my father is thinking about getting his first diesel pickup ever. he wants to use it for travel pulling a camper at apprx. 8000lbs. he said. but he's real scepticle about a gasser vs. diesel in the thinner air in the mountains where he wants to go. i told him that i didn't know but i would find out for him. he asks me questions like this all of the time since im gonna be goin to college to be a diesel tech. but i just dont know all the answers yet so i figured i'd ask all my buddies here .
so which would run better in the thin air of the mountains?
thanks in advance!

 

Can't beat a turbo diesel for pulling at high altitude

 

why do you say this. whats the reason do you know.
just curious.
thanks.

 

I , honestly, can't tell a difference in altitude in my truck. But i don't really pay that close attention to that.

 

My guess is the electronic fuel controls and the torque of the Cummins.

Whatever it is, mine pulled the same loads all over Colorado with much less straining and grunts than my Ford or Chevy gassers ever did....and with better milage. Second gear for the gassers was forth gear for the Cummins with a lot fewer RPM's.

 

the higher the altitude the thinner the air, meaning less air.

the less air the less power an engine can make.

a turbo charger helps combat this by forcing air into the engine, making power

 

thank you much that makes a lot of sense. i didn't even think about that.
are there any other reasons or is that the main one?

 

can't beat a turbo diesel for pullin period. especially a CTD

gas crap is so inefficient and worthless anyway

 

Especially with the wastegate. It can produce a great deal more pressure, but is held down by the W/G. As the pressure starts to drop the gate closes and pressure comes back up. Now if we ran around at max boost all the time you would feel a relitiv loss, but nothing like the precentage of a naturally asperated engine.

Randy

 

My dad is an old cummins guy who was once a certified mechanic back in the day, and these are his views. All of his semitrucks back in the day were all cummins and turned up with the timing slowed a little. He said, that when he left ohio, and got in the mountains with the thinner air that it would produce more smoke than in ohio due to the thinner air. it smoked because there was more fuel than air. EGT's would climb faster because the motor had to "work more to get its air". from the both of us, we think that you wont even be able to feel the difference when you hit the mountains. Hope I could help ya,
Wheelo

 

Here's what I think is a pretty complete explanation of why a turbodiesel is better than a gasser at high altitude:

As you know, air gets thinner the higher the altitude is.
Normally aspirated engines lose power at a predictable and repeatable rate as they climb to higher altitudes. (I forget what that rate is, but it's expressed as a percentage of sea level power per 1000 ft ascent)

As you also know, a turbocharger compresses air to a higher-than-ambient pressure before it goes into the engine. A turbocharger is not directly driven by the engine. (The importance of this will become apparent shortly)

Let's say you have an engine that runs a certain amount of boost at full throttle at sea level. Now, you take that engine to a high altitude, where the ambient air pressure is lower. Sounds like you'll end up with less pressure going into the engine, right? Not really. Remember, the turbo is driven by exhaust gases, and is thus free to turn at a higher speed to make up for the lower ambient pressure. This allows the turbo to develop pretty much the same boost pressure at high altitude as it did at low altitude. The difference is made up by the fact that the turbo can spin faster to accomplish this in the thinner air. There are limits, of course. If the ambient pressure got low enough, the turbo would overspeed and destroy itself trying to maintain a given manifold boost pressure while drawing from ever-thinner ambient air. For all practical purposes though, this won't happen. Driving altitudes are not high enough to cause this.

The turbodiesel's ability to compensate for low ambient pressure stems not from the fact that it's a diesel, but from the fact that it's turbocharged. A turbocharged gasoline engine benefits the same way at high altitude.

As a side note, a supercharged engine does NOT benefit the same way, as the speed of the supercharger IS directly keyed to engine speed, thus making it unable to spin faster than normal to make up for low ambient pressure.

 

8440 great answer. I've towed my 9,000 fiver all over the Rockies and the Sierra Nevada ranges with no ill effect. At higher altitudes you'll get alittle more smoke but the Cummins is a beast, it just keeps pullin. I've never run out of power and I've always been able to keep my EGT's in check. I wouldn't even consider a gasser!

Gary

 

And along these lines, the turbocharger will increase in speed to compensate for altitude, speed and load conditions. I recall a test engineer years ago who commented that a Varible Geometry Turbo he was working with in a medium-duty truck engine had a speed indicator attached to it. On a few of the 8%, 5+ mile grades in Colorado, that speed meter achieved 160,000 rpm! Consider how fast that turbo was really spinning.

Knowing this, it's imperative that if one does drive loaded through the mountians such as this, one also really needs to let the engine run a while, perhaps even a few minuites, prior to engine shut-down. That bearing holding the center of the turbo wheel shaft needs some cooled, clean oil to flow over it. Just advise your father of this condition should he choose to purchase (and enjoy) a diesel rig.

 

thank you all so much. you have now answered my question to my satisfaction. i appreciate it and i am sure that he will too. but i'm gonna have to wait til mornin' to let him know. but ya'll did a good job at explaining to me and it all makes sense as to why a turbocharged diesel engine is better in high altitudes than a gasser.
thanks again!

 

i one ever sees this old man driving a gasser one will know it is to keep from walking. nuff said.