I gutted the cat from my OEM midpipe yesterday.
 

There was barely any increase in sound, I was shocked! :Eyecrazy:

The increase in power was very noticeable and its not all in my head so it must be significant. Gotta love free horsepower!

The only problem I am having is when I let off the gas my exhaust system pops. If I am accelerating and I let off fast it sounds like a gun shot!

I thought if I recirculate my BOV it would solve the problem but it only helped a little.

What can I do to solve this issue?

beware of the flair my dude..its normal...no cat..=flmaes

crunk sed it

So this is normal?

Damn, I had no idea. lol

Hate to be the bearer of bad news, but gutting your cat actually loses power it's been dyno proven by lots of people. But the popping is normal without a cat.

no.

and especially not when turbo.

Where is the proof?

Import tuner and Car and Driver have dyno graphs to prove otherwise.

It causes turbulence in the exhaust stream, blocking more flow than it frees up.

loses power? im callin shenanigans until i see some info's

so you are saying that if you take an obstruction out of an otherwise SMOOTH pipe there will be MORE turbulence?

ok bill nye.

btw, which one of us has seen the inside of our catalytic converter? :uhh:

http://www.importtuner.com/tech/impp...ion/index.html

Here's a link.

The pipe isn't smooth, You hollow out the cat which is a larger diameter than the rest of it, the exhaust gas is allowed to expand in that area then when it's forced back into the smaller diameter pipe causing lots of turbulence.

I've seen the inside of a lot of cats, what's your point?

You can't really compare a miata to a turbo rotary. :uhh:

i've heard this as well.

My N.A. pops a couple of times when I let off of the throttle. As far as I can tell the cat is still in good shape.

gutted my cat and picked up 20 hp on my turbo setup.
So .....

That's about how much my butt dyno tells me too. :lol:

Well I may be wrong about it on turbo cars but there are exceptions to every rule. I want to see proof, your butt dyno doesn't mean anything. Lets see your dyno.

I see a lot of people telling me I'm wrong but no one has any proof to show me the contrary. That's all I'm asking.

And either way gutting your cat is for Honduh drivers.:lol::lol::lol:

all race cars have no cat i belive

First, that would probably depend on the rules of the racing league. Second, if they didn't have to have a catalytic converter, I seriously doubt they would take the stock cat + resonator combo and gut the cat. There are quite a few different RX-8 test pipes out there for a reason...

I never said having no cat causes turbulence. I know that some race cars don't have cat, but they have a proper race pipe. Like Zeon said they wouldn't just ghetto rig it up.

Gutting your cat yields more power because it eliminates an airflow/exhaust restriction. Every schoolboy knows this.

I would bet the exceptions are people who have chunks of partially melted honeycomb in their "gutted" cats.

The turbulence argument makes some sense, but would the expansion of the exhaust cause more restriction than the honeycomb. Going catless is like saying FTW, but getting more power is a beautiful thing > : )

No butt involved, butt a DynoPak was.. :)

The stock tune is rich, to prevent the cat seeing peak temperatures.

So it uses more gas, for less power, 'for the environment'......

If you tune the car for max economy OR power, the cat has got to go - burned out, gutted or replaced - keeping it is not an option.

S

I'm not a scientist, and I am not going to try to act like I am right either way, but honestly, thinking about the expansion/compression causing more turbulence makes sense to me in a way. I mean, when you think about, if the pipe gets wider, there will be a pressure drop - and then when it gets smaller again, there will be a pressure increase. Thus if you have a big empty chamber in the middle of an otherwise constant diameter pipe, it could increase back pressure. However, if you keep that flow going at a constant velocity, it will not create pressure drops within the pipe. Every race pipe I can remember seeing has been of a constant diameter - that isn't coincidence.

Again, I'm not saying I know all the answers, I'm just trying to think back to some of those horrid fluid mechanics labs I had to do as a junior.

thinking about the expansion/compression causing more turbulence

The point is not "is there a restriction?"

- obviously the diameter change will affect the flow, but even with the catalyst intact, the gas still has to expand then recompress......

The question is "is the empty chamber more restrictive than the SAME cavity filled with pounds of ceramic" to which the answer must be no.

S