Hay all. I've been looking at 300cpi cats on eBay. What brands are any good on there anyone tried? Cheers Kurt.

got a 100CPI Cat, sounds awesome when u got the foot to the floor

and silent as stock when you come off

You'll find that 100cpi is actually illegal in most states. It is actually quite loud - especially when its mated to a upgraded muffler.

Get 200cpi or higher. There's a few of them on ebay for only $160. Add on $150-200 for installation if you want flanges. Few members have fitted the ebay ones with sucess - TreeAdleyMan has bought from "Scotts Rods" and he's happy with its performance. I will be buying from that ebay seller as well. Will update with the outcome.

200cpi venom cat off ebay for just under $200 is what you need. i have the 100cpi version. and it is great. the 200cpi flows well and still keeps to reasonable emissions. volume won't change much.

ive got the Scotts Rods 100CPI 2.5", could be happier with it, and has still tood up with bits of the flex joints in it :)

This is the Scott's Rods one I have:

200 CPSI METAL CATALYTIC CONVERTER HIGH FLOW CAT 2.5" (http://www.ebay.com.au/itm/200-CPSI-METAL-CATALYTIC-CONVERTER-HIGH-FLOW-CAT-2-5-/110600933700?pt=AU_Car_Parts_Accessories&hash=item19c0545144)

200 CPSI (so legal) and 2.5" (right size to fit most Magna exhaust systems).

$159 and free postage, what's not to like!

Ring Scotts Rods for a Price fitted - you wont be disappointed - One excellent Tradesman....

I've used the magnaflow cats - 200 CPI, with no issues or problems at all.

Anyone no of any good 300cpi metal cats??

Anyone no of any good 300cpi metal cats??


Why are you specifically after a 300cpi one? Surely the whole point of getting a highflow cat is to get a high flowing cat? Are you worried about emissions or something?

Anyone no of any good 300cpi metal cats??

200 cpi cat is sufficent for 3rd gen magnas to pass emmisions tests.

If you want a 300cpi cat then you may as well buy an OEM cat with flanges to replace what you've got. And unless your current cat is on the way out then I doubt that you will notice any difference in performance.

This is the Scott's Rods one I have:

200 CPSI METAL CATALYTIC CONVERTER HIGH FLOW CAT 2.5" (http://www.ebay.com.au/itm/200-CPSI-METAL-CATALYTIC-CONVERTER-HIGH-FLOW-CAT-2-5-/110600933700?pt=AU_Car_Parts_Accessories&hash=item19c0545144)

200 CPSI (so legal) and 2.5" (right size to fit most Magna exhaust systems).

$159 and free postage, what's not to like!

So this would fit my TJ vr-x just fine?

So this would fit my TJ vr-x just fine?

Yep, can't see a problem.

It's a cut & weld job anyway to replace the cat.

Yep, can't see a problem.

It's a cut & weld job anyway to replace the cat.

awesome thanks, might just have to get me one haha

so what's the advantage of a 100CPI cat to a 200CPI cat ?

And also, 3" or 2.5" cat ?

About to buy but not sure which one to get in terms of size and cpi ?

so what's the advantage of a 100CPI cat to a 200CPI cat ?

More high flow but difference is unnoticable.
2.5 inlet and outlet Dan. cat size apart from that doesn't matter...

Anyone no of any good 300cpi metal cats??

More cells = more restricted exhaust flow. 100cpi is race track spec and illegal on the road. 200cpi gives improved flow and will pass emission control legislation.

Sorry would this Cat suit my TW AWD 200 CPSI METAL CATALYTIC CONVERTER HIGH FLOW CAT 2.5"

No aftermarket cat converter will bolt straight up. Generally speaking, cat's are not specifically for certain model cars.

A 200cspi cat is much smaller in length than the standard cat so it needs to be extended with some 2.5" steel tubing. It'll need to be welded up. It's best done by an exhaust shop however if you know how to weld then you could do it yourself I suppose.
I opted for having it done by a exhaust fitter for a whole $50. I also had flanges fitted up so the cat is removable. Sounds nicer and engine is more responsive.

