High Altitude???

[HookMeUp]

anybody have any experience with their CTD at high altitude? high altitude being 11,000 ft and above. Loss of power or poor performance. I remember when I had my 83 Chevy diesel that thing was a dog at high altitude and you didn't dare even try to tow anything with it. I am currently shopping for a new CTD and my wife has concerns, when she was growing up they had an escort diesel that quit on them when they were vacationing in the Colorado mountains. The thing wouldn't run over 10,000 feet.

 

[Forrest Nearing]

our cabin in Colorado is at 8,900ft. I've had my truck up in the 11k+ range.



obviously, you'll be down on power and the turbo will take longer to spool up, but I can't think of any other vehicle besides a CTD that I would want at high altitude!!



Forrest

 

[klenger]

I drove my 01. 5 all over Colorado. Runs great at high altitude (11,000 feet at Eisenhower Tunnel). I would pass a lot of vehicles that were running empty and I was towing my 10K 5er. I understand that the CTD turbo maintains close to sea level pressure up to about 10,000 feet. Someone please correct me if I am in error with the numbers.

 

[jetenginedoctor]

I drove my 01. 5 all over Colorado. Runs great at high altitude (11,000 feet at Eisenhower Tunnel). I would pass a lot of vehicles that were running empty and I was towing my 10K 5er. I understand that the CTD turbo maintains close to sea level pressure up to about 10,000 feet. Someone please correct me if I am in error with the numbers.

You're in error with the numbers.

 

[NIsaacs]

You're in error with the numbers.

What are the numbers, please? I feel like Klenger, that there is no loss of power up to 10,000 ft. I can see slower spool at low RPM, but once spooled it should maintain normal power.





"NICK"

 

[Forrest Nearing]

my truck feels like it has the same power once the turbo signs on, but EGT's are NUTS!!!



Forrest

 

[BHolm]

Pretty tough to spend much time OVER 11,000 ft in the continental US, most mtn passes barely get over that. Anyway, I also live at high altitude (7200ft) and regularly drive the truck over 11,000 ft passes. The turbo only has to produce about 1lb of boost to completely negate the effects of altitude, you will not have a problem with a turbo diesel lacking power, in fact they are awesome at high elevation. My '03s hauled big loads over Monarch pass, 11,312ft, last summer. The QC was towing 15,000+lbs and the dually was over 20k. Even the dually could maintain 40 mph at 27-28k gross. That is better than most empty cars can muster.

 

[jetenginedoctor]

What are the numbers, please? I feel like Klenger, that there is no loss of power up to 10,000 ft. I can see slower spool at low RPM, but once spooled it should maintain normal power.





"NICK"

You might feel like that's the case, but you're mistaken. Increased elevation results in a decrease in charge density, which results in loss of power. PERIOD. It's not a matter of pressure, it's a matter of mass flow, and the fact remains (whether anyone can "feel it" or not) that less mass airflow equals less power.

 

[jetenginedoctor]

The turbo only has to produce about 1lb of boost to completely negate the effects of altitude,

Wow. WRONG. . . . Where do you get that idea? Every 1000ft increase in elevation (temperature and humidity remaining the same) yeilds roughly 3% decrease in air density. Show me where you get this 1lb of boost idea???

you will not have a problem with a turbo diesel lacking power, in fact they are awesome at high elevation. My '03s hauled big loads over Monarch pass, 11,312ft, last summer. The QC was towing 15,000+lbs and the dually was over 20k. Even the dually could maintain 40 mph at 27-28k gross. That is better than most empty cars can muster.

The difference is in how you drive your trucks veruses how most people drive their 'empty cars' up a grade. It's as if you expect everybody to punish their vehicle going up and over a grade like they've got something to prove. Most people relaly don't give a flip, and aren't interested in dragracing up a hill.

 

[klenger]

You might feel like that's the case, but you're mistaken. Increased elevation results in a decrease in charge density, which results in loss of power. PERIOD. It's not a matter of pressure, it's a matter of mass flow, and the fact remains (whether anyone can "feel it" or not) that less mass airflow equals less power.

