How much does high elevation really affect engine performance?
Posted by czarfalcon@reddit | Autos | View on Reddit | 94 comments
This question popped into my head after a recent experience, so I figured I’d ask Reddit. I’m currently visiting Denver and we ended up with a Camry as our rental car, which is what we also have back home. Different trim, but still same engine. However, while driving on the highway I noticed that it feels much more sluggish than what I’m used to, so I started wondering if elevation plays a factor (where I live is only ~500ft, which is where my baseline is coming from).
It makes sense that it would - engines need oxygen, and there’s less of it at higher elevations - but maybe I’m not giving modern cars enough credit and they can adjust the fuel/air mixture accordingly. Or maybe it really is that simple!
If that is the case, what do people who live in higher elevations do to compensate for the power loss? Just accept it? Do turbos make more of a difference than they would at sea level?
NigraOvis@reddit
my car is stock "4.1 seconds 0 to 60" at 6000 feet, i can get \~5.1 seconds. so that's pretty noticeable.
Bot_Fly_Bot@reddit
It makes a huge difference. And yes, turbos help.
czarfalcon@reddit (OP)
I’m curious if dealers sell more turbocharged cars out here because of that. I’ve already seen way more AWD badges than I do back home, I wouldn’t be surprised if turbos are equally desirable. I already know if I lived here that would be higher on my wishlist.
BananaBeach007@reddit
Up in the sierras its the same AWD and cars like 4runners are the premium cars, but there is a big demand for turbo diesels as they do quite well.
manesag@reddit
It’s honestly much simpler than that. They have AWD cars because of snow and they think AWD is better than just getting snow tires. As for turbo, I’m sure if the dealer can upsell people on a turbo engine that’s more expensive, they would. Past that a lot of cars are turbo because of mpg and emissions
larz_6446@reddit
Turbos were invented just for this purpose for airplanes. Stuffing air into the motor allows you to add more fuel. MOAR power!
redoctoberz@reddit
Sorta- it allows you to maintain sea level engine power output at altitude. You’ll still have loss on the propeller blades as there is less air to “grip”.
The_dog_ate_my_work@reddit
The thin air permits higher true air speeds. The propeller will have less air resistance. The same indicated airspeed will yield higher true airspeed at higher altitudes.
https://youtu.be/g2yJ02CKWho?si=JMzt1Mct963W9QdK
redoctoberz@reddit
I understand TAS, I’m a certificate holder.
The_dog_ate_my_work@reddit
The efficiency loss on the propeller is only during acceleration.
redoctoberz@reddit
You might want to double check your work. If you want a real easy example look at "tip mach number"
Overall flight efficiency is determined by many factors, only one of which is the propeller.
larz_6446@reddit
Thin air. Gotta love it
EZKTurbo@reddit
On my old turbo car I noticed that at high elevation it couldn't develop the same max boost as it could at sea level. And I'm sure it would have been a complete dog without the turbo at all.
Gold_Rooster135@reddit
Question: if i buy a boosted car from Colorado, and drive back to wisconsin, would the massive elevation change destroy anything, Colorado 6000ft and wisconsin is 635ft
czarfalcon@reddit (OP)
Do you mean like aftermarket boost or just a normal turbo?
Gold_Rooster135@reddit
Yeah aftermarket turbo on a car that's dyno tuned in Colorado at 6000ft, would it be damaged driving to wisconsin which is 635ft
czarfalcon@reddit (OP)
I don’t know much about boosted/tuned cars so I can’t say for sure but I don’t imagine it would be a problem. If it’s tuned for a higher elevation you might need to retune it when you get home since there’s more oxygen in the air at lower elevations, but if anything that would mean you would need to run less boost to get the same power.
Gold_Rooster135@reddit
I just can't really find any info on it, since it's such a drastic change altitude/elevation
WhenVioletsTurnGrey@reddit
I run webers on a 289 V8. You need to adjust or re jet for different elevations.
We have a 2009 Yaris that we took up over the pass to Vail, CO. Man, that poor thing was struggling as we got up in elevation.
IndustrialDesignLife@reddit
I have a 1965 fastback Mustang with a 289 (stroked and bored to 305) that runs a 13.5 in the quarter here in Denver. In Detroit it ran a 12.8
It makes a huge difference
sonar_y_luz@reddit
Could track surface also account for some of that?
zneave@reddit
Man I'm jealous I want to put webers on my grandpa's 289 in his 66 mustang. They look so cool!
