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From: halb@tekig5.UUCP (Hal Bates)
Newsgroups: net.auto.tech
Subject: Re: Gas Mileage
Message-ID: <447@tekig5.UUCP>
Date: Mon, 27-Jan-86 00:16:35 EST
Article-I.D.: tekig5.447
Posted: Mon Jan 27 00:16:35 1986
Date-Received: Thu, 30-Jan-86 04:39:51 EST
References: <576@adelie.UUCP> <103@dg_rtp.UUCP> <372@watmum.UUCP>
Reply-To: halb@tekig5tes.UUCP (Hal Bates)
Organization: Tektronix, Beaverton OR
Lines: 103

In article <372@watmum.UUCP> gvcormack@watmum.UUCP (Gordon V. Cormack) writes:
>> > I have noticed that my gas mileage drops by 15-20% every winter
>> 
>> I think the effect has two major components, and I'm not sure which is
>> greater.  First, the thermal component.  The car is breathing colder air
>> in the winter, and this heat must come from somewhere.  In this case, in
>> order to get cold air to expand the "same ammount" as hot air (and hence
>> provide the same amount of power) more gas must be burned.
>> 
>> Second, the humidity component.  Winter air is *much* less humid than
>> summer air.  A little water in the air works wonders for power output.
>> 
>> And oh, yes, if you have snow and ice sitting on your car, the wind
>> resistance goes way way up, so scrape it every morning.
>> 
>> > Jeff Moskow  {harvard | decvax!cca!emacs}!adelie!jeff
>
>I didn't notice a "-)" on this posting, so I am taking it seriously.

I didnt notice a "-)" on this posting, so I am taking it seriously.

>The second point (about humidity) is absolutely false, and the
>first and third points (heating cold air and wind resistance of 
>snow) are absolutely insignificant.

I didnt know any thing is absolutely insignificant. I am glad, however,
the auto industry didnt say that about aerodynamics. I will say that
I wouldnt spend time freezing my ass to remove snow from my car to
save a few cents worth of fuel on a cold winter morn.

The second point about humidity is true. Some parts of the country
have high humidity in winter (west coast) others have low humidity.
Higher humidity will hold off combustion allowing for lower octane 
requirements or larger spark advance on the distributer. Both make 
for better fuel economy.

The internal combustion engine will perform the best with a large
amount of moisture present. One way to duplicate that high RH environment 
is to install a water injection system to your engine. Inexpensive, and 
the results are dramatic.

>Since I haven't seen a succinct posting of the factors involved in
>poor gas mileage, I will enumerate what I think are the most important
>ones:

enumerate? no shit; I didnt know that people enumerated in net.auto.tech. -)


>
>   (1)  Until the engine is completely warm it must run with the
>        mixture enriched (choke on) in order to get enough vaporized
>        gas to the cylinder to burn.  This extra gas is wasted.

Why then, is it necessaty to richen the fuel mixture? It seems the second
article states that. Why argue a point you both seem to agree on?

Automatic chokes waste fuel. They are improving the design,
and with u'p controlled injectors the choke control is excellent, but the 
spring controlled stuff is a real money eater. Gimmee a knob with CHOKE on 
the label.

>          
>   (2)  The tires, bearings, and transmission are stiffer in cold
>        weather.  However, this effect is much less significant than
>        (1).
>

This is true to some degree. Horespower is wasted in warming up the 90W
and bearing grease. This may take several miles to accomplish = loss of
fuel economy.

>   (3)  Many people let their cars warm up in cold weather, wasting
>        gas.  Also, many people take more short trips in cold 
>        weather.

It it true that warmup wastes fuel. So dont warm up for more that 30 seconds
unless the temp is very cold. All that is necessary for the engine to operate
is to get the oil up to pressure before moving out. Take it eaisy until warmup
occurres. It is better for a engine NOT to sit at idle soaking up that 
rich gas past the rings and into the oil (diluting it), fouling the plugs, 
and adding carbon deposits to the combustion chamber.

For the sake of argument, cold weather fuel economy has nothing to do with 
short or long trips, if the operator does his or her part. People still 
commute to work even in winter. But items like choke and warmup require a
thought process from the driver. The luxurey of getting into a warm
car means hardship on the engine and the waste of fuel may override the ill
effects on the engine will suffer in order to supply that warmth. 
A few years back I knew a guy who would start his engine (early in
the morn) gun it up to 3 or 4000 RPM and let it idle there for 20 minutes.
Then he was pissed when the engine started to use oil. Screamed - this car is
a lemon.  oh-well

>I have driven on many long highway trips in winter, and have noticed
>no significant difference between winter and summer highway gas
>mileage.  This observation illustrates that cold weather affects
>mainly the warm-up performance of the engine, not the steady-state
>performance.

Temp and humidity will effect all engines. Cooler (not freezing) air and
higher humidity will improve performance and warm dry air will be a detrement.

tektrinix!tekig5!halb