Fuel volitility involved in Temperature dependence of fuel mileage? quattro digest, Vol 1 #3342

[Louis A. Mulieri]

Hi John,
	Thanks for your response. I didn't think volatility would be a
factor if the injector sprays the fuel into the combustion chamber and if
the spray ignites as well as a vapor would. What's wrong here?

Note also that another audifan (Thanks Tom) responded:

[Your cooling system thermostat should keep the coolant temperature above
a basic minimum of about 190F or 87C no matter what the outside air
temperature, vehicle speed, or load.  You might want to check your fuel
injection control pressures, system pressures, intake air temperature
sensor, coolant temperature sensor to make sure they are sending the
correct values to the ECU and that your O2 sensor is working properly.
See http://www.sjmautotechnik.com/ficis.html   for the correct procedure.
Tom Chudzinski]

Lou Mulieri

>Message: 3
>To: quattro at audifans.com
>Subject: Re: Temperature and fuel mileage?
>Reply-To: j_shost at excite.com
>From: "John Shost" <j_shost at excite.com>
>Cc:
>Date: Fri, 26 Apr 2002 12:18:22 -0400 (EDT)

>Volatility is reduced at colder temps so more fuel is injected to
>compensate=2E

[My fuel mileage increases by 2-5 mpg when outside temperature increases
from 20-30 F to 60-70 F on my '88 5KCTQ. There does not seem to be much
difference in my dash gauge engine temperature when running in 20 vs 60 F
air. Is this because cold air can hold more fuel and my engine is not
compensating? Or does the engine temp reading sense non-mileage related engine
region? Or? ]