WhenVioletsTurnGrey@reddit
They are wicked. But, a lot of work to get them set right & some maintenance to keep them running good. Nothing better, when they are running, though
keb1965@reddit
You lose about 3% of the power for every 1000’ above sea level. It’s definitely noticeable, and if you drive a normally-aspirated car higher into the mountains, it can really be a slog.
I always coped with it by griping occasionally and by enjoying the extra pep when road tripping at lower elevations.
cache_hierarchy_tip@reddit
Yes this was super noticeable when I drove my 09 civic si in colorado when it is normally close to sea level. I didn't do anything at the time but I think one thing a person can do to alleviate this is to reset your ECU if you're going to spend time at altitude. It will then adapt properly.
asamz33@reddit
I,would pull the starter or choke (?) Give it more gas !
Xoferif09@reddit
Chokes don't work that way.
They literally choke the air intake lowering the amount of air that enters = less power.
jcforbes@reddit
Which would then make even less power. Engines work by burning oxygen, the fuel is only there to allow that to happen. If you add extra fuel beyond the optimal air:fuel ratio the flame front is too cold and you burn less oxygen.
donethinkingofnames@reddit
Most cars have been fuel injected for the last 35 years or so. Chokes are a carburetor thing.
neon57O@reddit
Less air equals less power. No matter what kinda computer is controlling it, no matter what kinda turbo you have.
Just how she goes
EverlastingBastard@reddit
The car compensates for the air density yes, but there is still less air and therefore less oxygen. The compensation doesn't make it more powerful, just makes it run at the proper fuel/air ratio regardless of where you are, elevation, or air temperature.
Forced induction helps significantly.
Dnlx5@reddit
If you are running knock based spark advance on a high compression NA car, you might be able to run more advance and get a little more power. This might compensate for some of the lost oxygen... but not much.
LeMadChefsBack@reddit
You will never get more power from less air.
Dnlx5@reddit
What I mean to say is that the car claws back a percentage of the lost power by running more advance. Still loses power, just not all of it.
LeMadChefsBack@reddit
And you are still wrong.
All things being equal (optimal tune for elevation) you are going to have less power the higher you go.
Obviously if you have a "bad tune" for sea level and a "good tune" for a higher elevation you *may* have more HP, but that is a silly comparison - Especially for any car made in the past 20-30 years with computer controlled fuel injection.
Dnlx5@reddit
This article discussed Ford's knock and timing strategy. They are known to be some of the more aggressive in the industry with their timing and knock strategy. Of course the turbo nature of the engines help even more in response to U/czarfalcon original question.
https://www.motorsport-developments.co.uk/Understanding_Ford_Ecoboost_Knock_Detection.html
LeMadChefsBack@reddit
I’m not going to talk to you any longer as you are unaware of the topic of conversation and you don’t understand the fundamental physics involved here.
Dnlx5@reddit
If you want to ignore my input and leave that is up to you. But you are the one uninformed on the latest technology and ignoring the ability of modern cars to adjust to elevation changes.
Dnlx5@reddit
Here is a white paper that discussed how Mazda was able to increase their compression ratio and employ knock reduction strategies to ensure they maintain stable combustion. This includes timing retardation and EGR, as well as piston design and high pressure fuel injection. This creates a wide margin of ecu power demand depending on current knock levels.
In July in Houston when the intake air temp is 140f these strategies will be used heavily to reduce power. While the extra oxygen is helpful. The engine will be effectively running lower compression and retarded timing. On the same day in Denver the IAT will be 70f, the car will use much more of its available timing and much less EGR. Still probably making less power, but at a higher Brake Specific Fuel Consumption.
https://www.mazda.com/en/archives/skyactiv/skyactiv-g/
LeMadChefsBack@reddit
That paper says nothing about the topic of this thread, and Mazdas Skyactive research isn’t about “getting more power at elevation” it’s about finding the optimal way to get closest to the ideal Stoichimetric ration for burning gasoline. That ratio is basically X amount of air and Y amount of fuel will give the most efficient burn.
REMOVING AIR MEANS LESS FUEL AND LESS POWER.
You are still wrong. THere’s no magic solution (other than adding more air, or a reactant like nitromethane) to get more power at a higher elevation.
Dnlx5@reddit
I never made the claim that you would get more power, only that modern cars can compensate for the loss to a degree.
The Mazda has the ability to introduce more air to the combustion chamber in Denver than in Houston by running less EGR. The paper explains that as an anti knock strategy, one that I am claiming would be needed in Houston in July. But less needed in Denver on the same day. Does that make sense? Yes it may still make less power, but it is compensating somewhat.
