high altitude test, why is it?

[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[:)]

[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...

[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

[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]

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

[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....

[Anonymous]

QUOTE: Originally posted by 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

Yeah, I used to see that smoke all the time on diesels when I was driving in the mountains.

It can be a pretty damn big cloud at times, not ideal to be following them... [B)]

[adrianspeeder]

Engines, gas or diesel, make the most power effieciently with cool dense air. This happens to be at a low altitude more often than a high altitude. I make cool air on even the hottest days because, I have an intercooler. That is a second radiator behind the normal radiator, whos function is to cool air after being boosted before going into the engine. Do locos have intercoolers?

Adrianspeeder

[Modelcar]

....Adrian....Help me clear this thought a bit....If your turbo is at "maximum boost", and the max boost is 25 lbs....and it is achieving this.....at the higher altitude....what "tells" the engine fuel management that it is not getting enough "air" so it reduces the fuel output to the engine, hence making less horsepower...?? Something is missing here...
Yes I know both type of engines [gas and diesel], need the volume of air at altitude to produce horsepower similar to the lower altitude....Both are effected, if they are not foce fed of air. I also know the transmission will have different shift points if not compensated for the altitude....[Years ago did testing [transmission], in the high altitude above Denver for our [BWA], units. I also understand your point on the intercooler.
I can see why your diesel's smoke if they are controlled by a chip to add more fuel even with full air press at any altitude. Your comments please...

[adrianspeeder]

Oh sorry, full boost going over the mountain was less than normal. I didn't have a gauge then, but guys have said that it can drop by 5lbs and they need to downshift to build back up full boost.
You wouldn't believe the amount of sensors on this rig. There in the turbo, in the air filter, in the cooler, in the radiator, tranny, transfer case, diffs, hubs, steering box, camshaft, crankshaft, and a barometer to find atmospheric pressure. And they are a b*#h when only one goes bad. A 20$ sensor on the rear diff went bad so the speedo didn't know how fast it was going, so the tranny didn't know when to shift, so the engine redlined, so the ecm shut down the injectors.
How the computer knows what is going on, i don't know, but there is probably a sensor for it.

Adrianspeeder

[Modelcar]

....Ok, Adrian...that is a bit funny...Yes, I'm aware of the work of sensors, etc....It might be wise to keep the warranty in effect for long term having that quanity of them. Last year I had a simple ox. sensor go bad on my S-10 and let the dealer handle it and it was to the tune of $250...!! I am aware of it's a matter of screwing in a new one, but checking it out and labor totaled it to that figure. Anyway....happy horsepower.

[adrianspeeder]

http://www.supermotors.org/getfile.php?id=133985&toggle=fullsize&filename=powerstroke

http://www.supermotors.org/getfile.php?id=133978&toggle=fullsize&filename=Diesel Engine
Here it is, a 7.3L power stroke turbo diesel. Really it is an International T444e like in school busses and garbage trucks

http://www.supermotors.org/getfile.php?id=133990&toggle=fullsize&filename=Turbo right
This is the turbo. The large black pipe on the right is the intake from the air filter. The silver pipe going off to the left is the hot boosted air going off to the intercooler. The insulated silver pipe coming up from the bottom is the return from the intercooler. Notice the sensors on the turbo front.

Adrianspeeder

[Modelcar]

....Neat Photos.

[Anonymous]

QUOTE: Originally posted by adrianspeeder

Do locos have intercoolers?

Adrianspeeder

Yes they do. On an EMD 645 or 710 they're 2 boxes just ahead of the airbox. The new EMD - H engine, they run down the entire lenght of the cyl. bank. On GE's they're 2 big oval shaped boxes between the turbo and intake manifold

[adrianspeeder]

Cool, i like intercoolers, this Cat diesel is using its cooler.



Adrianspeeder

[Modelcar]

Wow....that Cat engine should have water cooled exhaust manifolds if it is what looks like on a dynamometer installation.
Just look at the "cool" side of the turbo and wonder how the lubricating oil running through it survives...!

[Anonymous]

What are you doing with all that power adrianspeeder?

Don't tell me all you do with that truck is go to the video store and back!

[Puckdropper]

QUOTE:
Don't tell me all you do with that truck is go to the video store and back!

