Sponsored

Long Tubes with Stock Cats for no tune

crimson_crowd_eater

Well-Known Member
Joined
Mar 26, 2019
Threads
44
Messages
352
Reaction score
103
Location
Daytona Beach, FL
First Name
Tony
Vehicle(s)
2018 Mustang GT Premium
Vehicle Showcase
1
Hey all, I just wanted some opinions on a little custom exhaust idea that I have and I wanted to see if anyone has tried a similar thing. So I want to get some long tubes, probably 2m because they're pretty affordable and I've seen a lot of good reviews, but I also need to stay emissions compliant right now for my state and I don't want to tune my car because of my warranty. So, my idea was that I could cut out my stock cats and have a shop weld a flange in to my x pipe so they can be removed when I feel like it. I want to use the OEM ones because other cats wont pass emissions or require a tune or are simply just too expensive. Has anyone done this before or tried something similar? I know that most people probably won't take kindly to this and that I should just "tune the car and put cats back in for emissions" or something, but I also want to keep exhaust volume down a little from catless.
Is this even possible or will the stock cats require a tune due to the long tube headers?
Sponsored

 

AZ18yote

Well-Known Member
Joined
Nov 24, 2017
Threads
11
Messages
3,220
Reaction score
1,523
Location
Arizona
First Name
Bryan
Vehicle(s)
2018 Mustang GT Prem PP Magnetic
Hey all, I just wanted some opinions on a little custom exhaust idea that I have and I wanted to see if anyone has tried a similar thing. So I want to get some long tubes, probably 2m because they're pretty affordable and I've seen a lot of good reviews, but I also need to stay emissions compliant right now for my state and I don't want to tune my car because of my warranty. So, my idea was that I could cut out my stock cats and have a shop weld a flange in to my x pipe so they can be removed when I feel like it. I want to use the OEM ones because other cats wont pass emissions or require a tune or are simply just too expensive. Has anyone done this before or tried something similar? I know that most people probably won't take kindly to this and that I should just "tune the car and put cats back in for emissions" or something, but I also want to keep exhaust volume down a little from catless.
Is this even possible or will the stock cats require a tune due to the long tube headers?
No tune you run the risk of cel with lth without the defouler / spacer trick and even then some will still get it. You also will not get the same performance without tuning for lth. Also unsure if you could pass emissions like that. But it is an interesting experiment.
 
OP
OP
crimson_crowd_eater

crimson_crowd_eater

Well-Known Member
Joined
Mar 26, 2019
Threads
44
Messages
352
Reaction score
103
Location
Daytona Beach, FL
First Name
Tony
Vehicle(s)
2018 Mustang GT Premium
Vehicle Showcase
1
No tune you run the risk of cel with lth without the defouler / spacer trick and even then some will still get it. You also will not get the same performance without tuning for lth. Also unsure if you could pass emissions like that. But it is an interesting experiment.
Well would a cel pop up if the O2 sensors are still there with the stock cats? Shouldn't the remainder of the cats negate the cel? The car wouldn't necessarily know anything was different to my understanding, but maybe the increase in flow from the nature of the headers over the stock manifold might trip something.
Thanks for that thought, I didn't think about a cel.
 

OzS550

Well-Known Member
Joined
Apr 1, 2014
Threads
32
Messages
583
Reaction score
508
Location
Adelaide, Australia
First Name
Michael
Vehicle(s)
GT Fastback
The stock cats are physically quite big, I doubt they'd fit under your car after the long tubes. Stock, they're tucked up into the start of the transmission tunnel behind the stock short tubes.

Wouldn't quite be dragging on the ground after long tubes but I'm sure speed bumps would catch them.
 

EFI

Well-Known Member
Joined
May 19, 2015
Threads
62
Messages
4,792
Reaction score
4,048
Location
Masshole central
Vehicle(s)
5.Br0
Great idea on paper, not really that practical in the real world. Also depending on the dealer, you probably will get an engine claim denied due to the headers just like you would with an aftermarket tune. So doing long tube headers without a tune for the sake of keeping warranty is kinda pointless.

If you really want to do this, I would suggest to invest in some Kooks green cats, which are some of the best aftermarket units that mimic the stock ones for filtration.
 

Sponsored

OP
OP
crimson_crowd_eater

crimson_crowd_eater

Well-Known Member
Joined
Mar 26, 2019
Threads
44
Messages
352
Reaction score
103
Location
Daytona Beach, FL
First Name
Tony
Vehicle(s)
2018 Mustang GT Premium
Vehicle Showcase
1
The stock cats are physically quite big, I doubt they'd fit under your car after the long tubes. Stock, they're tucked up into the start of the transmission tunnel behind the stock short tubes.

