Altitude change from 5200ft to 650ft above sea level.

[Raspy]

Diesels engines are always inherently lean burning. That is, unless they are under full load and then you see some smoke. Brown is fine, but black means excess fuel that is not getting burned completely. This is the best indicator of the engine being at full power for a given RPM. Remember, they always take in a full charge of air, then the fuel is added to start combustion. At higher altitudes, they get less air, so they might smoke more at full load and lose about 3% of their power or so for every 1000' elevation. The mixture is constantly changing and can't be discussed in the same way as a gasser. There is no such thing as lean or rich adjustments on a diesel, that is what the throttle does. It's more about how aggressive the fueling ramps up and the maximum fuel delivered. Smoking does not necessarily mean rich.

White smoke at startup means cold cylinder walls and moisture with incomplete combustion. Brown smoke means good combustion and about 75% output. Black smoke means full power and either excessive fuel or poor atomization. It can also mean a bad injector if the engine is not putting out much power and smoking.

Turbocharged diesels with mechanical injection often have barometric compensators that ramp up the fuel based on intake manifold pressure. These should not smoke so much and should produce about the same power at altitude.

High pressure common rail injection diesels with turbo chargers measure the intake air temperature and the manifold pressure to select the right amount of injection and should smoke even less while producing good power. The computer gathers information and refers to a chart, or fuel map, to decide how long to leave the injectors energized for a given RPM and throttle position.

 

[Snaker]

I have an older Yanmar diesel 4 stroke and the manual makes no mention of altitude compensation. I'm not a diesel expert by any means, but I can tell say that the throttle on my machine controls the fuel only. The air intake to the valves is in a constant "wide open" condition so the cylinders will pull in all the air they need. That would suggest that the engine is designed to handle a varying air/fuel mixture that is always changing based on throttle position (little fuel-lot of air or lot of fuel-lot of air) vs. gasoline where the air/fuel mixture is kept relatively equal as the throttle controls both fuel and air.

If my theory is right then you would just be dealing with adjusting for power/smoke as others here have discussed if needed.

Side note: My last couple of snowmobile purchases have been used mountain rentals brought down to the flatlands. Step 1. on those gasoline 2 strokes is to change carb jets to richen or the engine will be toast.

 

[BethesdaEC]

I remember on my '79 Dodge van with a 318 engine, there was a section talking about re-tuning if the vehicle was going to be permanently operated at high altitude. New cars are so much easier, my 2000 Sable Wagon first and only maintainance item outside of fluids and filters was to change the spark plugs at 100K miles. Seemed I was changing the plugs, caps and wires every 30K miles back in the day, then the timing lights and idle adjustments, I don't miss it all.

 

[CowwFace]

I'm with Raspy on this one...

We live at 8500' and I've had my Ford F250 Diesel since 2004 with no adjustments (Cripes who know's how many computers are stuck in there??) but also my 2009 Kioti DK40SE and no adjustments.... one thing is the Glow Plugs seem to be very important up here for cooler starts (even in summer).. but otherwise no adjustments ...

If you're moving to LOWER elevation, sounds like you get to enjoy some more horses ... But what about the snow... you will miss the snow!!!


Tractor on

 

[Raspy]

Yeah, glow plugs are needed more at higher elevations, regardless of the temperature. With less atmospheric pressure there is less air in the cylinders and lower compression pressure. So, less compression heat to fire the fuel. Some engines are borderline starters anyway and as soon as there is a lower temp in the cylinder, for any reason, they need help. This is more the case with pre-combustion designs than with direct injection because there is more surface area for cooling compared to the volume of air. So, the compressed air cannot get hot enough to reliably start.

Diesels are often looked at through gas engine eyes and easily misunderstood.

 

[Jerry/MT]

Are diesel tractors tuned differently for higher vs lower altitude? If I move a the tractor from high to low altitude will I need to need to change anything?

I don't know the exact model and size. I know it is newer JD but I don't know HP etc. I will supply more info when I learn more.

Thanks to all!

My understanding of the way a normally aspirated diesel is controled is that when you set a throttle position you command an rpm level. As you increase the load, the governor adds fuel and allows a little bit of speed "droop".
As you continue to increase the load the fuel flow increases (and the speed "droops") until it reaches the ammount limited the inability to burn the increased fuel due to a lack of oxygen. This would cause a lot of black smoke and no more useful power could be produced. Since you cannot add anymore energy( because the fuel won't burn) to produce work, it's a self limiting situation.
There would be no need to worry about adjusting the injector pump going from higher elevations to lower elevations.

 

[Raspy]

Some governors work that way, as in generators and are called isochronous governors. And the droop is kept to a minimum. But in vehicles the governor is more likely to simply control the maximum and minimum RPM, while the throttle controls the rest of the range. This keeps the engine from going to full throttle with a slight change in the throttle pedal position and improves driveability.

The pumps are set up to only add as much fuel as the engine can burn. But then, at higher altitude, or while lugging, you can get some smoke. And smoke is not necessarily a bad thing. It just means the engine is producing all the power it can at that RPM. Not a huge black cloud, but a dark haze. Smoke is a fact of life with diesels at full power. If the atomization was better, it might produce the same power with a bit less smoke. Then catalytic converters and diesel particulate filters are added to reduce smoke and allow power.

A turbo is a better way to add power by simply pumping in more air and therefore allowing more fuel to be added, which pumps in more air yet and allows even more fuel, etc, until it's limit is reached.

 

[KennyG]

There is only 2.5 psi difference from sea level to 5000 feet. Diesel engines do not appear to be effected as much as gas engines due to the higher compression ratio and thermal efficiency.

Going back to basic Internal Combustion Engine theory, effect should be about the same on both gas and diesel normally asperated engines. The power (at a given engine speed) is directly related to the BMEP (brake mean effective pressure) in the cylinder. This is then directly related to the atmospheric pressure x compression ratio. If you reduce atmospheric pressure by 2.5 psi, that's 17%. Just googling around, I quickly found recommendations for stationary (generator) diesel engines to derate by 3% for every 1000 feet of elevation, which is consistent.

 

[MMH]

Raspy's right on!

Black smoke out of a diesel simply means that it is overfuled (more fuel being injected than the engine can burn). Short termoverfueling occurs in turbo'd engines when the increased load demand is initilly demanded. As the turbo spools up & delivers the air, the overfueled condition is eliminated. Continuous overfueling is bad - the combustion chamber gets very hot. Continuous overfueling often occurs when simple injection pump modifications are made w/ no other changes.

If the original poster is going from higher altitude operation to lower altitude, no modifications should be necessary. If he was overfueled before, he no longer will be (or not to as great an extent). He will simple enjoy more power & less black smoke!