wrightcomputing

iTrader: (5)

I have a problem with my RX8 the cat is over heating and the rear sensor is glowing bright red. I have had a few people look at it and now the Mazda Stealership have it and are going to do a diagnostic for me, to confirm or tell me what is the cause of the problem. I believe it is the front oxygen sensor.

If it is the front sensor it will cost about $500 for Sensor with fitting and it may need a new cat as it over heated but the cat is still under warranty. (Maybe more if the coils need doing etc.)

My thought is rather then give the Mazda dealer $500 I can get a straight through pipe manufactured and fitted for under $200 and I can get the sensor for $105.95 http://www.thepartsbin.com/catalog/?...=Mazda&md=RX-8 which I think is the OEM part.

Has anyone fitted a cat replacement pipe or can offer any advice such as how loud will it be with the rest of the exhaust stock?
You can gain HP and MPG with a cat replacement pipe but to get any gain will the engine also need to be tuned and how much would that cost?
How would the resale value of the car be effected, mazda will cover the cat replacement so maybe it would be worth getting a new cat and leaving it in the garage so I can make the car stock for resale at a later date?
Not such an important point but does anyone know what autocross class the car be in with no cat is that a SM or something?
I guess the real question is should I just pay and get stock replacement or get an upgrade that is cheaper but could be problematic?
Thanks for your help and I need to decide by tomorrow because thats when I get the diagnostics back.

paimon.soror

iTrader: (15)

If you dont plan on running a cat and running a straight pipe to the muffler its going to be loud and raspy, and not only that but it is going to drone like a beater civic inside the cabin. Resale value will go down the tubes without a cat since many people may not find a legal way to pass inspections (unless you masked the p0420 code and they dont use sniffers where you live).

wrightcomputing

iTrader: (5)

I know it is illegal but there are no inspection in florida so how would anyone know *(unless you told everyone on an RX8 forum) I guess the gain in HP and fuel economy is not worth the noise. I also heard it makes the car smell really bad without the cat.

paimon.soror

iTrader: (15)

Well not the inside, unless you have the windows open lol, but yes, it smells like straight up pollution lol. IMO it would only be worth it if you were going with a BHR midpipe or something dual resonated.

wrightcomputing

iTrader: (5)

I was talking to a guy in an exhaust shop and he would just cut out the cat and weld in a straight through Pipe and place the rear O2 sensor in the pipe, he said it would give me the check engine light but should run fine.

ganseg

iTrader: (5)

I ran a straight pipe as a test for going that way at the track. It was VERY loud and suprisingly I did not gain HP under 8,000 rpm.

I personally like the RB Dual Resonated and BlackHaloRacing midpipes.

wrightcomputing

iTrader: (5)

@ganseg How did the car run with the straight pipe, did you need to tune the engine to let it know the cat was not there.
The RB site says that the check engine light comes on do you know how to stop that happening.

paimon.soror

iTrader: (15)

You need to search man ... yes you can mask the CEL with a RB flash or a COBB access port.

ganseg

iTrader: (5)

The car ran fine. I did have tuned software but that is not required - the stock software will work fine too.

I did get the check engine light. I have heard of three options:

- buy a "plug non-fouler" at NAPA for $7. It is a spacer to out the o2 sensor further out of the exhaust stream. Not guaranteed to work but a cheap first step. Make sure it is deep enough for the o2 sensor by bringing the sensor with you when you buy it.
-supposedly you can buy a piece of electronics that produces an output like the o2 sensor should to fool the ECU.
- buy an AccessPort from MazdaManiac. He sets it up to not show the CEL for the rear o2 sensor.

paimon.soror

iTrader: (15)

No

wrightcomputing

iTrader: (5)

The CAT is currently under warrantee and I think it will be damaged from getting too hot. I think my best option at the moment is to get the dealership to repair the car as stock and keep the damaged cat which I can then get welded into a straight though pipe, try it out and/or use it for track days.