*thread mining* how great are the benefits of a high flow cat from the stock one (tw vr)? does it change the overall sound of the exhaust? does it help fuel eco?

On a stock VR-X system, it makes a slight difference in sound and didly squat difference to fuel usage.

For me it was more of a cheap cat replacement as the factory one is very expensive to replace. The hi-flow cat added a bit more in-cabin noise and the exhaust had a slight bit more of a growl - esp under high rev's. Nothing to sing home about but it was a nice note. I've got a video somewhere on how it sounds.

I don't think you find a definitive answer with actual proof.

If your stock cat is stuffed you will get some benefits, against a good condition factory cat benefits not enough to be noticeable in my opinion.

Sound..high flow cat I fitted made a noticeable difference in noise levels, enough of a difference that I fitted an extra resonator first chance I got (my exhaust was loud already though).

oh i see, might just wait until my stock cat has had it then

Cat converters get partially blocked throughout their lifetime. Having a full metal replacement rather than the ceramic one you have will more than likely have some performance benefit. No more than 2-3kw but anything that reduces restriction is helpful.

Waiting until yours is dead is a bit of a moot point. Once it is "dead" the car will become absolutely horrible to drive. Replace it now, there are a few floating around for about $100 or so, just buy full metal. Call up a few exhaust shops and one of them will be bored enough to fit it for $50 or so.

How much of a difference would a high flow cat make on a car with extractors + exhaust + tune?

Depends on how much work your original cat has had. Say if your car has 300,000km on it (which is at the top of the scale) then your cat may only be functioning at 50% its capacity (for example). In this case you could earn yourself a 5kw gain (again as an example). If your car has only 100,000km then the cat may be functioning at 80% efficiency, and you could only get a 2kw gain. It needs to be kept in mind that cat converters block over time and km, how blocked your cat is will change the gain that you could experience.

A high flow full metal cat brand new will work at 150% the efficiency as the stock one (for example) which reduces restriction, changes exhaust note and adds power and possibly torque.

As a rough guide, for an average car with an efficient cat on there now and a high flowing exhaust with extractors, expect 2-3kw atfw and 1-2nm of usable torque.

This is how my exhaust guy with 25 years of experience with exhaust systems has explained it to me. It needs to be taken into consideration that the magna cat is not generally considered as problematic for exhaust flow, and is in itself an efficient unit. Ask the 380 guys what gains they get from deleting their pre-cats and adding a high flow unit. You might be surprised.

is there a way to check the condition of the cat. i mean my car only has 80,000km, so i assume it would be in reasonable condition.

Most likely. Without significant engine modification the cat wears very slowly. Just make sure there are no dents on the unit, as this could indicate cracks in the ceramic material inside, which would warrant replacement.

Thanks dreggzy. Will keep on eye out

I think you can check the temperature of a cat too, and the hotter it gets the worse condition it is in. Not sure how accurate this is, just heard it from someone

I think you can check the temperature of a cat too, and the hotter it gets the worse condition it is in. Not sure how accurate this is, just heard it from someone

Correct. When the cat converts the gases, it also cools them to a degree. When the cat is not working at its full capacity, it will overheat, therefore causing restriction and increasing harmful emissions.

Even though I did hear about this I remember a particular instance where an exhaust place checked the temperature of cat and said was fine, however upon removal it was visually in poor condition. Once a new cat was fitted the car performed much better

What really? i thought i cat was meant to be the hottst part of the exhaust? Thats why my hi-flow car smeels like shit when the car is cold and the car smells normal after its been running for a while.

What really? i thought i cat was meant to be the hottst part of the exhaust? Thats why my hi-flow car smeels like shit when the car is cold and the car smells normal after its been running for a while.

Also true, due to the cat cooling the exhaust gases, it gets hot in itself.

Its when this heat goes above acceptable levels that the cat needs to be replaced.

Typically the "hottest" part of the exhaust will be inside the manifolds as hot exhaust gas hits the cast iron.

With your car at operating temperature, touch your extractors for 3 seconds with your left hand and then your muffler with your right. See which hand needs more skin grafts. (DON'T ACTUALLY DO THIS!)