Is altitude a problem?

[tab132]

I want to buy a JD 4010 or 4110 new, but one JD dealer said he couldn't in good conscience sell me that model because of my altitude. I'm about 8500 ft. I will be pulling a blade for driveway work. Any thoughts would help. /forums/images/graemlins/confused.gif

 

[Bob_Skurka]

YUP. The higher the altitude the greater the HP loss. I can't remember the figures but someting like 30% to 40% loss at 10,000 feet. IF that is correct, and I am not sure that I remember it properly, you are at 85% of 10,000 feet so you'd lose 85% of roughly 35% of your total horsepower.

The odd thing is that with a Turbocharged diesel engine, the effects are virually eliminated.

Regardless of brand you choose, at 8500 feet above sea level, I would recommend you pick one with a turbo diesel. That or buy a lot bigger tractor and realize you may get less than 70% of the power the engine is theoretically capable of producing.

 

[SkyPup]

You lose 3% of power from all normally aspirated gasoline and diesel engines for each 1,000 feet above sea level, so you are looking at approximately a 30% drop in power due to the lower air pressure.

A turbodiesel would not lose any power up to about 10,000 feet, it would only spin the turbocompressor faster to create the same amount of boost.

Diesels are also more difficult to start at these elevations due to lack of compression pressure required to heat the air to ignite the fuel charge when they are cold so be sure to have a glow plug diesel engine.

 

[BillG_in_TX]

SkyPup,

In this previous thread about power loss at altitude it appears that the consensus was a loss of 3% for every 1000 feet of altitude. Wouldn't that indicate about a 25% reduction at 8500 feet??

 

[SkyPup]

I'm sorry, there is about a 3% decrease in air pressure every 300 meters up from sea level, so that is about 3% every 1,000 feet of elevation.

A rule of thumb for an altimeter correction is that the pressure drops about 1 inch of mercury for each 1,000 foot altitude gain. If you're using millibars, the correction is 1 millibar for each 8 meters of altitude gain.

 

[Bob_Skurka]

OK, I knew I was not sure of the numbers when I posted, but between Bill & Skypup, I am now more confused.

It seems well established there is some loss.

What is the loss???? Please speak in SIMPLE terms. S-l-o-w and LOUD for those of us who get confused easy.

 

[JerryG]

<font color="blue"> Diesels are also more difficult to start at these elevations due to lack of compression pressure required to heat the air to ignite the fuel charge when they are cold so be sure to have a glow plug diesel engine.</font>
It depends on the tractor. Most turbo tractor have the same compression as their non-turbo counterpart. My MF 1440 is one example of this and I would bet that the new model JD with turbo's are the same. I will say that most if not all auto engines that are set up for turbos do have lower compression. The compression issue is a valid concern. If you do look at turbo tractors, that is one thing to make sure of before you buy.

 

[SkyPup]

Bob, just figure a 3% loss in total output for every one thousand feet above sea level.

The Society of Automotive Engineers (SAE) standard for measuring horsepower and torque (SAE J1349 JUN90) is based on 77 degrees Fahrenheit at 29.235 inches-Hg (inches of mercury) @ sea level with zero percent relative humidity.

 

[SkyPup]

Here is the formula for calculating horsepower loss at altitute:

hp loss = elevation (in feet) x 0.03 x hp @ sea level / 1000

 

[Bob_Skurka]

So I was actually pretty close!

Using 3% per 1000 feet, at 8500 feet he's lose 25.5%.