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Altitude problems with Diesel Cars?



 
 
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  #21  
Old October 15th 04, 05:49 PM
Adrian D. Shaw
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Yn erthygl , sgrifennodd
Neil Swingler :
The loop (Cime de la Bonette) is the 2802m bit. The road pass (Col de la
Bonette) is at 2715m. From the top of the loop.


Yes. See http://www.alpineroads.com/maritimes.php#bonette for more.

Adrian
--
Adrian Shaw ais@
Adran Cyfrifiadureg, Prifysgol Cymru, aber.
Aberystwyth, Ceredigion, Cymru ac.
http://users.aber.ac.uk/ais uk
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  #23  
Old October 21st 04, 09:25 PM
Abairsty
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Thanks,,,,,well the bits i understood,,,lol
  #25  
Old October 23rd 04, 04:59 PM
funkraum
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Jeremy Mortimer wrote:
funkraum wrote in
(Abairsty) wrote:


Heard someone mentioning that diesel powered cars struggle at
altitude, does anyone know if this is correct....seeing as im thinking
of driving up to val Thorens?


Both normally aspirated diesels and normal aspirated spark-ignition
engines are both normally aspirated: They fill from ambient air
pressure. Thus it makes not difference.

As you go higher, the air is thinner, and less of it will fill the
cylinder when the intake valve opens. Less air in the cylinder means
you do not have as much oxygen to burn with the hydrocarbon which
means less energy. Regardless of how the hydrocarbon is ignited.


...

Turbocharged, fuel-injected, carbureted and diesel engines all react
slightly differently at altitude but nothing you need be concerned
about.


If it's a modern diesel with electronic engine control it may compensate
for changes in air pressure anyway.


(Bonus question: if this is the case, what combination of fuel injection
and turbocharging is necessary or sufficient to deliver the same power over
a range of ambient air pressures? I can't remember how all these bits
work....)


Well ....

The gas turbine driven centrifugal compressor ("turbocharger") is an
air-compressor driven by a turbine which is driven by the hot&fast
exhaust gases.

(Ignoring a large number of complexities), as the engine turns faster
more exhaust gasses are produced to turn the turbine and this drives
the compressor faster, which pumps more air. At a certain point, it
will start pumping too much air for the engine to cope with.

Mostly, this is dealt with by a valve somewhere on the system which
opens to let the excess pressure out before it reaches the engine. A
valve on the exhaust side which lets out the pressure of the exhaust
gases to reduce the speed of the turbine, works well.

At altitude, the air is thinner and the turbocharger just spins up
until there is too much and it opens the wastegate valve, just the
same. The turbocharger does not care about the thinner air since it
just spins faster to deliver more.

Bear in mind it always wants to spin faster and pump more air than the
engine can deal with.

So that is the air side. 'Normally aspirated', ie engines with no
turbocharger, just have to let the piston suck in as much as it can on
the down-stroke. Too bad if that is not enough. Engines shipped for
export to places like the Andes and the Himalayas in truck and
locomotive applications used to be supercharged, a 'supercharger' just
being a Kompressor which is driven by a belt or gears et cetera from
the engine. This just makes the engine 'bigger' because, in total, it
now pumps more air. It is a band-aid really. The supercharger was
better than having to get out and push. And if you have ever had to
push a train, you will know how sweaty you get.

Ironically, steam locomotives work slightly better as the altitude
increases. So stick with steam: You know it makes sense.

In these times, where truck and locomotive engines are all
turbocharged (that is the breathy high-pitched whine you hear) they
are unaffected by altitude (except for, blah, blah, et cetera), but it
takes about thirty years for trucks from the G7 countries to reach
places like the Afghanistan and Kashmir.


Carburetors, fuel injections systems and other clever bits just add a
little dash of fuel in the correct amount. Just like the Angosturas
Bitters in the Gin (and Tonic).

Their role is important but minor. It's all about air and getting more
of it. The itsy-bitsy-teeny-weeny little bit of fuel which is added to
the huge volume of air is metered by a metering device, which is the
carburetor or a fuel-injector, fuel-injectors being organised by all
manner of whirly-gig arrangements, in these times run by computers.

Roughly: If you add too much fuel for whatever reason, then once the
fuel has burned all the oxygen in the charge of air within the
combustion chamber, the unburned fuel is vaporised by the heat,
forming smoke.

Of course, at altitude, there is less air being delivered and pumped
by the engine, so if you have a fuel metering system which is
none-too-clever, you might end up with more fuel than is 'just right'
because the metering system thinks the engine just received a full
charge of air, and it did not. This excess fuel just goes up as smoke.


All this is inconsequential, since real men go skiing by packing four
of them into a 1974 Taunus with duff piston rings and a badly set up
carburetor which leaves a blue haze of oil smoke as it is thrashed
along the autobahn, nose-up, tail-down, back wheels Turkish style, in
the classic bow-wave aerodynamic stance of the overloaded saloon car,
skis on top, windows down, beer bottles and cigarettes in mouth,
greasy shoulder-length hair dangling onto cheesy one-piece ski-suits.
Return should be with a dead animal strapped across the hood, perhaps
a dead chamois.



funk- 'go easy on the tonic' -raum

  #26  
Old October 25th 04, 07:41 AM
Jeremy Mortimer
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funkraum wrote in
:

....snip...

Thanks!

....unsnip...

Carburetors, fuel injections systems and other clever bits just add a
little dash of fuel in the correct amount. Just like the Angosturas
Bitters in the Gin (and Tonic).


You misspelled "pink gin". It doesn't have any tonic in it, either.

funk- 'go easy on the tonic' -raum


Exactly.

Jeremy
  #27  
Old October 25th 04, 05:04 PM
funkraum
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Jeremy Mortimer wrote:
funkraum wrote in


Carburetors, fuel injections systems and other clever bits just add a
little dash of fuel in the correct amount. Just like the Angosturas
Bitters in the Gin (and Tonic).


You misspelled "pink gin". It doesn't have any tonic in it, either.


Ah... but it would depend on whether it was a 'Pink Gin' or a 'Gin and
Pink' now, wouldn't it ...


funk- 'go easy on the tonic' -raum


Exactly.



funk- 'Tonic ? I never touch the filthy stuff' -raum

 




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