cat converters

[Fozz]

hey guys

im about to run 2,5inch pipe on my car and was wondering if any other car had a cat that would bolt on or if u guys knew of a cat that flowed bettter that would fit ive been told by some people to use an r33 cat is this right?

any help is apreciated

cheers

[Jonny Rochester]

Do a poll. I am wondering how many people here even use a cat, unless they have a stock JDM car. But we should be using them, right?

[Fozz]

<div class='quotetop'>QUOTE (Jonny Rochester @ Dec 26 2007, 12:09 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=458480)</div>
Do a poll. I am wondering how many people here even use a cat, unless they have a stock JDM car. But we should be using them, right?[/b]

umm yer i thought ud get raped by the cops if u didnt have one so id thought id be safe and use one

[psi_72]

haha cat, what cat officer, i didnt see no cat :2thumbs:
technically we dont need cats as the 86 didnt come with one from factory hence, not needing one.

[Jonny Rochester]

But if your car is engineered to use a different motor, like 4A-GE for example, maybe it should be using all the emission stuff that engine came with? Which includes a cat. I'm not sure.

But if your using a 2.5" pipe, any exhaust shop can help you. Cats are a fairly generic thing to bolt or weld in place. The exhaust shop can do it in 10 min.

[Wanabe_Garage]

did the ADM model even come with a cat?

Mine did not have one and was road worthied as such. I guess they weren't nessesary in 1983...

[Gilly]

if you do a engine conversion the emissions control that engine utilise must be used. this means any 4AGE/ZE/TE should run a cat and charcoal canister.

20v = cat
16v = cat
ZE = cat

use it, fine is like 10K highly doubt anyone has been made to pay that though

this is for QLD

R33GTST cat has been proven to flow as well as most aftermarket 2 1/4 2 1/2 cats as has the AC delco items used on the LS1 commodores

[Fozz]

thanks for the replies

yer i didnt relise most ae / ke didnt have cats my car was imported so the last people installed a cat on mine but its puniy as so i threw it away

[parrot]

My 2 1/4 inch has a 'high flow cat' of some sort put on by the exhaust joint.

I think dunnydores use 2 1/2 inch so you may pick one up cheap from one of them.

[dr1ft-pig]

whats a cat????







:P


my car is too low for the cop to see whats under there haha

[slydar]

i dont have one but im putting one in. nice piece of mind to know its closer to being properly legal. also doesnt hurt performance and does muffle sound a little. less emissions is a good thing too.

pretty much all win.

no adm 86s came with a cat that all happened in 86.

[Gunner]

i have a special cat, unlike all of the conventional ones, mine has a 2.5" pipe instead of that ceramic honeycomb, works just aswell tho lol

and according to emission laws worldwide, all motors post 86 must run a catalitic convertor, excluding, comercial vehicles, these didnt fall under these laws till 96 i believe i may be wrong but its close to it, as for the fines my first one was $1500, second time is 5000, and the third is court from what ive heard, thats where the 10-15k fine comes in

[poh_86]

i got a toda dummy cat. works good

but you suffocate in the garage with a closed door

[86xxx]

Unless you're running a forced induction engine (4agte or 4agze) you require some amount of back pressure to acheive a decent amount of power. A high flow cat is a good way of adding just a little back pressure.

Running a 2.25" system on a 4age with a high flow cat, high flow muffler (resinator if you're fussy) will provide more noticeable power over say a 2.5" with no cat (or even with a cat) and muffler. Bigger exhaust is only better on forced induction cars, where you do not want any back pressure at all. I fitted a 2.5" cat back (with cat removed) system to my 3sge celica (2.0L) with single high flow muffler and the power it DRAINED from the stock system with very poor quality cat, resinator and baffled muffler was amazing! It was noticeably different, and in a bad way! Sounded hella good, went like shit though.

