Which 4WD for vertical commuting?

I'm getting into a line of work where the baseyard is near sea
level, but the job site is above 13000 feet. The drive up is
usually done in a "company vehicle" - typically a Tahoe, Suburban,
or something similarly large - and involves about 35 miles of
narrow, twisty, hilly pavement with grades up to at least 17%,
followed by 5 miles of "You WILL use 4-LO on this" unpaved,
rock-strewn 12% grade washboard above 9000 feet, and then a
bit more pavement toward the end with some serious grades and
hairpin turns.

As I said, I'll typically do this in "their" vehicles, but next
time I buy a vehicle of my own, I want it to be something that's
up to it.

I know there's a pretty linear relationship between air pressure
and BHP, and have been told that mileage also suffers at elevation
(though I haven't been able to figure out via Google whether this
relationship is also linear), so I'm between a rock and a hard
place - I want something that'll still make it up the hills when
it's up a mountain, yet I don't want to have to have a monster
engine that only gets 3 MPG at the job site, since gas here is
well over $2/gallon.

So... I'm figuring I need something relatively small and light,
yet capable of dealing with the conditions. In a personal vehicle,
I'm not required to have low-range gearing, but it wouldn't *hurt*,
especially for engine-braking on the way down. I do want a bit of
ground clearance, so as not to smack any vital parts on stray rocks
while going up the washboard.

The choice may wind up coming down to which of the following is
most efficient:

1) A "car-like" thing with AWD (i.e. Subaru Forester)
2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the road
4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with Selec-Trac)

* I'm thinking a hybrid might be useful at higher elevation, since to my
knowledge, the electric motor won't lose efficiency due to elevation
like internal-combustion ones do.

Anybody have any thoughts? Thanks in advance,

-Dan
altitude

"Dan" <[email protected]> wrote in message
news:[email protected]...
> I'm getting into a line of work where the baseyard is near sea
> level, but the job site is above 13000 feet. The drive up is
> usually done in a "company vehicle" - typically a Tahoe, Suburban,
> or something similarly large - and involves about 35 miles of
> narrow, twisty, hilly pavement with grades up to at least 17%,
> followed by 5 miles of "You WILL use 4-LO on this" unpaved,
> rock-strewn 12% grade washboard above 9000 feet, and then a
> bit more pavement toward the end with some serious grades and
> hairpin turns.
>
> As I said, I'll typically do this in "their" vehicles, but next
> time I buy a vehicle of my own, I want it to be something that's
> up to it.
>
> I know there's a pretty linear relationship between air pressure
> and BHP, and have been told that mileage also suffers at elevation
> (though I haven't been able to figure out via Google whether this
> relationship is also linear), so I'm between a rock and a hard
> place - I want something that'll still make it up the hills when
> it's up a mountain, yet I don't want to have to have a monster
> engine that only gets 3 MPG at the job site, since gas here is
> well over $2/gallon.
>
> So... I'm figuring I need something relatively small and light,
> yet capable of dealing with the conditions. In a personal vehicle,
> I'm not required to have low-range gearing, but it wouldn't *hurt*,
> especially for engine-braking on the way down. I do want a bit of
> ground clearance, so as not to smack any vital parts on stray rocks
> while going up the washboard.
>
> The choice may wind up coming down to which of the following is
> most efficient:
>
> 1) A "car-like" thing with AWD (i.e. Subaru Forester)

If the 4 wheel part is as bad as you state this CAR won't survive the
first trip, and will cost you LOTS to repair. IE typical exhaust system
on a Subaru is over $1000.00 US

> 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)

Hybrids don't really help with a problem like this since they count on
the engine to produce power to turn the motor. They also are not useful
off road because of the extra weight also.

> 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the
road

Move up to a Trailblazer with the G80 rear LS differential and your in
better territory for what your use.

> 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with
Selec-Trac)

Not a bad choice but I would look at something that has selectable 4wd
not full time.

>
> * I'm thinking a hybrid might be useful at higher elevation, since to
my
> knowledge, the electric motor won't lose efficiency due to elevation
> like internal-combustion ones do.

