Effects of Elevation on Performance

[Haywood]

Anyone have any data/thoughts on what performance impact there is as the geographic elevation increases?  I have spoken to people who have provided subjective comments but I don't have any data to back those comments up.  I have heard that performance is reduced due to the 'thinner' air at higher elevations.  Most of my riding is done in the foothills and in the Rockies.

Should the bike be setup differently if you ride at higher elevations (richer fuel mixture, for example)? Is it worth worrying about or doing anything?

 

[Big Wall]

I don't have any data. But the computer for the fuel injector system will adjust for the thinner atmosphere as well as it can. Performance will be down compared to sea level though.

 

[Big Wall]

You may have to use a higher octane fuel also.

 

[Revlis]

The higher you get the slower you go!!! Wait I mean altitude has a direct effect on how high you get?

No No...I mean increased elevation means decreased performance.... FI can compensate so you do not loose ridability, but you will loose power...

Roughly 3% for every 1000' in elevation. Turbo's loose a whole lot less, but still loose some... Hang on...

 

[Haywood]

Roughly 3% for every 1000' in elevation.  Turbo's loose a whole lot less, but still loose some...  Hang on...

Rev:  thanks for that stat.  That's good to know.  I am at about 3500 feet here at home in the city.  A friend of mine from the bald a$$ prairie said he has to clutch up his ZX12 when he rides here, but at home he can wheelie with just the throttle. I figure it's the altitude and the dry thinner air here compared to his place.

Big Wall:  thanks for the info on the computer system -  I did not know that.  And I'll try using a higher octane fuel as well in the summer to see what, if any, difference it makes.

Thanks men!

 

[Revlis]

OK here you go.  A calculator to determine power loss and correction factors for engines.  

<span style='color:royalblue'>Engine Tuner's Calculator</span>

 

[Haywood]

OK here you go.  A calculator to determine power loss and correction factors for engines.  

<span style='color:royalblue'>Engine Tuner's Calculator</span>

thanks Rev! That's a sweet little calculator. I'm going to check it out some more, and maybe get some historical data from the summer months and run those through.

 

[stkr00]

Haywood,

You shouldn't need higher octane fuel. Higher octane DOES NOT increase power, it only resists detonation. You can actually lose HP by using an octane rating that is too high, because it takes more spark/heat energy to burn the A/F mixture completely.

The problem with higher altitudes is that the air is thinner (less O2), therefore, you have to bring in a larger volume of air to get enough for combustion, and the intake system can only pull in so much at a time due to the VE (Volumetric Efficiency) of the engine.

The MAP (Manifold Absolute Pressure) sensor measures the air velocity at the intake and the ECM will calculate the fuel rate(Injector Pulse Width) to compensate for the thinner air. The ECM can only adjust this down so far, and then you're left with a rich fuel mixture. If it's too rich, as in not enough air, then the ignition system will not be able to maintain complete combustion, and this is why you lose power. The higher octane only makes this worse.

You only need higher octane if you start experiencing detonation/knocking.

I'm sure some of the racing guys could probably explain this better, or correct my mistakes, but this is how I understand it.

Jim



<!--EDIT|stkr00
Reason for Edit: "spelling"|1069826773 -->

 

[stkr00]

Johnnycheese write his own fuel maps I believe. You may want to ask him if he's erer had to deal with this issue.

 

[Haywood]

Johnnycheese write his own fuel maps I believe.  You may want to ask him if he's erer had to deal with this issue.

stkr00:  thanks for the information.  What you say makes sense regarding the o2 deficiency.  I have only run regular gas with octane rating of 87 in my bike and have never encountered a pinging problem but I know guys who only run higher grades (my manual says that CDN bikes can run the 87 octane).  That's a good suggestion about reaching out to Johnnycheese.. I think I'll do that.