Given your handle (jetenginedoctor), I assume that you know a lot more about turbo-charged engines than I do. I do not intend any sarcasm in that statement.



Here is my understanding of how the turbo helps at altitude: At lower atlitudes, the system is designed to produce a maximum amount of boost. Any additional airflow that the turbo generates at lower altitudes is dumped through the wastegate. As altitude increases, the maximum amount of airflow that the turbo can develop is reduced, but does not affect peformance until the pressure drops below the point where the wastegate is used. In other words, at some altitude, the wastegate does not open and performance then drops off. Below this altitude, the engine will perform much like it would at sea level. The number I heard some time ago was 10,000 feet, but I have no idea where I heard that, and could very well be in error. I'd be interested to hear what altitude other members see a reduction in boost on a stock engine. I don't have guages, so I cannot say from personal experience. In any case, a turbocharged engine will maintain it's performance at altitude much better than a non-turbocharged engine, whether it's gas, diesel, or 100 low-lead.

 

[jetenginedoctor]

Given your handle (jetenginedoctor), I assume that you know a lot more about turbo-charged engines than I do. I do not intend any sarcasm in that statement.



Here is my understanding of how the turbo helps at altitude: At lower atlitudes, the system is designed to produce a maximum amount of boost. Any additional airflow that the turbo generates at lower altitudes is dumped through the wastegate.

Not exactly. The wastegate bypasses exhaust around the turbine and into the downpipe to limit the compressor discharge pressure. There is no dumping of airflow (at least not in this system) anywhere. It's simply giving the exhaust gas an alternate path around rather than through the turbine.

As altitude increases, the maximum amount of airflow that the turbo can develop is reduced, but does not affect peformance until the pressure drops below the point where the wastegate is used.

Wrong. The wastegate will still function the same way, limiting compressor discharge pressure to the same GAUGE pressure. In other words, the lower the ambient pressure, the lower the boost pressure in absolute terms. The turbo has to work harder to exert the same pressure ratio at higher elevation, so the wastegate opens later, increasing drive pressure, EGT, compressor discharge pressure, firing temperature, etc. All this has a further negative impact on the power produced by the engine.

In other words, at some altitude, the wastegate does not open and performance then drops off.

But that's not how it works. The greater the elevation, the lower the density of the air at the inlet of the turbocharger. This lower density (regardless of pressure) makes the turbocharger less efficient. Trying to create the same gauge boost pressure with the lower inlet pressure and density means the turbo has to work that much harder because it must acheive an even higher pressure ratio, adding a great deal more heat to the inlet charge, further reducing charge density. The lower density of ambient air at the higher elevation means that the charge cooler (intercooler) is that much less efficient again. The hotter, less dense air (forget pressure, remember mass of air as this is what makes power) results in a smaller cylinder charge, lower cylinder pressure, higher combustion and exhaust temps, and lower power.

Below this altitude, the engine will perform much like it would at sea level.

No, it won't. Trust me.

The number I heard some time ago was 10,000 feet, but I have no idea where I heard that, and could very well be in error.

It was in error.

I'd be interested to hear what altitude other members see a reduction in boost on a stock engine.

It's not a reduction in boost! BOOST DOES NOT EQUAL POWER!!!!!

I don't have guages, so I cannot say from personal experience. In any case, a turbocharged engine will maintain it's performance at altitude much better than a non-turbocharged engine, whether it's gas, diesel, or 100 low-lead.

That may safe to say, but it absolutely DOES NOT make it immune to the effects of increased altitude.

 

[crobertson1]

jetenginedoctor,



You sound offended or something. Thanks for the info though.



I live at almost 9,000 feet and the truck "feels" as powerful as when I go down to the Mile High City. Yes that's only a 3,700 foot change in elevation, but that's what I know. We tow at higher elevations and the EGTs are definetly harder to control. The issue of altitude shouldn't be an issue when deciding whether or not to puchase a CTD.

 

[BSchulte]

I posted a similar question last year on altitude concerns before going on vacation.

We put on 3,500 miles in the mountains with absolutely no performance loss. So go purchase your truck and have fun in the hills

 

[Rescue Ram]

It will run well...

