Choice between two Cat Converters
 

Hi Everyone,

I am split between two catalytic converters if anyone can help me. I have a 2004 Mazda Rx8 and the cat is finally dying. I am going to replace it with one of the two below (unless anyone can help me out with some third part in site). I would really appreciate the help if anyone is willing to take a minute to look into the two and let me know the differences or which would be the better buy. The cost of the two is not an issue.

1)
MagnaFlow DF Converter 23909: Advance Auto Parts

2)
Walker Direct-Fit Converter 55531: Advance Auto Parts

Of course the price of the two is different. But the lack of detail on both is killing me. I would really appreciate any assistance with this. I am tired of the getting the look when my car takes 10 seconds to start and I want to make sure I keep the engine good for as long as I can. I know this is a huge problem for keeping the engine working at top notch quality if it isn't maintained properly.

Again, Thank you for the assistance if you have an in site or recommendations.

Oh, and I am comfortable doing the work myself. Just not the welding.

There is a huge cat thread somewhere on here that covers those 2 options.

Are you sure your cat is bad?

Why does your car take 10 seconds to start? That doesn't sound like a cat problem to me...

https://www.rx8club.com/new-member-f...causes-249529/

I have been researching the checks for the systems and what occurs / what are the clues to what is bad. I have a ton of pressure before the filter and barely any pressure behind. So the cat is clogged for sure.

And thank you very much for that thread. That will come in handy in the future and now.. But everything is pointing to cat even the mechanic was saying the cat is a huge issue. Another mechanic thought that it might be time to replace the engine, but I am doing everything I can no to do that...

How are you measuring the pressure? That sounds suspicious as there is nothing in the ECU that measures pressure.


Your problem doesn't sound like a cat problem. If your problem is only when hot, get a compression test at a dealer. If it's all the time, replace your ignition.

I had a buddy drill a hole a very tiny hole and put a pressure gauge in when I started the car and let it run for a bit. The pressure before the filter was extremely higher than the pressure after the filter.

I hate the ignition tested twice. Both said it looks good.

Thank you all for the input. I really appreciate it.

By "filter" do you mean the cat element? (that isn't a filter at all)

I keep thinking air filter when you say it

Yes I am sorry. The cat element.

Gotcha. That is a great way to test the cat actually, i wish it was possible from the factory.

Would you happen to have any advise on which cat would be the best option? (The exhaust is also doing that spitting noise constantly when the car is idling which again leads me to the cat. I am going to take a video of the car idling lat this afternoon and upload it.) Oh and the low power at lower RPMs.

Since I personally hate cats, and don't think they should ever be on a rotary, I can't provide any positive opinion about any of them. Many burn out way too fast on top of the general distaste for them.

But perhaps this thread will help: https://www.rx8club.com/series-i-aft...s-cats-210330/

Thank you for the help!

Totally understand the motivation to fix the cat, but before making that investment you really should get your engine checked out. Hard starts are not a cat problem, they're an ignition or compression problem. If you had the ignition tested (how?), the compression is next. The spitting noise you mention has nothing to do with the cat either, if anything the cat would even out exhaust pulses, not create them.

That's not to say your cat isn't also bad, but the cat is something of a canary in the engine trouble mine. It doesn't clog for no reason.

I had a full check up on the engine. Replaced the ignition and made sure all cables and lines were good and in tact. The cat is for sure going bad, so before spending the money to replace the engine which I plan to do in a few thousand miles. I want to take care of this first.