how much does altitude affect MPG in a N\A diesel engine????

[trooper Tdiesel]

this is more or less a copy of what ive put on a diffrent site, figure i mite get more ideas hear as well

i set Google to its terrain mode, to help show the differences in passes.
my question is, having a avrege of 4,000 versus 6,000 feet thru the mountens, is that enuf to drive about an extra 100 miles to be a lower altitude

northern route its the one that's 100 miles farther, one pass at 6,000+ one at 5,000+ and one around 4,000 something.
I-84 to US 395 then I-90 across and down to I-25 for a short ways, then US26 too I-80
the other plus of going this way is for more then one grade your along a water way so the grade-eant is rather mild....
I-205 S to I-40 E - Google Maps



southern route I-84 all the way to I-80 east word.
two passes around 4,500 two at 5,500 one at 7,500 and another at 8,500
also for just about all of WY states 400 miles your at 6,000 to 8,000 feet

I-205 S to I-40 E - Google Maps


bolth ways still keep me in WY and MO state with lower priced fuel so that's not a issue.


my ride is a turbo model, but there are others making the trip that have the N\A model in the 2wd models.
a little info on where im headed.
IsuzuPup.com • View forum - Southeast U.S. - Memphis, TN June 2012


im loaded on the return with 5 JDM diesel engines so i have no real room coming back west. east word i have allot of space, could even transport a mid size car. for my fuel cost .60 a mile

[redpoint5]

Since you have a turbo, you won't notice a difference and might actually get better mpg at higher elevation (due to less dense air and less drag).

Going 100 miles out of the way is not going to save fuel, even for the NA diesels.

[oil pan 4]

Going from sea level to 4400 feet has hurt my milage quite a bit, a solid 2 mpg just vanashed.
If you had a turbo diesel the effect is rumored to not be as bad.

Diesels run most efficiently when you stuff as much air mass as possible into the cylinders as possible, that is why EGR and warm air intakes usually hurt miliage but cold air intake or water injection help milage.

When your cylinders are not filling with as much air you get to burn more fuel to do the same work, I get high EGTs just doing normal stuff above 4000 feet.
In clovis there is about 12% less air up there than at sea level.

[user removed]

Maybe I am missing something but most uphill climbs have a downhill stretch later, unless you are climbing to a plateau and not coming back down.

In fact I have had good success with getting better mileage in certain grade scenarios than on flat ground. I think atmospheric pressure drops 50% at 18,000 feet, but lower atmospheric pressure is like a governor in a diesel, as long as you have enough power to climb the grade.

regards
Mech

[trooper Tdiesel]

some info i copied from the other site.

remember that's 60hp at max RPMs 4,200

its about 40hp at 3,000 rpms

using the 6,000ft number
that's 8.4 hp lossed from 40hp making about 32hp

and 95 torque at 2,200 rpms drops to 75.05

now lets try it saying an avrege of 4,000ft
the 60hp number drops 8.4hp

the 40hp number drops 5.6hp

the 95 torque number drops 13.3



so ok lets compare "ball park" mpg numbers...........
1,292 miles for the northern route.
1,154 miles for the southern route.
for a total difference of 138 miles, now....
that's the distance from the ends of where the two routes go there ways, and return to one another.

now using those mile numbers, ill figure 4 different MPG numbers that are quite possible.
32, 34, 36, 38


staring with the southern route.
32=36.0625 gal
34=33.94 gal
36=32.055gal
38=30.368gal

now the northern route.
32=40.375gal
34=38.00gal
36=35.888gal
38=34.00


so it only takes about a 3.9 mpg difference to make it brake even....

as wako as this sounds, i think its possible that its close to brake even.... to drive an extra 138 miles on a road that's flatter :shock:

[oil pan 4]

You get those N/A diesels up to 6000 feet and it is going to suck.
They start running real high EGTs and you get melted pistons if you are not careful.