Do I Need my Air Pump
 

Is my air pump just for emissions? 1987 N/a

yes, however...

The 6-ports on an S4 N/A (86-88) are operated by backpressure from your cat. an the cat needs the air pump to survive. So, if you ditch your air pump, then your cat will brake, and your 6-ports wont work.

if you dont know what 6-ports are - do a search as that topic has been discussed more that Paris Hilton's legs.
-a

This is true but if you ditch the cat for a more... useful option :) then you don't need to worry about that either.

Now the question I have is where the backpressure is coming from. Is it something in the manifold or is it from the split air pipe?

Split air pipe.

thanks aaron.

What size is the belt that goes from your water pump to crank shaft? I heard that you can fit it on there if you remove your air pump instead of using the dual pulley for your alternator. Someone here was saying that in order to get it off after, you'll need to cut it, cause you pretty much pry it onto the belts in the first place.

I thought only the S5's worked this way and the only way around it was to wire up a electric airpump.. how does my friends S4 6-ports work with astraight exhaust and no airpump?
just wondering because I was going to remove my airpump and cat this week

They don't. :)

well then, that explains why his car with a streetport + exhaust + intake was even with my bone stock + restrictive exhaust..
hehe, ok then I guess we just figured out his problem :P

Er, I guess I shouldn't replace my cat with a straight through test pipe if I want to maintain functionality of my 5th and 6th ports. DAMN!

Is it the same way on the GTUs

you can replace the cat with a straight pipe. just tap into your air pump to acv hose and run your 5th and 6th ports off of that pressure. there are write ups on doing this and you should be able to do it relatively effectively with some basic tools and parts. i recommend making a T fitting instead of just drilling into the hose like the write ups say though. also, aquairum valves don't usually have enough flow to work properly.

https://www.rx7club.com/2nd-gen-archive-72/how-air-pump-auxilary-port-activation-330310/

Your sig says you have an S5. Your 6 ports are activated by the air pump. You can run a straight-thru exhaust without problems. You just need to keep the air pump and ACV.

PEOPLE!
The 6 ports on S4's and S5 are activated differently. S4's use back pressure from teh exhaust. S5's use the airpump. That means on an S5 you can tamper with teh exhaust without any 6-port reprucussions. On a S4, if you open up the exhaust, then the 6 ports will not activate unless you provide for their functionality in another way.
-a

does this also apply to turbos?? I have a full 3 inch exhaust on the way with no cat turbo back on a 87 (s4). Will i need to change anything??

turbos do NOT have 6th ports, they are just 4 port, so no you wont have this problem.

FFFWWWWHEEEW! Thats a relief. Now to go have a nice 2.5" test pipe made :devil:... The neighbors'll love me.