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.



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where do you get a dual alternator pulley?

Rotorhead



Racing Beat



Mazda Racing



Rotary Performance



Mazdatrix



and Banzaitoyota sells them

Do i have to remove all 3 cats or just the pre cats and leave the main? Also i'm debating the racing beat or apexi n1 dual exhausts, which do you think would work best when removing the airpump and acv?



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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.

if u were short on time and wanted to free up more power could u just remove the belt to the a/c instead of removing the whole thing

86 fc

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?

You can but you need something to activate the auxillary ports unless you wire them open which sucks IMO.

do you have to have a gasket for the ACV block? if not, ****, i'll make one.