29 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHDoes altitude affect performance?
Leading reported evidence
Adjust properly
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Leading evidence: 'Adjust properly' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust properly' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
29 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261027T003124Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hello all, I live in Keystone Colorado, where the altitude elevation is about 9300 feet. Once a week I drive to Denver, which is about 5200 feet, about 4000 feet less. Now I do understand the concept of fuel injection, but it seems the car is peppier in Denver as opposed to Keystone. Is that possible?
The way I understand it - As you increase elevation, density decreases which produces a negative in performance, especially in the dry hot summer months. Your case is reverse.
IMHO, the car's ECU is making thousands of adjustments during a drive cycle. If you drive the car regularly at 9300 ft and then take a one day trip 4000 ft down in elevation, it affects the combustion events - air-fuel timings. The car needs time to adjust properly. During this adjustment period you may notice a dip in performance.
I always enjoy this time of the year when driving the 996. It's loves the cooler dense air and you can really notice a performance jump.
I think the OP is noticing the same thing. Tell me if I'm wrong, but it seems the historical the Porsche flat engines always performed so much better in hill climbs than other engines. I remember reading an 50s article in MotorTrend comparing the corvette to the 356. The 356 with it's flat 4 engine beat the V8 on the hill climb.
In the article, Thoms said. "Match the two cars on a tight mountain road where the Corvette's torque and acceleration can't be utilized and you'll probably get there quicker in the Porsche. It just hangs on better in the turns."
I've never driven a 356 but have driven a 1959 and a 1962 Corvette. Both handled like a lumber wagon(see example below)! So...I would pick the 356 on twisties for sure even sight unseen.
Absolutely! I moved from the east coast to aspen many (many) years ago in a carbureted car. I barely made it over the pass doing 10 mph in the shoulder with the flashers on. Adjusted everything after I got there and no problem thereafter.
Smaller engine has less torque and needs appropriate, I.e. shorter gearing to drive a given car (weight). On a climb the shorter gearing will allow the engine to get on cam and increase rpm to reach max power rpm. A large displacement engine with higher torque but longer gearing will suffer disproportionately more than it gains from the higher torque.
It doesn't adjust in the sense that there is a long term adjustment to being operated at 9300 ft that then is re-adapted to 4k ft. As soon as a change in any of the inputs that govern ignition timing and/or injection duration is sensed it will respond immediately and always identically.
Naturally aspirated engines see a power loss of roughly 3% per 1000 feet of elevation gain. So 300HP at sea level is reduced to ~ 250HP in Denver and ~ 220HP in your home town.
This is very true...Drag Strips in Denver are notoriously slower Et's than Drag Strips in Baton Rouge......and Dynos have to be calibrated for elevation to be able to compare actual HP.......The Pilots from WWII who started Drag Racing after the war were the ones who introduced Nitrous Oxide to cars......It was what they used in Fighter Planes in WWII to be able to go faster and climb higher altitudes than the enemy in WWII to win the War !! ( Nitrous Oxide is a liquid Oxygen bearing chemical).....
I live at 80’ above sea level.
I’ve worked temporarily all over the US and Europe.
About 10-15 years ago I was shocked how poorly my 4 cylinder rental car (Toyota Yaris) drove when working in Laramie WY. (7200’)
I decided I never wanted one in the future.
I had to rent a Toyota Yaris just weeks later in Denver(5280’) and it felt much better, but still a bit sluggish.
In Tampa FL(48’) a similar Toyota Yaris drove like I expected. (I asked for the Yaris to see the difference)
The Yaris was not a bad car to drive as long as it wasn’t at high altitude.
I'm trying to give you guys some deep wisdom here.
Not only will you get great radio reception at high altitudes, but coming down the hill, you'll get GREAT gas mileage.
Put the car in neutral and let'r roll!
FWIW
Moist/humid air is less dense than dry air
Hot air is less dense than cold air
Less dense = less power
Going up a mountain on a dry hot day would be �less bad� than doing so on a hot and humid day.
A little automotive trivia...
While "hot moist/humid air" no doubt effects combustion/AFR, drivability, good FI can partially compensate for it enough to make for smooth running.
A carbureted engine needs to be down jetted.
Important to not mistake incorrect AFR/engine misfire, with HP loss at altitude...
So, "hot moist/humid air" is a small HP loss, not even really comparable to HP loss at elevation once AFR is compensated for...
Our 300hp engines make 2/3 the HP at 10,000' compared to sea level.
Turbo charging/super charging/nitrous oxide/oxygenated fuels, helps at elevation, but, there is no 100% compensation for less O2 at elevation.
Its just math...
https://calculator.academy/hp-loss-a...de-calculator/
It is a basic physics question...
Oxygen (02) is the horsepower "potential" ....you can't burn fuel without it....IE ....the more Oxygen (02) you can get into the cylinder, the more fuel you can burn, the more fuel you can burn the more power you can make.....so Oxygen (02) is the limiting factor for power potential...
Generally:
Decreased atmospheric pressure = decreased engine performance.
Increased atmospheric temperature = decreased engine performance.
Increased humidity = decreased engine performance.
Increased altitude should decrease atmospheric pressure and decrease atmospheric temperature. While there is usually a temperature drop, the altitude pressure decrease has a far greater impact = decreased engine performance.
In all of these cases, drag technically decreases too.
Engine AFR management plays in there too.
All this to say that generally the OP should have experienced a performance increase, but a unique set of conditions may have allowed his butt dyno to experience otherwise.
Curious to hear if he ever makes the same drive again and has a different outcome!
I can tell you all about cooling efficiency loss…3rd radiator, GT4 style intake vents, PDK cooler, 2.5l deep(er) sump…but I don’t get scary hot any more!
[Image-only post; no author-written text. Original image references:]
https://cimg3.ibsrv.net/gimg/rennlist.com-vbulletin/443x312/mindblownkrammer_f84a6b340e29b5231f46313fec58efe98eed4127.gif
[Image-only post; no author-written text. Original image references:]
https://cimg9.ibsrv.net/gimg/rennlist.com-vbulletin/200x200/dragdecrease_641e7665d2fd7e7beff9df2f29f4d623fa268144.gif
I remember my move to, and then from, Denver. About 3% loss for 1000ft altitude. Even turbo cars suffer since air density is still less. My truck was almost useless driving to breck. And, my rs3 feels significantly quicker down at sea level.
