Sponsored

Engine Mods that Do and Don't Work

bmpcamry09

Well-Known Member
First Name
Brad
Joined
Feb 13, 2026
Threads
8
Messages
512
Reaction score
1,056
Location
New Athens, IL
Vehicle(s)
2025 JLU Sport S 3.6 8AT
This will be a fun one, but after having a bunch of these under my supervision, I want to make this thread and explain why, not just put out some claims.

DONT WASTE YOUR MONEY ON:

COLD AIR INTAKES

-Our Jeeps do not have a mass airflow sensor, so even with tuning, there isn't much to change to "tune the intake" to your Jeep, a manifold absolute pressure sensor (MAP) is used to calculate aircharge in measurements of MG. I have not seen any measurable differences in aircharge volume from customers with stock intakes or with cold air intakes. The only "benefit" to one is for more sound. In the rare event that the intake is actually pulling in more air, the ECU is going to have to compensate for it by adjusting long term fuel trims, but it will not command more torque or power as a result. Torque ceiling on factory tuning is set to 272 foot pounds, and you will never command more than that on stock tuning. Even if you modify the Neural Network or other injector data within the tune to adjust fuel trims for an intake, I have never seen a measurable increase in torque or power. Metal intakes are even worse, as that metal rides right on top/behind the radiator and is soaking in all that heat, driving up temperature readings at your intake air temperature sensor.

PEDAL CONTROLLERS

-All of these, I don't care what the brand is, manipulate the 5 volt Canbus signal going from the pedal to the ECU. These manipulate the voltage output to increase throttle response. Yes, they accomplish that, but they do not add power, and it is a risky way to get pedal response, no matter how reputable the company is. $300-$500. If you have to have one, go with Banks Pedal Monster as they have a good failsafe strategy in place. Everything else can fry your Canbus and cause new issues if they go faulty.

THROTTLE BODY SPACERS

-These literally don't do anything, what they do is throw off the air volume calculations that your very advanced ECU is using to power your entire vehicle. Just stop.

FUEL INJECTORS

-Some dude on the JK forums claimed upgrading his JK injectors to JL injectors added a bunch of power, no, no it didn't, it threw off your fuel trims and confused the crap out of your ECU, larger injectors MUST be accounted for in tuning, there are even minor injector tuning differences on various different PUG platforms (IE the injector data from a Grand Cherokee 2.6 is NOT the same as in a JL Wrangler).

THINGS WORTH THE MONEY

Premium Fuel

-These engines prefer premium fuel, period. Most stock 3.6 engines will pull 3-5 degrees of timing at wide open throttle on 87 octane, unless the weather is cold. This 3 to 5 degrees of timing is costing you 10-25 HP/10-25 TQ. I see it over and over and over. Yes, the manual says 87 is fine, but you are riding the knock sensor threshold at all times with 87 in your tank. Remember, just because you can't hear pinging doesn't mean your knock sensors can't hear it. If your in the "I've always run 87 octane and have no issues" crowd, congrats and carry on, but I promise you, your not making advertised power. If you want to run 87 all the time, get custom tuned for. The tune will offset losses from crappy fuel and also provide a bigger safety net. These models have a long term knock retard strategy that will "learn" your octane and continuously pull timing if it keeps detecting knock, making it even more sluggish. ESPECIALLY you 2.0 guys. The 2.0 will pull 10 plus degrees of timing on 87 octane, causing extreme heat build up. I datalogged one this past week locally, and regularly saw -5 to -10 degrees spark advance at cruise, which is insane. It genuinely hurt my feelings. LOL

Custom Tuning

-Surprise, the tuning guy said tuning is worth the money. I shouldn't even have to explain this, but a good tune from a reputable tuner of your choosing (there aren't many to choose from........) will completely transform your vehicle. Forget about raw HP and TQ numbers, I am talking driveability, response, power, and so much more. A custom engine and transmission tune by me, Livernois, or whoever else, will be the best money you spend. Just know that no one is as picky as I am about how a tune feels or looks on a log.

Straight Through Design Mufflers or Muffler Deletes

-I have consistently noticed that customers with good quality exhausts, ones that you can see straight through the muffler or ones that remove the muffler completely, actually are gaining about 5 HP/5 TQ or more across the board. The hot exhaust gasses are allowed to get out of the combustion chamber just a nut hair faster, and this helps reduce detonation/knock/heat and does indeed help.

Heat Management Devices

-Ventilated hoods, cooling fan controllers, colder thermostats, and anything else that helps remove heat is your friend. Stock tuning has very very aggressive heat related timing nannies. You could be losing 20-40 horsepower if your engine temps are north of 210 on a regular basis and everything is getting heat soaked. I see it constantly in datalogs. Important on both 3.6 and 2.0 models, but even more important on 2.0. Colder thermostats, yes, they work. The earlier opening allows coolant to flow sooner, allowing the radiator to start doing its magic earlier.