Dnlx5@reddit
I'm angry!
Dnlx5@reddit
Answer me this, is it your opinion that
A. A 1970 Honda Civic , and a 2023 Honda Civic would lose the same percentage of their hp when driving from Houston to Denver.
Or
B. A 2023 Honda Civic would claw back a percentage of the lost hp using various techniques to compensate?
Dnlx5@reddit
Nissan did a few cars with the truck mechanical variable compression for the same reasons. https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHIVE/VC_TURBO_ENGINE/
Dnlx5@reddit
Actually the Houston Denver example is quite close on density altitude. Effectively the DA between those two places is only about 1000ft different. I wouldn't be surprised if a new Mazda 3 makes the same hp in both places. Assuming it's run on the same fuel.
https://en.m.wikipedia.org/wiki/Density_altitude
Dnlx5@reddit
No I am not.
In a simplified view, engine hp is limited by oxygen content, but this is not the case for modern production vehicles. Engine hp is now limited by many different things in order to ensure that power is made with maximum power/liter of fuel used as well as power/emissions produced.
To do this, many vehicles pull ignition timing as previously discussed, but also utilize things like EGR to limit oxygen induced in the engine. OP was asking "engines need oxygen, and there’s less of it at higher elevations - but maybe I’m not giving modern cars enough credit and they can adjust" and the answer is yes, modern cars do adjust to claw back some of the lost hp.
Worldly_Ad_2490@reddit
Turboes can speed up and compensate for the thin air. At high altitude a NA engine loses 3% per 1,000ft. So 15% in Denver.
biryebread@reddit
Yes, I live in MT which is kinda lower elevation for the mountain west (~3500ft). I notice the difference in my turbo cars between the coast and here, in a small N/A car I imagine it would be a big difference
blankblank@reddit
This was one of the first breakthroughs in airplane engines: figuring out you need to compress a ton of air and force it into the engine to make up for the low air pressure at elevation. Obviously, the effect is less for cars, even when driving in the mountains, but the principle is the same. The higher you go, the less air the engine is getting, and the greater the need for turbochargers or superchargers.
Historical_Usual1650@reddit
You're absolutely correct that high altitude can affect engine performance. At high altitudes, the air is much thinner, meaning there is less oxygen available for combustion in a car engine¹. In addition, the atmospheric pressure is lower at high altitudes, which can cause fuel vaporization issues¹. As a result, high altitude can have a significant impact on a car engine’s performance¹.
Generally speaking, an engine loses 3% of its rated power after every 1000 feet of altitude gain⁴. So if you have 100 horsepower at sea level before climbing to 5,000 feet, your engine will produce around 85 horsepower in elevation¹. At 10,000 feet above sea level, you can expect your engine to generate around 70 horsepower¹.
Modern fuel-injected vehicles have computerized engine-management systems that adjust to changing altitudes automatically¹. In the case of gasoline engines, higher altitude theoretically reduces fuel consumption by reducing the frictional forces at the throttle due to the wider throttle opening¹.
As for what people who live in higher elevations do to compensate for the power loss, it varies. Some might just accept it. However, using a turbocharger is an efficient way of minimizing your car’s power loss at a high elevation because turbochargers compress more air into the engine’s cylinders, which in turn makes up for the lower air density². Diesel engines are also more efficient than gasoline engines at high altitudes¹.
(1) High Altitude’s Impact On Car Engine’s Performance | Carhampt. https://carhampt.com/high-altitudes-impact-on-car-engines-performance/.
(2) Does Altitude Affect Car Performance? – Torque Guru. https://torqueguru.com/blogs/news/does-altitude-affect-car-performance.
(3) Does High Altitude Affect Your Vehicle’s Performance? - MotorBiscuit.com. https://www.motorbiscuit.com/does-high-altitude-affect-your-vehicles-performance/.
(4) Does High Altitude Affect Car Engine ? [Answer] 2023 | DynoCar. https://www.dynocar.org/does-high-altitude-affect-car-engine/.
Geck06@reddit
Enough that I wonder why my friends same model motorcycle is so much slower than mine. Until I remember that I only ever drive his in Colorado.
Reve_Inaz@reddit
This is the reason heavy EV's are dominating Pikes Peak nowadays. They keep the same efficiency at the higher altitudes, whereas the NA ICE lose power and thus speed.
bigjimnm@reddit
Turbocharged engines are much less affected. The canry is not turbocharged.
I live at over 7000 feet elevation (Los Alamos, NM) and having a turbo (or EV) is essential.
