CompuBob

At least this is what I think is going on..
I have a S4 N/A, I know the 5th and 6th ports are operated by exhaust back pressure, When I rev it to redline while looking at the ports the acutators do not move the slightest bit. I just installed a new exhaust system with a 2.5" downpipe from rotary performance with stock Y pipe going to 2 old school greddy pilot mufflers.
I have the vaccume tube hooked up to the nipple on the pipe just after the manifold.
Would they be opening when the engine is under load? also how much horse would I be missing up high? I think I'm just going to wire them open.

Let's just say my friends D15 civic hatch, slightly setup for 1/4 mile was pulling on me just by a little, but thats definatly not right at all!

CompuBob

I have an extra electric air pump laying around, I'm going to see about wiring it up the same way the S5 guy's have to do, so I can manually activate it or setup a throttle switch. My car has no low end torque to begin with and it's a bitch to get going from a stop without bogging. I dont want it worse.

casio

yea, engine needs load.
D15 or D16z6?

Icemark

Engine needs to be under load for them to work, and you will be loosing low end torque when starting out (making the car even slower in the 0-60) by wiring them open.

If you still have your air pump, then you can do this:
and they will work fairly close to stock.

Of course if you had searched you would have found that as well.

Kai

If he has a D15B7, it's not too bad. D15B8, Z1, or B2... well, that's bad.

Once upon a time, I had an S4 dyno'ed with the aux ports stuck closed, as well as a crapped out and clogged stock exhaust system. It put down 96whp/105lb-ft.

mr0pistons

A trick I used to see if they were working on my old S4 was to put some grease on the actuator (piston? the thing that moves) Take it out for a test drive. When you get back, if the grease is moved, they are working, if not...well they aren't.

NZConvertible

Just to clarify this thing about "load", since it gets mentioned a lot. What is needed to operate the S4 6PI system is not load as such but exhaust backpressure. To get backpressure in the exhaust you need high exhaust flow. To get high exhaust flow you need both enough revs and an open throttle. It is entirely possible to create exhaust backpressure with the car stationary and out of gear by simply holding the gas pedal down. This will create backpressure but it will also over-rev the engine because it has no load on it. The reason the auxiliary ports don't normally open when revving in neutral is simply because the throttle is not being held open wide enough and long enough, for obvious reasons. By putting load on the engine (i.e. driving it on the road or dyno) you can hold the throttle open without over-revving the engine. This applies to any engine operation that people say requires "load" (e.g. making turbo boost). What they really mean is that you need load to prevent the engine from over-revving while you hold the throttle open to create enough airflow.

One thing I've never seen anyone do on this forum is exhaust backpressure measurement, which is odd considering how easy it is to do and how important it is for S4 NA's. If you measure the pressure required to open the ports, and then measure the exhaust backpressure while driving, you'll know exactly when (or if) the auxiliary ports are opening.