Nearly got my 6PI issues sorted out now..... Theres just one more thing i'm having trouble getting my head around....

According to the FSM the actuators require a certain amount of air pressure to open (8.3 to 14.7kpa) and this pressure is supplied by the split air pipe.........

After reading other posts regarding the 6PI system i've noticed that people say it is exhaust velocity and not back pressure that is used to open the valves. I cant really see how exhaust velocity could produce the required 8.3+ kpa in the split air pipe.....
In my understanding of fluid dynamics a slight vacuum would be created in the split air pipe when there is high velocity exhaust gas moving past the opening of the split air pipe in the cat.

The only way i can see that pressure could be created in the split air pipe is by a build up of pressure (backpressure) in the cat.

If anyone can be bothered proving me wrong it would greatly appreciated..... The car i've been working on has the exhaust split right through just after the main cat. I would much rather fit custom piping rather than the poor flowing original cat converters. (possible performance gain if i can keep the 6PI working)

 

Well, You've obviously found the problem that s4 owners have.... when the cats are eliminated or malfunctioning the aux ports won't work correctly. If you downloaded the online book about the development of the Rotary - RE by KeneshiYamamoto you can see how the air control valve works to control backfiring during deceleration and provides preheated air for the cats as well as pressure for the actuators under load in conjunction with the dashpot and secondary throttle plates. This was all new to me until I read the complete document as to what was actuallly going on with the factory air system and why & how it all works together. When the air pump is eliminated it won't work properly. So us normal knuckleheads have to come up with a way to make the aux ports work correctly.

There are various means to make this happen & some work better than others with a differring cost involved. Some use an extra air pump & a rpm switch and vacuum solenoid to activate the aux valve system.

Some aftermarket exhaust systems (RacingBeat) have a back-pressure pipe to work the actuators. I've measured mine with a gauge & found it not very reliable considering the age of our actuators and engine efficiency - although the newer headers have been changed from the older ones according to direct correspondence with the designer.

You are between the rock & the hard place as to what to do regarding aux port activation. I made my own with a gauge and LED's that show port status. I had added an S5 intake with a VDI so I needed an extra actuator at a different rpm activation point so I had much more complexity.

You need a source for pressure to activate the aux ports. some people use the air pump with a adjustable bleed valve to manage the opening pressure for the aux ports. This is the cheapest & simplest way of doing it.

You need to have your ports rotating properly regardless of the means of activation. I found that once I had a proper source and some penetrating lube my ports started working correctly. I rigged some LED's indicating full port opening so I could know when they were open all the way - I used some door-jamb switches & some custom made brackets to hold them. You really can't feel it when they work right - it's too smooth in transition - but it makes a difference in both low end & high end torque.

If you have bad vacuum lines or questionable gasket seals or leaking or sticking injectors or other problems like a clogged catalytic converter or other air system problems you could be in for a long & trying time to get everything right. Also an old or abused engine could have compression issues or cooling issues along with electrical or timing difficulties.

So you can appreciate the difficulty of relating a definitive solution to your problem with the limited information available. The more systems you can check the more we can help.

Ramses666

 

Thanks again ramses.
I really appreciate you going to the time to give a detailed explanation.

I have not read, RE by KeneshiYamamoto as yet, will have to make it a priority to obtain a copy and read it.

!Australian spec! 1/89 S4 N/A (vac lines/compression ok)
Air pump was removed when my brother bought the car, not real keen on buying another one.

I think i might just look into the electronic actuation method..... can get a tandy electronics frequency switch kit, and possibly a couple of servo's make a simple controller for them........... maybe

 

http://smrmicro.com/re-ky.pdf

 

I went through all this 6PI BS on my old nonturbo. I tried the electric pump and everything, but it's hard to find one that can stand up to continuous hard use. Also the ports themselves like to stick. If I could do it again, I would install the factory smog pump (but keep off ACV and all the other BS), then use an Rtek 2.1's built in rpm switch to control a solenoid valve that will switch air from the smog pump to the auxilary port actuators. In that way, you get cockpit adjustability and the dependability of the stock airpump and ECU. You don't have to worry about electronics in the engine bay except the solenoid valve, but I think you might be able to just retrofit an OEM emissions solenoid (which can take the heat) or something, I'd have to look into it more.

And don't even bother trying to make custom actuators that are 100% electronic. Several people have tried it and nobody can make them reliable. It's not worth it.