Personally i've found that the best sizing for cat is the next sixe up in piping, so on a 2.25 system a 2.5 inlet/outlet cat is best, more cross flow area for the emissions to work their way though. This is supported by the fact that all cars i have looked at, from Holdens to Porsches have this same theory, so it must work.

I'd seriously recommend NOT going 2.5" pipe on whatever your car may be, unless is a 20V that's heavily worked or a 4agze. 2.25" is perfect for NA 1.6L - 2.0L.

[Nikkojoe]

Im running a 2.25" exhaust with a 2.5" high flow cat (works well)

[Ke70alex]

<div class='quotetop'>QUOTE (medwin46 @ Dec 27 2007, 11:48 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=459071)</div>
Unless you're running a forced induction engine (4agte or 4agze) you require some amount of back pressure to acheive a decent amount of power. A high flow cat is a good way of adding just a little back pressure.

Running a 2.25" system on a 4age with a high flow cat, high flow muffler (resinator if you're fussy) will provide more noticeable power over say a 2.5" with no cat (or even with a cat) and muffler. Bigger exhaust is only better on forced induction cars, where you do not want any back pressure at all. I fitted a 2.5" cat back (with cat removed) system to my 3sge celica (2.0L) with single high flow muffler and the power it DRAINED from the stock system with very poor quality cat, resinator and baffled muffler was amazing! It was noticeably different, and in a bad way! Sounded hella good, went like shit though.

Personally i've found that the best sizing for cat is the next sixe up in piping, so on a 2.25 system a 2.5 inlet/outlet cat is best, more cross flow area for the emissions to work their way though. This is supported by the fact that all cars i have looked at, from Holdens to Porsches have this same theory, so it must work.

I'd seriously recommend NOT going 2.5" pipe on whatever your car may be, unless is a 20V that's heavily worked or a 4agze. 2.25" is perfect for NA 1.6L - 2.0L.[/b]
medwin these are massivley oversimplified concepts - as with most rules of thumb they are a god start point but quickly loose there relevence with some proper research and inquiries into proper production of power in both na and turbo

not disagreeing with you, just pointing out that oversimplification can cost you just as much horsepower as bad workmanship....


as for the on topic.... i have heard nothing that contradicts gilly in regards to queensland regsso id take that as gospel ;)

the metal cats from what ive researchd do well, and any of the gtr cats are a good score, though the older ones may not be that much chop....

[johnny_08]

hey is a hot dog a type cat?

[rthy]

cats = emissions
dogs = sound

i bought a 2nd cat once... it looked funny how it was hollow inside o.0.. ah pickapart

[rthy]

<div class='quotetop'>QUOTE (medwin46 @ Dec 27 2007, 12:48 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=459071)</div>
Unless you're running a forced induction engine (4agte or 4agze) you require some amount of back pressure to acheive a decent amount of power. A high flow cat is a good way of adding just a little back pressure.

Running a 2.25" system on a 4age with a high flow cat, high flow muffler (resinator if you're fussy) will provide more noticeable power over say a 2.5" with no cat (or even with a cat) and muffler. Bigger exhaust is only better on forced induction cars, where you do not want any back pressure at all. I fitted a 2.5" cat back (with cat removed) system to my 3sge celica (2.0L) with single high flow muffler and the power it DRAINED from the stock system with very poor quality cat, resinator and baffled muffler was amazing! It was noticeably different, and in a bad way! Sounded hella good, went like shit though.

Personally i've found that the best sizing for cat is the next sixe up in piping, so on a 2.25 system a 2.5 inlet/outlet cat is best, more cross flow area for the emissions to work their way though. This is supported by the fact that all cars i have looked at, from Holdens to Porsches have this same theory, so it must work.

I'd seriously recommend NOT going 2.5" pipe on whatever your car may be, unless is a 20V that's heavily worked or a 4agze. 2.25" is perfect for NA 1.6L - 2.0L.[/b]

no car needs backpressure, if a car gains mid range power with extra backpressure then the cam selection is wrong (too much overlap).

