Recommendations on high flow cats wanted.

PinkieT

Well-Known Member
Joined
Jun 22, 2015
Messages
2,471
Reaction score
938
Location
Cleveland
I scored a deal on an off road 2.5" x-pipe and a Flowmaster 2.5" catback system to go with my BBK shorties when I do the PI head and intake swap on my 98 GT. They do an OBDII e-check where I live so I am going to buy a pair of catalytic converters. No, not interested in running no cats with MIL eliminators, or gutted cat bodies. Just recommendations on cats, please. I see a crapload of off-brand "racing" units on eBay for cheap, but don't know if I should trust them. Leaning towards Flowmaster 2220125 cats right now. Any other recommendations on a high flow cat for a mildly modded motor?
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
32,383
Reaction score
5,557
Location
Evansville Indiana
I got mine YEARS ago on a craigslist score of a lifetime for a magnaflow high-flow x that didn't even have a scratch on it $100. It has held up well but I would expect that for a big name like it was. I too am not sure I would trust cheap cats....
 

FivepointSlow

Well-Known Member
Joined
Oct 22, 2013
Messages
2,646
Reaction score
60
Location
Enfield, CT, USA
Even the stock replacements from Walker are 2 5/8 so that would be a high flow. No?
Stock cats are usually a honeycomb design, not sure what our stock ones are but I imagine just that.
High flow cats are usually straight through designs and are optimized for gas flow, unlike stock cats.

That being said I ran flow master high flow cats on my Crown Vic after my stocks kicked the bucket and I liked them but I wasnt pushing a whole lot of power to really get a huge difference out of them. Usually at stock power levels stock replacements are just fine but if you wanna future proof that cant hurt either.
 

evilcw311

Most Evil Member!
SN95 Supporter
Joined
May 9, 2010
Messages
7,456
Reaction score
2,134
Location
Louisville, KY
Never buy cheap cats. Had a muffler shop do that to one of our work vans once. Couple months later can woudnt run. Found out the cheap cat had melted inside and completely blocked the flow


Sent from my iPhone using Tapatalk
 
OP
OP
PinkieT

PinkieT

Well-Known Member
Joined
Jun 22, 2015
Messages
2,471
Reaction score
938
Location
Cleveland
Thanks, all. The Flowmasters are $56 bucks each at Summit. Not going to purchase for at least another week, so keep the ideas a'comin!
 

cobraracer46

Active Member
Joined
Apr 22, 2013
Messages
358
Reaction score
10
Location
BFE
Any other recommendations on a high flow cat for a mildly modded motor?

"high flow cats" is a common marketing term and I would argue that the factory H pipe is hard to beat. In other words, I would save your money and just stay with stock.

Here is what Kenne Bell has to say about "high flow" cats:

"MUSTANG CATALYTIC CONVERTERS.
SHOULD I REMOVE, GUT OR REPLACE WITH HI-FLO CATS?

In our opinion NO, NO and NO! Removing the cats is illegal in all 50 States as doing so pollutes our environment. Ever close your garage doors and smell exhaust without cats. You won’t like it. All because some “think” there’s big HP gains in them.

Most important, we’ve seen “0” HP gain even at 775RWHP (387.5HP per cat) with our own ‘05 Mustang test car. See “Header, Cat, X Pipe & Exhaust Tests” in Ford Tech section.

EARL’S AUTOMOTIVE
Also “0” HP (stock vs. gutted) Earl’s Kenne Bell supercharged 700HP “First Cobra in the 9’s.”

ST MOTORSPORTS
Ran back to back tests at 600HP and 700HP. Gutted cats vs. stock was “0” HP on their ‘06 Mustang.

KARL’S EAST COAST SPEED
827HP Shelby. Headers, 3” x pipe and no cats. 2HP!

“Hi Flo” cats? Really? Show us your flow tests. HP tests. Our 1000HP air flow bench reads 407 cfm stock and 549 cfm gutted and no HP gain at 775RWHP. Besides turning on your engine light, gutting or removing cats has another drawback – the exhaust gets raspy (noisy).

Still want to gut those cats – or buy some “Hi Flo’s?” We welcome any magazine to come to Kenne Bell and test back to back on any Mustang – ours or theirs. We’ll hook up the data logger and record back pressure, air flow, temperature, etc. and, of course, HP with and without cats. All at no cost – IF it’s printed in a magazine. And we promise the tests won’t be skewed by changing ignition timing, AF ratio, pulley (boost), x pipe, headers, exhaust etc. to increase HP. You know how that can go. “Cats and a tune,” Cats and a pulley,” “Cats and cat back . . . “ Just a typical Kenne Bell back to back cat test."
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
32,383
Reaction score
5,557
Location
Evansville Indiana
"high flow cats" is a common marketing term and I would argue that the factory H pipe is hard to beat. In other words, I would save your money and just stay with stock.

Here is what Kenne Bell has to say about "high flow" cats:

"MUSTANG CATALYTIC CONVERTERS.
SHOULD I REMOVE, GUT OR REPLACE WITH HI-FLO CATS?

In our opinion NO, NO and NO! Removing the cats is illegal in all 50 States as doing so pollutes our environment. Ever close your garage doors and smell exhaust without cats. You won’t like it. All because some “think” there’s big HP gains in them.

Most important, we’ve seen “0” HP gain even at 775RWHP (387.5HP per cat) with our own ‘05 Mustang test car. See “Header, Cat, X Pipe & Exhaust Tests” in Ford Tech section.

EARL’S AUTOMOTIVE
Also “0” HP (stock vs. gutted) Earl’s Kenne Bell supercharged 700HP “First Cobra in the 9’s.”

ST MOTORSPORTS
Ran back to back tests at 600HP and 700HP. Gutted cats vs. stock was “0” HP on their ‘06 Mustang.

