I'm looking at pre-silencers and race pipes for my 91 coupe na, neither have a place for the split-air pipe. Aux ports actuators on s5's are operated by the air pump rather than the exhaust, so I am wondering what will I lose, if anything?

 

Split air pipes only feeds air to make catalytic converters work. No cat=no split air pipe needed.

 

What he said. You can also block off the ACV as well at this point.

 

is the 6PI system still going to work without the split air pipe hooked up? I'm having to run without right now and I was wondering if the air pump still supplies pressure to the 6PI system without the split air pipe

 

It will. If you don't have to worry about emissions in your area, there's no worry. But at that point, your air pump is useless and you may as well pull it and grab a dual-sheave alt pulley, ACV block-off, and grab sleeve inserts like Atkins or Pineapple and run without the aux ports.

 

Run without the aux ports and VDI huh?

That's not logical.

 

I meant to add later on that you should wire VDI open. My bad! Playing with my mud toy today while I wait on parts for the 7 so I got a little distracted.

 

There is practically no benefit to removing the air pump on an S5. Wiring the vdi and aux ports open just makes the car slower.

Keep the air pump and the aux/vdi ports working as normal.

 

The systems mazda designed actually work, theres no reason to remove them. I noticed a massive increase in low and mid range torque with the system working correctly, which is exactly what they are designed to do

 

In a 100% stock application, I agree with you guys completely. However most of these cars are frakensteined and pieced together. Mine is ported very generously on the inside of course but the outside too so my aux sleeves don't even fit. I'm in the process of making a custom manifold. So it doesn't make ME slower per say, but absolutely on a stock application.

 

ACV is still needed for the aux ports and VDI on S5. Though I've read of a way to do it without them but using the air pump pressure and something or other(rpm switch, bleeder valve, etc.). Can't remember as I ditched the sleeves, rods, and all with my setup, with no current plans of going back.

 

The wrath of the forum will now come upon you at the mere mention of this, as the posts following this one are beginning to reflect.

 

Dak, could you send me a pm about removing the rods and making sure VDI is wired open? I'd like to do that before I put mine back together in a few days.