I've recently did an emissions removal on my 88 gxl. my question is how long will the cat last without the airpump until i get around to getting a test pipe.

 

well i'm just assuming that your car won't last very long since the average fc runs pig rich. so why don't you just pull off the cat and ram a metal pipe thru it until you destry the screen and catalyst material and then bolt the cat back up until you can buy a test pipe? just a thought.

 

you didnt answer the question...


youll be fine man. the airpump just dilutes the **** out of it. thats it. doesnt cool it down or anything.

 

[QUOTE=rotorhead_izzy;8698222]well i'm just assuming that your car won't last very long since the average fc runs pig rich. QUOTE]


sorry i meant to say "cat" instead of "car" my mistake.

 

its really hard to tell, could work fine for years, could burn out tommarow. its a 20 yr old cat converter allready. ive drove oen with a cat and no air pump for over a year and it never melted or burned out. but u never know

 

Modern cars have the ECU in Closed loop at idle ,along with a 02 sensor before and after the converter to monitor the efficiency of the converter and make fuel adjustments. They need no air to be mixed with the exhaust gas prior to the converter, because the afr they are putting out is close to 14.7 afr.

Converters work more efficiently when the afr entering them is approx 14.7afr. That's why your car, whos engine is NOT in closed loop at idle, has an air pump to mix fresh air with the exhaust gas to approximate a afr of 14.7afr prior to the converter.

The converter oxidizes (burns 'em up) the gasses. If the mixuture is too rich, the too rich mixture will overwhelm the cat, and it will eventually turn to a piece of crud. I've no idea how long a time it takes. One thing to remember, is that when your doing normal driving, the 02 is in closed loop and putting out a mixuture of approx 14.7 afr, so your not hurting the converter at that time. It's working just like a car with a airpump/ACV etc.

Depending on the car, the ACV is dumping the air overboard a LOT of the time when your doing normal driving. It does that because your in closed loop and don't need the air to be mixed with the exhaust gas. Whatever.

 

so pretty much what you're saying is i can leave it on until i've broken my motor in. and supposedly its a high flow cat (came with the car not sure how true this is) if that changes anything

 

I wouldn't expect the cat to last long at all without a supply of fresh air to light it off. When I first got my GXL, my BACV was plumbed incorrectly, causing it to dump the air pump's output to the relief silencer. My HC output was 1800ppm! After I got it corrected and got the car smogged, I put on a header and a high flow cat. When I took off the old pre-cat, I found that it had started to melt and spatter bits of itself all over the main cat. I had driven the car maybe 500 miles.

 

I'm really saying I don't know. What I do know, is that if you actually driving the car in a normal manner, the engine is in closed loop and there's little harm being done by the lack of ACV and airpump. But when your idling, your doing harm to the converter because the normal idle afr for a stock RX, is in the 12-13 afr range and not close to the 14.7afr the converter is best at converting from.

ScrapFC has an answer I'd be more comfortable with. Then again, if that converter has been on the car for years, it's got little life left in it anyway imho.