home register FAQ memberlist calendar

Go Back   Turbobricks Forums > Mechanical > performance & modifications

Reply
 
Thread Tools Display Modes
Old 10-23-2020, 12:44 PM   #1
BeaverMeat
Board Member
 
Join Date: Aug 2020
Location: Vancouver Island
Default To cat or, not to cat

Wanting to install a high flow cat on my custom 5.0 swap exhaust. Anyone install cats in their 5.0 or LS swap and where is the optimum placement?

The car has headers that lead into a 2” Y-pipe into a 3” single all the way to the rear.

Is it best to use two spun cats on the 2” Y-pipe right behind the headers, or one cat on the 3” single after the y-pipes?


NOTE: I know all the rhetoric. “It adds weight” or “it reduces performance” yadda, yadda, yadda. It’s not 1985... for practical purposes I want my car to stink less...
BeaverMeat is offline   Reply With Quote
Old 10-23-2020, 12:52 PM   #2
culberro
Ronald Culberbone III
 
culberro's Avatar
 
Join Date: Feb 2010
Location: Portland, OR
Default

I run 2x 2.5" cats on my 5.slow drift car. They are positioned to be just in front of the trans crossmember. I mounted them in this location to have increased ground clearance on a lowered car, and two 2.5" cats have more flow potential than a single 3". I mounted them with cheap v-bands. If they fail, I can easily swap them out or replace them with a straight section of tubing.

You could easily run a single 3" cat further back as well.
__________________
Cult Person. Pissing in your Kool-Aid.
culberro is offline   Reply With Quote
Old 10-23-2020, 12:53 PM   #3
Harlard
Hurlurd?Harland?Bueller?
 
Harlard's Avatar
 
Join Date: May 2007
Location: PDX
Default

Yes, running a cat is always a good idea on a street car.

Just to argue with Bobbert, a single 3" would be cheaper and simpler.
__________________


Herr Harlard am Erstens

1979 242 DL

Quote:
Originally Posted by t8fanning View Post
My knob has a big chunk of steel on it
Harlard is offline   Reply With Quote
Old 10-23-2020, 01:39 PM   #4
BeaverMeat
Board Member
 
Join Date: Aug 2020
Location: Vancouver Island
Default

Quote:
Originally Posted by culberro View Post
I run 2x 2.5" cats on my 5.slow drift car. They are positioned to be just in front of the trans crossmember. I mounted them in this location to have increased ground clearance on a lowered car, and two 2.5" cats have more flow potential than a single 3". I mounted them with cheap v-bands. If they fail, I can easily swap them out or replace them with a straight section of tubing.

You could easily run a single 3" cat further back as well.
Quote:
Originally Posted by Harlard View Post
Yes, running a cat is always a good idea on a street car.

Just to argue with Bobbert, a single 3" would be cheaper and simpler.
Good to know. Wasn’t too sure if a modern 3-way cat could be placed right after the header. I know if it’s placed closer to the heat source it helps with efficiency but, you run the risk of burning it up.

Having a singe after the Y may be cheaper... bobbert does have a good point about flow potential with having two.

Well... if there is anything worth doing, it worth doing rightz
BeaverMeat is offline   Reply With Quote
Old 10-23-2020, 03:59 PM   #5
740atl
educator monkey
 
740atl's Avatar
 
Join Date: Apr 2010
Location: USA
Default

Less combustion stench with the cats.

They’ll be slower to get going but will still be functional. Make some heat shields around them.
740atl is offline   Reply With Quote
Old 10-23-2020, 04:19 PM   #6
fatcatbestcat
Professional Hack
 
fatcatbestcat's Avatar
 
Join Date: Oct 2019
Location: Toronto, ON (Canada)
Default

Meow.
__________________
Doing the wrong thing the right way.

Quote:
Originally Posted by redblockpowered View Post
Will you do $14.99 shipped?
Quote:
Originally Posted by IansPlatinum View Post
please no more prying things with screwdrivers and bashing things with hammers!
fatcatbestcat is offline   Reply With Quote
Old 10-23-2020, 04:27 PM   #7
blkaplan
50 shades of beige
 
blkaplan's Avatar
 
Join Date: Jul 2002
Location: Rockville, MD
Default

Quote:
Originally Posted by Harlard View Post
Yes, running a cat is always a good idea on a street car.

