Engine/Transmission (1994 - 1998) High Altitude Driving

[rosebunch]

Hi all,

I would like to know what if anything, can be done for problems at high altitude. I have a 95 tst #5 DTT and some other stuff. I moved my Son to Colorado Springs last summer and when I arrived into the high altitude, I could feel a definite loss of power, mileage, and lots of smoke. It would start from a standstill like a stone. :{ Once the turbo spooled up, power was better.

Are there any adjustments I can make to get better performance at this altitude? Are there any sensors that should auto adjust for altitude but may be malfunctioning?



I am headed there again in May pulling a 32' 5th wheel which is much heaver than the u-haul trailer I pulled last summer



Down here at sea level, I get good power, 16 - 22 MPG depending on foot, hardly any smoke:-laf .



Thanks for any help:

Bob R.

 

[MMcCallie]

My truck will hopefully join me here in CO soon and i'd like to know how it should be tuned as well. Only guy here that i know with a Cummins has 2004 and runs twins in his F-350 and says he never has any problems associated with altitude. That won't be an option for me and i'm gonna have a lot of fuel for the stock turbo to manage. I'm told EGTs are higher at altitude. My Water/methanol injection should help.

 

[Vaughn MacKenzie]

rosebunch I thought Ephrata was at least 500' elevation

Do you have a big turbo? A built auto makes it more difficult to spool the turbo due to the lower stall RPM, so that's part of the problem. You might try dialing the plate back a little to control smoke, but I would make sure all your intercooler clamps are tight and you don't have any boost leaks.

I didn't have much trouble with my '96 at 7000+ feet but it has a manual trans. The '98 12v spools good without smoke at 6000 ft but it's stock.

Vaughn

 

[rosebunch]

Vaughn,
Thanks for your input. I have the stock turbo but it does boost to 30 lbs with the TST #5 plate kit. I have checked the boost clamps and I can not find any leaks in the boost hoses.

Colorado Springs is 6800 ft above and yes, I did stretch it a little. The highest point in Ephrata is 1101 above sea level. This is at the Ephrata air port.

Bob

 

[robertyoke]

higher altitude = higher egt's

higher altitude = less power

higher altitude = lowered throttle response



welcome to colorado!





-robert

 

[rosebunch]

Gee thanks. robert, I was hopping for something more encouraging than "Welcome to Colorado" . But judging from the overwhelming responses I have received, I guess what it is - is what it is!

Bob

 

[cojhl2]

I drove OTR from sea level to sea level over the mountains and actually I could not tell the difference.



Of course this was all freeway, but with 80K 65mph no problem.



The lighter aur has got to make some difference, but it should not be much from what experience I have.



So I dunno, maybe something needs tuned up on bob R's engine.

 

[Gene Arnold]

I'm not a scientist, a pilot, or a mechanic, but I've heard for many years that there is a 3% loss of power for each 1000 feet of increased elevation above sea level. The higher you go the less dense the air (just ask the teams that play the Denver Broncos). That is why a turbocharger or a supercharger is so valuable in the higher elevations. However, no matter what you do with an engine to optimize it, you'll still have less available oxygen to burn.

My old 12valve does a great job pulling my 34 foot Airstream at high elevations, but I always take it easy. Of course, being retired, I have more time to get there than some of you guys!::-laf

 

[cojhl2]

I'm at the edge of a cliff of my knowledge here, but it seems to me if you can build say 15-20 psi boost, would that not be the same air density regardless of the ambient air pressure? Hence the same amount of O2.



edit: Or is there a psig thing in play here??

 

[Forrest Nearing]

what Colorado lacks in oxygen, it more than makes up for in scenery!!! can't wait to go to the cabin this summer

 

[rosebunch]

Thanks for all the input. Still not sure if all is normal. All I know is I get significantly better performance at the lower elevations than in Colorado. Do love the scenery! I am retired also so am not in as big a hurry as I used to be. I do try not to hold up traffic while pulling the 5th wheel if possible.