Still have the engine there generating power for high demand time ,and
off roading is a HIGH demand time. Plus it's just not worth the extra
money when the mileage is actually taken into account. You do know that
most hybrids are REALLY not getting close to the claimed mileage
figures. There are even web sites and a few folks are planning on
lawsuits because of this.


>
> Anybody have any thoughts? Thanks in advance,
>
> -Dan
> altitude




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[email protected] wrote:
| I'm getting into a line of work where the baseyard is near sea
| level, but the job site is above 13000 feet. [...]

Hmm, Alaska?
I'm assuming in the US for the rest of this post...

| The choice may wind up coming down to which of the following is
| most efficient:
|
| 1) A "car-like" thing with AWD (i.e. Subaru Forester)
| 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
| 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the road
| 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with Selec-Trac)

I used to own a Cherokee with part-time 4WD. I currently own a 2002
Subaru and am restoring an old CJ7. AWD is great technology, but for your
commute I'd prefer a stouter vehicle and drivetrain type.

Have you looked at the Jeep Liberty CRD? That's the upcoming 2005 Liberty
with a turbocharged "Common Rail Diesel" engine. It has 295
ft-lbs of torque, and good flatland mileage to boot (27mpg predicted).

Even if diesel engines have a power drop with elevation as gas engines
do, starting with a high-torque engine gives you reserve torque for when
you need it (at 13000'...). Plus, diesel fuel lags gas prices.


| * I'm thinking a hybrid might be useful at higher elevation, since to my
| knowledge, the electric motor won't lose efficiency due to elevation
| like internal-combustion ones do.

You are right, an electric motor would not lose torque with elevation.
However, a hybrid running solely off electric would not have enough oomph
to pull the vehicle up a steep sketchy road, at least not for long.
Powering a vehicle on level ground with electricity doesn't require the
same energy.

hope my two cents help,
-Brent

Turbo diesel ... mmmmm ... if it meets North American standards, I'm
thinking that diesel is a likely candidate for one of those "power modules"
.... not that you'd really need one .... and the turbo will compensate
for the altitude ... turbo diesel ... the ideal jeep engine imo. Hmmm ...
with one of those, I could pull a MUCH bigger boat.

"Brent Burton" <[email protected]> wrote in message
news:[email protected]...
> [email protected] wrote:
> | I'm getting into a line of work where the baseyard is near sea
> | level, but the job site is above 13000 feet. [...]
>
> Hmm, Alaska?
> I'm assuming in the US for the rest of this post...
>
> | The choice may wind up coming down to which of the following is
> | most efficient:
> |
> | 1) A "car-like" thing with AWD (i.e. Subaru Forester)
> | 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
> | 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the
road
> | 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with Selec-Trac)
>
> I used to own a Cherokee with part-time 4WD. I currently own a 2002
> Subaru and am restoring an old CJ7. AWD is great technology, but for your
> commute I'd prefer a stouter vehicle and drivetrain type.
>
> Have you looked at the Jeep Liberty CRD? That's the upcoming 2005 Liberty
> with a turbocharged "Common Rail Diesel" engine. It has 295
> ft-lbs of torque, and good flatland mileage to boot (27mpg predicted).
>
> Even if diesel engines have a power drop with elevation as gas engines
> do, starting with a high-torque engine gives you reserve torque for when
> you need it (at 13000'...). Plus, diesel fuel lags gas prices.
>
>
> | * I'm thinking a hybrid might be useful at higher elevation, since to my
> | knowledge, the electric motor won't lose efficiency due to elevation
> | like internal-combustion ones do.
>
> You are right, an electric motor would not lose torque with elevation.
> However, a hybrid running solely off electric would not have enough oomph
> to pull the vehicle up a steep sketchy road, at least not for long.
> Powering a vehicle on level ground with electricity doesn't require the
> same energy.
>
> hope my two cents help,
> -Brent

[email protected] (Dan) wrote in message news:<[email protected]>...
> I'm getting into a line of work where the baseyard is near sea
> level, but the job site is above 13000 feet. The drive up is
> usually done in a "company vehicle" - typically a Tahoe, Suburban,
> or something similarly large - and involves about 35 miles of
> narrow, twisty, hilly pavement with grades up to at least 17%,
> followed by 5 miles of "You WILL use 4-LO on this" unpaved,
> rock-strewn 12% grade washboard above 9000 feet, and then a
> bit more pavement toward the end with some serious grades and
> hairpin turns.

