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3.6 power loss at elevation

FrickinAdam

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Tune-ability probably has a lot to do with it im sure. IDK personally, just adding my experience. Been in CO my whole life so you kinda get used to a little loss in power. When we had Mile High Nationals at Bandimere those cars always had a harder time racing at elevation and posed a challenge for the teams, so im sure there is truth to power loss at elevation and the ol butt-ometer. =)
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TheRaven

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Tune-ability probably has a lot to do with it im sure. IDK personally, just adding my experience. Been in CO my whole life so you kinda get used to a little loss in power. When we had Mile High Nationals at Bandimere those cars always had a harder time racing at elevation and posed a challenge for the teams, so im sure there is truth to power loss at elevation and the ol butt-ometer. =)
Had to be fun for you back when the Wrangler had 190hp (at sea level).

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.
 

FrickinAdam

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Had to be fun for you back when the Wrangler had 190hp (at sea level).

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.
Well now thats just a silly thing to say right. Just because something loses power at elevation its not like going up the mountain is like a horse and buggy before forced induction. Going fishing in the mountains in a 78 F250 camper special with my gramps was great. yeah the 400ci got around 8-10 miles per gallon but thats why you had two gas tanks =) We just enjoy our vehicles and no one really cares about the elevation, its just a part of living here. doesn't mean something isn't true.
 

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Well now thats just a silly thing to say right. Just because something loses power at elevation its not like going up the mountain is like a horse and buggy before forced induction. Going fishing in the mountains in a 78 F250 camper special with my gramps was great. yeah the 400ci got around 8-10 miles per gallon but thats why you had two gas tanks =) We just enjoy our vehicles and no one really cares about the elevation, its just a part of living here. doesn't mean something isn't true.

Jeep Wrangler JL 3.6 power loss at elevation the-office-michael-scott
 

DonH63

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I can easily testify to this condition. I lost 21% HP and TQ going from sea level (Houston) to 7,000 ASL (Colorado Springs) with my 3.6L--it was VERY noticeable EVEN with 5.13 gearing.

Anyone who does not feel the difference has not spent enough time between the two...

Power vs. Elevation.webp
Exactly. I live in CO, and our house sits at ~7500' (friends live not too far away who are at 9000'+). Driving off the lot in the Springs (~6000') the power loss is already "baked in" so we don't notice. Driving back and forth to work (7500' to 6500' and back) I never noticed a difference, though I know it is there (albeit only a few %), but highway traffic and such masks it. Heading up mountain passes at 10,000'+ I start to notice, but less so off-roading even higher because I'm usually crawling along in lower gears anyway. We have family in MO and other lower-altitude places, so I definitely feel the extra power there and loss coming back home, but after a few days back home the lower power feels normal again. If you live at sea level'ish you probably don't realize how much extra power you have, and if all your time is spent a mile high you don't realize how much power is missing, because it is normal for you (me, whomever). And how much power my engine makes, or doesn't, didn't factor into our decision to live here, or other family folks' decision to live in MO (OK, GA, etc.)
 

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So with the 2.0 etorque turbo, I had more high altitude power than any vehicle that I have ever driven out west. Very gutsy, at both merging onto the interstate and high speed acceleration to get around something suddenly.

my question is what gas octane level should I be using At altitidude With the turbo? I stayed with 87.
 
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CarbonSteel

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Exactly. I live in CO, and our house sits at ~7500' (friends live not too far away who are at 9000'+). Driving off the lot in the Springs (~6000') the power loss is already "baked in" so we don't notice. Driving back and forth to work (7500' to 6500' and back) I never noticed a difference, though I know it is there (albeit only a few %), but highway traffic and such masks it. Heading up mountain passes at 10,000'+ I start to notice, but less so off-roading even higher because I'm usually crawling along in lower gears anyway. We have family in MO and other lower-altitude places, so I definitely feel the extra power there and loss coming back home, but after a few days back home the lower power feels normal again. If you live at sea level'ish you probably don't realize how much extra power you have, and if all your time is spent a mile high you don't realize how much power is missing, because it is normal for you (me, whomever). And how much power my engine makes, or doesn't, didn't factor into our decision to live here, or other family folks' decision to live in MO (OK, GA, etc.)
Fully agree and had I been here in CO the whole time (to your point) I would not have noticed it as much, but once I did and knew the difference especially with the shifting dragging out in CO versus TX it became a showstopper (the cracked head or block that happened was the final nail in the coffin).

Now that I have 330HP and 415TQ (in a different platform with twin turbo) and soon to be 355HP and 433TQ, that is nearly unaffected by altitude, there is no going back to a NA engine for me.
 
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Zandcwhite

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Sure, but you have to get INTO "the turbo" first.