KARL’S EAST COAST SPEED
827HP Shelby. Headers, 3” x pipe and no cats. 2HP!

“Hi Flo” cats? Really? Show us your flow tests. HP tests. Our 1000HP air flow bench reads 407 cfm stock and 549 cfm gutted and no HP gain at 775RWHP. Besides turning on your engine light, gutting or removing cats has another drawback – the exhaust gets raspy (noisy).

Still want to gut those cats – or buy some “Hi Flo’s?” We welcome any magazine to come to Kenne Bell and test back to back on any Mustang – ours or theirs. We’ll hook up the data logger and record back pressure, air flow, temperature, etc. and, of course, HP with and without cats. All at no cost – IF it’s printed in a magazine. And we promise the tests won’t be skewed by changing ignition timing, AF ratio, pulley (boost), x pipe, headers, exhaust etc. to increase HP. You know how that can go. “Cats and a tune,” Cats and a pulley,” “Cats and cat back . . . “ Just a typical Kenne Bell back to back cat test."

Do you have any examples of a comparison between a +20 yr old used cat and a new high flow?
 
OP
OP
PinkieT

PinkieT

Well-Known Member
Joined
Jun 22, 2015
Messages
2,471
Reaction score
938
Location
Cleveland
"high flow cats" is a common marketing term and I would argue that the factory H pipe is hard to beat. In other words, I would save your money and just stay with stock."

I have a factory 2.25" exhaust that is 21 years old, old enough to vote and drink whiskey in all 50 states. I am going with the shorties and 2.5" pipes all the way. The hassle of cutting the old cats off and putting them on the new X pipe would be more costly than buying a set of new Flowmasters. They would also neck down the 2.5" flow to 2.25" at the cats, which could only negatively effect flow.
 

trebor3170

Member
Joined
Mar 25, 2019
Messages
105
Reaction score
34
Location
Salisbury, MD
I'd say, just go with what gets you through inspection, is it a sniff test or just visual? and not worry about it otherwise. Here in MD, my neighbors son bought a 99+, that had an aftermarket h-pipe w/2cats, and it wouldn't pass inspection, even though on the eastern shore, only Queen Annes Co. has emissions inspection, but there is a visual, and his didn't have 4 cats (don't know if he had the CARB# or not). BTW, I have read the same reports that cr has, don't know what the difference would be with a 20+ year old cat, but I think the point is, a "high flow" cat really flows no better than an oem replacement.
P.S. my 95 still has the original H pipe w/4cats, although it is pretty much stock anyway:rolleyes:
 
OP
OP
PinkieT

PinkieT

Well-Known Member
Joined
Jun 22, 2015
Messages
2,471
Reaction score
938
Location
Cleveland
OBDII plug-in test on emissions. No sniffer, it reads codes. Visual check on the cats, but if it has one on each bank and passes the plug-in check I doubt if they would look for more.
 

OLD H2S

Well-Known Member
SN95 Supporter
Joined
Jul 4, 2015
Messages
1,190
Reaction score
230
Location
Silver Spring Maryland
They are all made to the same internal grid spec. or they would not work. The only way to increase the flow is to increase the in/out openings. Going from 2 1/2 opening to 2 5/8 opening is massive increase in flow CFM.
Remember this engine only flows 500 CFM at 5000 RPM and that is with the heads off.
 

DKblue98GT

Well-Known Member
Joined
Dec 19, 2009
Messages
1,406
Reaction score
333
When I got my last emissions test I swapped in my stock H pipe for the catless X I normally have . The guy plugged it in and did the test and since he was fat he didn't even look under the car...
 

RAU03MACH

Legend
Joined
Apr 23, 2019
Messages
6,716
Reaction score
6,508
Location
NEW MEXICO
Here in my state there is no state inspection or emission test yet, running off road x pip.
no cats ,but I did keep all the emission stuff just incase it comes up.
that stuff gets expensive .
 

evilcw311

Most Evil Member!
SN95 Supporter
Joined
May 9, 2010
Messages
7,456
Reaction score
2,134
Location
Louisville, KY
Kentucky is a bunch of old fat slobs. They aren’t climbing their fat asses under anything. That’s probably why we have no emissions here.


Sent from my iPhone using Tapatalk
 

96blak54

Moderator
Staff
Joined
Feb 21, 2011
Messages
9,977
Reaction score
2,806
Location
In the shop
Notice how Kentucky thrives! Beautiful plush green rolling hills. Well....its cause we cut out the cats in our cars! Burn coal for electricity...carbon monoxide from exhaust is what plants thrive on! No sence in holding back all the wonderful nutrients in the tailpipes....let it flow!

Sent from my SM-G900P using Tapatalk
 

evilcw311

Most Evil Member!
SN95 Supporter
Joined
May 9, 2010
Messages
7,456
Reaction score
2,134
Location
Louisville, KY
Notice how Kentucky thrives! Beautiful plush green rolling hills. Well....its cause we cut out the cats in our cars! Burn coal for electricity...carbon monoxide from exhaust is what plants thrive on! No sence in holding back all the wonderful nutrients in the tailpipes....let it flow!

Sent from my SM-G900P using Tapatalk

Thrives??? If you mean being the highest in the country in cancer rates, top 5 highest in pollution......,,,,,,oh yeah.......thriving all right....


Sent from my iPhone using Tapatalk
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
32,383
Reaction score
5,557
Location
Evansville Indiana
Next to the most polluted river in the nation in what has been called "the sacrifice zone". I could see how it could cause someone to start believing in crazy conspiracy theories.
 

Latest posts

Forum statistics

Threads
77,435
Messages
1,502,106
Members
14,917
Latest member
virocanah

Members online

No members online now.
Top