High Flow Catalytic Convertor?

[90blackcoupe]

I share the same thoughts as you. But I personally think that a free flow (no cat) cat is a loss in power (except in turbo applications). I ran one for a while and it felt way better with a CAT in place. And it will sound like shit lol. Thats why I said "if you don care..."

But ill tell you, those aftermarket ones suck in longevity compared to oem. They dont filter that great either.

I agree with you. After running a test pipe for 3 years finally came across an oem prelude cat for my h22a, put it in noticed a difference right away bottom end torque feels better, not stinky any more and best of all I passed emission legit.

[deevergote]

The bottom end feels better because of the restriction. That's one reason why a bone-stock Accord can feel torquier than one with a full I/H/E setup.

[90blackcoupe]

The bottom end feels better because of the restriction. That's one reason why a bone-stock Accord can feel torquier than one with a full I/H/E setup.

Yea that's true, I got my accord with the test pipe. Spent time finding the right cat, didn't want an aftermarket cause I know they don't last. Your right about the stock accord since it was tunned to run with whatever it came with stock, as oppose to modifying may result in loss of power since ecu is not programmed to run with the changes made. Its all about keeping that 14.7:1 a/f ratio for best power/efficency.

[MortsAccord]

If you gut a cat it shouldn't mak ethe car lose any bottom end at all. Theres nothing good about backpressure. People get exhaust theory messed up, what your overlooking is scavenging, and exhaust velocity. Thats why increasing the diameter of a pipe in your exhaust system increases power, but loses Tq in the low end, because the car cannont scavenge the same way it once did with the smaller diameter pipes.

Although certian manifold styles(log type) are never good and ANY 4-2-1 header type will be an improvement. A prime example would be a stock 99 mazda 626 header. It also has 2 CAT's in the system, one of them is imediately after the 4-1 merger, its actually closer to the exhaust ports than most people are able to mount turbos.


I have a gutted cat on my CD5, it really didn't change the noise at all. Its now just a resonation chamber/test pipe. Then again I have an Apexi WS2 siting on the end so being quiet is easy. My car has a knock off exhaust system on it with the shitbag muffler changed to a good one.

In the future.. http://www.mandrelexhaustsystems.com/servlet/StoreFront
this place has the pipe I'm going to use for a 3" exhaust system. We ordered pipe for my friends 626. Good bends.

[deevergote]

You clearly didn't understand what I said regarding gutting the cat.

[MortsAccord]

The bottom end feels better because of the restriction. That's one reason why a bone-stock Accord can feel torquier than one with a full I/H/E setup.

Did I misunderstand this?

My car doesn't stink either. I think some cars that have gutted cats(probably because they were clogged) burn a LOT of oil and that is the "eye burning stink" most people smell. Not the uncatalyzed exhaust.

Oil additives such as zinc, can cause cats to clog up if the oil leak is bad enough and the car is not driven for extended trips @ highway speeds/loads to burn it out.

[deevergote]

That comment has nothing to do with a gutted cat. Or a clogged cat. It is regarding the restriction a properly functioning cat provides. And yes, an exhaust restriction will provide greater torque at a lower RPM at the cost of high end flow. Exhaust flow velocity through a narrow space is high at low rpm, where it would not be with a larger, unrestricted exhaust. This is why our cars come with very small piping in comparison to "performance" piping.

My point about the hollow cat is that you end up with a chamber that causes turbulence. A hollowed-out cat will potentially cause more of a restriction than a properly functioning cat.

[MortsAccord]

And yes, an exhaust restriction will provide greater torque at a lower RPM at the cost of high end flow. Exhaust flow velocity through a narrow space is high at low rpm, where it would not be with a larger, unrestricted exhaust. This is why our cars come with very small piping in comparison to "performance" piping.

My point about the hollow cat is that you end up with a chamber that causes turbulence. A hollowed-out cat will potentially cause more of a restriction than a properly functioning cat.

Well you can't just say it will make more tq with that restriction. That's not possible. I believe it to choke the upper end so much that the lower end feels that it has more tq. When in actuality the low end tq is slightly less or identical, but the high rpms suffer so much its obfuscating whats really going on.

[deevergote]

I didn't say it MAKES more torque, it said it makes more torque available at lower RPM. That's why a car with a peashooter exhaust feels like it really moves from a stop, but it really can't get out of its own way when you wind the engine out.

[Losiracer2]

I had one of these on my H22 before I went to a larger 2.5" one....passed emissions fine here in AZ with the prelude engine and this on there


Random Technology Cat. Converter I got,

[wed3k]

I had one of these on my H22 before I went to a larger 2.5" one....passed emissions fine here in AZ with the prelude engine and this on there


Random Technology Cat. Converter I got,

california emissions are way harsher than anywhere else. saw a 04 accord fail the other day.

[shadowdlink]

I remember back then when I asked the muffler shop for a high flow magnaflow CAT.
A few things I picked up:
The car was noticeable louder, and the car did pick up some speed. But that was just the butt dyno back then. By going full exhaust the car really seem to pick up just a bit, though I'm not sure if you're willing to sacrifice ride comfort just to pick up a few horses.