high altitude test, why is it?

[mudchicken]

All you lowlanders think that all locomotive rack settings are set for 500 feet above mean sea level? The few older NS, CR, CSX locomotives (EMD or GE) seen around here tend to smoke at transition for obvious reasons....

[adrianspeeder]

Even at max boost, under full load and throttle, the engine sometimes cant get enough air. I have a performance computer chip on my truck. When my diesel is set to the stock setting (240hp, 525#ft torque), the turbo supplies enough air to keep air/fuel ratio balanced. Except when i was running hard up a mountain and pulling a trailer. The stock computer read that there was not enough air (remember this is at full boost) and compinsated with less fuel. Now my new programmable performance chip lets me increase hp by 125 and almost 150 #ft torque. Thats a real kick in the pants, but dosent do anything to increase air. Turbo still only can put out 25 pounds of boost. The chip mainly just adds fuel by tricking the stock computer, and changing the tranny shift points. That extra fuel gets a heck of a lot more power, but because it is a rich mixture, it smokes. (handy to put snotty ricers and sports cars in their place.)
This is how my and every other truck diesel works, and other than the size and the final drive, I see little difference in a loco diesel.
Any railroad mechs to add thoughts?

Adrianspeeder

[Modelcar]

....Why is it necessary to reduce fuel at higher altitude if the vehicle is turbo or supercharger equipped....? Intake air is under pressure into the engine with the blowers so why can't it handle the normal amount of fuel...and make the normal amount of HP.....

[adrianspeeder]

A diesel engine is greatly affected by high altitudes, more so than a gas engine. Due to the fact that power is directly proportional to the amount of air that is drawn into the bore by the piston. At high altitudes, less air is drawn in and causes power loss. A turbo or supercharger forces air into the engine offsetting the altitude problem. Also, the fuel system must compensate with the amount of fuel injected. Less air + normal amount of fuel = one unhappy EPA guy. They smoke like crazy unless the engine is de-rated. My diesel truck has a barometric sensor to adjust the amount of fuel as i change altitudes. Towing a trailer over a mountain once, I could feel less power even with the turbo pushing max boost. (it was also smoking) The high altitude test shows what the engine can do at its worst performance area.

Adrianspeeder

[Puckdropper]

I sure would have hated to WALK to the top of Pike's Peak...

What is the effect of the altitude on engines? I didn't feel any real difference out in CO as compared to IN...

[Anonymous]

What is the real reason to why a new locomotive in North America has to perform such that test? Is it something about low air pressure effect on engine operations?

Karn[:)]