I personally used a metal cat, the smallest size was 2.5inch but I adapted it to 2.25 inch.

here is a picture of it:

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/148405.jpg



and in my system:

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/148404.jpg

[Todd]

nice pipes :D

[rthy]

thanks

thats thats over two weeks solid worth of work your looking at there! to do an average job is straightfoward, to do an as perfect job as possible by yourself is very hard indeed!

[MARKE70]

i recently put a decent exhaust on my GZE - 2.5 mandrel mild.

I thought wat the hell i throw a cat on, like slydar said doesn't hurt in anyway bar cost and it makes the car slightly more legal.

i bought a magnaflow stainless steel cat. seemed to be the "ducks nuts" of the cats.

So yer pick the car up drive home, park in drive way get out open gates to drive in turn around and notice like shiny glitter shit in the air behind my car like 20m high lol.

i thought shit thats weird oh well might just be little bits of the cat that blow out for first few ks of driving.

Driving to the next track day my mates were like dude there is a shit load of metal pouring out of your exhaust hey, i was like lol how weird.

Anyway got to the track pulled the muffler off to chuck my "track pipe on" and my muffler was like a big shiny heavy maraca. It was totally full of little bits of crystaly looking metal shit which i assume is that platinum coating or some shit?????

Is this normal or has my ducks nuts cat given way to the almighty GZE POWA!!!!!!!!!!!

[Gunner]

sounds like it

[MARKE70]

in that case warning to all DONT GET MAGNAFLOW LOL

[Gunner]

though an over retarded car will kill a cat

[86xxx]

<div class='quotetop'>QUOTE (Sam_Q @ Dec 29 2007, 09:48 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=459997)</div>
<div class='quotetop'>QUOTE (medwin46 @ Dec 27 2007, 12:48 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=459071)
Unless you're running a forced induction engine (4agte or 4agze) you require some amount of back pressure to acheive a decent amount of power. A high flow cat is a good way of adding just a little back pressure.

Running a 2.25" system on a 4age with a high flow cat, high flow muffler (resinator if you're fussy) will provide more noticeable power over say a 2.5" with no cat (or even with a cat) and muffler. Bigger exhaust is only better on forced induction cars, where you do not want any back pressure at all. I fitted a 2.5" cat back (with cat removed) system to my 3sge celica (2.0L) with single high flow muffler and the power it DRAINED from the stock system with very poor quality cat, resinator and baffled muffler was amazing! It was noticeably different, and in a bad way! Sounded hella good, went like shit though.

Personally i've found that the best sizing for cat is the next sixe up in piping, so on a 2.25 system a 2.5 inlet/outlet cat is best, more cross flow area for the emissions to work their way though. This is supported by the fact that all cars i have looked at, from Holdens to Porsches have this same theory, so it must work.

I'd seriously recommend NOT going 2.5" pipe on whatever your car may be, unless is a 20V that's heavily worked or a 4agze. 2.25" is perfect for NA 1.6L - 2.0L.[/b]

no car needs backpressure, if a car gains mid range power with extra backpressure then the cam selection is wrong (too much overlap).

I personally used a metal cat, the smallest size was 2.5inch but I adapted it to 2.25 inch.
[/b][/quote]

I beg to differ on this statement that "no car needs back pressure." I have found, through my own trial and error, speaking to exhaust shops and engine builders, and reading numerous engine building books that there is a fine line between too much back pressure and not enough. Getting this amount as close to perfect as possible is a fine art, and based of what i said in my first post, they are rough places to start.

