Catylictic convertors

your opinions please. For a turbo set up, using 2 1/2" piping is it nescessary to use a full metal cat? Will a high flow ceremic on be sufficient? And any recommendations on brand would be fabo.

Both my cars ran the stock Micra back cat. Throw the front one away.

yeah I've done that... I wuz thinking of buying a 2 1/2 " cat. to match the exhaust system when it comes......

Hi Fred, i think in the past most people with turbo cars have just used the standard Cat from something like a commodore/falcon/skyline that has a 2 1/2" exhaust as standard. Apparently they don't restrict flow that much, especially because they are so much larger than the standard micra one.

hmmmm.... I remember early on a commodore one was of choice anyone remember model #?

Generally vn v6. I just used an off the self hiflow ceramic on mine. I only had a 2in mandrel bent exhaust though. Not sure what brand the cat was.

I was going to get one off ebay but I might check the wreakers for a VN , hopefully in good nick and cheaper. Thanks for the opionions, troops. Just wondering Hack, using the standard cat with larger diameter piping did you flange down to cat entry size?

why dont you remove all cats. no restrictions at all then?

Four figure fine if you get court. The qld rta are know for carring gas analysers on there trucks

Australia is a bit of a police state, nice weather though ;) Good to see you around, snoopy.

Been fairly busy playing around with the new (old) toy. Between it, work & the army I don't get much free time these days.

4 figure fine?! that is harsh. i mean we would get a slap on the rist but cant see us getting fined that harshly. least your Country clean then eh lol

Yes flanged it down to fit Micra cat. If you look at the Micra cat inside diameter bigger than outside.Yes evidently the Commodore one is a good fit. I think Cisco at one time went this way?

i used a highflow cat, was 2 1/2 each side..cost me about $250 bucks.

it was a magnaflow/carsound one.

thanks guys.... it'll all go in the poohter and see what comes out the other end.

do you really need a new one? i have a spare micra cat converter in the shed and the inlet and outlet are 65mm or just over 2.5"

Alex

is that an offer?

Alex is saying the factory cat converter has 2.5" input and output standard.

The standard UK K11 cat converter is good enough for a 115kw SR20DE in a primera. I think its good enough for a 1.3L micra.

sorry! Thanks yom!

VN V6 commodore factory cat made by "AC Delco" with this brand stamped on it are the popular ones. You can pick them up for great prices too from a Holden spares place. They are known as the highest flowing factory cat that was made. Obviously just make sure its not shattered or anything inside it before you buy it. I think I got one for $70 or something. Two separate exhaust places told me that these flow as good as the aftermarket $200-$300 "performance" ones and if you can source one, then definitely grab hold of it.

I think there may be a bit of BS with all this "high flow" cat stuff. I'm not certain, but I reckon the diameter has to be the main thing, as the interior tunnel designs don't appear (just by eye) to be greatly different between models. I have always wondered whether its a standard fear they put into car enthusiasts to make them think they are losing power unless they buy an aftermarket "high flow cat".

That said, I destroyed 2 separate high flow cats (one was an expensive aftermarket one, cost me about $240 in 1999), the other was the VN cat. They both ended up shattering and rattling to pieces. Most likely due to the drastically different mixtures that blue monster was running compared to say a factory micra, plus it was pushing a lot of gas out the tail pipe through these things.. But I'm sure being 2.5" capacity they would have been more than able to handle the pressure from blue monster, they are designed for V6/V8s etc. I'd say it was more to do with mixtures and or vibrations/harshness or a combination.. My 2.5" exhaust ended up being reasonably rigid just due to the tight fit and how it needed to hang and be positioned.

I was advised to go for a metal high flow cat. These are immune to shattering and flow as good as you can get - probably equal to a well flowing normal cat. After that was installed, no problems whatsoever. That said, I sold the car a coupla months after it was installed, so I never owned it for long enough to know, but I'd say being metal you wouldn't have many issues. It was a bit more expensive, I think $300-$400, but after all the investment and custom stuff blue monster had, it was worth it just to avoid future hassles.

If I was ever to start over again with a custom turbo project, I would just immediately install a metal cat and be done with it. Those aftermarket "high flow" cars are too expensive to risk one shattering on you.

I'm pretty positive this is the case too cisco.

Better flowing = less friction. Ceramic cat converters work on the idea that friction = heat. So you make friction and this heats the ceramics up which burns away various parts of the exhaust gas. And when they get too hot (when there's extra fuel for comnbustion added like a really rich mixture with unburnt fuel) they can melt and break apart. Not to mention block and explode from unburnt fuel igniting inside the ceramics (fuel has a low flash point remember).


Metal cats work in the exact same way, except they're harder to block and can withstand much higher temperatures.

So the basic idea is that the more your cat converter flows, the worse emissions your car emits. Clearly the ADR's would not allow for this.

From my understanding anyway.