Wouldn't quite be dragging on the ground after long tubes but I'm sure speed bumps would catch them.
Yeah I thought they might have some clearance issues in a new location, I'll definitely have to check into that.
 
OP
OP
crimson_crowd_eater

crimson_crowd_eater

Well-Known Member
Joined
Mar 26, 2019
Threads
44
Messages
352
Reaction score
103
Location
Daytona Beach, FL
First Name
Tony
Vehicle(s)
2018 Mustang GT Premium
Vehicle Showcase
1
Great idea on paper, not really that practical in the real world. Also depending on the dealer, you probably will get an engine claim denied due to the headers just like you would with an aftermarket tune. So doing long tube headers without a tune for the sake of keeping warranty is kinda pointless.

If you really want to do this, I would suggest to invest in some Kooks green cats, which are some of the best aftermarket units that mimic the stock ones for filtration.
Well, the issue with that is that a dealer would have a much harder time trying to prove that headers violated anything. A tune can be easily blamed because it overwrites factory software and is actually changing something. I'll definitely look into it more though, thanks for the advice.
 

IrishStallion

Well-Known Member
Joined
May 11, 2020
Threads
4
Messages
722
Reaction score
393
Location
Missouri
Vehicle(s)
18 gt mustang
Save your money until you can do it right. Plus running catless without a tune can run rich due to COT not being shut off in the tune. That is Cat Over Temp protection.
 

AZ18yote

Well-Known Member
Joined
Nov 24, 2017
Threads
11
Messages
3,220
Reaction score
1,523
Location
Arizona
First Name
Bryan
Vehicle(s)
2018 Mustang GT Prem PP Magnetic

Sponsored

FruityJudy

Well-Known Member
Joined
Nov 13, 2018
Threads
15
Messages
887
Reaction score
766
Location
South Alabama
Vehicle(s)
2018 Mustang GT A10
I would be willing to bet the hp gains would be less than 5hp doing this setup. Sure is a lot of work to do all that and still MAY have to argue a warranty claim when the fact is you are already concerned about your warranty
 

Zelek

Well-Known Member
Joined
Feb 11, 2016
Threads
101
Messages
4,763
Reaction score
4,621
Location
Round Rock / Hutto, TX
First Name
Matt
Vehicle(s)
2021 Mustang Mach 1
If you are doing long tubes and not tuning the car, it's not worth the effort especially when it comes to emission headaches. You're better off doing something like the MAK cat deletes.
 

JasinEdward

Well-Known Member
Joined
Aug 3, 2015
Threads
26
Messages
900
Reaction score
527
Location
Spring Hill
First Name
Jason
Vehicle(s)
2015 5.0 Roush Stage 1
I just had long tubes installed and have a tune.... I still have the p0141/0161 codes because the rear o2's are not hooked up. My tuner is telling me there is nothing they will do to help. The connector pipes did not come with the bungs for o2 sensors. What are guys doing to get rid of the cel in this case?
 

AZ18yote

Well-Known Member
Joined
Nov 24, 2017
Threads
11
Messages
3,220
Reaction score
1,523
Location
Arizona
First Name
Bryan
Vehicle(s)
2018 Mustang GT Prem PP Magnetic
I just had long tubes installed and have a tune.... I still have the p0141/0161 codes because the rear o2's are not hooked up. My tuner is telling me there is nothing they will do to help. The connector pipes did not come with the bungs for o2 sensors. What are guys doing to get rid of the cel in this case?
My ARH came with o2 extensions and required hardware for install. Never had an issue after tuning.
 

WildHorse

N/A or GO HOME
Joined
Jun 28, 2017
Threads
216
Messages
8,462
Reaction score
6,533
Location
Home World: CLASSIFIED
First Name
ⓇⒾⒸⓀⓎ ⓈⓅⒶⓃⒾⓈⒽ
Vehicle(s)
'17 S550
Vehicle Showcase
1
LTH without a tune not worth the effort without a tune? Lol. Barring the fact of the rear o2 that may or may not throw a cell without the CAT, what does the PCM care ? It's not reading anything there except for A/F, ethanol content, temps (front o2), & CAT efficiency (rear o2). Even if it does throw a CEL for the rears you ain't gonna lose any horsepower.
Sponsored

 
 




Top