I'm not seeing a need & justification for 4WD in this, with its added
cost, complexity & maintenance. I'd want a substantial (not big but
not light) 2WD that would be heavy enough to be fairly stable in
unpredictable crosswinds but small enough not to present a lot of sail
area, a higher-ratio diff (such as sold for towing like 4:11 etc.), &
wise tire selection. My sense is that in one of those big land-yatch
Burb's or etc, one is advised to use 4-Lo just to have better control
of the behemoth @ low speeds. YMMV

I agree with the Jeep Liberty CRD suggestion.

We have a similar situation here in South Africa (Sani Pass which tops out
at around 3000m -about 9000ft) and I can tell you there is no substitute for
a turbo diesel at altitiude.

I can't comment on the jeep other than to say that in SOuth Africa it
competes against all the soft roaders (Rav, Freelander etc) and is the only
one with Low Range. I can tell you about my Landrover Discovery Tdi which is
probably fairly similar except that the jeep engine is newer and more
powerful.

I regularly get < 10l/100km on the open road and it doesn''t get too much
worse driven sensibly off road. I can get up Sani Pass in High Range which I
could never do in my petrol powered SerIII landrover.

Re the other vehicles you mentioned. A proper 4x4 has a seperate ladder
chassis and this tends to make it a lot more rugged. Ideally a solid leaf
sprung front diff would be first prize but I understand that the newer jeeps
are IFS.

In Lesotho they had a thing called the Lesotho Highlands water project
(basically building a big dam and selling the water to South Africa) and I
know they could only use leaf sprung vehicles mostly old hiluxes. The IFS
nissans and Isuzus lasted about two weeks before the front suspension was
stuffed.

I hope this helps you make a good choice.

Regards
Stephen

"Bowgus" <[email protected]> wrote in message
news:[email protected]...
> Turbo diesel ... mmmmm ... if it meets North American standards, I'm
> thinking that diesel is a likely candidate for one of those "power
modules"
> ... not that you'd really need one .... and the turbo will compensate
> for the altitude ... turbo diesel ... the ideal jeep engine imo. Hmmm ...
> with one of those, I could pull a MUCH bigger boat.
>
> "Brent Burton" <[email protected]> wrote in message
> news:[email protected]...
> > [email protected] wrote:
> > | I'm getting into a line of work where the baseyard is near sea
> > | level, but the job site is above 13000 feet. [...]
> >
> > Hmm, Alaska?
> > I'm assuming in the US for the rest of this post...
> >
> > | The choice may wind up coming down to which of the following is
> > | most efficient:
> > |
> > | 1) A "car-like" thing with AWD (i.e. Subaru Forester)
> > | 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
> > | 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the
> road
> > | 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with
Selec-Trac)
> >
> > I used to own a Cherokee with part-time 4WD. I currently own a 2002
> > Subaru and am restoring an old CJ7. AWD is great technology, but for
your
> > commute I'd prefer a stouter vehicle and drivetrain type.
> >
> > Have you looked at the Jeep Liberty CRD? That's the upcoming 2005
Liberty
> > with a turbocharged "Common Rail Diesel" engine. It has 295
> > ft-lbs of torque, and good flatland mileage to boot (27mpg predicted).
> >
> > Even if diesel engines have a power drop with elevation as gas engines
> > do, starting with a high-torque engine gives you reserve torque for when
> > you need it (at 13000'...). Plus, diesel fuel lags gas prices.
> >
> >
> > | * I'm thinking a hybrid might be useful at higher elevation, since to
my
> > | knowledge, the electric motor won't lose efficiency due to elevation
> > | like internal-combustion ones do.
> >
> > You are right, an electric motor would not lose torque with elevation.
> > However, a hybrid running solely off electric would not have enough
oomph
> > to pull the vehicle up a steep sketchy road, at least not for long.
> > Powering a vehicle on level ground with electricity doesn't require the
> > same energy.
> >
> > hope my two cents help,
> > -Brent
>
>

