '89-'91 high compression rotors would work great. You could even modify your stock intake manifold to work on this setup. The stock manifold will not bolt up to the early 4 port housings though. If you are so serious about this that you would go out and build an entirely different engine and replace the induction system then stay fuel injected. Use a Haltech or equivalent. Your stock ECU will still get you easily in the 14's though (trust me!) but it won't be optimally tuned. A carb is a technological step backwards. Its like trying to learn how to walk after you already know how to run. A carb can not compensate for barometric pressure changes, altitude, temperature, fuel economy vs sheer power (on its own). Carbs are however very simple and capable of good power. All of the REAL race cars out there use EFI. NASCAR's use carbs but they also don't know how to turn right Carb or EFI you'll get great results either way but the deck is strongly stacked in favor of a custom efi setup for many more reasons other than those I listed.

 

Thanks rotarygod....

 

i don't know about all that carb mumbo jumbo, I drove a 84 se with rb exhuast and then drove my car w/ dell carb and rb exhaust and it's like night and day difference.