What is the best high-flow cat and where can i get one? I'd love to eliminate the cat but won't b/c of warranty issues. Thanks guys.

 

I don't think that the warranty will be effected by no CAT anymore than a HF CAT. Neither is stock....and they will probably treat the change from stock to either the same.

 

Both are warranty voidable items. But the straight pipe will probably check the CEL light. The best hi-flow cats out there right now are the SR Motorsports & RP Motorsports units.

 

Which is quieter? The SR motorsports or RP motorsports unit?

 

Why would a high flow cat void warranty? More precisely, on which part? Only the catback is after it.... so logically it could somehow void the warranty on the muffler.
Just curious...

 

One - it is an emissions item and any alteration to an emissions item violates the entire powertrain warranty and is a Federal felony.

Two - it is monitored by the PCM via an O2 sensor, so its presence or lack thereof will affect fuel delivery.

That said, I took mine out and replaced it with a test pipe when I only had 4k miles or so. No CEL or any other problems for that matter, but my exhaust sure is stinky!

 

Has anyone ever looked into trying expanding the exhaust diameter to fit a larger diameter high flow cat? It seems to me that a larger diameter would not only flow better, but be more efficient, and most importantly also lower catalytic temps allowing for better tuning and the car to not go into granny mode so easily.

... seems to simple though to actually work

 

Felony? Could you please point to the law that states that.

Also, a street legal cat can be used by a car owner as a replacement part. Car companies have different requirements or laws than individuals. That is to Mazda has to make the meet the new draconian Tier II requirements, but that doesn't mean a replacement part has to.

Now there is some speculation as to whether the part has to be damaged before the owner can replace it. Some say you can't touch the part unless you think/know it broken. Regardless, the law at that point is unenforcable. If you have to, damage your factory cat and put on an aftermarket street-legal version. For the RX-8 this is a very valid story since it is by far the lowest point on the underside of the vehicle.

The government (not necessarilly the EPA) is very leary of making a car manufacturer a sole source for a particular replacement part. (albeit, the factory cat is supposed to last the "life" of the car.)

So the entire powertrain is effected? They can deny me a claim on my transmission because I have a different catalytic converter? That is quite far reaching. (I will save the debateable Magnuson Aftermarket Bill of Rights for another day)

I am going to take a guess that that is against the law, but still not necessarilly a felony.

 

To meet Tier II the RX-8 cat HAS to be very thermally reactive. It has to heat up quickly. It is the cold start emissions that are the EPA's concern since this is about the only time the car ever actually pollutes any measureable way.

-Mr. Wigggles

 

Ah, true. It is a civil penalty to remove a CAT as the end user with a $25,000 fine.
As a professional, it is a felony.
Clean Air Act section 203(a)(3)

As far as violating the MM act, what is law and what is probable are two different things.
It is cheaper in the long run for Mazda to say your warranty is void and then wait for the law suit than it would be to do otherwise.

The reality is that removing the CAT does little if anything adverse to the drivetrain.

 

I would see why is unlawfull to remove it - but to change it to a high flow one should not be punishable. Plus, the RP one should be CARB certified soon... and as it retains the O2 sensor, unless you get a CEL, how can it damage the engine? But true, MNAO can claim whatever they want - they even told me that is normal for the car to shoot 200mL of engine oil in the air intake, causing the car to almost stall driving in traffic on the highway... How is that any safer than a high flow cat - beats me...

 

For a replacement cat to be legal, it would just have to pass the same emission test as the original one, that's all. It probbaly includes an ageing test. So it is quite costly.
A replacemnt cat (or no cat at all) will not damage the engine in any way. No cat might trigger a CEL if you fit the cat monitor HEGO back in place.

mazdaManiac, did you re-connect your cat monitor HEGO?

 

Exactly! a couple months after i got the car i hit a medium size rock and it made a pretty good clunk sound. I didnt immediately notice any damage, but recently i was checking the under side of the car after an oil change and noticed two big dents in my cat. It IS the lowest point of the car. My question is can those dents have messed up my cat? And how would i be able to tell that my cat is not normal.
And if it is "ok" could there be internal damage? Any thoughts on this is appreciated.

 

True, but idle startup egt's aren't that high (relatively) and have low flow- i'd think you wouldn't see much difference at idle/startup with a larger diameter cat.

 

The dimpled cat you see underneath is actually the heatshield, offset from the cats' body by about 3/8". So a sizeable ding on the outside could mean no cat damage, the cat body itself is fairly robust, solid steel, not thin like a muffler. The catalyst itself even has a ceramic 'wool' between the steel and the honeycomb.

That said, a really good bash will crack and powder the ceramic, no doubt. The first sign would be a CEL or chunks of cat rattling around in the muffler body.

S

 

Thanks, that is very helpful. I will keep a eye on it.

 

Yes, it is in the OEM location.

 

Yeah, your exhaust would stink b/c you are smelling the pure emissions from the vehicle that the cat would have caught. Just don't breathe them long cause you will pass out. It is illegal to cut the cat off but there aren't state emissions tests in Alabama (where I live) so many people do it regardless of what vehicle they drive. The thing is, I'd like to keep it becuase I heard one with the cat off and it had the weedwhacker on steriods sound and I detest that.

 

I had my car on a lift for the 1st time, and noticed a scratched heatshield and some exposed insulation. Does the Supercat come with its own heatshield, or is the old one reused? Please refer to the below 3 photos.

Underside

Scratch

Closeup