In article <[email protected]>,
"fanie" <[email protected]> wrote:

> I agree with the Jeep Liberty CRD suggestion.
>
> We have a similar situation here in South Africa (Sani Pass which tops out
> at around 3000m -about 9000ft) and I can tell you there is no substitute for
> a turbo diesel at altitiude.
>
> I can't comment on the jeep other than to say that in SOuth Africa it
> competes against all the soft roaders (Rav, Freelander etc) and is the only
> one with Low Range. I can tell you about my Landrover Discovery Tdi which is
> probably fairly similar except that the jeep engine is newer and more
> powerful.
>
> I regularly get < 10l/100km on the open road and it doesn''t get too much
> worse driven sensibly off road. I can get up Sani Pass in High Range which I
> could never do in my petrol powered SerIII landrover.
>
> Re the other vehicles you mentioned. A proper 4x4 has a seperate ladder
> chassis and this tends to make it a lot more rugged. Ideally a solid leaf
> sprung front diff would be first prize but I understand that the newer jeeps
> are IFS.
>

> I hope this helps you make a good choice.
>
> Regards
> Stephen
>
> "Bowgus" <[email protected]> wrote in message
> news:[email protected]...
> > Turbo diesel ... mmmmm ... if it meets North American standards, I'm
> > thinking that diesel is a likely candidate for one of those "power
> modules"
> > ... not that you'd really need one .... and the turbo will compensate
> > for the altitude ... turbo diesel ... the ideal jeep engine imo. Hmmm ...
> > with one of those, I could pull a MUCH bigger boat.
> >
> > "Brent Burton" <[email protected]> wrote in message
> > news:[email protected]...
> > > [email protected] wrote:
> > > | I'm getting into a line of work where the baseyard is near sea
> > > | level, but the job site is above 13000 feet. [...]
> > >
> > > Hmm, Alaska?
> > > I'm assuming in the US for the rest of this post...
> > >
> > > | The choice may wind up coming down to which of the following is
> > > | most efficient:
> > > |
> > > | 1) A "car-like" thing with AWD (i.e. Subaru Forester)
> > > | 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
> > > | 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the
> > road
> > > | 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with
> Selec-Trac)


Another choice is the Kia Sorento. Its size puts it right on the edge
of the small / midsize category; journalists have placed it in both
categories.

Like the aforementioned Jeep, it is a 4WD vehicle with a low gear. It
has separate body on frame design, with a "ladder" chassis design.

It comes in both gas and diesel flavours, although I've read the diesel
engine is not that impressive. I can speak for the gas version though.
The 3.5 litre engine does a very good job in moving the car around.

"Dan" <[email protected]> wrote in message news:[email protected]...
> 1) A "car-like" thing with AWD (i.e. Subaru Forester)
>
A turbo runs strong at altitude which would be a good reason to consider the Forester.
A 40mm chassis lift is easily installed, but low range gearing probably isn't an option.

If it's rugged enough for the rough spots it will be a lot more fun elsewhere.

