16vCorey PowerDork
Feb. 20, 2014 3:37 p.m.

I'm going to be doing some work on my 944 soon, and I'm sure the stock cat is tired. I'm planning on using the stock exhaust but welding in a new cat and muffler. What's the best high flow cat for the price?

captdownshift Reader
Feb. 20, 2014 3:42 p.m.

I've had luck with the magnaflow OEM grade 50 state legal and bosal, any others I've used with monitors enabled have popped codes within 40k

FSP_ZX2 Dork
Feb. 20, 2014 3:42 p.m.

Magnaflow is what we used on the ZX2 when we were in ST class and had to run a cat.

Swank Force One MegaDork
Feb. 20, 2014 3:47 p.m.

I use a small Magnaflow spun cat on the Cherokee.

http://performance-curve.com/search.aspx?find=608396

This one. No real complaints.

Brett_Murphy UberDork
Feb. 20, 2014 4:33 p.m.

I was looking on Special Stage to see what they run. I'm not sure how they would work for ODBII inspections, but I figure if they can stand up to a rally car, they'll be alright on my beaters.

16vCorey PowerDork
Feb. 20, 2014 7:45 p.m.

I'm not worried about inspections, I just want something that flows better than a 30 year old converter that makes the exhaust less harsh. I've driven cars with no cat, and they always stink and burn my eyes.

novaderrik PowerDork
Feb. 20, 2014 11:15 p.m.

if you can smell the exhaust of a car without a cat, then you are either overly sensitive or the car needs some tuning.

Appleseed UltimaDork
Feb. 21, 2014 12:15 a.m.
Swank Force One wrote: I use a small Magnaflow spun cat on the Cherokee. http://performance-curve.com/search.aspx?find=608396 This one. No real complaints.

$64? Damn. I hope I remember this when I work on the P71.

impulsive Reader
Feb. 21, 2014 5:56 a.m.

I've run 2 spun cats from this company: http://www.thunderboltperformance.com/

passed emissions with them and I doubt you'll find anything cheaper. but in my experience the Magnaflow cats will last longer.

impulsive Reader
Feb. 21, 2014 5:59 a.m.
GameboyRMH MegaDork
Feb. 21, 2014 6:39 a.m.

I got some good suggestions in this thread:

http://grassrootsmotorsports.com/forum/grm/determining-ideal-catalytic-converter-placement/74398/page1/

Edit: Really just one:

http://www.randomtechnology.com/products.html

Feb. 22, 2014 8:47 a.m.

I used a Magnaflow replacement CAT on my wife's Sunfire 2.2

The gas mileage picked up considerably after replacing the factory unit around 120K

16vCorey PowerDork
Feb. 22, 2014 9:23 a.m.
novaderrik wrote: if you can smell the exhaust of a car without a cat, then you are either overly sensitive or the car needs some tuning.

Maybe I am, but the last two cars I've driven without a cat I could tell the difference pretty easily, and they were both bone stock with no running issues ('90 325i and a '94 Passat GLX).

Brett_Murphy UberDork
Feb. 26, 2014 7:51 p.m.

The Magnaflow cats seem to come in "OEM" and Federal grades. The price difference between the two is $50, and the "OEM" claims to have more catalyst. I'm going to take the chance on a universal fit Federal model for the RX-8.

Hal SuperDork
Feb. 26, 2014 8:16 p.m.
GameboyRMH wrote: I got some good suggestions in this thread: Edit: Really just one: http://www.randomtechnology.com/products.html

I have a Random Tech cat on my Focus. In fact it is one of the first 5 they produced in 2002. I have had no problems with it and it has passed MD emissions testing every 2 years since 2002. The first couple tests were on the rollers and OBDII since then.

alfadriver PowerDork
Feb. 27, 2014 7:10 a.m.

I wish they would tell you more details of the catalyts...

Are the "spun" one metallic bricks? The metal substrate ones do flow better than most ceramic ones, but also weigh a lot more, and cost a lot more for the base brick.

I've only seen round metallic bricks. All of the other ones would be cermaic substrates.

Even with those- it would be nice if they told you what the substrate was- 400/6, 600/4, 600/3, 900/2? It does matter.

If all the bricks were made the same, the more you pay, they should have more precious metals on them- Pt, Pd, Rh. all of which are above $1000/oz.

All of that matters depending on what your goal is. If it's to make a performance car smell a whole lot less, to the point of nothing- it's worth the money to spend on the catalyst materials. If it's just to use the rules and have a catalyst- if you can stand the weight, a metallic substrate is the way to go, but lower on the metals so that the exotherm isn't overly hot.

If you are on a budget- ceramic substrates work just fine. If you can manged to find a 600/3 brick, that would be the way to go. But being that most of the cheap one are 400/6, that's just what you get.

FWIW, there are only a couple of companies in the country that deal with precious metals, particularly making them into catalyst washcoats. Heck, there are only a few companies that even make the bricks. Which is another way of saying- most of the aftermarket parts come from the same places- even with a bunch of different names on them. The only part that can be done virually anywhere is the can on the outside.

Leafy
Leafy Reader
Feb. 27, 2014 9:33 a.m.
impulsive wrote: I've run 2 spun cats from this company: http://www.thunderboltperformance.com/ passed emissions with them and I doubt you'll find anything cheaper. but in my experience the Magnaflow cats will last longer.

Another +1 or the thunderbolts. Only like $30 and last 3 times as long as those piece of E36 M3 magnaflows, and pass OBDII emissions.

N Sperlo MegaDork
Feb. 27, 2014 9:47 a.m.

You can buy this guy for $100.

cdowd Reader
Feb. 27, 2014 10:34 a.m.

In reply to N Sperlo:

The cordless ones work better for a quick exit with your new cat.

N Sperlo MegaDork
Feb. 27, 2014 10:41 a.m.

I don't think it would be in the "budget".

Hal SuperDork
Feb. 27, 2014 2:49 p.m.
alfadriver wrote: I wish they would tell you more details of the catalyts...

I have no idea what the substrate in my RT cat for the Focus is but I can describe it. It looks like small scale corrugated roofing, more like the size for the corrugated middle section of cardboard. A sheet of that material has been rolled up like making a jelly roll and slid into the can and then the ends welded on. You can blow thru it and feel the air coming out the other end easily. You can also see a light shined in the other end.

It was installed on the car in 2002. It passed the roller/sniffer emissions test in MD twice before they changed to OBDII plug-in testing and has never set a code.

alfadriver PowerDork
Feb. 27, 2014 2:58 p.m.

In reply to Hal:

that would be a metallic substrate. don't know about the washcoat, but that would be one that flows quite well.

impulsive Reader
Feb. 27, 2014 7:39 p.m.
Heck, there are only a few companies that even make the bricks. Which is another way of saying- most of the aftermarket parts come from the same places- even with a bunch of different names on them. The only part that can be done virually anywhere is the can on the outside.

many moons ago(12+ yrs?) when I first heard of and purchased a Thunderbolt cat, the dl info was they were allegedly the same as Dynatech cats at a fraction of the price.

scottsrods None
Dec. 16, 2016 6:04 a.m.

Hi fellas, just found this thread on google and would like to ask something. I am in need of high flow catalytic converter and i was just looking at the ones presented at the link i made. But, it clearly states that they are all suitable for patrol engines and i drive an petrol Toyota. Is there a difference between the diesel and petrol ones or they are universal?

Dusterbd13 PowerDork
Dec. 16, 2016 7:01 a.m.

Im not sure if canoe or honest, as the link goes to a website that is the same as screen name.

The thunderbolt are what i typically use.

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