Auxillary Port Valve Trouble

[Kev41]

If anyone knows any tips to help with the auxillary port system on an '86 13B N/A I could use some help.

When I hook them up to a low pressure air source they open and close but when put to the exhaust there is nothing. I have read many articles on how the system should work but have no idea how to diagnose what part could be wrong. My air pump seems to be working and the sillinoids click and make noise but I'm still getting nothing.

I ended disconnecting them from the exhaust and they now open but stay open and its causing low end power loss. I autocross this car as well as drive it daily and would like to have that power.

Also I recently bought an engine from a guy in chicago who said it was from a '91 RX7. I have heard that this engine might have a little more stock hp and was wondering one if there was a way to tell from looking at the engine if it is from a '91 and two if it will fit/work with my '86 car.

[FerociousP]

The engine has more stock HP because of the s5 specific parts like ecu, VDI, and higher compression. As you cannot use s5 manifolds in an s4 car without disabling the VDI, and you are using an s4 ecu, you will only be seeing the benefits of the high compression, which will not grant you the 20hp difference between stock s4 and s5 motors. there are other minor differences but they are just that... minor.


You know you have an s5 if:
- If the UIM has four tubular pipes instead of the "brick" style right after the throttle body.
- If the TPS has two sensors instead of one.
- If the OMP is electrically controlled
- If it has no EGR valve on the top of the shortblock

With that said, if the motor was rebuilt then it could have weird internals, lower compression rotors, etc... but if all those possibilities are there then most likely you have yourself an s5.

[Kev41]

Thanks for the info I will check the engine for those points.

Would you happen to know about the Auxiliary Port

[NoDOHC]

The auxiliary ports are actuated entirely by exhaust backpressure. This means that a higher flowing exhaust will not allow them to open at all due to lower backpressure.

They are slightly adjustable, but not very much so. I saw a guy bypass his ACV and using an orifice in the outlet of the airpump, actuate the ports using that technique. The simplest trick is to install a 12V air pump and an RPM switch and use one of the stock air solenoids from the rats nest.

From what you are describing, the ports are open at all times, as you said that unplugging the line makes them open. Unplugging the line should make them shut. You make have an exhaust plug (like melted cats) that is making backpressure at very low revs.

[Kev41]

I do have a custom and by custom I mean made by myself and my dad who is a motorcycle mechanic at the local bike shop. I was thinking about buying the RB header and presilencer will this combo create enough back pressure or do I need the whole system

[My5ABaby]

For clarification, how are you testing to see if the ports work? They won't work without backpressure so you'll need to be putting strain on the engine. You can rev it to 218309238rpm in neutral and they still won't open.

[Kev41]

They seem to open when I test it in neutral

[My5ABaby]

They open when you rev your car in neutral without putting any auxiliary air into the system?

[NoDOHC]

They open when you rev your car in neutral without putting any auxiliary air into the system?


The S4 ports work fine in Neutral, it was the S5s that required the car to be in gear.

The exhaust backpressure is primarily caused by air flowing through the exhaust meeting restrictions that require a differential pressure to overcome. This backpressure is the same with the transmission in neutral at WOT as it would be with the transmission in gear at WOT.

The S5s are computer-controlled, so they do require the car to be in gear.


I do have a custom and by custom I mean made by myself and my dad who is a motorcycle mechanic at the local bike shop. I was thinking about buying the RB header and presilencer will this combo create enough back pressure or do I need the whole system


Exhaust backpressure is not your friend. It does not help power, fuel economy or engine life at all. You want less backpressure. The ideal backpressure is negative (scavenging using tuned exhaust headers).

What you need is the means to make the aux ports open without having backpressure - the simple solution is the 12V air pump and the solenoid from the rats nest.
Rpm switches are easily acquired and easily installed (use the tach wire). Many people have done the 6PI that way with success.

[Max777]

dude, if you want help, there is a write up on Kevin Lander's website, rotaryresurrection.com with a how-to on opening the exhaust ports.

Personally, I would just take the sleeves out, and not fuck with it... but if you want to keep them, then I will help you install all this shit, provided you have a heated garage or a shop to work in.

Hit me up on facebook or something, (max schrepfer)

[Kev41]

Thanks for all the info guys I plan on trying to get through the winter with the way it is but will use this info for spring