Examples

1) My first car, ST162 3sge Celica (bless her soul lol) came standard with 2 inch system, cat at front, resinator and then baffled muffler on rear. Went quite hard. Me, being young and stupid, made (must say was a decent job fabbing it up) a cannon, more of an oval shaped one, not bad looking, fitted it and sounded brilliant and went just as well as standard. I must've been getting more stupid as time went by, as i bought some 3", yes 3 INCH, pipe and made the rear section from ust in front of the rear suspension under centre of car into this cannon muffler. Sounded like shit, went like a truck with a blown turbo (not very well at all!!), but looked trick as under the car :P took it (shamefully!) to the exhaust shop and had a hot box fitted and replaced the 3" with 2.25" from in front of suspension and went MUCH better! then got bored with that, made a full mandrel bent 2.5" 304 stainless system from where the cat was, back. Removed the cat and had 1x high flow Lukey race muffler on the rear, into droopy 3 inch tip. The best sounding car i have ever heard, better than a 4age revving its tits off, the resination was prime!!! Didnt go as well as the previous setup however, and after being defected for excessive noise (102dB) it was back off to the shop to have a set of extractors and 2.25" full system, high flow cat and sports muffler fitted. This was the BEST setup i had on this car, and proved to me that too big is a very bad thing as far as performance goes. Which makes sense if you think about it, without a slight amount of back pressure the engine is 'breathing' and 'exhaling' but as the exhaust valves are closing there is also more air getting out, thus resulting in a lesser explosion as there is less compressed air in the cylinder.

2) My current car, VY Storm Ute, 3.8L Ecotec V6. Factory headers, leading into single cat, had 2.25" cat back standard exhaust system through a front muffler and then a very boxy rear one. Was too quiet, went well though. Fitted a rear muffler, addeda bit of a bark, no affect on power. Too quiet still, removed front muffler, noticeable power drop, as well as revs surging between gears. (So basically cruising along, clutch in to change gears and where it use to drop in revs, this new found reduced back pressure is not providing the engine loading it once did to cut the revs, so they climbe 500rpm before dropping to the newly found gear''s revs. No, this is not incorrect driving, Bustin can vouch for that. :2thumbs: ) Had 2.5" cat back system fitted, front muffler plus rear resinator, no change in power but gain in noise and note. Researching with Sureflo (sydney exhaust maker, with in house dyno) i have found that extractors, into twin 2.25" through twin cats and x-merge, into twin 2" is optimum for the 3.8, he has dyno results of his wife's car with this system fitted and a number of others to compare to. Reason for difference in power, backpressure gained from the cross sectional area difference in 2.5" pipe and twin 2.25/2".

3) Les Walkden Rally Subaru WRX, now the main Subaru team in the Australia rally championship. Have found that optimum exhaust sizing for their vehicles is 2.75" (strange and rare size). Now this doesnt really fall into line with my statement of bigger is better for forced induction engines, but no expense would have been spared in finding this out, along with optimum shape and route of exhaust. I think this size may be required to produce max power but stay with in rally australia noise emission levels, im not really sure. But im going to still say that bigger is better with forced induction, its been proved over and over again for years that upping the exhaust sixe on a factory turboed car increases power and response, cant argue with the facts.

Last but not least, (if sam can show off his i can too :P) the exhaust i hand made to go on my 86. No cat fitted as yet, but not the bolt out section for where it will go. 3" mandrel bent 304 stainless system, all way from turbo. Hope you all a likey! :-)

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161871.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161872.jpg

http://i197.photobucket.com/albums/aa148/medwin46/Sprinter/18.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161874.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161875.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161876.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161877.jpg

http://i197.photobucket.com/albums/aa148/medwin46/Sprinter/PB200339.jpg

[Gunner]

with turbo cars, especially lower power cars (250-350hp) a 2.5 inch exhaust, compared to a 3" system, the 2.5 helps bring the car on power quicker. not always tho.

i know that usually a 3" will give good power and torque across the entire rev range, but yeah u dont see many of the big teams overseas running huge exhausts on lower power cars, like sprint and rally cars. all comes down to testing i guess.

medwin i want your exhaust.

[86xxx]

<div class='quotetop'>QUOTE (gunbz-r @ Jan 3 2008, 09:50 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=462672)</div>
medwin i want your exhaust.[/b]

You can buy it for $20k in cash, i'll throw in a free car :P

hehe

[Gunner]

lol mate i would if i could.