Agitated-Pen1239@reddit
I live in ABQ but work in Santa Fe. Such a huge difference in power even between the two. My car is turbo and I still feel the difference pretty significantly, I live at 5.5k feet down in ABQ
bigjimnm@reddit
We get to ABQ all the time, and there's definitely more power there. It's about the lowest place we ever go with our cars.
czarfalcon@reddit (OP)
It’s funny how different features are more (or less) desirable in different regions. Where I live turbos are nice (more power is always better, right?) but definitely not essential, AWD isn’t needed at all, and I’d trade heated seats for ventilated seats in a heartbeat given the choice. Looks like I’d have a very different set of priorities if I moved up here.
SirAlfredOfHorsIII@reddit
Watch the grand tour special where they go up in elevation to see how much it effects the engine. They were commenting on how much power the engine was losing as they climbed. Plus also how little they could breathe
Agitated-Pen1239@reddit
My i30 n-line is substantially slower where I live, which is 5.5k feet. When I go to Las Vegas at 2k feet it's a huge difference in power, tiny turbos at elevation still get choked out.
1800lampshade@reddit
WWII aircraft are a good read on how they dealt with altitude performance to remain competitive in combat.
Superchargers with gears!
19Ben80@reddit
Air + fuel + spark = bang
Less air or less fuel = smaller bang
Rude-Manufacturer-86@reddit
Car detects less dense air, compensates by adding fuel, to try and add power.
czarfalcon@reddit (OP)
But turbo = more air = bigger bang, right? So I can see how it would be more desirable to have the higher up you are.
19Ben80@reddit
More air = good when also more fuel (bigger injectors needed) Less air = bad
czarfalcon@reddit (OP)
Does it need bigger injectors or can the car’s computer just tell it to pump more fuel in faster?
As you might have guessed, I am not a mechanic
19Ben80@reddit
Not technically no but to get the most out of the turbo it generally does.
You could set the boost lower to compensate for the lack of extra fuel
daffyflyer@reddit
Depends, basically you control injectors by just opening and closing them, the longer amount of time you open them the more fuel comes out. Once you get to the point where they're open 100% of the time, you can't make any more fuel come out, and you usually need bigger injectors (or more fuel pressure, or both)
Rude-Manufacturer-86@reddit
Isn't the rule 10% HP per 1000 feet?
CabbageaceMcgee@reddit
I recommend The Grand Tour: Columbia Special and also the episode where they drive Jaaaaags.
novascotiabiker@reddit
I follow a YouTube channel that does car reviews in Colorado,I believe most cars they run in the 1/4 mile are 1 second slower or a little more compared to sea level
NigelShiftright@reddit
They TURBO -- that technology goes a long way to solving this problem.
I had a non-turbo Mercedes diesel up at 10,000 feet and the damn thing would barely move.
Ay-Caramba_Dude@reddit
The rule of thumb of heard is that you lose 3hp per 1000 ft above sea level. Be careful passing cars, especially in the mountains.
czarfalcon@reddit (OP)
Yeah, I’m not planning on taking this up to Pike’s Peak or anything, but it was absolutely noticeable when trying to overtake on I-25.
That would mean about 15 less hp than what I’m used to, in a car that only makes ~200 in the first place. I guess I’m glad we got an upgrade from a Corolla then!
MerkinMuffley1@reddit
You’ve lost 30hp, not 15, out of 200, youre basically driving a 90s corolla at that point. 170hp is very meager and you should definitely be rethinking overtaking vehicles
Jdibs77@reddit
I actually took a first gen BRZ (so...about 200hp) up to the top of Pike's Peak. I can't say I really felt THAT much of a difference just being in Colorado in general. But yeah the power loss gets REAL as you trek up that mountain. Plus you're going uphill, VERY uphill.
Not a fast car to begin with, but holy shit it was so slow. I had to basically floor it and run at like 4000+ RPM to get anywhere
600whp_GT500@reddit
Its 3% of your engines horsepower per 1000 ft.
HarveyMushman72@reddit
When I sold parts, we sold leaner jets with new carbs as we are at 5,000 feet. Out of the box, they are set up for sea level.
daffyflyer@reddit
Even in the best of circumstances with the ECU doing it's best to keep everything the same, you'll still lose power linearly with lower air pressure. a 1.0ltr engine in 0.9bar atmosphere is functionally a 0.9ltr engine in terms of how much oxygen it can get and how much fuel it can burn. Doesn't matter what AFR you run, there simply is less oxygen to go round.