This,

It's good to be considerate of everyone around you.
__________________
www.BEIGEPOWER.com
Kaplhenke Racing Facebook
Quote:
Originally Posted by DarkKratoz View Post
The only safe bet is Ben.©
blkaplan is offline   Reply With Quote
Old 10-23-2020, 05:46 PM   #8
Ursan
Bored Member
 
Ursan's Avatar
 
Join Date: Jun 2004
Location: Rational National
Default

Run with a cat. Don't be that guy.
__________________
Quote:
Originally Posted by 740freak View Post
how psi a stock can support?
Quote:
Originally Posted by speedn_j View Post
So I’m a racist big deal who cares. Deal with it.

Quote:
Originally Posted by Bready View Post
I admit I'm stupid...

1990 780t Kind of Modded 1994 945t Pegz, Tintz, Hidz.
"Rear Wheel Drive, the way God intended. If a car is being pulled from the front, doesn't that mean it's being towed?"

"Lister, you are a polyp on the anus of society." - A.J. Rimmer
Ursan is offline   Reply With Quote
Old 10-23-2020, 08:53 PM   #9
mikep
The MP
 
mikep's Avatar
 
Join Date: May 2003
Location: 38° 27' N 75° 29' W
Default

area of 3" is 2.25x the area of 2". So I would go with the 3" since it should flow more, it's simple, and it will light off eventually. Not ideal for hybrids, but you will have it cooking for longer periods of time.
__________________
Quote:
Originally Posted by leecatd8209 View Post
Being dead has a funny way of messing up your small business, too.
mikep is offline   Reply With Quote
Old 10-23-2020, 09:32 PM   #10
2turbotoys
Astro Zombie
 
2turbotoys's Avatar
 
Join Date: Nov 2007
Location: Reading pa
Default

You could always use a free flow cat like this, and it's only $40 in stainless steel

http://www.siliconeintakes.com/dsm-i...ter-p-320.html

Properly tuned cars don't stink much more than factory cat cars
__________________
Feedback thread https://forums.tbforums.com/showthread.php?t=144924

1978 242, 5.3 L33
1979 242, MS, R brakes
2006 V50 T5 AWD @ 17 PSI
2turbotoys is online now   Reply With Quote
Old 10-23-2020, 11:04 PM   #11
BeaverMeat
Board Member
 
Join Date: Aug 2020
Location: Vancouver Island
Default

Quote:
Originally Posted by blkaplan View Post
This,

It's good to be considerate of everyone around you.
Quote:
Originally Posted by Ursan View Post
Run with a cat. Don't be that guy.
It never had a cat for the last 17 years and he drove it in the summer only. Never noticed the smell until it got colder outside.


Quote:
Originally Posted by 2turbotoys View Post
You could always use a free flow cat like this, and it's only $40 in stainless steel

http://www.siliconeintakes.com/dsm-i...ter-p-320.html

Properly tuned cars don't stink much more than factory cat cars
That’s just a test pipe to “fool” da man.

The extent of tuning on this car is a OE 1989 5.0L with a 70mm throttle body, K&N filter, headers, and cat-less exhaust. That’s it. Crappy cams and all.

Stinks like any old 5.0L
BeaverMeat is offline   Reply With Quote
Old 10-23-2020, 11:55 PM   #12
2turbotoys
Astro Zombie
 
2turbotoys's Avatar
 
Join Date: Nov 2007
Location: Reading pa
Default

I know what that is, was kind of a joke. Tune it then. Ever get behind an old carbureted car? That stinks. Most modern cars with a proper tune do not have that problem. You can not get a tune for that engine? If not, get a high flow cat.
2turbotoys is online now   Reply With Quote
Old 10-24-2020, 12:54 AM   #13
BeaverMeat
Board Member
 
Join Date: Aug 2020
Location: Vancouver Island
Default

Quote:
Originally Posted by 2turbotoys View Post
I know what that is, was kind of a joke. Tune it then. Ever get behind an old carbureted car? That stinks. Most modern cars with a proper tune do not have that problem. You can not get a tune for that engine? If not, get a high flow cat.
I comes down to cash.

Column A: get a cat
Column B: get an ECU

Cost to value... the cat wins.
BeaverMeat is offline   Reply With Quote
Old 11-01-2020, 12:06 AM   #14
LC4CARL
Aero challenged
 
LC4CARL's Avatar
 
Join Date: Sep 2008
Location: Vancouver, WA
Default

Here's a Magnaflow I had years ago. Super easy to place.











__________________


@PDXvolvo on IG
LC4CARL is offline   Reply With Quote
Old 11-02-2020, 12:30 PM   #15
blkaplan
50 shades of beige
 
blkaplan's Avatar
 
Join Date: Jul 2002
Location: Rockville, MD
Default

Quote:
Originally Posted by BeaverMeat View Post
It never had a cat for the last 17 years and he drove it in the summer only. Never noticed the smell until it got colder outside.
Its not just smell. Your nose is not a full spectrum exhaust gas analyzer.

