How Does Driving At High Elevation Affect Your Engine Power? Here's What You Should Know

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Think backmost to subject people successful school. You were taught that nan Earth is simply a gigantic sphere pinch a bladed furniture of ambiance complete it. Despite what Flat Earthers claim, nan aerial we respire does not request a container, for gravity itself is nan container. (If you request reminding we unrecorded connected a globe, watch livestreams of nan Earth from nan ISS and witnesser nan curve.) 

Despite nan separator of abstraction having a sanction (the Kármán line), there isn't a hard, defined delineation betwixt "air" and "no air", but much a wide area astir 50 to 62 miles up wherever aerial density is truthful low, craft can't enactment aloft. Air unit drops nan farther from Earth's aboveground we travel, and while the unit astatine oversea level is 14.7 pounds per quadrate inch, it's only astir 60% of that connected apical of Pikes Peak successful Colorado.

Cars request aerial conscionable for illustration group do, but nan symptoms of altitude sickness present otherwise betwixt you and your Honda. While you'll get dizzy, nauseous, and weak, your car will conscionable get weak. The wide norm is that each 1,000 feet you climb, your car loses 3% of its horsepower. A 300 hp 1995 Mustang Cobra R astatine oversea level, for instance, will only make 210 hp astatine 10,000 feet. If you're going to thrust astatine precocious altitudes for immoderate magnitude of time, owners of older carbureted cars (or caller carburated cars for you fans of Cobra and 356 replicas) will person to rejet your carbs, among different modifications, to compensate for vaccum unit drops. 

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Even if those oxygen atoms don't want to participate your car's combustion chambers, they won't person overmuch of a prime if you've sewage a turbocharger aliases supercharger. At least, forced induction makes it imaginable to get nan conditions basal to compensate for altitude-related powerfulness loss. Unfortunately, turbochargers and superchargers are unintelligent pieces of machinery, and will nutrient boost willy-nilly if allowed. To dress up for powerfulness losses astatine higher elevations, 1 of 2 scenerios has to happen.

In script one, nan motor uses strict machine controls to show each facet of capacity truthful it tin compensate for air-pressure variance. The conveyance must beryllium capable to comparison throttle position and motor speed, cognize if nan engine's moving excessively rich | aliases excessively lean, and power really overmuch unit to merchandise from nan wastegate, if any. Turbo wastegates modulate boost pressure, which is awesome because you don't want chaotic boost to destruct costly parts. (And yes, you tin usage a wastegate pinch a supercharger; Motor Trend reports that Stenod Performance has done it pinch centrifugal superchargers.) 

In script two, nan turbocharged aliases supercharged car is group up to run astatine a fixed altitude permanently. If, say, you're moving a supercharged car astatine 10,000 feet, you tin switch pulleys to alteration nan magnitude of boost going to your motor truthful you person nan aforesaid powerfulness arsenic your sea-level friends. The math-inclined among you tin moreover fig retired really overmuch boost you request pinch nan Performance Trends Blower Boost Calculator.

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Air heats up arsenic it's compressed, and successful gasoline engines, this tin go a problem. Between piston compression and spark plug ignition, pockets of nan air/fuel substance tin detonate erstwhile and wherever they consciousness like. The higher nan compression ratio, nan much apt this is to happen. This arena is called knock, detonation, aliases ping. Sure, terrible sound mightiness sound for illustration harmless, distant, crackling, but it tin ace pistons aliases rustle caput gaskets.

Thankfully, gasoline pinch accrued octane ratings prevents sound successful high-compression engines, and moreover lets your Ford EcoBoost motor really make its advertised horsepower. Octane isn't a constituent aliases an additive, it's a standing of a fuel's stableness and its guidance to unwanted combustion.

As elevation increases, little oxygen is making it into your engine, which intends nan chances for sound goes down. So, your motor tin person compression that would beryllium rather precocious astatine oversea level (say, 12:1), but pinch nan decreased oxygen content, it wouldn't request high-octane fuel, because nan ambiance itself will trim nan compression ratio. So, successful immoderate of America's much elevated locations, substance stations will transportation 85 octane gas. If your car's going to make little powerfulness anyway, why not return capable it pinch cheapo gas, right?

No, don't do it! Modern computerized engines are designed for circumstantial operating windows, and if 85 isn't successful that window, you're asking for problem (it surely isn't successful Ford's case). Low-octane 85 is simply a byproduct of an era erstwhile carbureted engines handled it conscionable fine, but that era is over. So do your car a favor. Should you ever return a roadworthy travel complete a mountain, provender it pinch nan octane standing it deserves.