Dan wrote:
> I'm getting into a line of work where the baseyard is near sea
> level, but the job site is above 13000 feet. The drive up is
> usually done in a "company vehicle" - typically a Tahoe, Suburban,
> or something similarly large - and involves about 35 miles of
> narrow, twisty, hilly pavement with grades up to at least 17%,
> followed by 5 miles of "You WILL use 4-LO on this" unpaved,
> rock-strewn 12% grade washboard above 9000 feet, and then a
> bit more pavement toward the end with some serious grades and
> hairpin turns.
>
> As I said, I'll typically do this in "their" vehicles, but next
> time I buy a vehicle of my own, I want it to be something that's
> up to it.
>
> I know there's a pretty linear relationship between air pressure
> and BHP, and have been told that mileage also suffers at elevation
> (though I haven't been able to figure out via Google whether this
> relationship is also linear), so I'm between a rock and a hard
> place - I want something that'll still make it up the hills when
> it's up a mountain, yet I don't want to have to have a monster
> engine that only gets 3 MPG at the job site, since gas here is
> well over $2/gallon.
>
> So... I'm figuring I need something relatively small and light,
> yet capable of dealing with the conditions. In a personal vehicle,
> I'm not required to have low-range gearing, but it wouldn't *hurt*,
> especially for engine-braking on the way down. I do want a bit of
> ground clearance, so as not to smack any vital parts on stray rocks
> while going up the washboard.
>
> The choice may wind up coming down to which of the following is
> most efficient:
>
> 1) A "car-like" thing with AWD (i.e. Subaru Forester)
> 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
> 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the road
> 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with Selec-Trac)
>
> * I'm thinking a hybrid might be useful at higher elevation, since to my
> knowledge, the electric motor won't lose efficiency due to elevation
> like internal-combustion ones do.
>
> Anybody have any thoughts? Thanks in advance,
>
> -Dan
> altitude
jeep liberty turbodiesel. turbo is less effected by altitudes.

9000 ft 12% grade. Ha, that is nothing. My grandfather's Cadillac will do
that any day. I did Mauna Kea in Hawaii 13,700 ft 15% grade dirt road and
17% paved section in a front wheel drive Chrysler minivan at 4:00am in the
morning. And yes, there are signs all along that insist you "WILL" use a 4WD
vehicle only. There was not even a hint of traction problem. When we got to
the top, the oxygen is so thin that I felt like passing out just walking
around. The Chrysler engine ran perfect. Any fuel injected engine should be
able to compensate for the altitude. Who cares about some lost horse power.
You are not doing the Pikes Peak hill climb race are you.
Now, it would be a completely different story if it was snowing or raining.
Let say you do drive a stock 4WD up a mountain road in heavy rain. If you do
make it with some momentum, how are you going to get down without running
into the danger of sliding off the road 2WD or 4WD would not matter at that
point. I would stick with 2WD. If it slips, is telling you to turn around.
Given that you are not into 4wheeling anyway, I would get the most
economical car with auto transmission rather than manual for torque
multiplication. Wash boards should not be a problem for most cars unless you
got a low sports car.

Ben


"Dan" <[email protected]> wrote in message
news:[email protected]...
> I'm getting into a line of work where the baseyard is near sea
> level, but the job site is above 13000 feet. The drive up is
> usually done in a "company vehicle" - typically a Tahoe, Suburban,
> or something similarly large - and involves about 35 miles of
> narrow, twisty, hilly pavement with grades up to at least 17%,
> followed by 5 miles of "You WILL use 4-LO on this" unpaved,
> rock-strewn 12% grade washboard above 9000 feet, and then a
> bit more pavement toward the end with some serious grades and
> hairpin turns.
>
> As I said, I'll typically do this in "their" vehicles, but next
> time I buy a vehicle of my own, I want it to be something that's
> up to it.
>
> I know there's a pretty linear relationship between air pressure
> and BHP, and have been told that mileage also suffers at elevation
> (though I haven't been able to figure out via Google whether this
> relationship is also linear), so I'm between a rock and a hard
> place - I want something that'll still make it up the hills when
> it's up a mountain, yet I don't want to have to have a monster
> engine that only gets 3 MPG at the job site, since gas here is
> well over $2/gallon.
>
> So... I'm figuring I need something relatively small and light,
> yet capable of dealing with the conditions. In a personal vehicle,
> I'm not required to have low-range gearing, but it wouldn't *hurt*,
> especially for engine-braking on the way down. I do want a bit of
> ground clearance, so as not to smack any vital parts on stray rocks
> while going up the washboard.
>
> The choice may wind up coming down to which of the following is
> most efficient:
>
> 1) A "car-like" thing with AWD (i.e. Subaru Forester)
> 2) A compact SUV with AWD (i.e. Ford Escape Hybrid*)
> 3) A compact SUV with part-time 4WD (i.e. Chevy Tracker), 2WD on the road
> 4) A compact SUV with full-time 4WD (i.e. Jeep Liberty with Selec-Trac)
>
> * I'm thinking a hybrid might be useful at higher elevation, since to my
> knowledge, the electric motor won't lose efficiency due to elevation
> like internal-combustion ones do.
>
> Anybody have any thoughts? Thanks in advance,
>
> -Dan
> altitude

