After putting on my new x-pipe (see here for details) I now have to deal with the air pump. Has anyone put a metal valve on the end of the pipe to control the backpressure enough to make the sound stop?? or would this be bad. I guess it might smoke a little bit if I did that (?). I don't want to "delete" the air pump yet. If I slighty block the pipe with my finger while it's running, the noise stops, but there is still air flow coming out of it. Or, would it just be better to get a 21" belt and "jumper" the fan?? Thanks

 

I took apart my air pump and removed the vanes. That fixed the sound. I still use it as a belt tensioner.

 

You could get the euro belt tensioner... it's basically an idler pulley that mounts where you have your smog pump, and it allows you to use the same belt and tension it essentially the same way you do now.

 

Or remove the air pump and use a 20 or 21 inch belt direct from the crank pully to the fan. That's what I did and it works like a charm

 

How do you tighten the belt then?
Ed M
85 928S, 88 928S4

 

loosen the fan carrier, slip the belt over the fan pully, tighten the fan carrier and the belt snugs up.

 

Air pump removal:

https://rennlist.com/forums/928-forum/132878-short-fan-belt.html

 

Where can one find the euro belt tensioner? I currently have the 21" belt installed, but it's a little loose.

 

Replace the viscous, belt-driven fan with an electric (Hayden) fan available from Pep Boys, etc. Gets rid of that belt completely!

 

It right next to the hen's tooth.

I've looked and settled for the re-purposed air pump. All bearing, no pump.

 

Ditto

 

I'm running 4 9" fans on a custom Murph928 bracket. Works great, as long as I'm moving more than 25mph, the fans are not needed. Also tested in 85+ degrees.

 

I will plumb my smog pump into the intake plenum somewhere AFTER the MAF sensor. that should make it go fast and run tight, yo.

 

Then I can say my 928 is supercharged, schweet

 

Thanks for the reply's guys. I used a tip from SHRKBIT to take care of it for now....""The air pump or diverter valve started trumpeting, we silenced it by disconnecting and capping the vacuum line to the diverter valve.""
This took about 10 minutes from hood open to hood closed (the quick fix) and seemed to work fine. I used a stainless machine screw of the proper diameter to plug the vacuum line. When I get an afternoon free, I'll completely remove the air (smog) pump. I don't think it will be needed anymore with aftermarket cats. I wouldn't mind to install electric fans either.