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Engines at Altitude

Bullitt

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I live in Colorado Springs and specifically chose the 2.7 because of the high altitude that I'll have my Bronco on a regular basis. I'm on Pikes Peak quite a bit as well as many mountain passes. 2.3 would be ok, but things get pretty sluggish up high and not enjoyable at all.
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peta8368

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You already mentioned turbos are good, they can "manufacture" their own atmosphere. That being said, there is still less O2, so the ultimate amount of power is reduced.
Is that really true? Genuinely wondering. I thought the overall make up of the air (% of O2, % of N, etc) is still the same, there's just less of everything in a given volume. So if the turbo is compressing the mixture to the same PSI as it would at sea level, it would give you about the same oxygen for burning, therefore produce about the same HP. Is that not correct?

Also, with my previous cars, especially on stock tune, the turbo is capable of producing way higher pressure than the ECU allows. So I would expect the turbos to be more than capable of compensating at altitude. With aftermarket tune, the requested pressure is a good deal higher, so there's less margin above that, then the smaller stock turbos could run out of efficiency and not produce the same PSI as it would at sea level.

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Peter
 

Mattwings

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Is that really true? Genuinely wondering. I thought the overall make up of the air (% of O2, % of N, etc) is still the same, there's just less of everything in a given volume. So if the turbo is compressing the mixture to the same PSI as it would at sea level, it would give you about the same oxygen for burning, therefore produce about the same HP. Is that not correct?

Also, with my previous cars, especially on stock tune, the turbo is capable of producing way higher pressure than the ECU allows. So I would expect the turbos to be more than capable of compensating at altitude. With aftermarket tune, the requested pressure is a good deal higher, so there's less margin above that, then the smaller stock turbos could run out of efficiency and not produce the same PSI as it would at sea level.

No?

Peter
It is my understanding that there is actually less oxygen at higher altitudes, not just “thinner air”. The turbo can overcome much of the difference, but the ultimate available oxygen is less as you go up. It’s particularly true in planes, where piston engines are limited by ultimate efficiency above a certain altitude. Not sure of the actual chemical composition or limits.
 

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When I moved to Colorado Springs many years ago, I had to rejet my carburetor to not run too rich. Modern engines adjust fuel/air mixture as needed, so no worries on a new vehicle. it will still work adequately.
 

The Bronze

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At altitudes we drive at, it is less of an issue with amount of oxygen, but with a lack of pressure to push the air into the engine. Up in Woodland park, right up the pass from Colorado Springs, (8500') The air pressure was 75kpa, compared to around 85kpa in the Springs or around Denver. That is 12% less air, creating less compression and lower power. On turbo motors, that change is less under boost conditions, but until you spool up, you will be living with lower power levels. Even when you are boosted, you will still be at lower power levels than at sea levels, but not nearly as bad as with naturally aspirated engines.
 

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I live up 25 in Denver - youve got nothing to worry about on the power issue especially with forced induction.

I have a n/a RAV4 and my wife has a n/a a challenger GT - they are both fine in the mountains. The ECU compensates on the fly- it’s not like carb days. Yes, they lose a bit of power, but they run fine. Turbo applications will lose even less.
 

RunninRiot

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One element to consider is mountain driving. I have two big inclines that I have to merge onto often that can get sketchy with our 4cyl. I had to teach my gf that she has to mash the gas from the stoplight all the way to merge to integrate with the flow safely. My old Honda Pilot handles that with no problem. Also passing and changing lanes can get interesting when you are driving in the mountains. My thought was to go 2.3 for the 2door and 2.7 for the 4.
 

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Having grown up in Colorado and one of my favorite drives is Argentine Pass, I don't see either the 2.3 or the 2.7 having problems at altitude. There will be noticable power loss but both engines have more hp and torque then any vehicle I ever taken above 13000'.
 

Akula22

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Have to admit I greatly appreciate all the insight from the Colorado crowd. We are planning to move that way within the next couple of years so glad to know there is a big Bronco community.
 

sko

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I quite often find myself camping close to 10k, so I decided on a 2.7. Rather have more power than too little. Plus the 2.3 would be running higher RPMs more often then the 2.7, IMHO.
 

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Wizard1183

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A simple tune will fix any concerns you might have. Just like a carburetor. You tune it different up north than down south.
 

HideoutBronco

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Generally you want to use the lowest octane that does not cause detonation. On newer more advanced knock sensor applications on turbo engines things are more adaptive...20yrs ago if ran 14lbs of boost and 13:1 on 91 you were put in a straight jacket.

Octane rating is the resistance to burn or ignite. The reason you have lower octane at altitude is in part with less air it can be harder to ignite so a lesser octane is available.

The MAF measures the air, volume and density. It does this by heating two wires that are being cooled by the air flowing over it. The meter measures the voltage it takes to keep the wires at x temp...more air more volume/mas. Hence the Mass Air Meter. Using this air information and other inputs it changes timing and fuel tables accordingly. Think of it as several ven diagrams to find targets and set limits.
Owners manual for Bronco is very specific for high octane at altitude.
 

HideoutBronco

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I drive everyday at 6500-7000ft. I have had my 2.7 as high as 9,700. I really have not noticed much of a different from where I picked it up at 600ft.

The turbo helps a lots, but there is no replacement for displacement but you your 2.3 should still be OK.

I also have a supercharged Range Rover Sport that does just fine....my boat however, needed to be re-propped and my naturally aspirated vehicles are dogs up here.
 

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I have been driving a loaner 4 cyl. BB for the last 4 weeks, did 2500 miles, including engine break-in. I live at 6000 feet and took it to 11000 on excursions. Now, this is with AT, but I can confirm this puppy rides really good, plenty of power, acceleration is awesome, spools up plenty fast, and if you put it in Sport-mode, you better hold on to your grab handles!
I think the tuning is really good, so good, that I have doubted my selection of the 2.7 on my own BD.......
 

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Is that really true? Genuinely wondering. I thought the overall make up of the air (% of O2, % of N, etc) is still the same, there's just less of everything in a given volume. So if the turbo is compressing the mixture to the same PSI as it would at sea level, it would give you about the same oxygen for burning, therefore produce about the same HP. Is that not correct?

Also, with my previous cars, especially on stock tune, the turbo is capable of producing way higher pressure than the ECU allows. So I would expect the turbos to be more than capable of compensating at altitude. With aftermarket tune, the requested pressure is a good deal higher, so there's less margin above that, then the smaller stock turbos could run out of efficiency and not produce the same PSI as it would at sea level.

No?

Peter
I can confirm, my trade in for the Bronco was a 2019 Toyota 4Runner TRD Off-Road. Above 6000 feet that thing was terrible. It barely was able to pull a tiny 2000 lb trailer. I had to crawl over Wolf Creek Pass st 35mph. With the Bronco 2.3 with AT, zippy snap, no issue at all.
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