I do like having a better acceleration so I don't slow others down, but in Colorado it's iffy & smokey.



I am going to call Cummins Northwest and see what they think.



Bob

 

[JPittinger]

I'm at the edge of a cliff of my knowledge here, but it seems to me if you can build say 15-20 psi boost, would that not be the same air density regardless of the ambient air pressure? Hence the same amount of O2.



edit: Or is there a psig thing in play here??

There's less O2 per unit volume at altitude: psia at sea level=14. 7, psia in CO (Denver) is approx. 12. 2. The ratio of N2/O2 is roughly the same at 79/21, so the partial pressure of both are down for a total of 2. 5 psi difference. For the same mass of O2, you would have to run 12. 5 psig in CO vs 10. 0 psig at sea level. Its a little harder to compress 12. 5 vs 10. 0, hence the loss in efficiency.



I'm 2 cold ones in and its been a while since I got my ChemE PE, so feel free to correct my logic.

-JJ

 

[Forrest Nearing]

I wouldn't bother contacting Cummins, I assure you it's normal

 

[JWashburn]

I live at 7800 ft here in CO.

The answer is more air. It is just more important to have a free flowing system from filter to where that smoke rolls out. To date, timing and the PDR cam helped the most. PDR Stage 2 head goes on soon.

Water/Meth would be effective, probably the most cost effective, and simplest to implement.

 

[cojhl2]

There's less O2 per unit volume at altitude: psia at sea level=14. 7, psia in CO (Denver) is approx. 12. 2. The ratio of N2/O2 is roughly the same at 79/21, so the partial pressure of both are down for a total of 2. 5 psi difference. For the same mass of O2, you would have to run 12. 5 psig in CO vs 10. 0 psig at sea level. Its a little harder to compress 12. 5 vs 10. 0, hence the loss in efficiency.

-JJ

Thanks JP,, good explanation.

 

[Vaughn MacKenzie]

There's less O2 per unit volume at altitude: psia at sea level=14. 7, psia in CO (Denver) is approx. 12. 2. The ratio of N2/O2 is roughly the same at 79/21, so the partial pressure of both are down for a total of 2. 5 psi difference. For the same mass of O2, you would have to run 12. 5 psig in CO vs 10. 0 psig at sea level. Its a little harder to compress 12. 5 vs 10. 0, hence the loss in efficiency.
-JJ

Yes very good explanation. Another because the density of exhaust gasses are lower you have that much less to drive the turbo. Max boost decreases as you climb.

 

[JWashburn]

With the help of a website altitude vs. pressure calculator I found that the pressure at my home altitude is ~580 mm Hg. At sea level its 760 mm Hg. That's 24% less than at sea level, and 24% less for any given rpm of the turbo. Absolute compression decreases by the same amount. PDR claims their cam flows 30% more air as I recall.

In order to gain back the same charge air density at sea level, water/meth injection would need to lower the input temp by 126 F by my calculation at 68F ambient.

 

[rosebunch]

Thanks for all the input.

I am not sure what or how you do the "water Meth" is this a mixture of water and methanol? Hate to show my ignorance but sometimes it just comes out



I used to run water injection in an old Ford gasser I had. Is this similar concept?



Thanks

 

[MMcCallie]

Yes, water/methanol injection is the same on gas and diesel engines. Do some searches, there are many manufacturers offering excellent kits. Mine is devilsownonline.com, most popular is snowperformance.net, coolingmist.com is another. It is also possible to build your own kit. Even straight water will make a very noticeable difference. Water/methanol injection offers multiple benefits, especially on diesel engines.

 

[rosebunch]

Thanks MMcCallie,
I checked out the websites and some others. Think it might be to pricey for me when I am only going to be at hi altitude a few weeks a year. May do it later if visits become intolerable. I have some other $$$ commitments right now.