Hey gang,

I bought my fc4 about 3 months ago. It had some exhaust problems that I fixed (Bad Cat). When fixing the bad cat I noticed that the exhaust manifold connected directly to the motor, i.e. no reactor.

There is no cat on the car now just a presilecer from another project and two high flow mufflers. The sound isn't bad.

I've read through the arcives and found that the secondary ports open by back-pressure from the exhaust. Because of the less restrictive air flow through the exhaust I don't think my secondary ports are opening when their supposed to.

Is there a way to check for this?
Or should I just do the 6 port thing anyway?

Also I've heard about adding an rpm switch and air pump to bypass this problem.
Does it work? Is it any better than porting?

A point to any other cheap HP mods would be appreciated.

Pyrocloud

 

what part of tampa. I'm in clearwater.. in regards to your post

You said you have a series 4? (86-88.5)? well in that case yes backpressure is was makes your 5th and 6th ports work. try putting some grease on the actuator rods.. they can be seen just above the exhaust manifold. go out a do a couple of passes revving past 4-5 thousand rpms. when you park see if the grease has moved. if not than they are not working.

let me know.. and i'm sure any of the guys would be more than happy to help you out.

-Markus

 

Well,

I checked it out and their not moving.
This area in the motor compartment is filthy.

I'll try to post some pics tonight.

In reply: actually I live in Gulfport.
What's going on in the area? Any clubs?

 

hey, I live in Safety Harbor, I drive a white 87' GXL.

 

You can either wire them open, which leave's you with less low end power, but you get more top end... or else you can get a pre-silencer from racing beat that will still open them up. I have heard about electronically opening them up, but it is a big job.. and I know nothing about it.

 

try cleaning them. I found one of mine was stuck now they vboth work ok.

 

As long as your backpressure sensing tube is hooked up, that exhaust should still produce enough backpressure. You need to take the actuators off, clean them up, and also see if the sleeves turn freely by hand or if they're stuck.

Clubs in FL? See my sig...

 

I'll remove the actuator and clean that whole area tomorrow.

Is there anything else I should do while that area is exposed?

I know that everyone has probably heard this one but, is wiring the actuators open worth the low end loss?

So many people in the area!
My fc4 has some damage in the front and passenger qrt pan. So I'm not really sportin' it ya know. Wainting for some extra scratch.

After I fix the body damage, joining the MRCCFL sounds like a great idea.

I had no idea it was this big!

 

It's best just to fix the system and use it as Mazda had designed.

The only reason to wire them open is you haven't been able to fix the problem. But to wire them open means you had to get the sleeves to rotate (therefore unsticking them if they were stuck), so you're already halfway to fixing them.

 

What is the backpressure sensing tube?
Intake or Exhaust?
The only thing on the manifold is the o2/s.

 

You said the car has a presilencer. Does the presilencer have a tube leading back up to the engine bay?

 

If backpressure activation is impractical, Kevin at www.RotaryResurection.com has a writeup in his tech section "airpump 6PI". It's cheap & crude but effective and elegant in it's simplicity.

To see that they open I tee in a pressure guage with a tee so I can blow in the tube & see at what pressure they open.
Then I extend the tee'd line inside the car & go for a drive to see when it hits that pressure.

 

www.rotaryresurrection.com

Resurrection has two "r's" after the "u."

 

I don't like the idea of using aqurium parts under the hood. There for fish tanks not cars.

 

Wasn't thinking clearly last night.

This tube is not hooked up. Someone welded it to the end of the header bracket and never hooked it up.

Therer are two hoses attached to the metal down tube.
I assume that the small one works the actuators. What does the big hose do?