Nullpop66

My 2007 RX8 has been acting strange lately. RPMs not matching right, dragging when shifting gears, and rumbling/vibrating in second gear. I red line it at least once a day when I drive it, and I noticed its revs sounded muffled, and they were not as sharp as they originally were. It has died twice on me since the first signs it started acting strange.

The engine light came on today, so I went to the local automotive store so they could scan it. The results said a "Leak" and "No flow". A gentleman parked next to my car asked about it, and I told him everything that was happening. He told me he had two RX8s of his own, and offered that I ran it hard for roughly twenty minutes, and "look under the car, find something glowing red, and beat the filter out of it." That or buy a new "pipe". He said that he went through this with one of his RX8s, and he just bought "pipes".

Ever since my RX8 has been acting odd, Ive been a lot easier with it. I'd like to know the best way to fix this cat, and how to prevent this from happening again?

Like I mentioned, I do drive it rough half the time as well as red line it (or at least get close) before I shut it off. Someone told me red lining the vehicle before shutting it off helps prevent flooding, and carbon build up. If this is true, I'm not sure. I've examined some of the forums but none quite match my situation.

BigCajun

iTrader: (1)

I've never heard that description for a code.
He must have been interpreting what the cause was.
Usually a code for a bad cat is P0420 'below efficiency threshold'.
Redlining while out of gear is unnecessary and probably does more harm than good.
Flooding is an issue only when you have other underlying problems, usually from ignition problems, weak battery, or starter.
No special procedure is necessary for shutdown, but be sure it's warmed up before driving it at higher RPM.
Best solution for the cat issue is to take it off and replace it with a midpipe.
Bad ignition components cause misfires, Misfires kill cats, bad cats kill engines.
If it's bad, remove, replace, or gut it ASAP.

Nullpop66

Alright, thank you for the info! Is there any best way to remove a cat?

CelestialGryphon

iTrader: (1)

Generally I like to use a skinner to get all that pesky fur off. OH! You meant from the Car! Nah. Nothing besides getting under and pulling the midpipe, that's where it all is anyway.

BigCajun

iTrader: (1)

If you can get it on a lift or jack it up high enough to get jackstands under it to get under it safely, it's not hard.
There are 3 nuts and bolts holding the front and 2 nuts on studs in the rear.
A couple of crossmembers that have to come off.
You can unplug or unscrew the O2 sensor.
If the fasteners are rusty, soak them with PB Blaster overnight preferably.
If you gut it, be sure to take the O2 senfor out first so you don't damage it.

BigCajun

iTrader: (1)

If you plan on getting a midpipe, the BHR is the consensus favorite, expensive but worth it.
Check your state's emissions testing to solve if they check it.
Unless you're in California, there are ways around it.

CelestialGryphon

iTrader: (1)

What BC said. +1 for BHR, might be a fanboy but it's definitely a solid product. I run a BHR catted mid to the rear with an HKS hi-power. Co's emissions aren't as bad as CA's but I passed the second time around. Sounds good, flows well, a little loud at high revs. Or you can always keep the stock exhaust on and just run a resonated midpipe with the nice cat on it. As long as your ignition is healthy your cat should be fine.

Nullpop66

Thank you guys so much. I'm pretty noobie when it comes to rotary engines haha. I appreciate all the tips you all gave. Looking forward to fixing it this afternoon!

BigCajun

iTrader: (1)

Read this DIY to help you fully understand the pros & cons of what it's all about.

Nullpop66

I read through the DIY, that cleared up a lot! Thank you. I do have one final question though. A mid pipe; I've been told you can use this for a catalytic converter. Have any of you had first hand experience with mid pipes? Do you like it?

BigCajun

iTrader: (1)

Well, you can get a midpipe with a cat, see BHR again.
I have the BHR resonated midpipe (no cat) with stock exhaust, I'm very happy with it, almost 30k on it with no issues.
There are discussion threads about midpipes, judge for yourself, but I highly recommend it.
Great fit and quality, deep tone with no rasp or drone.

BigCajun

iTrader: (1)

To be clear, a midpipe without a cat does not replace a cat.
If you need a cat for emissions testing, you must get a cat.
A cheap cat will not last with a rotary engine, a temporary fix for emissions testing only.

CelestialGryphon

iTrader: (1)

If you need a cat for emissions, get one. Like the Big Chief said, don't skimp on a cheap cat, it will melt. I've got 1500 miles on the BHR cat. No problems, and I premix.

Nullpop66

Emissions arent needed for me. I looked some up, and they're about 300 dollars? I went to a shop yesterday and they said they'll charge $25 to cut the Catalytic out. With the Midpipe and insulation its roughly anywhere from $500 to $600 dollars.

Steve Dallas

The available Magnaflow cats do not fare well with the heat output by our engines. They tend to fail within ~6 months. These engines require a very robust cat. Your real options are to buy a healthy used cat or a BHR catted midpipe.

Nine13

iTrader: (1)

Can I buy a cheap cat, pass emissions, then take it off? Or will a cheap one burn out before it clears the codes?

Steve Dallas

Cheap ones last around 6 months, so you should be able to swap it back and forth with a midpipe for emissions purposes. I did that for a few years, before I got sick of the stench. It only needs to be installed for between 50 and 150 miles before the codes reach ready state.

CelestialGryphon

iTrader: (1)

The BHR Midpipe has a great sound. I can't say that for any of the others because, well, I'm the only RX8 I know locally with a BHR midpipe. But I like it.

Nullpop66

I ordered a catalytic converter off of RockAuto. Probably not the best thing I could have done, but money is tight and it will last long enough before I can get a nice one. It's been shipped, and on its way. $221, real metals. Didn't bother to look at the cheap ones, lol.

Steve Dallas

^ Stay on top of it. If it clogs, it will damage your engine.

It is very important to maintain the health of your ignition system. Weak ignition is what causes most cat failures, although heat alone kills a large number of the less robust cats on the market.

BigCajun

iTrader: (1)

$221 IS cheap.
It probably won't last long.

Nullpop66

Cheaper*. Money is tight. When there's more, I will definitely buy a better one. I have the part, I'm still waiting to get it up in. My engine light went away, and it's not acting weird anymore. Only rumbling in second gear. As soon as I find someone with a stand, I'm getting it put in.

xcape68

So my check engine light is on and I need a CAT.... if I replace it with the BHR will the check engine light remain on?

Steve Dallas

All cars are different, so it is impossible to say with certainty, but the cat BHR uses should be sufficient to pass the ECU's tests. If you think you need a cat, have it inspected for clogging IMMEDIATELY! Clogged cats kill engines very quickly.

Edgar Gonzalez

So I own a Mazda rx8 2004. The car died out on me because of low fuel. I recently replace the fuel pump, ignition coils, spark plugs and the catalytic converter.
Well I got the car running but it had a burning smell. I looked under the car to see that the cat was glowing red. I popped the hood and smoke was coming from the dip stick reservoir. I pulled the spark plugs and noticed that the new ones I just replaced were covered in rust and debris. If anybody can point me in the right direction it would be greatly appreciated.