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Hey guys,

I need a new cat for my road/race car. I'm not too concernd about noise as it's essentially a race car with road registration, and I generally only drive it on the road to bed in tyres, brakes and to the occasional track day.

What I am looking for is the least restrictive cat that is still legal to use on a "road" car. I've seen a few guys talking about the Magnaflow cats and seen mention of the Metal Cat ones, but can anyone give me some advice on these or others worth consideration?

Cheers.

Dunno how legal it is, but it is a cat.
Mine was called generically, a 100 cell Race cat.
It is very short and very free flowing.
The Magnaflow (high flow ) cat I had was 300 cell.(ie more restrictive)
Difference between either one of these, and the huge oem SE cat was very noticeable.

All I know about cats is go for the right number of cells for your application, and make sure the inlets match your exhaust diameter (many cats have too small inlets/outlets which cause restriction).
Note; Cats are worth money as scrap metal for the platinum in them. I am told there is between $20 and $150 worth in a cat.

I've been doing a bit of research to see if there are actually any legal requirements for catalytic converters but so far only found this:

Motor Vehicle Standards: National initiatives to reduce the harmful environmental effects of motor vehicles are coordinated by the Motor Vehicle Environment Committee (MVEC), which oversees research on motor vehicle emissions and prepares strategies that can be adopted by the government.

Emission standards for new vehicles are set by Australian Design Rules (ADR) under the Motor Vehicle Standards Act. The standards require that motor vehicles manufactured after 1986 must operate on unleaded fuel and have anti-pollution devices (catalytic converters) fitted. These initiatives have contributed to a reduction in lead levels and other pollutants in our air.

In July 1996, new rules were introduced to diesel vehicles sold in Australia to significantly reduce the quantity of emissions. Further emission reductions for petrol vehicles are required for all models manufactured since January 1997. New ADRs introduced in 1999 set out a program of emission requirements up to 2007, and complement the introduction of cleaner fuels.

And then this in regards to testing:

Motor vehicle air pollutants
For pre-1986 vehicles, the percentage volume of carbon monoxide should not exceed 4.5 per cent and 400 ppm (parts per million) hydrocarbons. For post-1986 vehicles, emissions should not exceed 2 per cent carbon monoxide and 250 ppm hydrocarbons. The reading for carbon dioxide will be quite high if the car is performing efficiently (around 15 per cent). Carbon dioxide contributes to greenhouse gases but is an unavoidable result of burning fuel.

Not sure how you'd find out about whether or not you'd pass the emissions test unless you voluntarily submitted your car for one.

At this stage looks like a 100 cell Metal Cat might be the go.

Is this for a turbocharged application?

If you read the fuji exhaust thread, theres information there from SMB regarding cats.

SMB recommend in N/A mx-5s their 200 cell cat, (high quality unit, but pricey)
They only recommend their 100 cell in a forced induction application.
Naturally, a 0 cell would be the best ;) - but illegal.

For reference, the Flyin' Miata cat is a 300 cell, so avoid that and look for 200 cells with the same inlet/outlet diameter as the rest of the system.

(unless you are forced induction, then look for 100 cells.)

It's not for a forced induction system but it will be a reasonably high out put NA application, somewhere around 170-180hp at the flywheel.

I'll have a read of the fuji exhaust thread, thanks.

T&C put a 3" metal cat in mine (don't know what brand tho). It's quiet enough. They recommended metal over ceramic for a registered track car cause of the number of times it gets thumped over ripple strips. Apparently the ceramic ones don't like it much. Last time I had the headers off I had a look in the cat. No broken bits inside but there were quite a few dents on the outside, so it looks like it might have been good advice.

the issue is going to be about noise level. If your neighbor dobs you in you can easily get a notice to have your car checked at your expense. A local radio presenter copped one of these notices and whilst his car was within limits there was a cost to test and a cost in the form of the time to take it to the test station. Harley riders seem to get away with noisy old bangers and you probably will get away with it even if noisy-you weigh the risk.

The whole system will still need to comply with Lakesides noise restrictions, so it won't be overly loud.

manga_blue wrote:T&C put a 3" metal cat in mine (don't know what brand tho). It's quiet enough. They recommended metal over ceramic for a registered track car cause of the number of times it gets thumped over ripple strips. Apparently the ceramic ones don't like it much. Last time I had the headers off I had a look in the cat. No broken bits inside but there were quite a few dents on the outside, so it looks like it might have been good advice.

This is true, there is really no reason to go ceramic, its just the cheaper alternative.

I have a Metal cat and 2.25"piping, offset pipe muffler exhaust and pod filter in my car. It was poping 92-93dB at the last lakeside event.

project.r.racing wrote:I have a Metal cat and 2.25"piping, offset pipe muffler exhaust and pod filter in my car. It was poping 92-93dB at the last lakeside event.

Sounds very similar to what I'll end up with, 200 cell or 100 cell Metal Cat?

TCR wrote:

project.r.racing wrote:I have a Metal cat and 2.25"piping, offset pipe muffler exhaust and pod filter in my car. It was poping 92-93dB at the last lakeside event.

Sounds very similar to what I'll end up with, 200 cell or 100 cell Metal Cat?

No idea. But the exhaust went very load after the installion of the cat. I can ask my mechanic tomoorow who does my exhasut work.

That'd be great, thanks.

the only disadvantage to a 200 or 100 cell cat is it will most likely cause your check engine light to come on due to the change in emissions.