off road h-pipe

Parker Lewis

forum member
Joined
Dec 9, 2009
Posts
56
Reaction score
12
What about excessive heat on a non-daily driven modified car? With long tubes and the cats so close to the floor the interior temperatures could get pretty dang hot. Would going to an off-road H-pipe keep the temperatures lower? Don't the cats heat up and stay crazy hot, or are the cats the same temp as the rest of the exhaust?

Politics, personal bias, and performance aside, is there a noticeable temperature difference between catted and non-catted mid pipes on a non-FI car?
 

Juice

forum member
Joined
Aug 24, 2017
Posts
4,622
Reaction score
1,904
As it has been stated, the rules have been there. Enforcement was not.
I ran cats on my supercharged fox. Vortech setup has CARB cert. Ecam I picked for emission compliance. Car passed the sniffer test (thats all that was than) Now with OBD 2 scans, a lot of ppl got through inspections with shit turned off. Now they realized that those did not have enough emissions monitors so clearly shit got disabled.
This is NOT a chicken or egg.

This is delete/disable emissions stuff vs leaving those intact when modding.

If that isnt clear enough, I have nothing else to add.
My coyote swap has cats, and nothing is disabled.
Im done here.
 

Juice

forum member
Joined
Aug 24, 2017
Posts
4,622
Reaction score
1,904
What about excessive heat on a non-daily driven modified car? With long tubes and the cats so close to the floor the interior temperatures could get pretty dang hot. Would going to an off-road H-pipe keep the temperatures lower? Don't the cats heat up and stay crazy hot, or are the cats the same temp as the rest of the exhaust?

Politics, personal bias, and performance aside, is there a noticeable temperature difference between catted and non-catted mid pipes on a non-FI car?
You just dont get it. Cannot remove cats legally.
 

Ryan D

Junior Member
Joined
Jun 25, 2021
Posts
42
Reaction score
3
Location
Southern Kentucky
You just dont get it. Cannot remove cats legally.
Can’t do 71 in a 70 legally either, or make a right on red at some intersections even though it’s 3 am and not another vehicle within 2 miles. In some instances, common sense has to come into play I think.
 

Parker Lewis

forum member
Joined
Dec 9, 2009
Posts
56
Reaction score
12
I'm not disagreeing with you Juice. I'm not trying to argue. I am simply looking for real world feedback for my questions. Not all cars are street cars, some are used off road:

Don't the cats heat up and stay crazy hot, or are the cats the same temp as the rest of the exhaust? Is there a noticeable temperature difference between catted and non-catted mid pipes on a non-FI car?
 

tjm73

of Omicron Persei 8
S197 Team Member
Joined
Jun 9, 2010
Posts
12,092
Reaction score
1,638
Location
Rush, NY
Politics, personal bias, and performance aside, is there a noticeable temperature difference between catted and non-catted mid pipes on a non-FI car?

It doesn't matter. Law says they have to be there and you can't remove them. Hotter or cooler with or without them just doesn't matter. For decades we've gotten away with removing them. Those days are winding down. If a car is registered, it's a street car as far as the EPA is concerned.
 
Last edited:

Ryan D

Junior Member
Joined
Jun 25, 2021
Posts
42
Reaction score
3
Location
Southern Kentucky
It doesn't matter. Law says they have to be there and you can't remove them. Hotter or cooler with or without them just doesn't matter. For decades we've gotten away with removing them. Those days are winding down. If a car is registered, it's a street car as far as the EPA is concerned.

He’s asking a technical question, so it does matter. He didn’t ask the legality of it. Cats work via an exothermic process, heat is given off as the chemical reaction takes place, so yeah, there would be some increase in exhaust gas temp at the pipe exit, how much I have never seen any info that measures it tho I’m sure there’s some out there. Probably be fairly minimal temp difference in the grand scheme of things.
 

Laga

Senior Member
Joined
Aug 10, 2019
Posts
991
Reaction score
518
Location
Chicago
He’s asking a technical question, so it does matter. He didn’t ask the legality of it. Cats work via an exothermic process, heat is given off as the chemical reaction takes place, so yeah, there would be some increase in exhaust gas temp at the pipe exit, how much I have never seen any info that measures it tho I’m sure there’s some out there. Probably be fairly minimal temp difference in the grand scheme of things.
From google.
“Reactions over a 3-way catalyst at near stoichiometric air-fuel ratio are exothermic but gas residence time within the catalyst is so short and mass-flow rate through the catalyst is so high at anything above very light loads that temperature differences between the catalyst inlet and catalyst outlet are often less than 10-20C. (50°F-68°F). So basically nothing.
 

