Back fire + exhaust modifying question

[Tagged]

Hey guys, got two questions today.

First one is that my car seems to be back firing a lot more than before, could there be anything wrong causing this?

As to the exhaust question, a friend told me that theres this "thing" in the exhaust which filters out the carbon or whatever that pollutes the air. And this things being there restricts the air flow of the exhaust, if I get rid of it the car could gain 5 to 10 hp. The down side is that this is illegal?

Can any1 confirm the above for me?

Thanks guys

[Malcolm]

The thing your mate is talking about is the catalytic converter. It oxidises carbon, carbon monoxide and unburned hydrocarbons into carbon dioxide, significantly reducing the nastiness of what comes out your tailpipe.

Assuming the vehicle in question is the AE111 in your avatar, you wont see more than a couple of HP unless it's very rooted/blocked.

[RobertC]

4age 20v backfire lots I wouldn't worry about it.

Your mate is referring to removing the catalytic converter and replacing it with a straight pipe.

On a 20v you might gain 1 or 2 hp but certainly not 5-10. Will pass a wof fine with a de-cat.
Will make the exhaust note bit raspier.

If you have got money to burn get a high flow metal cat which is nicer to the environment.

[gt4dude]

After a certain amount of kms it becomes ineffective doesn't it?

Someone who owned my car previously smashed out the cat, we noticed when it came off for a new downpipe

[Tagged]

lol 1 to 2 hp....I wouldn't bother than. And I like the stock exhaust a lot more than most of the aftermarket ones anyways.

Thanks guy for your answer

[gt4dude]

yeah definitely 4age sounds better through a muffled system than through a free flowing system.

allthough... I've heard with the right stuff in the exhaust line, you can make an altezza sound grunty and eliminate those infamous altezza sounds.

so if it can be done for an altezza...

[gt4dude]

it's some combination like 2.25 or 2.5 straight through with 2 or 3 cobys and barrel muffler on the end or some shit.

4age already comes with adequate headers and a decent exhaust size

[Malcolm]

After a certain amount of kms it becomes ineffective doesn't it?

Yep, they degrade over time, not sure to what degree or how long it takes before they become ineffective, but newer cars degrade more slowly than older ones