5th and 6th ports and exhuasts systems
 

now on my 86 na fc i have one precat right after my o2 sensor and far i can tell its a straight pipe from there to my mufflers. i want to do my exhuast system further but and left with the discovery of back pressure in the 86-87 engines opening the 5th and 6th ports. i have no air pump hooked but and was wondering what i can do to my exhuast to keep some back pressure. would it be possible to use the one precat i do have on my system and just change the back stock mufflers to free flow mufflers with silencers? i need some advice id like to keep my ports opening just fiine.

Racing beat sells an exhaust system that will work.

Otherwise you can convert your aux ports to an electronic system and then do whatever you want with the exhaust.

I have the stock manifold with a 2.5" pre-cat elim. pipe, to a high-flow cat with the backpressure tube (from a rotary shop near me) to a 2.5" y-pipe that splits to two 2" pipes, to the stock mufflers. I don't have the money to afford the mufflers I want yet so I'm still using the stock mufflers.
With this set-up my aux. ports still work, opening at the same RPM as stock.

great replys but id have no idea how to wire the ports electronically and i have just the first pre cat with free flow mufflers. is the one precat enough to keep the ports in an operational fashion?

Precats are located before the split air pipe, which should have no effect on the pressure further downstream. Your ports are probably not opening right now, but only you can check. A simple test is to smear a little grease on the actuator shafts, then go for a test drive. Rev it up past 3800 RPM under load, then come back and see if the grease moved.

hmm i do see that split air pipe does go to where my main cat once was.(i dont yet have the jdm mufflers on installed) and where are these actuator shafts and how would i go about greasing them up.

The actuators are right above the exhaust manifold.. the shafts stick out of the top of the actuators..I think you also have to remove the grease afterwards, otherwise it'll collect dirt.

Read the emissions section of the FSM if you still cant find them

thank you i will have a look later. i just was hoping i would have enough back pressure but if its past the precat should i just eliminate it then? and maybe get more pressured mufflers? neways ill respond to whether or not they open with no cat and stock mufflers(whitch i drilled twenty two 1/4 inch holes in the back of each one for more flow) would u recomend just eliminating the precat buy a high flow cat and go free flow from there?

like I said mine open fine with a high flow cat, so that should work for you

You can hollow out or replace the precat with an open pipe. Another option if you don't want to keep emissions is a presilencer from Racing Beat. It will have a small pick up tube to connect to the split air pipe, and it apparently still allows enough pressure to build inside the tube to activate the actuators. Just keep in mind the presilencer is longer than the main cat was, so it's intended to be used with their NA downpipe. The two will replace the 2 precats and main cat, or whatever you have in those locations right now.

i have mine opening up electrically and use pace setter headers and generic mufflers with cut cats. it sounds good (not high pitched, not twangy) its loud but it works great.

all great replys thank you is there a specific place to find these RB exhuast pieces or does anyone no of a place to get a good deal?

yea but they want like 700 dollars for there set up im looking for junk yard scrounge specially since my gf just wrecked our windstar into a deer less than an hour ago and totalled it.

can isimply run the split air pipe back before the precat to help build pressure?

If you're going to make a custom connection for the aux. port actuators, keep it separate from the split air pipe. Make it small diameter (~ 1/4" would be good) and have it dedicated to the actuators. Block off the original connection from the split air pipe so exhaust doesn't leak. Some headers have a little pick up tube coming off of them just for the port actuators.