TinyFC87

im replacing the stock exhaust on my 87 fc N/A. i need to know the best way to keep the 5-6 ports running after i remove cat and put mufflers on it. ive heard that they stop working. some info would me out a lot want to get it done in the next week or two. our local rotary expert said it whould be fine with midpipe and mufflers.

some info from experience would help. just want second opinion

BlaCkPlaGUE

Get yourself a pre-silencer from racing beat. It doesn't restrict flow and it helps with the noise. Make sure you get the n/a version as it has a aux-port-activator tube that goes into the engine bay. You can then do the air pump mod (minus the air port and using the pre-silencer of course) on this tube.

happy trails.

flamin-roids

If you go with racing beat exhaust the header itself has a pipe coming off it for backpressure. The 5th and 6th are actuated by back pressure via a small pipe coming from the cats. Some replacement cats will have this pipe. But its necessary for your ports to work.

TinyFC87

i dont think im going to get a new header just from the bottom of the header back.
i know were that little pipe is but what do i have to do or hook up to it for the ports work after i put in midpipe?? this air pump mod expalin it for me please.

flamin-roids

Yeah what air pump mod? I'm sorry. I have a S5 so no air pump mods for me. You'll have to figure something out.

Icemark

You don't have an air pump???

If you do, use the dump line from the ACV

flamin-roids

I do. I just can't remove it or else my ports won't open. Unless theres a method of removing it and getting the ports to open.

Icemark

Not with a free flowing exhaust.

flamin-roids

So it was my understanding that S5 ports are actuated by the air pump. I have straight 2.5" exhaust and my ports open perfectly. And I've been told the ECu has something to do with it.

Icemark

Yep, that is exactly right for a S5.

For the S4 as TinyFC87 has, he would want to just run a line over from the dump port on the ACV.

7th Heaven

yeah:

S4 - 5/6 ports activated by exhaust backpressure
S5 - 5/6 ports activated by air pump

Bob_The_Normal

I'm tired and in "stupid-ricer" thinking mode but I'm wondering if it'd be possible to have the 5/6 ports open by switch?

I mean, just for the fun of being able to turn them on whenever you feel like it... that'd be pretty cool.

I should go out and take a look at how they are activated normally and see how a switching system could be put into it... I'm guessing it wouldn't be easy and would include small electric motors...

Any info on something like that?

--Gary

MichaelFregoe

iTrader: (1)

DO A SEARCH........ THIS IS PROBABLY ONE OF THE MOST FREQUENTLY ASKED QUESTIONS OUT THERE. THIS ISN'T ROCKET SCIENCE!


http://www.geocities.com/MotorCity/G...RSCHEMATIC.JPG


http://www.geocities.com/MotorCity/G...1308/rx-7.html

MichaelFregoe

iTrader: (1)

http://www.geocities.com/MotorCity/G.../6PortFix1.jpg

http://www.geocities.com/MotorCity/G.../6PortFix2.jpg

MichaelFregoe

iTrader: (1)

I had to make the necessary pieces and assemble them.

I used a stainless steel 1/2 inch bolt (4 inches long total that had 2 inches of thread) and cut the head off 1.25 inches above the threads. I then drilled into the side of the bolt with a 1/8 inch drill bit HALFWAY THROUGH the bolt. I then drilled longways into the bolt from the thread end until the two holes met. REMEMBER because of the extreme heat of the rotary use only stainless steel! I then selected a nice spot on the pre-cat and drilled a 1/2 inch hole 2 inches back from the front flange. I screwed a nut on the piece and inserted it into the hole and had the NUT only welded in place on the pre-cat. I positioned the inlet hole around 1/3 of the way into the inside of the exhaust pipe. Position the hole so that exhaust gasses coming out of the engine go into the hole you drilled into the bolt. Get a 1/2 inch to 3/8 coupler nut and drill the 3/8 end to 11/32 and tapped the hole to accept 1/4 inch pipe threads. I then installed some new metal brake line into a 90 degree fitting I bought at NAPA. I cut the brake line 6 inches long and attached the line that goes to the actuators.

The reason for the brake line is that the exhaust gets so hot that the rubber line will MELT without some kind of stand off from the exhaust piping. Mine just happened to open about 3600 RPM under load. The mazda spec is 3600-3800.

(Michael has three pictures of his contraption)

oztofrdm

https://www.rx7club.com/2nd-gen-archive-72/how-air-pump-auxilary-port-activation-330310/

i will take a pic. tonight to show you what i have made so you can take all you acv and emissions

oztofrdm

this is what i made to make the aux ports open, the big hose connects directly to the air pump

oztofrdm

the other pic is way to big to post but like i said it connects directly to the air pump. i havent worked out the kinks yet i just took off the air dump screw off to allow more air to dump into the open because the hole ways to small and opening the ports at 2500rpm. my bay is completly taken apart so when i put it back together i will let you know if my task was successful.
hope this helps you out