Thoughts, Cat-back exhaust = better mpg?

KurtP

Well-Known Member
First Name
Kurt
Joined
Oct 9, 2020
Messages
2,062
Reaction score
2,147
Location
VA
Vehicle(s)
Mojave
Occupation
Only Fans Content Creator
. I can't post results unfortunately.
Yeah...kinda what i figured.

It is an erroneous assumption to make that peak power and efficiency are the only two metrics OEM’s are concerned with.

There are cars that show very little improvements with exhaust changes at “normal” power levels, like the Hellcat, but this jeep is not one of them. The dyno’s we have and the tests Ive done prove it. Youre not going to bolt it on and immediately see 2mpg. No way no how. But it does contribute a key component to the strategy for those that like it.

Now, whether those gains are worth it? Thats for each individual to answer. Im adding the ypipe to mine as well. On the fence about upgrading the down pipes on account of noise.





Advertisement

 

cannonFodder

Member
First Name
Nathan
Joined
Sep 23, 2020
Messages
21
Reaction score
31
Location
Clearwater
Vehicle(s)
2020 Gladiator
Take your entire cold end off and run around with just your Y-pipe. Yes it will be loud, but do your best to drive the same and see if you get your MPG to increase......... I can't post results unfortunately. As much as the Stellantis fights for MPG, they are not going to leave an easy gain on the table like exhaust mod.

"I have the data..."

"I can't post results..."

Then you don't have the data, it's as simple as that.
 

Courtsm3

Well-Known Member
First Name
Kayle
Joined
Nov 22, 2020
Messages
97
Reaction score
73
Location
Whistler
Vehicle(s)
2020 Jeep Gladiator Sport S
Occupation
Thin Blue Line
I worked with Chrysler for several years and got to speak with several Chrysler engineers as an SRT sales specialist. This what I learned in conversation during a SRT training day.

1. Noise pollution/nvh (not always)
2. emissions
3. Cost
4. Design and fitment
5. Falling back on noise is vehicle comfort for 98% of road goers. Majority of car buyers dont want noise. If that leaves a few hp/tq on the table then so be it. Obviously not in SRTs case.

The above doesnt apply to every vehicle on the road but I would put the Gladiator in line to 4 out of those 5. They tune to the best of their abilities while maintaining low nvh/comfort. I never dynoed my 392 charger but my mopar intake and catback , to me made little to no difference. 485bhp was maybe 500bhp, it was all noise. A car like that was already tuned with a 2.75” nearly straight through exhaust from factory with a rather large high flow intake.

Just my 2 cents. Not everything applies to every platform. My 2.3 2008 mazdaspeed3 made dyno proven 15whp just with an intake for example.
 

KurtP

Well-Known Member
First Name
Kurt
Joined
Oct 9, 2020
Messages
2,062
Reaction score
2,147
Location
VA
Vehicle(s)
Mojave
Occupation
Only Fans Content Creator
-Both of these intakes were designed by mopar engineers. One without a nvh constraint

-one of these airboxes more closely matches the size and outlet diameter of all the other current 3.6 pentastar applications.

18020BE0-29DA-41BE-9172-49024614B9D3.jpeg
15242FCE-D25D-43E0-B308-318C435BDF5A.jpeg
 

WXman

Well-Known Member
Joined
Mar 1, 2017
Messages
2,135
Reaction score
2,382
Location
Bluegrass region of Kentucky
Vehicle(s)
2020 Jeep Gladiator
Occupation
Meteorology and Transportation
This is incorrect.

stoich is only a part of how the engine pumping works and what the ECU is doing to fuel adaptations, and has to be considered in aggregate of a piece of equipment in motion against air resistance. Throttle angle, load, wind resistance, rolling resistance, etc all get a say in what effect stoich closed loop operation has on a driving vehicle.

Stoich mix at closed loop operation doesnt happen in a lab, where the only factor of fuel economy is the raw amount of fuel sprayed.....
This is incorrect.

There are multiple exhausts that make 10+lb/ft of tq through chunks of the rpm band on an otherwise stock truck on the market today. You wont ever see your money back on MPG difference, and any noise that results may or may not be worth it to you, but to say the stock exhaust is as efficient as others is incorrect.
The factory exhaust on JL and JT models is extremely restrictive. Loops, 90 degree angles, the whole nine yards. I completely agree that it would be easy to make 10 lb/ft of torque with a free flowing exhaust. In fact, when engineers were asked how the Ram made 305 HP while the Jeep made 285, they responded that it was simply a result of the space available for a more free flowing setup in the Ram.

As far as stoich goes, at the end of the day the fact is that more air requires more fuel. Period. Obviously there are environmental variables that alter things slightly, but when it's all said and done the air and fuel ratio is kept near an ideal threshold. And so, my earlier post wasn't "incorrect", it was actually correct. Noboby is going to stuff more air into an engine and see less fuel consumed. That's not how it works.
 