[email protected] (Benjamin Lee) wrote:
> I did Mauna Kea in Hawaii 13,700 ft 15% grade dirt road and 17%
> paved section in a front wheel drive Chrysler minivan

What a coincidence, Benjamin - that just happens to be the job site I
was talking about. I go up the paved section all the time in 2WD
vehicles, but I've seen a few too many shots of things that've gotten
busted on the dirt road due to either unsuitable equipment or lack of
driver clue... I calculated the average grade on the unpaved bit at
only 12%, not 15%, but I could be wrong, I dunno.

> And yes, there are signs all along that insist you "WILL" use a 4WD
> vehicle only.

And those of us who _work_ up there use 4WD vehicles, which is why
I want my personal vehicle to be one. That said, I realize that a
BIG part of the logic behind that is the low-range gearing, and even
that is mostly for coming DOWN (since missing a turn when you've got
a steep 1,000-foot hill to go down is... bad? and I know there
are a small number of non-4WD vehicles with low-range gearing.

> When we got to the top, the oxygen is so thin that I felt like
> passing out just walking around. The Chrysler engine ran perfect.
> Any fuel injected engine should be able to compensate for the
> altitude. Who cares about some lost horse power.

Where "some" is 40%? I'd better be starting with plenty of BHP if
I'm going to be deprived of almost half of them. Oh, and a
similar effect on fuel economy. A friend has a "cold air intake"
on his Dakota RT, and says that helps with things at altitude, and
it looks like turbos do too... I'm learning a lot in this thread.

> Now, it would be a completely different story if it was snowing
> or raining.

Mmhmm... and I think you know what the weather can be like on MK?
And yes, I know, how many wheels are driven doesn't matter much in
140mph winds...

> Let say you do drive a stock 4WD up a mountain road in heavy rain.
> If you do make it with some momentum, how are you going to get down
> without running into the danger of sliding off the road

Low-range gearing and engine braking, just like I do on a dry road.
(Did you know the rangers on MK can go from Hale Pohaku to the summit
and back without touching the brake pedal?)

> 2WD or 4WD would not matter at that point.

Sure, if the 2WD comes with low-range gearing too.

> Given that you are not into 4wheeling anyway, I would get the most
> economical car with auto transmission rather than manual for torque

I can drive either, but that's probably good advice.

> Wash boards should not be a problem for most cars unless you got
> a low sports car.

Yes... as long as the grader's knocked any big rocks out of the way.

-Dan

--
Dan Birchall, Hilo HI - http://dan.birchalls.net/ - images, words, technology

>
> What a coincidence, Benjamin - that just happens to be the job site I
> was talking about. I go up the paved section all the time in 2WD
> vehicles, but I've seen a few too many shots of things that've gotten
> busted on the dirt road due to either unsuitable equipment or lack of
> driver clue... I calculated the average grade on the unpaved bit at
> only 12%, not 15%, but I could be wrong, I dunno.
>
> > And yes, there are signs all along that insist you "WILL" use a 4WD
> > vehicle only.
>
> And those of us who _work_ up there use 4WD vehicles, which is why
> I want my personal vehicle to be one. That said, I realize that a
> BIG part of the logic behind that is the low-range gearing, and even
> that is mostly for coming DOWN (since missing a turn when you've got
> a steep 1,000-foot hill to go down is... bad? and I know there
> are a small number of non-4WD vehicles with low-range gearing.
>

