Airpump Removal
Thread Starter
Senior Member
Joined: Oct 2001
Posts: 10,906
From: Peoria, AZ
After removing the airpump on an S4(86-88) n/a, you need to get a dual alternator pulley to prevent waterpump cavitation at high rpms.
You must also get rid of your cats as they will clog without the air injection supplied by the airpump.
When you remove the cats you need backpressure from the exhaust to activate the 5/6th intake ports@ 3800rpms on n/a(s) only, turboII are 4 port motors. Most aftermarket exhaust companies supply a vacuum nipple on a cat replacement pipe to supply the backpressure. If you make your own pipe just weld on a bung or vacuum nipple and connect the hose from the ports.
If you want, you don't have to, you can now take off and block off the air control valve, its located on the lower intake manifold, and a hose goes from the airpump to the valve. K2rd sells block off plates, make sure to also use some gasket maker on the block off plate. Now just cap off the vacuum lines that were running to the air control valve. The air control valve injects air into the cats.
You can also remove the air silencer. Its hidden under the windshield washer resouvier. When the air control valve is not injecting air into the cats it is being bypassed to the atmosphere and the air silencer just quiets it down.
People remove the airpump to free up some hp(parasitic drag) and make it easier to work under the hood and less slop in the way.
You cannot remove the airpump on s5 n/a(s) as it is needed for proper operation of the VDI, unless you want to mess around with electronic activation..
S5 turboII(s) do not have the vdi so you can scrap it.
You must also get rid of your cats as they will clog without the air injection supplied by the airpump.
When you remove the cats you need backpressure from the exhaust to activate the 5/6th intake ports@ 3800rpms on n/a(s) only, turboII are 4 port motors. Most aftermarket exhaust companies supply a vacuum nipple on a cat replacement pipe to supply the backpressure. If you make your own pipe just weld on a bung or vacuum nipple and connect the hose from the ports.
If you want, you don't have to, you can now take off and block off the air control valve, its located on the lower intake manifold, and a hose goes from the airpump to the valve. K2rd sells block off plates, make sure to also use some gasket maker on the block off plate. Now just cap off the vacuum lines that were running to the air control valve. The air control valve injects air into the cats.
You can also remove the air silencer. Its hidden under the windshield washer resouvier. When the air control valve is not injecting air into the cats it is being bypassed to the atmosphere and the air silencer just quiets it down.
People remove the airpump to free up some hp(parasitic drag) and make it easier to work under the hood and less slop in the way.
You cannot remove the airpump on s5 n/a(s) as it is needed for proper operation of the VDI, unless you want to mess around with electronic activation..
S5 turboII(s) do not have the vdi so you can scrap it.
Senior Member
Joined: Aug 2002
Posts: 1,801
From: Eastern PA
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Joined: Jul 2002
Posts: 5,181
From: My BIG ol TURBO-DIESEL
Senior Member
Joined: Aug 2002
Posts: 1,801
From: Eastern PA
You can remove just the pre cats. If removing the main cat, you should keep in mind your backpressure pickup tube still needs to be hooked up.
Both exhaust systems are good quality. Its a matter of opinion. I prefer RB for the more stock appearance and the Apex N1 I believe is one of the loudest out there.
Both exhaust systems are good quality. Its a matter of opinion. I prefer RB for the more stock appearance and the Apex N1 I believe is one of the loudest out there.
Junior Member
Joined: Sep 2003
Posts: 17
From: fort wayne indiana
ok i took care of my ac. now i am on to a new question. i have a bad exhaust leak at my cats so can i just replace my cats with a strait pipe and keep my stock mufflers on withough dealing with the o2 pump?
