3.6 power loss at elevation

[Remorseless]

My 3.6L 2020 JLUR was insanely anemic here, but it was a manual. Yeah, I stupidly assumed that Wranglers were like all the other vehicles I bought where the manual was more performant.

I think the thing with the Wrangler is that "performant" always has to be framed through the lens of off road performance. While I'm someone who believes that autos make for better wheelers in terms of being easy on both drivetrain and driver, manuals definitely scratch the itch of driver engagement better. You have total control of the vehicle while it's doing its thing on its "race track". Performant, but just when in 4L lol

Sponsored

 

[Remorseless]

I have a 392 so don't know what the manual says for others. I read an article from an engineer a few years ago in some engineering magazine (do not recall which one, was not a car magazine) that said it could take a few tanks of gas for the algorithm to adapt (recalibrate). Feedback from the knock sensors and such will act "instantly" but the power curve algorithm intentionally takes some time to average out short-term variations. I was told the same thing about my 392 when I asked but I'm an EE, not an ME, so rely on others. I do understand feedback. My point was not that it will run on low-grade fuel, but rather that I personally stick with whatever octane I usually run when going on trips. YMMV.

With the 2.0 the manual tells you to use premium fuel for best performance. IMO, it's wise with a little turbo like that to just feed it the highest octane you can get so it has additional overhead. That's the approach I've taken with it anyway.

 

[DonH63]

With the 2.0 the manual tells you to use premium fuel for best performance. IMO, it's wise with a little turbo like that to just feed it the highest octane you can get so it has additional overhead. That's the approach I've taken with it anyway.

That would be my approach, especially with a turbo that might be ping(octane)-sensitive. Of course my 392 manual says premium as well.

 

[Remorseless]

That would be my approach, especially with a turbo that might be ping(octane)-sensitive. Of course my 392 manual says premium as well.

If you can afford a 392 you can afford race gas Don. Don't be cheap.

 

[DonH63]

If you can afford a 392 you can afford race gas Don. Don't be cheap.

I buy premium. It's a little lower octane here but (just) meets spec. The GC lives on midgrade.

Race gas? Isn't that like alcohol? Besides, I already said I didn't get it for racing, whether Mt. Evans/Blue Sky, Pikes Peak, or Daytona.

 

[Remorseless]

I buy premium. It's a little lower octane here but (just) meets spec. The GC lives on midgrade.

Race gas? Isn't that like alcohol? Besides, I already said I didn't get it for racing, whether Mt. Evans/Blue Sky, Pikes Peak, or Daytona.

But if you're gonna have a 392 you might as well waste tons of money in stupid expensive fuel every time you rev it just to hear it make noise.

 

[jeepingib]

I'm not dragging out this dead horse again. There are pages and pages of discussion on it, anyone who is interested can go read up on it.

 

[JeepinJason33]

I live at 6,200' with a 3.6L on 37's. Regearing to 5.13 and a pedal controller made all the difference in the world. I know the pedal controller simply adjusts the quickness in response, not the actual hp, but it does seem to reduce the lag. I drug the JL behind my motorhome down to Brownsville and noticed a bit more pep, but nothing that "felt" like the numbers suggest it should with the 3% for every 1,000'. My neighbor has a 2.0l and we wheel all the time at 12,000' and above. I never seem to have problems keeping up with him on the freeway over the passes on the way there. Off road when you are running trails I don't think it matters much at all as it is all low speed anyway.

I run 85 up here which is our 87. I have ran several tanks of premium through it in a row to see if the mileage or performance would be better. Running the same route to work, I could not feel or realize any difference in performance or MPG. I know there are a ton of variables to play with there, but after a month or so of constant premium, I felt like it was a waste of money and went back to 85. I do run premium in my M5 as required.

He has had trouble with his turbo twice now with 60k on his engine. My 3.6l was replaced due to a cracked block at 25,000 miles. Not sure there is a perfect Jeep engine. I love the 4.0 though! My other rig is a 97 TJ that I supercharged after I moved here from VA. That made a huge difference and I would love to do it to my 3.6 but they don't make one that works with the stupid Etorque.

 

[58Willys]

I’ve built and raced motorcycles, built motors, I’m very tuned into performance and drive ability. I’ve had my 2018 3.6 6sp to just shy of 10,000 feet, and have really not noticed much loss of power. I think PCM does a very good job of compensating for altitude. That 3% chart might work for carbureted engines, but I don’t think it applies to fuel injected motors very well. YMMV.