Again, i'm NOT saying that there is NO difference. Just that it's a small one that we make into a much bigger one in these discussions.
The turbo passes the 3.6L in torque at 2k rpms at sea level. Being the huge difference in elevation power loss at 8k feet (8%vs24%) it probably passes the 3.6L before 1,800rpm. That's literally below the cruising rpms that the 8 speed will even hold a gear cruising, let alone any situation where the power difference would come into play like accelerating, maintaining speed up a steep grade, etc. Any place you would actually be using the power, the 2.0t is already making more torque at sea level and way more torque at altitude. Are we really comparing power loss at idle? I don't care if the thing losses all of is power at idle (ess for all those on here that hate it), in under a second if you push on the throttle the thing is above the 2k rpms. It doesn't need any time to "get into" the turbo. It's there already at cruising rpm and in a fraction of a second from stopped.
 

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The turbo passes the 3.6L in torque at 2k rpms at sea level. Being the huge difference in elevation power loss at 8k feet (8%vs24%) it probably passes the 3.6L before 1,800rpm. That's literally below the cruising rpms that the 8 speed will even hold a gear cruising, let alone any situation where the power difference would come into play like accelerating, maintaining speed up a steep grade, etc. Any place you would actually be using the power, the 2.0t is already making more torque at sea level and way more torque at altitude. Are we really comparing power loss at idle? I don't care if the thing losses all of is power at idle (ess for all those on here that hate it), in under a second if you push on the throttle the thing is above the 2k rpms. It doesn't need any time to "get into" the turbo. It's there already at cruising rpm and in a fraction of a second from stopped.
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.
 

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That's why many piston aircraft engines have turbos.
Yup. That's why supercharger and turbochargers were invented -- to improve high altitude performance in aircraft engines. It was only several decades later that they were fitted onto automotive engines to increase power output.
 

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Zandcwhite

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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.
There are pages and pages proving the 2.0t makes more torque at any usable rpms and any altitude than the 3.6L and that gap grows by 2% for every 1k feet above sea level, and yet some keep talking about the 3.6L having an advantage down low? Down below usable rpms where neither engine makes any power? The 2-300 rpms from 1600 to 1900? Pay attention to the tach next time you drive around and see just how little time your engine spends there. The 3.6L suffers detonation pretty significantly if you try to lug it down that low under load anyway so it's literally an unusable advantage. The turbo is tiny and spools almost instantly as a result. It's not a 77mm turbo that needs 4k rpms to spool up but that's how some act on here. How does the same guy argue a 24% power loss is not noticeable across the entire power band also argue that a 24% torque advantage across a 250 rpm range below 2k is significant? I don't get it.
 

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There are pages and pages proving the 2.0t makes more torque at any usable rpms and any altitude than the 3.6L and that gap grows by 2% for every 1k feet above sea level, and yet some keep talking about the 3.6L having an advantage down low? Down below usable rpms where neither engine makes any power? The 2-300 rpms from 1600 to 1900? Pay attention to the tach next time you drive around and see just how little time your engine spends there. The 3.6L suffers detonation pretty significantly if you try to lug it down that low under load anyway so it's literally an unusable advantage. The turbo is tiny and spools almost instantly as a result. It's not a 77mm turbo that needs 4k rpms to spool up but that's how some act on here. How does the same guy argue a 24% power loss is not noticeable across the entire power band also argue that a 24% torque advantage across a 250 rpm range below 2k is significant? I don't get it.
Jeep Wrangler JL 3.6 power loss at elevation {filename}
 

DonH63

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So with the 2.0 etorque turbo, I had more high altitude power than any vehicle that I have ever driven out west. Very gutsy, at both merging onto the interstate and high speed acceleration to get around something suddenly.

my question is what gas octane level should I be using At altitidude With the turbo? I stayed with 87.
I'd just stick with whatever octane you normally run. It takes a while for the engine to recalibrate, and the turbo forces air into it, so dropping to a lower octane (like in the carb days) doesn't do much of anything. What I find vexing about gas is the state is still in the carb day and gets lower octane than other states, even though altitude isn't really a factor any more, so mid for us is more like low grade in MO. When we travel I tend to stick with the same octane.
 

Zandcwhite

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I dunno man, if you're at elevation you're going to spend a lot of time holding revs where the 2.0 is definitely in the turbo. Max torque at 2500ish RPM. At least 50 wheel torque more than the 3.6. No deficit there.

Jeep Wrangler JL 3.6 power loss at elevation {filename}


Edited to add - to be clear, I do agree about perception. While the engine does lose power, whether it's a big deal or not is all about user perception.
At least 50 ftlbs at sea level. At 10k feet that jumps to 110 ftlbs, nearly double the 140 that the 3.6L is struggling to put out at that point. What's even wilder is that the 2.0t would be putting out more torque at 10k feet and 2500rpms than the 392. 90% of its 285 ftlbs is still 256.5. 70% of the 392s 350ftlbs at 2500 rpms...245. That's how much of a difference both altitude and forced induction make illustrated as plain as day. Bump that up to 14k feet and I think the 2.0t might actually win a drag race against a 392. So much for waiting for it to "get into" the turbo.
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