Hi Guys,

I have a question that I cant seem to find the answer for searching the forums.

My motor setup is almost done, this is what I am running:

Stock sequentials with simplified vaccum system (all block off plates from the banzai kit are being used). Air pump removed via the greddy pully kit. After market downpipe, pfs catback, stock main cat (until i get standalone at which point i will replace this with a straight midpipe).

My question is, the air tube (on the main cat itself) that ran from the air pump to the main cat (before I deleted the air pump and all associated pipes), does this need to be blocked off? I assume if it is not blocked off some exhaust gas will just be blown out the tube (as it passes through the main cat) which is probably not good so is there a blockoff plate that somone sells for this? do people just weld somthing over it?

I just wanted to know what the best option is (again this is temporary since i will soon be getting stand alone and a midpipe to replace the stock main cat but I just want to know what the best thing to do with the open air pipe coming of of the main cat is)

Thanks in advance!

 

If you removed the air pump you need a high flow cat/ or mid pipe (watch for boost creep, the wastegate must be ported to prevent it with a midpipe). The stock one relies on the air pump to stay clean and keep it from getting clogged. If you run the stock cat without an air pump it will clog up.

Do you have a PFC? If not the car will be in limp mode.

 

I didnt realize the main cat would clog if I didnt have the air pump.

I thought I could run the stock main cat with no air pump and the only problem would be that the emissions would never pass.

Looks like I am buying PFC, Midpipe and getting the wastegate ported...

The RX7 money drain never ends...

Thanks for the info man!

 

I don’t know what factual base for this is. The air pump injects air only under a few conditions (three way CAT) to burn NOx, staved oxygen creates too much nox and co rather than co2. The injection of air greatly increases the combustion temps in the CAT and probably shorten life faster than no air. Cat clog from high temp breakdown of the catalyst support structure. Before NOx limits almost all Cats were only addressing HC emissions and without air injection.

 

I think the "remove the air pump you'll clog the cat" is an old wives' tale. Maybe true on an FC or something, but the FD does have a much better design for the main cat. I've seen many cars run the main cat with no air pump and were okey-dokey.

Now, if you have the stock ECU and remove the air pump, you'll have a weird idle and weird on/off throttle transition. The stock ECU is fudging the O2 sensor numbers to compensate for air pump air in the exhaust. No air pump and it fudges the wrong way giving you some weird driveability problems. With the PowerFC this isn't an issue.

Dale

 

Can I run a catless midpipe with the power fc and NOT have to port the wastegate or does it absolutely need to be ported

 

If you do nothing else then yes, as you will get boost creep like crazy. A less intensive alternative if you decide to go midpipe would be to reintroduce exhaust restriction since increased flow is what causes the issue. I used a 2.125 inch inner diameter restrictor plate and I have no creep. Of course if you want more power then you want more flow, so then you will need to port the wastegate, but until that time...