Yes you need one.

Can you remove your airpump if you have a high-flow cat or would they still clog?



In an s5 the airpump is needed to actuate the vdi and 5th and 6th port. is there anything else it is needed for? Doesn't it supply air to the oil injectors?

any cat needs the air pump, cats like to see 14.7:1 mixture and the air pump adds air to the exhaust at idle and low speeds to acomplish this, without the air pump its too rich for the cat to live

how does the air get into the exhaust? is it through the ACV then through the channels in the rotor housings?



and, do the oil injectors need air from the air pump as well?

The acv pushes air from the airpump through the split air tube to the cat. There should be a long pipe going to the cat.

Just curious, i have been running a straight pipe on my s5 for a while, didnt realize that the cat operated the 5,6 ports.. What exactly is the VDI and is there anything I can do to work around it? I have been debating wiring the 5,6 ports open since i understand they havnt been operational since i put in the straight pipe i guess.. Thanks guys.

S5 doesn't run that way, S4 works off back pressure. In an S5 you should be fine as long as the air pump and acv are working.

Good stuff, so is there actually any of the ratsnest I can actually remove or just leave it?

There are, but I am not up to speed on all the details so I don't want to steer you in the wrong direction.

hey guys i have a quick question. Im new to here and all i have a black 89 gtus with 64k orig. miles. It has race beat full exhaust with the race header. I need to know about the air pump thing i just put a small breather on the hose that went into the air box when i removed the air box system and put a nice new cone filter on the end of the maf. Is that ok just to put a small air breather on the fairly large hose that went into the air box. thanks for your help and i love mazda and my new rx7.