KurtP

Well-Known Member
First Name
Kurt
Joined
Oct 9, 2020
Messages
2,062
Reaction score
2,147
Location
VA
Vehicle(s)
Mojave
Occupation
Only Fans Content Creator
The factory exhaust on JL and JT models is extremely restrictive. Loops, 90 degree angles, the whole nine yards. I completely agree that it would be easy to make 10 lb/ft of torque with a free flowing exhaust. In fact, when engineers were asked how the Ram made 305 HP while the Jeep made 285, they responded that it was simply a result of the space available for a more free flowing setup in the Ram.

As far as stoich goes, at the end of the day the fact is that more air requires more fuel. Period. Obviously there are environmental variables that alter things slightly, but when it's all said and done the air and fuel ratio is kept near an ideal threshold. And so, my earlier post wasn't "incorrect", it was actually correct. Noboby is going to stuff more air into an engine and see less fuel consumed. That's not how it works.
Well, it’s actually exactly how it works.....you cant cruise efficiently if you have insufficient power to keep engine load outside of open loop fueling, or have to increase engine load to the point you trigger a downshift. Given the tq converter lock up schedule of the gearbox and how lean it it runs, you do significantly better by having a touch more fueling. And in fact would probably do better if we were to trim o2 voltage richer than 14.7 by a just a little bit, but id have to test it to at what point enrichment becomes less efficient than revs. By reducing tq request by lower throttle angles you can stay in over drive gears for longer periods of time.

We can see this play out perfectly in applications where we can control o2 lambda and track fuel economy. I trim o2 voltage on my motorbike down to generate a 13.5afr in closed loop. This is equivalent to adding roughly 8% fuel. My mileage decreases in that application when geared down by roughly 5%. Fuel molecules do not combust and generate a constant power change in a given cylinder chamber volume, so you can, quite literally, get more bang for your buck. What is interesting, however, is that if i replace the shorter geared rear sprocket and gear back up, that same 8% fuel increase presents no mileage loss at all. Because the gearing is so tall, at stoich additional engine load and throttle angle has to be applied, when a 13.5-13.6 burns better and runs the gearing more efficiently...again, this is not 14.7 in a lab. Its findign what afr drives the gearing through the environmental factors with a given combustion chamber. Sometimes its about the afr; often times its about the raw number of fuel molecules in a given combustion chamber...but it’s always relative to turning the drivetrain through the environmentals.

The ram gets more power because its tuned hotter, has a larger intake, and the exhaust.....which it can support on account in no small part to how much more efficient its cooling system is than on the glad. And why is it in real world driving a Ram with a hemi gets better fuel economy than a gladiator v6? At 14.7afr is has no only more cylinders but also a higher relative displacement per cylinder than the 3.6 does. Its because at that 14.7, given load, it is able to cruise more efficiently despite more fueling requirements. If it were simply about the amount of fuel sprayed, absent any other factor, this would not be the case. Same with the 392 Rubicon. Its already showing it will beat v6 economy.
 
Last edited:

smlobx

Well-Known Member
First Name
Eddie
Joined
Jun 28, 2018
Messages
1,455
Reaction score
2,027
Location
Smith Mt. Lake, VA and OBX
Vehicle(s)
WK2 Ecodiesel, F-350 Diesel, Gladiator Rubicon, GT3 RS, 986S
Occupation
Semi retired consultant
-Both of these intakes were designed by mopar engineers. One without a nvh constraint

-one of these airboxes more closely matches the size and outlet diameter of all the other current 3.6 pentastar applications.

18020BE0-29DA-41BE-9172-49024614B9D3.jpeg
15242FCE-D25D-43E0-B308-318C435BDF5A.jpeg
So which is which and what is the one in our stock JT?
 

KurtP

Well-Known Member
First Name
Kurt
Joined
Oct 9, 2020
Messages
2,062
Reaction score
2,147
Location
VA
Vehicle(s)
Mojave
Occupation
Only Fans Content Creator
So which is which and what is the one in our stock JT?
The larger one is the mopar intake the smaller the factory JT. The mopar is closer to what is in my woman’s grand cherokee
 

snide

Well-Known Member
First Name
Big Al
Joined
Jun 15, 2020
Messages
50
Reaction score
20
Location
o|||||||o
Vehicle(s)
'20 Gladiator
Let me understand this correctly. You have a Jeep Gladiator and you want better gas mileage? :CWL::CWL::CWL::CWL:
 
OP

Rubiwoo

Well-Known Member
First Name
Michael
Joined
Jul 8, 2020
Messages
121
Reaction score
84
Location
California
Vehicle(s)
2020 Jeep Gladiator Rubicon
Occupation
Self Employeed
  • Thread starter
  • Thread Starter
  • #28
Let me understand this correctly. You have a Jeep Gladiator and you want better gas mileage? :CWL::CWL::CWL::CWL:
Yep. Why settle if it's possible. I got almost 20mpg on my drive from California to Mexico. If I can get 21-22, that would be cool.
 
OP

Rubiwoo

Well-Known Member
First Name
Michael
Joined
Jul 8, 2020
Messages
121
Reaction score
84
Location
California
Vehicle(s)
2020 Jeep Gladiator Rubicon
Occupation
Self Employeed
  • Thread starter
  • Thread Starter
  • #30

Advertisement




 



Advertisement
Top