Sounds like you are much more familiar with MK than I am.
Although not on MK, but from playing around steep hills in a 2WD cars, there
is one significant difference. In a typical car, the brake force on the
front wheel is designed to be higher than the rear since all the weights are
on the front. When you are climbing a steep hill and stalls, first thing you
do is step on the brake. That results in the front wheel locking up. When
the front wheel locks up, you can't steer. Next thing is the car starts
slide backward down the hill with the front wheels locked, and the car goes
off the road. You have to let the brake go to make a correction, then press
on it again to slow down. Is quite dangerous. ABS brakes in theory should
solve that problem, in the Toyota Camery that I tried, the ABS brakes were
not designed for reverse operation, so I was back to the square one.
In part time 4WD, you can't lock the front wheel because the front are
connected to the rear, so you get much more stability in braking. If you
have a AWD, you won't get the same amount of stability since there is a
differential in the middle.
From what I saw, MK is no where steep enough to for all these to happen if
is dry. But, there is always that someone out there who manage to run off
the road.

> > When we got to the top, the oxygen is so thin that I felt like
> > passing out just walking around. The Chrysler engine ran perfect.
> > Any fuel injected engine should be able to compensate for the
> > altitude. Who cares about some lost horse power.
>
> Where "some" is 40%? I'd better be starting with plenty of BHP if
> I'm going to be deprived of almost half of them. Oh, and a
> similar effect on fuel economy. A friend has a "cold air intake"
> on his Dakota RT, and says that helps with things at altitude, and
> it looks like turbos do too... I'm learning a lot in this thread.
>

I would question the 40% reduction in power. In a carbureted engine, yes,
because the fuel mixture will be off. For fuel injected engines, the
computer has a ambient air pressure sensor to compensates for it. There may
be less oxygen up there, but is definitely not 40% less oxygen. MK is not
the same as Mt Everst. If you must have the same power, then a turbo charger
theoreticall will compensate for the altitude. The thinner air allow the
turbo to spin faster which gererates more pressure for the intake. You get
the same power on ground and up there.

[email protected] (Benjamin Lee) wrote:
> > > When we got to the top, the oxygen is so thin that I felt like
> > > passing out just walking around. The Chrysler engine ran perfect.
> > > Any fuel injected engine should be able to compensate for the
> > > altitude. Who cares about some lost horse power.
> >
> > Where "some" is 40%? I'd better be starting with plenty of BHP if
> > I'm going to be deprived of almost half of them. Oh, and a
> > similar effect on fuel economy. A friend has a "cold air intake"
> > on his Dakota RT, and says that helps with things at altitude, and
> > it looks like turbos do too... I'm learning a lot in this thread.
>
> I would question the 40% reduction in power. In a carbureted engine, yes,
> because the fuel mixture will be off. For fuel injected engines, the
> computer has a ambient air pressure sensor to compensates for it.

Ah, that's cool then.

> There may be less oxygen up there, but is definitely not 40% less
> oxygen. MK is not the same as Mt Everst.

Right. Atop Everest, you'd have about 66% less oxygen than at sea level
- significantly less than Mauna Kea's (much more survivable) 40% reduction.

> If you must have the same power, then a turbo charger theoreticall will
> compensate for the altitude. The thinner air allow the turbo to spin
> faster which gererates more pressure for the intake. You get the same
> power on ground and up there.

Cool!

-Dan

--
Dan Birchall, Hilo HI - http://dan.birchalls.net/ - images, words, technology

In article
<[email protected]>,
"Benjamin Lee" <[email protected]> wrote:

> I would question the 40% reduction in power. In a carbureted engine, yes,
> because the fuel mixture will be off. For fuel injected engines, the
> computer has a ambient air pressure sensor to compensates for it. There may
> be less oxygen up there, but is definitely not 40% less oxygen.

The 40% less oxygen figure is just about right. A commonly used
approximation is that oxygen concentration drops off exponentially with
altitude, with half as much for every 5500 m increase in altitude. Since
13700 ft is about 4175 m, that means that the oxygen concentration at
the summit of Mauna Kea is about 2^(-4175/5500) = 0.591 times as much as
at sea level. Now whether 40% less oxygen results in 40% less engine
power is another question.

David, who hasn't summitted Mauna Kea using 2WD, 4WD, or AWD but who has
been to the top of 4392 m high Mt. Rainier using 2FD (two-feet drive)
twice

--
David Ryeburn
[email protected]
To send e-mail, use "ca" instead of "caz".