It will run circles around a 6. 2 NA at altitude any day of the week. :-laf

You and your wife will both be pleased.

 

[RTillery]

The Eisenhower Memorial Tunnel is located approximately sixty miles west of Denver, Colorado on Interstate 70. It is the highest vehicular tunnel in the world, located at an elevation of 11,013 feet at the East Portal and 11,158 feet at the West Portal. The Tunnel traverses through the Continental Divide at an average elevation of 11,112 feet. The facility lies entirely within the Arapaho National Forest and is divided by two counties, Clear Creek County at the East portal and Summit county at the West portal.



With that said, your Cummins will go up either side faster than you want to negotiate the curves with relative ease. If you are towing, a set of gauges will let you monitor things. If you are running bobtail, hammer down and smile and wave as you pass everybody else!!!

 

[NIsaacs]

jetenginedoctor,



I can agree with all you have posted, if we were talking about Naturally Asperated gas or diesel engines, even the turbo comments. However, Cummins advertises no loss of power to 10,000 ft. Is that a true statment? Probably not, but it is close enough for this Redneck. You are making a moutain out of a mole hill with our comments regarding no loss of power. All we are saying is it is not enough to mention.



I do thank you for the lesson and have learned from it.



Will I dragrace up hill if the condtions are right? "Yup" (sorry)





"NICK"

 

[robertyoke]

jetenginedoctor,

I can agree with all you have posted, if we were talking about Naturally Asperated gas or diesel engines, even the turbo comments. However, Cummins advertises no loss of power to 10,000 ft. Is that a true statment? Probably not, but it is close enough for this Redneck. You are making a moutain out of a mole hill with our comments regarding no loss of power. All we are saying is it is not enough to mention.

I do thank you for the lesson and have learned from it.

Will I dragrace up hill if the condtions are right? "Yup" (sorry)


"NICK"

loss of power ?? I dont know . sloooow spoooool up. most definitely & way higher egt's..... as a bonus.

 

[SKelly]

I live at 9,600' according to the GPS on the dashboard of my truck. I travel every day (towing and empty) over some of the highest passes in the US, Eisenhower, Loveland, Bethoud,Rabbit Ears ect. . I notice higher EGT's and engine temps than at sea level but my s. o. p. dyno does not register much difference in power. What I do notice is the CTD does not seem as effected by the altitude as the gassers I aslo have, VW R32, Audi 1. 8T, Jeep Rubicon, '85 Toyota.



One other interesting point though. The Audi 1. 8T, which is also turbocharged is second fastest up the passes. The turbos help alot with the lack of oxygen up here.

 

[BHolm]

Punish my vehicles???? No, actually I run them as designed, thank you. Jetboy, you really are making a HUGE deal out of this and I think you are wrong anyway. Nowhere in your posts do I see any real evidence that your statements are correct.



NA engines lose power due to less dense air and lower pressure. The NA engine has to "suck" air in where a turbocharged engine has a force feeding system that eliminates the pressure problem at as low as 1psi. Yes the air is less dense so it takes a larger charge to provide the same amount of oxygen for the given amount of fuel. To say that a turbo doesn't compensate for this is ignorant IMO. It most certainly does, and rather effectively in my experience (and that of everyone else living in the mtns that has replied). So I guess we are all wrong.



If you have some eveidence that can show the loss of power, I would love to see it. Anybody know of a dyno located at high altitude?



Just a quick anaology for forced induction at altitude. I drag race my old Buick at 7000ft. My buddy runs a supercharged engine that dynos at less power than my NA car at sea level. His is about 450hp and mine 485hp, cars are similar enough in wieght. His car runs 1. 5 seconds faster in the QM than my car at altitude. My car runs 1 second faster than his at (near)sea level. The only changes made are in carb jetting, mine far more drastic than his. Forced induction works to virtually eliminate the effects of altitude in real life. It appears that in the lab I am all wrong though :-{}

 

[TX Gooseneck]

Should run fine. I lived near Breckenridge when I had my 95 F-350 and that thing would smoke like a train going over Hoosier Pass. You have an equalizer though in the form of a turbo.