Yes its true,,, if your car is well-tuned you have less of a need for a cat but you are thinking mostly about steady-state cruising when the car is warm. Accel / decel + warmups are not clean.

You can pass a sniffer test with just a stead state load without a cat if the car is tuned well, but that same car on a dynamic dyno will quickly fail.
blkaplan is offline   Reply With Quote
Old 11-02-2020, 12:41 PM   #16
linuxman51
BRANDSCHUTZVORSCHRIFTEN!
 
linuxman51's Avatar
 
Join Date: Dec 2002
Location: mont, AL
Default

they don't really kill power either as long as they're sized reasonably and not clogged full of ****
__________________
"They bum rushed them in their own crib, they drank all their beer, they partied with their ladies and they left with the trophy"

Now with in-house Dyno tuning!

Megasquirt Tuning!
Plug and play LH 2.4 Megasquirt, now with stealth mode!
linuxman51 is offline   Reply With Quote
Old 11-02-2020, 01:31 PM   #17
dalek
Benchracer Tribe
 
dalek's Avatar
 
Join Date: Oct 2005
Location: Orange Alert, NC
Default

Quote:
Originally Posted by LC4CARL View Post
Here's a Magnaflow I had years ago. Super easy to place.
I do dig your hobbit cat. P/N?
__________________
"you can't leave your thingy hanging in public... you can get arrested."
"What's Arkansas supposed to be, Kansas for pirates?" Forg
"I think I can touch the tire. Damn! I can touch the tire! That hurts!" 240Psycho (on the back seat of my 94 Jetta while I was driving to a J/Y)
"Use the barbed adapter like what I use to inflate the air camping mattresses and my dates." FTF Engineering
i am inspired. i will replace my windsheild... with an intercooler.swedishK
Feedback!
dalek is offline   Reply With Quote
Old 11-02-2020, 02:09 PM   #18
240wagonguy
Board Member
 
Join Date: Oct 2013
Location: Weare, NH
Default

I'm running no cats on my ls swapped C10 and there's no stinky combustion smell.
__________________
1985 740GLE sedan winter beater Cali car.
240wagonguy is offline   Reply With Quote
Old 11-02-2020, 03:06 PM   #19
mikep
The MP
 
mikep's Avatar
 
Join Date: May 2003
Location: 38° 27' N 75° 29' W
Default

I'll have to disagree with the idea that you can tune away hydrocarbons. I can smell any vehicle with no cat. I worked for Datsun in the late 70s and early 80s, and we had cars with and without. The ones without a cat definitely got the hose when they were running in the shop. The CO is another story, of course, and now I know all cars need the hose.
mikep is offline   Reply With Quote
Old 11-05-2020, 12:20 AM   #20
BeaverMeat
Board Member
 
Join Date: Aug 2020
Location: Vancouver Island
Default

Quote:
Originally Posted by LC4CARL View Post
Here's a Magnaflow I had years ago. Super easy to place.











Went to a muffler shop and there telling me the only way to fit a cat is with a single unit on the 3" pipe. They suggested to go with a 2.5" inlet model... it would "work" but, I still maintain going with a small 3" inlet cat like yours.

I'll have to go back and show them the magnaflow mini-cats. I don't think I need the heat shield if its that small.



Quote:
Originally Posted by 240wagonguy View Post
I'm running no cats on my ls swapped C10 and there's no stinky combustion smell.
That's because it's an LS with it's fancy pants electronics and sensors, individual ignition coil packs, and more accurate "cold wire" MAF.

A 5.0 H.O. is just a classic 302 with mid-80s "hot wire" MAF electronic sequential fuel injection that controls the engine by fuel delivery only.


LS is a Playstation... the 5.0. is an Atari.

Last edited by BeaverMeat; 11-05-2020 at 12:35 AM..
BeaverMeat is offline   Reply With Quote
Old 11-05-2020, 02:11 AM   #21
Toybox
mostly lurking
 
Toybox's Avatar
 
Join Date: Dec 2018
Location: Nor Cal
Default

Quote:
Originally Posted by linuxman51 View Post
they don't really kill power either as long as they're sized reasonably and not clogged full of ****
I've always suspected as much... good to know what a tuner has seen firsthand, thanks!

I wish we were allowed to deviate dimensions, in California. It makes intuitive sense to reduce restriction by increasing pipe size, for example a 3" cat in the middle of a 2.5" system. With cone-shaped transitions, to ease the flow. But that type of free thinking ain't good for us, apparently.

Quote:
Originally Posted by BeaverMeat View Post
LS is a Playstation... the 5.0. is an Atari.
Toybox is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 09:59 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.