Fuel/oil mixture and elevation?

[FXDL]

the way i understand is the higher your elevation the more oil you should in your gas. since the higher the elevation the more you have to lean out. i live at 5700ft above sea level and decided to break in my 6400 on 32:1 rather than 50:1 not sure if this right but anyone have any thoughts on this?

 

[computeruser]

Nope.

 

[bullittman281]

Hello,
Run premium oil at reasonable ratios. Set the carb for the current conditions and your golden. The conditions can vary at the same location from day to day so keep an eye on the carb settings and roll with it.

Bullittman

 

[Sledcrazzy]

thats a new one! nope oil mix stays the same, you will have to adjust your fuel- air mix by leaning down your H jet cause there is less oxygen at 5700

 

[kevlar]

keep the same oil ratio, adjust carb when up high and again when running at a lower elevation.

 

[sawman2077]

I run mine at 40:1 no matter the elevation. I have never heard of that one.

 

[JayB]

the way i understand is the higher your elevation the more oil you should in your gas. since the higher the elevation the more you have to lean out. i live at 5700ft above sea level and decided to break in my 6400 on 32:1 rather than 50:1 not sure if this right but anyone have any thoughts on this?

You're on the right track but it's such a small amount it won't really matter. I forget the exact numbers, but-
Air density decreases by 2% per 1000 ft. elevation
You're at 6000 ft.
you'll lean out the mixture by 12% to make up for the less dense air
oil mixed at 50-1, so also 12% less oil used

To make it right again mix at 44-1??? I know my math isn't exactly right, but close enough. I sure wouldn't go with 32-1. It's way more than needed.

 

[elliott]

I cut daily and all day at 9000 feet for the past four years. I use 50:1. No problems and good performance if carb is set right.

 

[litefoot]

If you bought it where you live, then the dealer already set the fuel/air mixture. Leave it and the oil ratio alone. If you sometimes cut at higher elevations then you'll run somewhat rich...not a problem.

 

[litefoot]

You're on the right track but it's such a small amount it won't really matter. I forget the exact numbers, but-
Air density decreases by 2% per 1000 ft. elevation
You're at 6000 ft.
you'll lean out the mixture by 12% to make up for the less dense air
oil mixed at 50-1, so also 12% less oil used

To make it right again mix at 44-1??? I know my math isn't exactly right, but close enough. I sure wouldn't go with 32-1. It's way more than needed.

More like 3%. But it has nothing to do with oil ratios...

 

[Jtheo]

I break in my new saws with 40:1 and richen up the mix a tad to compensate for more oil and less gas in the mix.
I broke two 7900's in that way with no problems.

I don't see a problem as long as the carb is properly adjusted.

 

[timberwolf]

More like 3%. But it has nothing to do with oil ratios...

????

If there about 10% less air by weight going into an engine at 3500 ft additional elevation and the engine turns the same RPM there is also about 10% less fuel going it and by that also 10% lubricant.

Sure there are people that run 50:1 at elevation and people that run special oils at 60:1 75:1 or 78.63:1 their saws may not fail due to lack of oil every time. But if you want your saw to have as much oil in the cylinder each stoke at 10,000ft you will need a richer mix than you would at sea level.

Just another reason to error on the rich side of 50:1

 

[ShoerFast]

Sea level there is about 14.7 PSIA of pressure pushing air into a naturally aspirated engine.

At 6000' there is only 11.7 PSIA or so. Link:

Fun facts... Link:

A 660 running 7.0HP at sea level will only be 5.6HP at 6000'

Take a 660 up to 9000' and you will only have 4.9HP



I like a higher ratio of oil, 40 : 1 works for me.

But at any altitude or temperature, a slight burble out of the wood, that clears in the wood will be your best power in a saw engine.

Fun question...

What would have more power, a 660 at 6000' on a 105 deg day?

Or the same 660 at 9000' on a -10 deg day?

 

[CGC4200]

40 to 1

I live where the elevation above sea level is 300' to 600'.
I have some old saws & newer 2-stroke equipment, I run all of them
on 40:1 mix, they might carbon up, but I have not burned up any
pistons.

 

[Patrick62]

8000 ft above average

So I am down 24%, which is why I call a 440 a limbing saw...
40:1 is what I run. I did think of that altitude thing a year ago, and the local Stihl guy said "there is sufficient oil at 50:1 to go to like 80,000 ft."

I said bull feathers, it would be meaningless past 24,000 as there would be insufficient compression to start the engine.

 

[FXDL]

Well i'm going to break in my 6400 this weekend on two cords. i bought 2 gallons of non-ethanol gas and mixed it 32:1. after these 2 gallons i'll go with dolmar 50:1 oil my dealer gave me