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I have an issue that I have noticed for a few years now, and this weekend really bugged me.

It appears I loose power at Altitude.

I live at +600m (~2000ft) ASL, and work at +50m ASL, and whenever I visit the high country which is starting at +1500->1860m (4900->6000ft) ASL, I start to notice the power issues.

The symptoms are; accelerating through 2nd, 3rd, i'll get what feels like "mis-fires" or micro steps in power, or where the revs momentarily hold revs then continue to climb. Generally speaking while flicking through the corners, it gets your attention but it's gone as quick as it appears. For the last 4-5years i've been noticing it, it hasn't really bothered me, and each time I put it down to spark plugs, or something else.

This weekend, I noticed it more attempting a wheelie for a photo op.

On initial take off from stationary, it was obvious to me the bike just wasn't lurching forward like usual. Attempting the wheelie itself (power-ups), the front never lifted. Several attempts and my mates bagging me out, I resigned.

Next day, also hot, back at lower Altitude, straight up no issues.

My only thought is a defective oxy sensor that isn't throwing an error code?

Does anyone have any experience with this?

Bike; '08 Daytona, only mods are the intake flap permanently opened (pipe blocked).
 

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2016 Diablo Red Thruxton 1200 R
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I could b wrong but usually with the carbed bikes major altitudes difference will effect the bikes tuned performance and a EFI bike will still run ok but slightly restrictive with the thinner air. Just like us humans once u reach higher elevations the air gets thinner and breathing becomes harder. With proper jetting and tune u might find that balance to perform well in lower and higher altitude, but then it can b one of those situations where u can’t have it both ways depending on how big of a altitude difference there is. Any time I moved to a different location or a different state if there was a major altitude difference I would have my bike retuned.
I don’t know if it’s just me but one thing I have always done is have a biked tuned early in the morning when the air is fresh and cool to get the ultimate performance tune and not in the later day when it’s super hot and dry, it does make a difference when it comes to tuning The air quality and condition the bike is breathing at the time. when A bike is being tuned at the current air temp at that time it can make a difference how the bike performs in other different temperature ranges and elevation changes It will encounter during your ride through the day.
So if your bike was tuned in a very low altitude setting it will struggle and choke in the higher altitudes or vice versa.
Just some food for thought that might help with the situation or I could b totally wrong...lol... FTG
 

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I used to own a small aircraft....had no fuel mixture adjuster for alt.

Lack of power is very noticeable as you gain hight....all to do with decreased oxygen the higher you go....at 10.000ft my engine was near usless...and quite lumpy as it was running very rich with lack of oxygen.

Turbo charged engine are better at altitude.
 

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While your EFI is supposed to compensate for altitude changes, it is only somewhat effective. You still have less air pressure because of the lower barometric pressure. Depends on how sophisticated the system is. The system really needs to be able to see absolute manifold pressure and compensate for the altitude. It is still never perfect.
...J.D.
 

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One thing you may try when going to high altitude next time is to add e85 or whatever ethanol fuel you have there, no more than 10% of total fuel. The oxygen atoms carried in the fuel really helps rich jetted bikes both on hot days and in high altitudes i've noticed.
 

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I have an issue that I have noticed for a few years now, and this weekend really bugged me.

It appears I loose power at Altitude.

I live at +600m (~2000ft) ASL, and work at +50m ASL, and whenever I visit the high country which is starting at +1500->1860m (4900->6000ft) ASL, I start to notice the power issues.

The symptoms are; accelerating through 2nd, 3rd, i'll get what feels like "mis-fires" or micro steps in power, or where the revs momentarily hold revs then continue to climb. Generally speaking while flicking through the corners, it gets your attention but it's gone as quick as it appears. For the last 4-5years i've been noticing it, it hasn't really bothered me, and each time I put it down to spark plugs, or something else.

This weekend, I noticed it more attempting a wheelie for a photo op.

On initial take off from stationary, it was obvious to me the bike just wasn't lurching forward like usual. Attempting the wheelie itself (power-ups), the front never lifted. Several attempts and my mates bagging me out, I resigned.

Next day, also hot, back at lower Altitude, straight up no issues.

My only thought is a defective oxy sensor that isn't throwing an error code?

Does anyone have any experience with this?

Bike; '08 Daytona, only mods are the intake flap permanently opened (pipe blocked).
Not familiar with daytona EFI's, but do they have an air pressure sensor?
Exhaust 02 sensor may be out of its operating parameters in very high altitude, without there being an actual fault.
 

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No matter how good the EFI is....it cannot make up for the lack of oxygen at those altitudes....it maybe able to weaken the fuel off but the engine will then just run at reduced power anyway.
 

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2004 Daytona 955i, 2018 Indian Roadmaster, 1980 CB650C in resto
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A good closed-loop EFI (where the computer gets all the input data it needs from real-time sensors) will keep the air/fuel ratio correct for the engine conditions. You shouldn't run rich or lean as parameters like temperature, altitude, and phase of Europa change. But as nickjaxe says, you'll still lose power. My house, by virtue of altitude, has 25% less oxygen than it would at sea level. That means a sealed volume, like a cylinder inhaling to bottom dead center, has less potential/chemical energy than the same cylinder at sea level. Turbos can help make up for that, but nothing else will.

I've ridden EFI motorcycles from sea level to 12,000 feet. Mostly my Daytona. I've ridden my Indian Roadmaster from sea level to over 10,000 feet. Both lose power, but I've never had stuttering or misfires.

Altitude effects led to one of the most exciting moments I've ever had on Misty, my 955i Daytona. I'm used to riding it between 5000 and 10000 feet. That's where the vast majority of my time on that bike has been. Well, once on the Pacific Coast Highway I was waiting for a slow pickup to turn and open up the road for me. He finally did, I hit the gas (no clutch, no downshift, just TWIST) and up came the front end in a huge wheelie! It seemed huge to me, because it was the second wheelie I've ever pulled, but I kept my wits about me (I keep them in a matchbook, along with several matches and a small watch) and brought it down gently. Laughed into my helmet for the next five miles.

Here's the ride report covering that story, if anyone would like to read it.
 
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