Matt told me what this was today but I couldn't remember so I looked it up after I couldn't find it here. I imagine a lot of people that move here wonder as it's definitely noticeable.
The formula is Horsepower -(Elevation *.03 * Horsepower / 1000) with the part in parenthesis being the power loss.
So my ~65hp KTM is making the sea level equivalent of 55hp at 5,280' and only 42hp at 11,991'. My ~190hp BMW was making 160hp at 5,280 and 121hp at 11,991.
Or you can use this calculator
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Power loss at our altitude is right around 21% for a N/A or supercharged motor, and about half that for a turbo motor.
From what I've read and learned is closer to 2% per 1000' above sea level but the formula is not linear…Originally Posted by big_sur
I would love to see dignified outfit take a few NA/SC/TC cars and a mobile dyno and run the cars at sea level and every 1000 ft up to 12k feet graph the results - same cars, same fuel, same dyno…only variable being elevation.
Last edited by 3point5; Sun Aug 4th, 2013 at 10:23 PM.
The formula is actually fairly close to being linear, as it's mostly pressure based (Although both those formulas aren't even close to accurate, it's more like 3%/1000ft). Where it gets to be non-linear is the result of slightly differing particle makeup of the air in different parts of the world, and F/I cars being more efficient at different altitudes.
That's pretty much impossible, as there is no way to isolate elevation as being the only factor, at least not fairly. What octane do you allow, does it change? Do you give a benefit to the forced induction cars that are out of their peak AE range at altitude? Do you allow the supercharged car to increase boost levels with altitude since S/C cars lose boost with altitude, even though they lose about the same amount of power as an N/A motor does with altitude? What about the turbo car that only loses about half of the power as the S/C and N/A cars with altitude?
Essentially we don't get high test here because we don't need it.
"Octane is the ability of a fuel to resist knock, and high-compression engines tend to knock more. The obverse of that is that lower-compression engines can run on lower-octane gas. Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It's a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they're well above sea level--and all of those states are. Hopefully, by the time you get back down to denser air, you've burned off most of the low-octane stuff, and can refill the tank with higher-grade fuel. "
Elevation is essentially the pressure part of the ideal gas law. Turbos and S\C make boost which is pressurized air, so they'll be affected differently, but you can use the formula to get a pretty good approximation for N\A. Here's the long explanation if you've got a minute:
"This paper will address the affects of how higher altitudes affect the horsepower output of automotive vehicles as well as things you can do to compensate for this phenomenon. As many people are relocating to the state of Colorado, this subject has become a common of discussion among new residents and the automotive service industry. Altitude has a very significant affect on vehicle horsepower and is often misunderstood by vehicle owners. Some owners are told that their vehicles will lose up to 20% horsepower by being in Colorado, but there is much more to the story than a simple statement like that. Let's explore some simple facts about the affect of altitude on horsepower. It is best to have access to a calculator to complete this activity. Many cell phones has built in calculators for easy access. We will use some common automotive mathematical formulas to calculate "theoretical performance" values.Our case study vehicle will be a Ford with a 5.4L (330 CID). The first learning objective will be how to convert liters to cubic inches. The easiest method to do this is to multiply liters (5.4) by 61.024. (5.4 x 61.024 = 329.53) Most manufacturers will "round up" to the nearest number, so 329.53 would become 330 cubic inches. Our example vehicle specifications indicate that it delivers about 300 HP and 365 lb ft of torque. These specifications are the result of engineering testing and measurements. These values are determined by using a Society of Automotive Engineers (SAE) correction factor to keep horsepower and torque publications standard and consistent. The engineered calculations and measurements are factored and corrected to sea level and are often referred to as "sea level performance".
With the example vehicle generating 300HP at sea level, if we use the following formula to correct for changes in altitude, we can calculate the theoretical power loss at any altitude. (HP x Altitude [in feet] divided by 1,000), then multiplying the answer by 0.03. Then, subtract that answer from the stated vehicle horsepower. The total formula would be written as:
(HP X Altitude [in feet] / 1,000 X 0.03 - HP)
Let's work with the example of the Ford vehicle using this formula. The altitude of Colorado Springs, CO is about 6,000 feet. The formula with actual values inserted would look like this: (300 X 6,000 / 1,000 X 0.03 - 300) 300HP times 6,000 equals 1,800,000. Then, 1,800,000 divided by 1,000 equals 1800. Then, 1800 multiplied by 0.03 equals 54 (horsepower). 54 horsepower subtracted from 300 equals 246, which is the new theoretical vehicle horsepower at an altitude of 6,000 feet. Now, calculate the vehicle horsepower at a new altitude of 8,000 feet.
These calculations do not include major influencing factors such as ambient temperature or vapor pressure and are used just for a reference. The manufacturers and the aftermarket industry use ambient air temperature and vapor pressure in their horsepower gain calculations for their "add-on" performance products to determine the added horsepower gain. If you want to try and compensate the loss of horsepower of your engine by installing aftermarket parts that are designed to enhance engine performance, you would use the same formula. Let's say that you wish to install a cold air intake system on your vehicle and the advertised specifications say that it will add 12 HP to your vehicle. We must use the same altitude correction formula to determine the actual gain for vehicle operation in Colorado. (12HP X 6,000 / 1,000 X 0.03 - 12) = 9.84HP now, adding the 9.84HP gain to the original 246HP gives you a total of 255.84HP (theoretical) for your vehicle.
