Date: Wed, 11 Jan 2012 19:52:30 -0700
Reply-To: OlRivrRat <OlRivrRat@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: OlRivrRat <OlRivrRat@COMCAST.NET>
Subject: Re: Was:Re: Oil in Coolant Morphed to "Power at Altitude" or
something like that.
In-Reply-To: <CAHTkEuKUBYEN_c60bNq4vymz0+PMAYqAC6CMR+v5edSBSWdrvQ@mail.gmail.com>
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Don & ~
You actually answered your own ? before you asked it. In a
ComputerControlled FuelInjected N'A' vehicle (especially if it is
OBD2) the lack of AirDensity @ Altitude is compensated for by lowering
the amount of gas' that is injected into the IntakeManifold so as to
attempt to maintain a StoichiometricFuelRatio. It happens in a
Carburated vehicle also but to a lesser extent. It is the lowering of
fuel (Gas+Air) amounts that causes the loss of power ~ 18% here in ABQ
@ 5000' & 25% @ 7000' in Taos. It's not just an Altitude thing either
~ Low Atmospheric Pressure ~ High Temps ~ High Humidity ~ all lower
the AirDensity & can produce similar results. An advantage that we
ConcreteBlock drivers do get from less AirDensity @ Altitude is less
WindResistance.
ORR ~ DeanB
On 11 Jan , 2012, at 10:53 AM, Don Hanson wrote:
> On Tue, Jan 10, 2012 at 6:22 PM, Larry Plotkin <zeplotkin@gmail.com>
> wrote:
>
>> Finn wrote:
>>
>> Klip, klip ...
>> ... I moved from NJ to Taos, NM ... At 7000 feet here in Taos, I
>> believe
>> that the hp loss is around 21% ... Is there anyone listening that
>> is at a
>> similar altitude... I
>> would have no problem getting to say 75 mph at sea level in the 87...
>>
>> Well, I have no tech help for you but ... I ran my 87 Wolfy hardtop
>> 4sp
>> (stock everything except 27x8.5 14 tires) in the northwest near sea
>> level
>> for 11 years and then moved to the AZ mountains where I've been for
>> nine
>> years, at 7000 feet. I changed nothing, adjusted nothing, and
>> noticed no
>> change in performance. 75 is easy as ever. Coming up here from
>> the desert
>> ain't fun, a crawl in 3rd gear often, but climbing near 6000 feet
>> in two
>> hours, that just goes with the vehicle. So I guess I'd be looking
>> for
>> something to fix, not an inherent limitation of elevation.
>>
>> (And I guess I'd have to add that Taos must be way better than
>> anything in
>> NJ, at any speed.)
>> lp
>>
> There is a significant loss in power from any internal combustion
> engine
> as altitude increases.. Someone will probably know the numbers
> exactly but
> I'd guess about 20% power loss at 7000' above sea level as compared
> to sea
> level on a normally aspirated motor is about right. Forced induction
> motors are less affected by elevation gains, and of course, engines
> with
> carbs...they are more affected than fuel injected motors.
>
>
> Combustion in the motor is very dependent on oxygen and simply,
> there
> is less oxygen as you gain elevation...A turbo or supercharged motor
> can
> adjust and pack in more combustable mix...maintaining better power
> as you
> gain altitude. A fuel injected motor can adjust it's mixture to
> compensate for less oxygen, keeping the air fuel ratio correct as you
> climb up...but it must just diminish the amount of fuel to
> compensate for
> the diminished oxygen in the atmosphere. A carbed motor loses power
> two
> ways in that there is less air to burn stuff AND since it doesn't
> adjust to
> this...the air fuel ratio gets 'out of spec' and it runs rich, further
> losing power that way.
>
> If you doubt this...check it with a watch or something next time
> you go
> from ocean to mountains...do a simple 0>75mph timed run both places
> and you
> will certainly find it takes significantly longer at elevation to
> reach
> your target speed.
>
> On a side note: I have noticed a significant increase in miles per
> gallon at higher elevations in my inline Jetta gas motored
> vanagon....I get
> around 23mpg as my normal fuel consumption overall, but when I
> venture into
> the high mountains I have seen fuel economy jump to(max) 26 miles per
> gallon on several occasions... Wonder what causes that, exactly?
>
> Don Hanson
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