 

[Reinen]

The engine runs in closed loop and is constantly recalibrating. The manual states 91 octane is recommended under heavy loads and hard use, which I'm pretty sure mountains fall under but yes the Jeep will run on low grade fuel.

Well, not necessarily. Being in a high altitude state my octane options are 85/88/91. 85 is a no-go. I find 88 is perfectly fine in the mountains going from 5300ft to 8700ft in 8 miles during the winter with temps 0-32F. When I'm off-road in 100+F temps in summer is when I need 91 octane, even at the lower altitudes.

So I use 88 for 10 months of the year, 91 in July/Aug. But I'm in a rather extreme high altitude and hot desert environment that most people won't experience. 87 is perfectly fine for most people, unless you're towing or doing serious rock crawling.

 

[Grey24Rubi]

I’ve built and raced motorcycles, built motors, I’m very tuned into performance and drive ability. I’ve had my 2018 3.6 6sp to just shy of 10,000 feet, and have really not noticed much loss of power. I think PCM does a very good job of compensating for altitude. That 3% chart might work for carbureted engines, but I don’t think it applies to fuel injected motors very well. YMMV.

This is meant to be a joke, especially the last part, right?

 

[Zandcwhite]

This is meant to be a joke, especially the last part, right?

Maybe he's got that new fuel injection that injects the missing oxygen too?

 

[Zandcwhite]

Well, not necessarily. Being in a high altitude state my octane options are 85/88/91. 85 is a no-go. I find 88 is perfectly fine in the mountains going from 5300ft to 8700ft in 8 miles during the winter with temps 0-32F. When I'm off-road in 100+F temps in summer is when I need 91 octane, even at the lower altitudes.

So I use 88 for 10 months of the year, 91 in July/Aug. But I'm in a rather extreme high altitude and hot desert environment that most people won't experience. 87 is perfectly fine for most people, unless you're towing or doing serious rock crawling.

I didn't mean to imply you couldn't run low octane fuel in the mountains, more so that of all the places I'm likely to want the best performance possible it's at elevation. From trying to accelerate up a steep grade to wheeling at elevation every bit helps in my opinion.

 

[TheRaven]

Then why the hell did you feel the need to chime in? You obviously care deeply.

You, sir, need to make sure you understand what i'm saying FIRST, before you formulate your commentary on it. Almost all of your recent replies to me have been spent rebutting claims of fact I didn't make (there's that damn strawman showing up again!).

Like this one for instance - I didn't "chime in" on the subject that meme was referring to. I truly do not care to discuss that particular subject (the numbers behind power loss at elevation) because we are all in agreement on it. Despite that fact, you seem to think it's prudent to scream those numbers at me repeatedly. I've tried in the past to explain this to you and others who have done the same but I just end up getting screamed at for it so now i'm just going to disregard it.

With the 2.0 the manual tells you to use premium fuel for best performance. IMO, it's wise with a little turbo like that to just feed it the highest octane you can get so it has additional overhead. That's the approach I've taken with it anyway.

Agreed...I always used premium. Turbo engines see far more variation in effective compression than an N/A engine and thus the chances of severe detonation are higher. Yes the computer SHOULD be able to catch it and compensate but for me, this is one thing that's across my comfort line. I sleep better at night running premium on an FI motor.

 

[Ratbert]

You, sir, need to make sure you understand what i'm saying FIRST, before you formulate your commentary on it. Almost all of your recent replies to me have been spent rebutting claims of fact I didn't make (there's that damn strawman showing up again!).

Like this one for instance - I didn't "chime in" on the subject that meme was referring to. I truly do not care to discuss that particular subject (the numbers behind power loss at elevation) because we are all in agreement on it. Despite that fact, you seem to think it's prudent to scream those numbers at me repeatedly. I've tried in the past to explain this to you and others who have done the same but I just end up getting screamed at for it so now i'm just going to disregard it.

It's only a straw man when it's an inaccurate representation of what someone said. I asked why you chimed in on the topic if you, in fact, didn't care. Now you're saying you didn't chime in on that subject, but you clearly did:

Additionally, from an objective standpoint, the 2.0l is only marginally better, and only so once the turbo is spooled - taking off from a standstill is going to be even worse because of the 2.0s low-end torque deficit.

If you're confused as to what a straw man fallacy actually looks like then you might consider reading this text from our resident expert on the subject:

Reading these forums one might think that nobody in Denver could drive anywhere before turbocharged motors became commonplace. Yet people who live at high altitudes have been towing, wheeling, and racing long before then.

Sponsored