I have been doing the timing belt and put in the Porkensioner this winter. As part of the project I also decided to delete the air pump. I have all of the hardware removed.

But, on reinstillation of the air conditioner compressor bracket that connects to the old air pump bracket, this leaves the bolt too long. Should I just put some washers in to make up the difference of the deleted bracket or do I need to try to use a shorter bolt. Just want to make sure I'm doing it correctly.

Also, what have you all used to cap the pipe left attached to the cats to avoid the resulting exhaust leak?

Thanks.

 

I tapered a piece of wooden dowel in a suitable sized hose and used that as a cap to cover the hole with another hose clamp. So a 2 to 3" piece of hose, 2 hose clamps and a piece of wood. That's it.
HK

 

A few washers with the same thickness as the bracket is the simplest fix.

X-pipe.

Cheers,

 

Yeah, thats next.

Thanks guys.

 

If you look at the tensionor for the old air pump you will find a washer that I determined to be the perfect replacement for the space the tensioner are used to consume. Circled in red Item 14 from the attached section of the prarts catalog.

 

Why did you remove the air pump? No appreciable hp gain and it does affect the emissions somewhat and can affect O2 readings. The air pump on an S4 is nothing like the air pump on a 1973 Ford Granada.

 

I will be getting high flow cats with an Xpipe in the very near future that do not need the air pump. Since it will serve no purpose, why not get rid of the parasitic drag, and the extra weight? Plus it cleans up the engine bay a little and makes access to a few areas a little easier.

Need any other reasons?

 

It has been my experiencxe it is best to leave the emmissions equipment on cars, especially those on high performance european cars like ours. The whole system is integrated and runs best with it. Parasitic drag? probably less than 1hp. Weight? best to lose a few personal pounds. Seems the best performance techs make sure their cars have all emmisions compnents in place. (Greg Brown). Again, the air pumps on our cars, unless seized, are beneficial. It is incorrect to think there are significant advantages in terms of weight reduction, hp recovery, performance increase, to be gained by removing emissions equipment unless you are building a purpose built track car for a specific RPM range. All of the above and your car runs cleaner. YMMV

 

I was under the impression that with modern high flow cats, the extra air injection that the air pump provides is completely unnecessary. The air pump only functions on start up to help add air to the cats to help them warm up the cats for better function more quickly.

So, given that the air pump valve shuts off after the car warms up, I'm not sure how it would affect a properly running car. Given that I was doing the timing belt and installing a Porkensioner, it made sense to get the cheaper non air pump bracket and get rid of the extra component.

 

The 928 air pump runs all the time. The valve under the airbox diverts air from the cats (or head on ROW engines) to the airbox at WOT so the stock over-rich WOT mixture cools the exhaust, instead of burning.

That's what I use. Thoughtful of Porsche to include the delete part on the standard assembly.

If you don't have that part, you need a 6mm | 1/4" washer with a 8mm | 5/16" hole (or two 1/8").

 

Ahh, thanks Ken, I knew the valve shut off air flow under certain conditions but wasn't entirely sure which ones. Something new to learn everyday here.

Also, thanks 76FJ55 and Ken for the pointer on the washer. I have that and will put in on tonight.

 

Air Pumps typically inject air into the exhaust just past the manifold to help in the continued burning of fuel before it gets to the cats. Makes for cleaner air and cooler cats. Might also affect the O2 sensing of a false too rich condition if left off.

 

On the later 928 the airpump injects into the mid part of the cat not up by the head as in the early cars. the cat is separated in to two sections the first I believe is to reduce NOx and the second chamber to oxidize CO. My understanding is that the air is injected in front of the second section to increase the oxygen potention and promote the oxidation reaction from CO to CO2. All this takes place after the O2 sensor so it should have no effect on mixture.

 

Can't wait to get rid of mine. Hopefully will get it out of there before SITM.