Quality Engine Oil

-I have tuned several Jeeps now that showed knock/detonation on one log, then I tell them to change their oil, and the knock goes away. Fresh oil every 3000-5000 resists heat and low speed preignition (LSPI), the SN and higher rated oils are a must have as the technology has evolved over the years a lot, I LOVE Valvoline Restore and Protect, Valvoline Advanced Synthetic, and Penzoil Ultra Platinum. Use 0w20 if you'd like, but I use 5w30. Not trying to start that war here.

I also like the Baxter oil filter adapter, and plan on adding one to my 2025 soon. I like the idea of keeping oil in the top end of the engine on start up so that the engine can jump out of high lift mode (defaulted on start up) as fast as possible and reduce center lobe camshaft wear. But I wouldn’t call it a performance mod.
Sponsored

 
Last edited:

alphawolff

Well-Known Member
Joined
Jul 31, 2023
Threads
1
Messages
3,376
Reaction score
5,645
Location
california
Vehicle(s)
2021 JLU
Good information here. I've been preaching that the PUG needs a minimum of 89 octane for years now. The 2.0L is especially rough without 91.

Something to note is colder thermostats will almost certainly cause a CEL in the winter (P0128). You might need to tune it out. I'm a big fan of vented hoods, they help tons.
 
OP
OP
bmpcamry09

bmpcamry09

Well-Known Member
First Name
Brad
Joined
Feb 13, 2026
Threads
8
Messages
512
Reaction score
1,056
Location
New Athens, IL
Vehicle(s)
2025 JLU Sport S 3.6 8AT
Case in point, I did a little back road 0-60 run this morning with my 93 octane tune. Tune only. No other mods. Doors and roof off so some weight reduction help too. 😬😬😬

 

Stan B

Active Member
Joined
Jan 25, 2026
Threads
2
Messages
41
Reaction score
47
Location
Michigan, USA
Vehicle(s)
2019 JLUR 3.6L M/T, 2006 Dodge Ram 2500 diesel, 1994 Impala SS
This will be a fun one, but after having a bunch of these under my supervision, I want to make this thread and explain why, not just put out some claims.

DONT WASTE YOUR MONEY ON:
...
Look at this guy with his fancy data and science! If JC Whitney was still around, they'd probably send you a cease and desist! 🤣

Excellent info tho. I'm really liking the idea of that oil filter adapter.

I'm a big fan of vented hoods, they help tons.
Do you have a certain design you like, or are you talking about things like making the Rubicon vents functional?
 

croppz

Well-Known Member
First Name
Zach
Joined
Apr 6, 2026
Threads
8
Messages
358
Reaction score
597
Location
North Carolina
Vehicle(s)
2021 JLU Rubicon 2.0T
Rollin a grenade early this morning I see!

Great info
 

Sponsored

Pape

Well-Known Member
Joined
Jul 4, 2023
Threads
16
Messages
1,915
Reaction score
2,037
Location
Quebec
Vehicle(s)
JLU Sahara
The JL 3.6 does run hot, If I was not to be 6 months a year in the 19X F, I would indeed, be addressing the heat.
 

croppz

Well-Known Member
First Name
Zach
Joined
Apr 6, 2026
Threads
8
Messages
358
Reaction score
597
Location
North Carolina
Vehicle(s)
2021 JLU Rubicon 2.0T
Look at this guy with his fancy data and science! If JC Whitney was still around, they'd probably send you a cease and desist! 🤣

Excellent info tho. I'm really liking the idea of that oil filter adapter.



Do you have a certain design you like, or are you talking about things like making the Rubicon vents functional?
I made my rubicon vents functional and it helped a lot with heat especially idling in traffic on my commutes. Stole this pic from a guy on FB but this was the difference in temp between non functional and functional rubicon vents. It definitely lets heat out a lot faster

Jeep Wrangler JL Engine Mods that Do and Don't Work IMG_6318
 

WannFly

Well-Known Member
First Name
Priyo
Joined
Jul 30, 2021
Threads
41
Messages
888
Reaction score
1,280
Location
Atlanta
Vehicle(s)
2021 Rubicon 4Xe, 2026 MOAB
Build Thread
Link
Occupation
Cyber security
whats your take on reusable engine filters? I have one on my 2.0, but I have recently learnt that they do more harm than good. for the 6.4L I am sticking to the factory ones. The 2.0 will no longer see lot of dust, so I am inclined to leave it as is. We do get crap load of pollen in spring though
 
OP
OP
bmpcamry09

bmpcamry09

Well-Known Member
First Name
Brad
Joined
Feb 13, 2026
Threads
8
Messages
512
Reaction score
1,056
Location
New Athens, IL
Vehicle(s)
2025 JLU Sport S 3.6 8AT
whats your take on reusable engine filters? I have one on my 2.0, but I have recently learnt that they do more harm than good. for the 6.4L I am sticking to the factory ones. The 2.0 will no longer see lot of dust, so I am inclined to leave it as is. We do get crap load of pollen in spring though
I have never had issues with performance drop in filters but I would also check it and oil it routinely to keep it pristine. Many people just neglect them and that leads to the issues. FWIW, I don’t plan on using one this go around, factory filter makes me feel the best.
Sponsored

 
 







Top