Knocking out HoneyComb

[robert112]

My friend and I want cheap powerupgrades and we are thinking of undoing our exhaust and bringing a screwdriver/hammer to the honey comb and knock that f#*$& sh#*($ right out...

I heard there's a 10k Fine on this and a 10kw peformance upgrade... 1kw for 1 grand... lol

anyway, any comments/thoughts before we turn into clowns and perform this act

[400kwgtr]

i read an article in zoom a few years back where they did a dyno run on a car, then they took the cat converter out and ran it again. Guess what total power gain 0.00 kw... $10000 fine for o kw... um

[wreckedhead]

i think knocking the honey comb out is only good for high performance cars.

[Abo Bob]

http://www.skylinesaustralia.com/forums/sh...ead.php?t=42940

[Bass Junky]

Don't do it.

Care for the environment.

Care for your wallet.

Buy a bleed value and up the boost for the same performance gain, or just buy a big arse cat.

Is it worth the risk?

[predator]

but it shoots flames..

[ed]

I thought a hollowed out cat caused turbulence in the exhaust system and gave no increase in power?

[cereal]

but it shoots flames..

damn straight!!! haha

if you really wanna hollow out your cat the best way to do it is to put a pipe through it...this will cause not turbulance & will also give the impression that it hasn't been hollowed out....unless you have to do an emissions test

[Cool Hand Luke]

The one on my RB20 180 was gutted, at was tested with the over rich stock ecu in and was told its fine and drive on... i dont think its a big deal if a few cars dont have them to be honest, seeing as how many race cars, bikes, trucks and everything else pollutes the atmosphere...

[Bass Junky]

I guess it depends on how fat your wallet is.

[WazR32GTSt]

My friend and I want cheap powerupgrades and we are thinking of undoing our exhaust and bringing a screwdriver/hammer to the honey comb and knock that f#*$& sh#*($ right out...  

I heard there's a 10k Fine on this and a 10kw peformance upgrade... 1kw for 1 grand... lol

anyway, any comments/thoughts before we turn into clowns and perform this act

myself also being a fan of CHEAP power upgrades i so DO IT!

just buy another stuffed cat and keep the current one you have as a 'spare' in case you get epa'd and have to change it before an inspection...

knock it out and buy some 3" / 2.5" pipe from an exhaust shop and whack it in, held by some spot welds or something

honestly just look at the thing and if you can tell me its not going to be a restriction with a straight face then i'll................

[dojobi]

I still can't work out why people do this. Is the environment really worth the pitiful 2kW you'll get?

[whatsisname]

Simply knocking out the honeycomb centre of a cat will probably result in less power, as the cat then becomes an expansion camber to help the exhaust gases slow down (takes time to fill the inside of the cat).

Replacing the cat with a straight through pipe, or fitting a straight through pipe (same dia' as rest of system) in the middle of it WILL result in more power. In the case of a turbocharged engine considerably more power!

Those of you who are all high and mighty about pollution of the environment, how often do you actually replace your cat? They have a very limited effective life. Once they begin to deteriorate the only thing they're good for is robbing power. NZ’ers don’t have to run cats at all – I'd rather breath the atmosphere in “Un zud” than Sydney!

[Pawley]

Matthew!!! tsk tsk tsk

[whatsisname]

I didn't say I don't have a cat Paul I do! It's just that "sometimes" I leave it on the bench in my garage

[hungry6]

The one thing ppls never mention is the general engine nore after gutting a cat. especially on a rb25 with a 3 1/2" exhaust

is the sound of the exhaust note. it is much angrier and clearer, althought ppls say it doesn't produce any additional power maybe true, but u want to produce the power as quick as u can not sometime this year.

[dojobi]

Those of you who are all high and mighty about pollution of the environment, how often do you actually replace your cat? They have a very limited effective life. Once they begin to deteriorate the only thing they're good for is robbing power. NZ’ers don’t have to run cats at all – I'd rather breath the atmosphere in “Un zud” than Sydney!

Well I know my cat was replaced when my car got complied, so I'd say it's still functioning quite well. What I was trying to get at was that I think we should try and do our best to cause as little damage to the environment as we can (especially since we drive performance cars). Possibly gaining a few kW for removing something that is probably still functioning quite well is a pretty questionable move to me.

EDIT: Just thought I'd add this - Removing it for the track or dragstrip I can understand, as you want to get that slight advantage and get a lower time, but to have it off all time I just don't get it.

[dan_the_man]

How much different will the car sound without a cat?

[WazR32GTSt]

if gutting the cat makes no difference, then why do people claim to 'fell the difference' when they go to a 'high flow' cat which (from what i have interpreted) is just a normal cat flanges but with a greater volume inside?

it ain't any bigger in diameter it must be less restrictive..!

conclusion drawn by me: if high-flow cats make a difference then so does gutting the cat.

bring on the disagreements!

[Cubes]

My old VL picked up 0rwkw also, I was told it was due to the cat not having a pipe welded through the center.

Its no good having that big hollow area where the gas has to fill then try to squeeze down again in to the diamater of the pipe. It creates back pressure.

+ it made a horrid tinny sound from the cat convertor after that, made the exhaust louder but there was no performance gain. I think thats maybe why it felt quicker but made no more power?!

I very much prefer the noise of a car with a CAT!