Turbos are a different situation though, they can happily compress the air and solve the problem, lets say our 1.0ltr engine runs 1bar of boost. That means in 1.0 bar atmospheric pressure, the engine sees 2.0bar and it's more or less functionally a 2.0ltr engine.
If we take it to somewhere that's 0.9bar atmospheric pressure then the turbo will still bring the pressure up to 2.0bar, so it'll still be functionally a 2.0ltr engine.
The difference is though, it'll be basically be doing 1.1bar worth of work to compress that air, the higher we go the harder the turbo has to work, and it'll get less efficient and output hotter and less dense air, losing you some power.
Depending on the specs of the turbo, if you go high enough it eventually won't be able to compress the air enough and you'll have to lose boost and more power.
That's the short version of it, if you want to know more, then look at compressor maps for turbos and learn how that stuff works :)
heartfullofsomething@reddit
2-3% per 1000 ft. I living in Aspen. So my already slow Subaru outback (175hp) is making around 25hp less
TehGogglesDoNothing@reddit
Air density in Denver is about 82% of sea level. That means you get about 82% of the power out of a naturally aspirated engine.
asonofasven@reddit
I live around SLC, UT (4,300 ft) and I can tell my 2004 Tacoma never made any of its advertised 190 HP. But my 2 turboed cars, 2013 Fusion 2.0L Ecoboost and 2021 Civic Hatchback 1.5L always felt peppier than their HP numbers.
timmcg3@reddit
Definitely a noticeable difference with a NA car. My Toyota 86 was the worst, it wasn’t very powerful to begin and got considerably worse at elevation. All my cars since then have been turbo or supercharged and have far more power to begin with so it’s barely noticeable.
64Olds@reddit
Spent a week in the Chilean Altiplano (high desert) with a 2014 Forester once. Thing drove like an absolute dog. Back at sea level, it was great.
v60qf@reddit
Yes.
Source: Top Gear Bolivia special
LeMadChefsBack@reddit
Or, in the real world - the Pikes Peak International hillclimb.
TotesNotADrunk@reddit
I see you're a man of culture as well
TotesNotADrunk@reddit
I see you're a man of culture as well
Barely_stupid@reddit
I had my GT350 in Colorado and calculated it was down about 100HP.
terroristteddy@reddit
It'd be down about 80-90 in the Denver Metropolitan area.
Barely_stupid@reddit
I was out west a bit more. The Eisenhower Tunnel is 11,100 feet. Still made neat noise in the tunnel though!
19Ben80@reddit
Air + fuel + spark = bang
Less air or less fuel = smaller bang
asamz33@reddit
I am very curious about this.
I am on my fourth car with turbo diesel: Cherokre crd 2.8
Golf 6 110 tdi Audi a6 3.0 tdi quattro Nissan t31 2.0 dci
Nothing ever happens if it is steep. Right pedal to go forward.
Elevation has never been an issue.
I trust that turbo + diesel may sound strange outside EU but all the ponies are there all the time.
I believe it should be same for a gas / petrol engine because of injection also.
Any carburated gas or diesel engine will suffer from elevation. Just by physics. It is a matter of density
With a turbo or a compressor you can offset this. ( turbo / compressor max specs in mind of course)
I drove also several gas car in elevation and never noticed anything wildly diff.
I care to learn of your experience !
czarfalcon@reddit (OP)
Turbo diesels are relatively common in the US for pickup trucks, but diesel cars have basically been dead since the VW emissions scandal.
I suppose it’s just a difference in what I’m used to. Since I live somewhere at low elevation, I’m used to a certain amount of power from that specific car and engine and I could feel the difference at high elevation. I’m sure if I lived somewhere at high elevation, it would eventually become normal to me.
Sullypants1@reddit
It’s the turbo doing the work. Same as a turbo gas engine would do. It’s not the fuel type but getting a full charge of oxygen or not is the difference.
TW1TCHYGAM3R@reddit
Not just engines can be effected by high elevation. (yes I know the lower oxigen levels are the issue with engines)
I used to live (moved last March) on a mountain about ~2000ft above sea level and I used to have shift shock issues with my Mazda3 automatic transmission. Reset the TCM and everything is back to normal.
The newer Mazda3's use a multi-clutch torque converter transmission and the high elevation seems to confuse the TCM causing it to have inaccurate clutch points causing shift shock.
Since I moved to somewhere much closer to sea level I haven't had issues since. Mazda even made a TSB and a new TCM firmware to help with the issue.