Why VW's get bad gas mileage?

Timothy J. Lee wrote:
>
> The EPA's measuring of emissions also means that it does not measure whether
> the battery is at a different charge level at the end of the test.

Wow. *That's* a good point. How much does a full battery discharge
translate into in MPG?

--
Mike Smith

In article >, Mike Smith > wrote:
>Timothy J. Lee wrote:
>>
>> The EPA's measuring of emissions also means that it does not measure whether
>> the battery is at a different charge level at the end of the test.
>
>Wow. *That's* a good point. How much does a full battery discharge
>translate into in MPG?
>

Hard to say, but recharging it using the altanator does add engine load. It
won't be free (MPG wise). This is why with the AC on hybreds see such a
large milage drop off, adding electrical load obviously limits the
electricity available to battery. I wonder what happens to hybreds when the
heater is on in winter (MPG wise)?

fundamentalism, fundamentally wrong.

Rico wrote:

> In article >, "Keep on Plonkin'" > wrote:
> >
> >"Jon R. Patrick" > wrote in message
> . 188.18...
> >>
> >> We need to stress here that the EPA does the testing and BY LAW the
> >> automakers must put on the sticker EXACTLY what the EPA tells them.
> >> It's illegal for them to over- OR under-state their fuel mileage.
> >>
> >> Just a little FYI.
> >>
> >> JP
> >>
> >
> >FYI, your statement is incorrect. According to its own information, the EPA
> >does not buy every car and test it for gas mileage. The EPA sets the test
> >procedure, the manufacturers test their own vehicles, and the EPA confirms
> >the tests on a small percentage of vehicles. In fact, the actual gas
> >mileage is not even measured-- it is calculated based on a vehicle's
> >emissions. See:
> >http://www.epa.gov/fueleconomy/420f05045.htm
> >for more information.
> >
> >
> >What Vehicles Are Tested?
> >Not every vehicle is tested for fuel economy. Instead, manufacturers are
> >required to split each model into smaller groups, based upon the various
> >options available that can impact fuel economy (such as vehicle weight,
> >transmission type and engine size). A vehicle from each of these groups with
> >the highest projected sales must be tested. Also, passenger cars and light
> >trucks with a gross vehicle weight rating (GVWR) greater than 8,500 pounds
> >are exempt from fuel economy requirements, and are not tested for fuel
> >economy (however, they are still subject to Federal emission requirements.)
> >
> >Manufacturers test all the vehicles at their laboratories. EPA confirms
> >about 10-15 percent of the vehicles at its National Vehicles and Fuel
> >Emissions Laboratory in Ann Arbor, Michigan.
> >
> >
> >
> >How are Vehicles Tested?
> >
> >Vehicles are driven over identical driving patterns by professional drivers
> >in controlled laboratory conditions on a dynamometer, which is like a
> >treadmill for cars. The conditions that occur during driving, such as wind
> >drag and inertia are accounted for on the dynamometer. There are two types
> >of tests that are conducted: city and highway tests.
> >
> >The city test is approximately 11 miles long and simulates a stop and go
> >trip with an average speed of about 20 miles per hour (mph). The trip lasts
> >31 minutes and has 23 stops. About 18 percent of the time is spent idling
> >(as in waiting for traffic lights). A short freeway driving segment is
> >included in the test. The engine is initially started after being parked
> >overnight.
> >
> >The highway test simulates a 10 mile trip with an average speed of 48 mph.
> >The vehicle is started "hot" and there is very little idling and no stops
> >
> >
> >
> >How Are the Label Estimates Calculated?
> >
> >Fuel economy estimates are calculated from the emissions generated during
> >the tests using a carbon balance equation. We know how much carbon is in the
> >fuel, so by precisely measuring the carbon compounds expelled in the exhaust
> >we can calculate the fuel economy.
> >
> >After the vehicles have been tested, the results are adjusted downward to
> >account for conditions that occur on the road that can affect fuel economy
> >which don't occur during laboratory testing, such as cold temperature,
> >aggressive driving, excessive use of power-hungry accessories, among others.
> >The city is adjusted downward by 10 percent, and the highway by 22 percent.
> >The equation for calculating the city or highway average fuel economy, given
> >in miles per gallon (mpg), is:
> >
> > FEave = (total sales / [(sales1/FE1)+ (sales2/FE2) + ...+ (salesn/FEn)]
> >
> >The calculation for combined fuel economy weights the city at 55 percent and
> >the highway at 45 percent using the following equation:
> >
> > FEcomb = 1 / (( .55 / city FE) + (.45 / hwy FE))
> >
> >
>
> When you were reading this (and thanks for the information) did you see if
> any accessorys are turned on? What I mean is if the headlights are on, then
> that is extra load on the generator which in turn adds load to the engine.
> Same obviousily with the radio and any other electrical stuff in the car.
>
> fundamentalism, fundamentally wrong.

I use to perform emissions testing during the late 1970s. Back then, as best as I can remember,
all the accessories were turned off. Before the test, the car was taken on a 10 minute drive
and parked for 12-24 hours at 68°-86°F. The temperature in the dyno room was controlled at this
temperature range also. The car was pushed onto the dyno, a hose connected to the exhaust pipe
and a fan placed in front of the radiator. The city test was done first, and there was about a
5 minute pause with the engine shut off about one quarter of the way through. When tested the
driver followed a trace on a strip chart, unless the car could not accelerate fast enough to
keep up with the trace, in which case the chart was labeled WOT (wide open throttle). The shift
points on manual transmission vehicles would be shown on the trace and I think were provided by
the manufacturer. After the city test we did a short cycle test where the vehicle was
accelerated to a given speed and then brought to a stop. After this the highway test was done.

PHRED