You better believe it is. You see, no one bothered to explain to adrainspeeder that you have to PAY for the videos you get! He needs the power to get away! ;-)

j/k, of course.

[jchnhtfd]

same kinds of things happen to aircraft engines -- both piston and turbine (jet) types. The thing to remember about 'boost' is that what you really need to know is manifold pressure ('boost' plus atmospheric) -- and that needs to be controlled or at the very least accounted for. If your engine and its controls are really set up right, you can get sea level horsepower up to some maximum altitude, depending on the maximum boost from your turbocharger/supercharger -- and, among other things, that's part of high altitude testing. Another thing, though, is that that thin air is also needed to keep stuff cool (like traction motors) and less of it means less cooling. So the high altitude testing checks that, too. And so on...

mudchicken -- I'll be some of those older diesels with low-altitude racks and no compensation smoke! Yeek! (or yuch!)

[adrianspeeder]

See that huge oil filter, and i think that green hose goes off to an oil cooler. That is a dyno torture test for CAT.

Well, i use my truck for antiquing and hauling the jet skis to the lake and the four wheel drive for safety when it drizzles.

Whoa, some yuppie got ahold of my keyboard. It IS a work truck, and hauls my trailer of mowers, also tow a six ton race car hauler, dont even feel it back there. (till i need to stop). That diesel is super efficient and super powerful. Ford is not kidding when they call it the superduty. It is a serious rig, and i recommend it to anyone that needs a work truck. I like the 20mpg on highway (remember almost four tons), and diesel is 1.62 vs gas 1.89. And my bronco likes premium 2.11! Oh, and the diesel is warranted 100,000 miles parts and labor. I have seen these engines outlast 2 trucks. Guys swap em into gas trucks that blew up at 100,000 miles.

You could say i have a bad case of "diesel fever"

Adrian"diesel"speeder

[Anonymous]

QUOTE: Originally posted by adrianspeeder

See that huge oil filter, and i think that green hose goes off to an oil cooler.

The green hose is the cool water to the engine. The oil cooler is the cylindrical shaped object above the oil filter.

[dharmon]

QUOTE: Originally posted by jchnhtfd

same kinds of things happen to aircraft engines -- both piston and turbine (jet) types.

Which is why aircraft will always climb to the highest altitude practical for the flight (wind dependent). As an aircraft climbs, the power for a given throttle position decreases, but so does fuel flow. The higher they go (to a point) they are much more fuel efficient and as the air thins the true airspeed increases. Down at low altitude, turbine engines generate alot of power, but use ALOT of fuel. Which is many types of military aircraft and commuter airliners are still turboprops. They are still not efficient at low atlitude, but much more so than pure jets. Now to put it in a railroad perspective, the UP Turbines were quite powerful, but at the low altitude they were operating at, their effieciency was kind of wasted because fuel flow was so high.

For aircraft, thin cold air (meaning high altitude) achieves the best efficiency (power + speed). Cold thick air (Maine wintertime at sea level) equals the most power but higher fuel flow. Hot thin air (El Paso in summer) the worst because exhaust temperatures restrict an already altitude reduced fuel input. Hot thick air (Florida summer) second worst, because temperature will have a greater effect than density.

[oltmannd]

Turbocharged RR diesels do fine at altitude. Blower engines do not. A GP38 will smoke like crazy at 5000 ft. The difference is, for a given throttle setting, the turbo will spin faster and will maintain proper air box pressure. The turbo will be more prone to surge, which is why they have to do high altitude testing. Surge is a function of the compressor design and pressure differential over the compressor. With increasing speed, at some point the compressor will stop being able to move air from the intake side to the outlet side. When this happens, it "unloads" the compressor, the turbo speed runs away, air wooshes backward through the compressor and the engine starves for air and emits a great cloud of smoke. Once the airbox pressure drops, the compressor can start grabbing air again and things return to normal.

[Anonymous]

Diesel engines are diferent from gas engines in that only air is entering the cylinder when the intake valves or ports are open. Diesel engines draw much more air than is actually necessary for combustion most of the time, although this is changing with new engines that recirculate exhaust gases.

The gasoline engine works on a constant volume cycle. When the valves have closed, all air and fuel that will enter the cylinder have done so. Thus, volume remains constant.. As combustion begines, pressure rises. As the piston falls, pressure drops because all fuel has burned and the original volume was a combination of fuel and air.