You can continue to calculate the horsepower gain for aftermarket products until you find a combination of products that will bring your vehicle horsepower back to sea level specifications for the altitude your vehicle operates at. In the example of the Ford vehicle in this document, we would have to find products that would increase the horsepower of the 5.4L engine to about 370HP at sea level to obtain the factory 300HP at 6,000 feet above sea level. Have fun!!!"
Most stock cars don't need the octane, but there are a few that could use the extra points (Mainly the high specific output F/I cars). Once we get into modified cars though, there are plenty that could use the octane. My best friend has a 335i, from 93 octane to E85 he can bump boost enough to put down about 70hp more. Chalk that up to crappy turbochargers and a less than ideal intercooler. Crappy turbos for outright power, they're fantastic for spool and response.
I was more talking about the 2% per 1000ft, I didn't actually calculate that other formula for accuracy.
On air pressure alone, I lose 20.4% from sea level to my driveway in Colorado Springs, so pretty close to a 20.4% power loss for normally aspirated and supercharged cars, and 10.4% for turbo cars.
FYI for an NA bike/car figure about 1-1.1 seconds loss in 1/4mile also. This equates to the HP lost.
All that being said, what can we do to combat this issue, anything? I have noticed the 14 is a little sluggish especially after I have climbed a few thousand feet.
Aside from turbocharging, nothing really. Normal modifications are still going to help, just not as much as they would at sea level.
Turbocharging only exposes your motor to about half of the losses as N/A. But they also make waste gates that increase boost pressure with altitude so essentially no losses are incurred. These are mainly for airplanes but they'd work in a car too.
Go down or boost.
Turbo's do help but it depends on the size of the turbo and boost controller\EFI. A turbo is essentially an air pump that shoves pressurized air into the intake manifold. The reason you lose power at altitude is the air is less dense (lower pressure). The reason turbo's may or may not be affected as much is because if the turbo is big enough and the fuel management system can adapt, the intake manifold pressure is the same regardless of altitude since your boost controller maintains the psi (boost). The limitation comes in because the air being pumped by the turbo is less dense and the turbo needs to move more of it to maintain the same psi, which may or may not be possible depending on the size of the turbo, fuel management system, and rpm of the turbo. Most modern turbo cars will adapt to altitude to some extent, but they usually don't make quite as much power because they use smaller turbos to decrease lag, which then can't fully offset the less dense air.
less weight = more power (whether the bike or the person)
Bulldog's Motto: F*ck around and I'm going to bite you!!!
Basically you have limited options:
1. Standard intake, exhaust and PCIII
2. Trim down the weight of the bike or yourself
3. Gear down and up
4. Power adder, Turbo or NOS just for the mountains (man that would be silly)
5. Get more displacement
*Edit - all summed up above basically, I should have hit reload before posting
I didn't see anyone mention re-gearing and that is a good one...do it to all my bikesSure I lose maybe 20mph on top end speed, but 160mph to 140mph is no big deal to me for the added low end power.
I chose not to gear my S1000RR, even though it could certainly use it as 1st runs out to 93mph. My reason is because I do a lot of highway riding, and 6,000rpm on the highway is already higher than I'd like it to be.
But changing sprockets is a great way to liven it up at altitude.
O really?
R^2 is how linear it is. The closer to 1 the more linear....
I like aaron...Not really…get 18 cars (6 NA, 6 SC, 6 TC)…fill their tanks up with gas…get a dyno…set the dyno up at each elevation point and give each car 9 pulls…average the pulls to get a HP figure for each of the 18 cars at each elevation point…repeat at each elevation compare each car ONLY TO ITSELF…develop a hp curve…at the end of the testing you'd have 18 curves…combine and average all the NAs, all the SCs, and all the TCs figure the loss of each category...
nice graph...O really?
R^2 is how linear it is. The closer to 1 the more linear....
So mathematical, you've eliminated every variable possible.
Except that 93 octane is dished at sea level, but not at elevation. Some cars would need the 93 at sea level, some would still need it at elevation.
Then we run into a modern 335i, which actually adds boost with elevation. Kinds throws off your comparison when the car just counteracts the entire thing you're trying to test.
And of course you'd regulate temperature right? And how would you regulate engine temperature? You realize the new 911 turbo adjusts it's coolant temperatures by nearly 70 degrees depending on conditions? 70 degrees does slightly impact engine power you know.
Because these variables make such an impact on performance, you obviously would want them eliminated, making it only about air pressure. Which in this case there's no purpose, as I've already told you how much power you'll lose if it was solely based on air pressure, 20-21% in an N/A or S/C car, half that in a turbo car.
As Aaron mentioned, there are so many more variables. For example on my GTP I could run a smaller blower pulley (more boost) at altitude then anyone down at sea level because of the thinner air. If you ran that small pulley down low you'd get so much knock you'd actually lose power.
Hell you could get 6 stock cars and run them on a dyno and most would be different readings...that is how much even same car has variables.
I'm waiting for my new geared down sprockets for my ninja. -1 +7. It should be gnarly. And I'll top out at about 105 or so which isn't bad for the street I shouldn't be going that fast anyway xD
Nicole
Street: 08 Suzuki SV650S
08 Kawi Ninja 500 *SOLD*
Track: 03 Yamaha R6
MRA corner worker
You serious....+7!!!!!You a stunter or something because that is the only time I ever heard of a set up like that.
It's a 500. That will make it accelerate like most of our bikes in the power band.You serious....+7!!!!!
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