i had a 2.5" cat back put on my au and it has just started to rattle wen the engine is turned on for the first time in the mornings so i need another one... anyone know how much they are for a high flow??

hey mate, do a search, theres plenty of info on hiflows around, but my guess is around 200 dollars

about $200 or a bit more. know an zorst fitter well. if your looking for another 1 or 2 hp its worth every penny

well i got my 2.5" magna flow cat converter for 155 on ebay delivered.....it just needs piping and flanges so that will set me back about another 40.....so about 200 fitted probably.

remove the cat & shack the cuts out of it. if it doesn,t rattle then its not the cat. if it is, just get a AU cat from the wreckers for $50 bucks, hackling involved.

there are alternatives to a hi-flow tho which sometimes tend to be very over-rated

1) A good AU one will fit and they are just as good as a hi-flow one if not better.

2) If your willing to risk it you could do a custom job and get rid of cat and put a 2.5" pipe straight through from headers back and just put cat cover over top. If cops pull u up, there isnt much chance u will get caught, it just is a bit louder and tends to be a bit more fumey at the back. So thats an idea too if u dont care about environment too much and dont scared to run risk.. as cops wont really find it anyways unless they pull it off.

Personally id go the first idea b4 u fork out the cash for a hi-flow. Can get an AU one for about $40 from wreckers, a little cheaper then 200 for a hi-flow

option 2 can land you a $20,000 fine cant it?

sure can.

20k for a business but 5k for an individual
Get normat cat converted to 2.5' inlet and outlet flanges thats all most high flows are

still 5k isnt worth it

nah no way not for what you pay for a high flow or reflange on exsisting cat.

i gave him the choices, I said personally I would go with a) lol

move to NZ and just take it off.

see i can't see how people can get anal about the pollution when most other countries don't require cats. if your goin to tell A from australia he's a p3nis for not running a cat what would you say to B from NZ that doesn't require one ? the only reason cats are law in nsw is because of the amount of cars on the road and if every one of them didn't have a cat then there might be some negative effect on the ozone layer.
The vast majority of people having cc's in their car are covering the minority of them not having one.
A gutted cat might sound better but the straight through pipe will give you performance gains. putting a shroud around a 2.5" pipe is a dead giveaway when you hit it and it sounds like a china bowl.
gut cats for diagnostic purposes & replace when funds become available. thats the idea. were not all out to destroy the world around us, too many people are doin a good enuf job of that already.
IMO cats are to counter poor running cars. if your car is running economically & efficiently there shouldn't be any need for one.
do you feel guilty every time you mow your lawn with your 2 stroke wipper snipper pouring out heaps of 2 stroke oil smoke out ? or your 4 stroke 'bogged & strugglin' (briggs n stratton) lawn mower ? or the dirt bikes out there that are 2 & four stroke wihtout cats, or the road bikes or commercial vehicles without cats ?
do you say a prayer for them before bed ?
theres far more companies out there releasing deadly carconagenic toxins being solid liquid & gas from factories around the world that are umpteenth greater than that of an ecomomically, efficient running 4 stroke cumbustion engines.
get a high flow if you want to comply it's the bottom line. if you think you will get away with it do what you want then it's your own fault when you get caught. people need to be informed & make an educated descision that suits their own particular application. if you can't make that desicion yourself then you need a mechanic. or to do some research.
you could ask for an opinion on here, get 5 different ones & do which one you think would suit you best, that derides the point of asking for help in the first place. only you can decide what you think is right, then if it's wrong you only have yourself to blame. hence why you can't get cats removed or gutted from an exaust shop, but if you know them well enuf they recommend doing it!
try different things, do some R&D then you will know for SURE whats best for your particular application.
getting a car to go well is about a good balance, not bits here and there.

Ok here i will write out a quick sumary of CC's as to a document i have found in amongst Jamin's car research...
Firstly he states that a catalytic convertor only provides an environment where a chemical reaction takes place, in which toxic combustion by-products are converted into less toxic gasses. Still toxic tho.

2nd point - according to statistics 10years of ALL cars runing around without CC's on would amount to about the same amount of polutions and toxins as wat is created in the manufacture of these CC's (damn good point

3rd point - The requirement for the engine to run at the stoichiometric point means fuel economy is not as good as that of a "lean burn" engine running at a mixture of 20:1 or weaker. This increases the rate at which fossil fuel resources are consumed and the carbon dioxide emissions of the vehicle. (best point of all i personnally believe!)

4th point - Catalytic converters are estimated to account for 50% of total nitrous oxide (dinitrogen oxide, 'laughing gas') emissions to atmosphere. While N2O emissions in these concentrations are not harmful to human health, it is a potent greenhouse gas, accounting for around 7% of the overall greenhouse effect despite its small concentration in the atmosphere.

5th point - catalytic convertors dont work with leaded cars as catalytic poisoning occurs (not sure how relevent these days it is)

He then concludes in the negative section by stating this:
I can only conclude that catalysts have reduced toxic emissions and the incidence of smog at the expense of increased global warming.

Now positive:
Roles of a catalytic convertor:
1. Reduction of nitrogen oxides to nitrogen and oxygen
2. Oxidation of carbon monoxide to carbon dioxide
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water

This only efficiently happens when the catalytic converter receives exhaust from an engine running at the stoichiometric point. this is 14.7 parts oxygen to 1 part fuel, by weight(important).
If an engine could be held at the strict stoichiometric point for the fuel used, it is theoretically possible to reach 100% conversion efficiencies.(i dont believe possible tho as there are too many variables)

Jamin then has some diagrams and formulars i wouldnt have a clue wat they mean so ill just type up his last statement. Dont ask wat it all means lol.
CC's are designed to reduce combined NOx+HC emissions from 12 gram/BHP-hour to 3 gram/BHP-hour or less.

I hope this helps as a kind of neutral third pary opinion all though i tend to get the feeling that Jamin was leaning towards the negative sides to having a catalytic convertor.

I personnally feel that for legal reasons they should be on there. But reading the pro's and cons i think that a CC is more of an engine restrictor
and a kill joy rather then an environment saver. Just a few thoughts for you all anyway