The Diesel cycle is called a constant pressure cycle. Only air enteres the cylinder. When compression is complete, injection begines. pressure rises with combustion. As the piston falls, pressure remains constant, as injection continues to "feed the fire". Diesel fuel has a higher heat value than gasoline and needs more air to burn completely, this with the fact that diesel burns slower, greater combustion time per stroke is why Diesel engines produce more than twice the torque as horspower with a higher fuel efficiency.

locomotive engines do have intercoolers.

Supercharging, whether by blower or turbo is when intake manifold pressure is higher than atmospheric pressure.
The blower on a two stroke diesel is not for supercharging. The pressure provided by a blower for a two stroke Diesel is only a few inches of water. This is to help exhaust scavenging.

A guage measures the difference in pressure between a given source and the atmosphere. Such a measurement in an engineering environment is denoted PSIG for measurements in pounds per square inch. A measurement of absolute pressure in pounds per square inch is denoted PSIA. 25 pounds of boost at sea level is not the same as 25 pounds of boost at high altitude.

Surging happens in turbine engines when the compressor stage produces more air than can pass through the turbine and "burps" or "farts". Newer Diesel engines have this problem because manufacturers have gone to using smaller turbos that can spool up quicker, and improvements in design have made them more efficient.

[Modelcar]

...That explaination helped me to understand why diesel is capable of more torque than gasoline engines....

[passengerfan]

A little railroad history look at the problems the D&RGW had with the diesel powered Prospectors of 1941in the high altitudes of Colorado and into Utah. Even though the diesels were turbocharged they were never designed to operate in Mountain Goat country like the Rio Grande opertaed in. The little streamliners ran overnight and the Salt Lake and Denver engine house crews used to bet on whether the arriving Prospector would be under its own power or be pulled by steam each day until they were withdrawn from service and finally returned to Budd where they were eventually scrapped.
Early diesel powered trucks had the same problems in the mountains and they certainly were prone to smoking more than usual especially the early GM diesels, that is why it was recommended they burn #1 diesel instead of the more common #2. Many drivers discovered that when operating in the south many stations had pumps that dispensed Kerosene, of course no road use taxes so very cheap. The GM diesels ran great on this kerosene and the stacks were always clean. Later GM finally worked out the problems with the earlyt model diesels and they now burn #2 same as all other diesels. Number 1 diesel was more expensive and another trick drivers used was to fill with number 2 and add a gallon of the pink Automatic transmission fluid to each tank and this helped the old GM diesels run clean especially in California where fines were the order of the day for trucks emitting heavy black smoke. Remember once filling my truck in California with stove oil when I found no diesel was available anywhere in the area and i was desperate for fuel. Truck ran fine and no smoke was visible, even better since it was an emergency the state of California never received any road use taxes. Finally gave up on GM diesels and never had any further problems. In fact one Cummins diesel I should have bronzed, put 631,000 miles on it and never had a wrench applied to it. That must have been some kind of record.

[Anonymous]

I was hoping my explanation would help to show how a Diesel engine can be affected by altitude because of the nature of the fuel and its combustion cycle.

Stove oil? wow! and it ran ok? I guess its pretty similar to kerosene or diesel fuel and it probably doesn't have all the additives.

I've always thought of Cummins like a trilobite, They haven't changed in millions of years and they don't need to they're perfect. I believe inline engines are truely durable, and the Cummin's simplicity in design is its greatest asset.

[Modelcar]

...What is the difference at high altitude....one atmosphere...?

[adrianspeeder]

Ohhhhhh man, Dont ever be pulled over with ATF in a diesel tank.
Off road or Farm diesel fuel is dyed red because there is no highway tax on it, and it is only about 70cents or so. The fine in PA is about 2000 bucks for burning dyed fuel. The ATF is also red, so if the trooper takes a tank sample, your screwed. A diesel will burn lots of stuff that you wouldnt think to burn, and as a hint to a thread i will be posting soon, you can catch me out back of the local burger king.

Adrianspeeder

[Anonymous]

" A diesel will burn lots of stuff that you wouldnt think to burn, and as a hint to a thread i will be posting soon, you can catch me out back of the local burger king."-Adrianspeeder

??? frenchfry grease ???