So... I have a 1996 FD RX 7 with PFC, Blitz NUR spec Catback exhaust street ported engine. I am planning on deleting my air pump (Air pump is bad squealing noise when starting the car) I have the block off the plate and idler pully ready to install. And I was wondering if I need a high-flow cat or downpipe before deleting my air pump? I still have the stock cat and I read that the JDM RX-7 comes with after market down pipe?(correct me if I'm wrong)

 

You don't need a high-flow cat or down-pipe.

Although you might hurt the stock cat a bit due to no airflow to help light it off on startup/low load everyday driving. JDM Rx7's have a down pipe without a pre-catalytic converter in them as Japans emissions restrictions are slightly more lax on startup emissions. Sounds like you got everything you need! Good on you for keeping an idler pulley to keep the tension on the water pump.

 

You will clog the stock cat without an air pump. The car will need to be tuned after deleting the air pump. It is my understanding that the airpump causes the AFRs to read lean on the o2 sensor and the then stock computer or PFC fudges the numbers. You can get by with the stock JDM downpipe, but it is pretty restrictive.

I just did this. Bought a used HKS dp, had an o2 bung welded on it further down the pipe for an AEM wideband, sent it to Calico Coatings to have it ceramic coated, and installed it with a Bonez high flow cat. Also had to replace the stock fuel pump, with something more powerful. It was a whole lot of work and I still have not gotten the car tuned yet.

At a minimum you could get by with keeping your downpipe, installing a high flow cat, and having somebody dyno tune using a wideband probe.

 

Just unplug it

 

So I need a cat that allows enough flow so that it doesn't clog up and enough restriction so it doesnt lean out?

 

If you are stock right now, hold off until you can get a PowerFC. You don't want to remove the air pump with a stock ECU, the car will run like crap.

Air pumps rarely fail. Are you sure it isn't a bad or misadjusted belt? Are you sure it's the air pump and not something else?

Removing the air pump has a whole world of things that go with it - you need an idler pulley, PowerFC, and some sort of solution for the cat. If you are going to have to pass emissions, you will want the air pump.

Before you go further you need to do more troubleshooting to isolate the noise, or at least post up what you have done to show that it's the air pump.

If it IS the air pump for right now I'd just get a good used one and be done with it. They should be a dime a dozen used.

Dale

 

Either the stock cat or a hi-flow cat will provide enough back-pressure to avoid boost creep...which is the lean condition I think you’re asking about.
I’m not sure about the stock cat, but a hi-flow cat like the Bonez is fine without an air pump. I’ve been running one with no emissions for 15 years and no issues.
But I think you need a stand-alone before going without an AP

 

Edit

 

the rotary engine needs to be run rich to avoid misfires, and Mazda adds the air pump so the converter sees a normal mixture, without the air pump it will just run too rich all the time and ruin the converter

 

That's partly due to the stock 1980's-style injectors. With newer injectors it's possible to idle closer to stoich, which should avoid needing an air pump to keep a cat converter alive.

 

the 2% CO in the intake doesn't help either...

 

do you happen to have a picture of where your bung is welded? and how you routed everything? Also do you know if you HAVE to delete the air pump to install the aftermarket dp on a jdm car?

 

Not sure what you are asking on the weld-on bung.

You don't have to remove the air pump to install a downpipe on a JDM car. You can actually leave the whole air pump system on the car even with a straight pipe.

Read my post above, you really can't remove the air pump unless you have an aftermarket ECU like a PowerFC. Well you can if you want a car that idles and runs terribly.

Dale

 

i do have a Power FC on the car currently. So that’s not an issue. What prompted me asking initially was a few threads stating that it had to be removed for an aftermarket DP install.

also, I’ve seen on numerous occasions that you’re a man of great knowledge with these cars. I do have more questions but they are not related to this thread, can i DM you?

 

I would start a new thread, I'll reply and so will others, hopefully it will help others out that are having similar problems.

Dale