Ryan D

Junior Member
Joined
Jun 25, 2021
Posts
42
Reaction score
3
Location
Southern Kentucky
From google.
“Reactions over a 3-way catalyst at near stoichiometric air-fuel ratio are exothermic but gas residence time within the catalyst is so short and mass-flow rate through the catalyst is so high at anything above very light loads that temperature differences between the catalyst inlet and catalyst outlet are often less than 10-20C. (50°F-68°F). So basically nothing.

Thanks for that info. I wasn't off in my thinking it would be a negligible amount of heat.
 

Parker Lewis

forum member
Joined
Dec 9, 2009
Posts
56
Reaction score
12
Yeah Ryan you nailed it. I wasn't looking to jump into a legal debate, just had the technical question. Anyway thanks for weighing in.

Let's all hope we can continue the automotive hobby long into the future.
 

AHaze

Member
Joined
Dec 31, 2019
Posts
304
Reaction score
170
Location
Edmonton, AB
Sounds like you need an adjustment to your tune.
The AFR goes to around 11:1 at full boost because holes in pistons are bad. There's going to be unburned fuel in the exhaust.
It trapped at 117 MPH with a 3100' DA on the stock 3V long block and 91 octane last weekend. I'd say the tune is working OK.
 
Last edited:

Dan07

Junior Member
Joined
Jun 8, 2020
Posts
15
Reaction score
4
This post saved me a couple thousand so thank you. Was thinking on installing a full Kooks, but if they don't really do anything until your fully built. It is not worth it.
 

Pentalab

forum member
Joined
Mar 5, 2013
Posts
5,211
Reaction score
1,093
This post saved me a couple thousand so thank you. Was thinking on installing a full Kooks, but if they don't really do anything until your fully built. It is not worth it.
LT's make a helluva big difference. However there is virtually no improvement between hi-flow cats and no cats.
 

mulage

Junior Member
Joined
Aug 27, 2021
Posts
6
Reaction score
0
Location
Central, NC
goodness looks like i started something here, i am primarly looking for off road h-pipe
because my car has a cut & clamp x-pipe and i don't like the sound and i want the
car louder!!

so i guess i am out of luck on finding a new one
 

pass1over

I like it LOW
Joined
Oct 9, 2011
Posts
1,510
Reaction score
236
Location
Trenton, FL
I would just get a local muffler shop to build you an H pipe. Should be super easy for them to do
 

JEWC_Motorsports

S197 Junkie
S197 Team Member
Joined
Aug 22, 2010
Posts
20,471
Reaction score
1,596
Location
Texas
I'm not disagreeing with you Juice. I'm not trying to argue. I am simply looking for real world feedback for my questions. Not all cars are street cars, some are used off road:

Don't the cats heat up and stay crazy hot, or are the cats the same temp as the rest of the exhaust? Is there a noticeable temperature difference between catted and non-catted mid pipes on a non-FI car?
Yes cats heat up and stay hot, thats how they supposedly burn off nox.
 

Midlife Crises

Senior Member
Joined
Jul 20, 2019
Posts
1,836
Reaction score
1,253
LT's make a helluva big difference. However there is virtually no improvement between hi-flow cats and no cats.
Simple, unscientific test more than a year ago for my setup. Make what you will of it. Stock manifolds and cats= 18psi on the boost gauge. Kooks long tubes and Kooks 2.5” high flow catted X pipe= 16psi on the boost gauge and finally Kooks long tubes with Pipes 2.5” off road (cat less) H pipe = 15.5psi on the boost gauge. No tune adjustments were made when swapping these parts and they were not done on the same day but I am going to say there is a notable difference in performance. My Butt Dyno feels the stock headpipe was docile compared to the more open “and lauded” headers and the cats did not make a great deal of difference. I was on race fuel and I love the smell!:driver:
 

Latest posts

Support us!

Support Us - Become A Supporting Member Today!

Click Here For Details

Sponsor Links

Banner image
Back
Top