One reason DRLs shouldn't be opposed...

Actually, you apparently failed basic physics. The formulas have been
accepted for over a century, and aren't disputed for the purpose of back
of the envelope calculations like these by anyone with any engineering
experience.

nate

 

Apparently you do -- otherwise you'd see there's nothing "dubious" about
the maths presented in the original article, as further evidenced by your
steadfast refusal to elaborate beyond your childish "It's dubious! It is
too! Is too! IS TOO IS TOO IS TOO IS TOO!" rant.

If you see problems with the maths, point them out. T-H-X, the audience is
listening.

 

| > Suggest you read this message three or four times -- slowly -- to let this
| > basic mathematic concept seep into your brain.
|
| I have no problem with basic math, I just don't accept dubious formula's
| written by who knows who. I think you will believe anything if it supports
| your position. I am not as naive.
|
|

What specific part of the formula applied to the equation do you believe to be
"dubious"? If you have different calculations and/or results, please share
them.

 

This is typically only true on larger engine cars and the rare small
car. I think it was CR that just tested several manual and automatic
small cars recently and all but one got better mileage with the manual.


Matt

 

Any references to support this? I find it very hard to believe that the
ECM can't control the fuel injection sufficiently accurately to control
emissions during shifts. Manual transmissions are rare because buyers
don't buy them. Detroit (and Europe and Japan) make what sells and
manual trannies simply don't sell well anymore.


Matt

 

You need to read up on the theory of alternators and then you will see
that what you wrote above is very wrong and shows a complete lack of
understanding of alternators.


Matt

 

Well, at least this makes more sense than the emissions claim.


Matt

 

He didn't even have to use anything but multiplying and dividing. It's ALL
basic math. Those dubious formulas all come from the simple equation of X
x Y = XY. If the percentages are throwing you off then continue bing
dubious.

-Bruce

 

Here is some silly math for you -

Assume 2 turn signal bulbs at 5 watts each used for DRLs
Assume 12,000 miles a year at average speed of 35 mph
Assume 50% of driving during the day (probably a low percentage)
Assume 30% efficiency for the transformation from gas to electricity
(very optomistic)
Assume Energy contnet of gasoline 115,000 BTUs
Assume 100,000,000 vehicles in regular use in the US (it is actually
about double this)

12,000 miles at 35 mph = 343 hours = 171 daylight hours
2 5 watt bulbs for 171 daylight hours equals 1,710 watt-hours
At 30% conversion efficiency this equates to 5,700 wh = 20,000 BTU
So, running the two DRLs during the day for a year consumes about 0.2
gallons of gasoline
Addtional gas used by 100,000,000 car in the US, if they all had DRLs -
20,000,000 gallons.....

At every step I think I picked conservative numbers. I came up with half
the gas wasted that was mentioned in the original article. However, I am
probaly low by more than a factor of 2.

DRLs are wasting gas.

Ed

 

More than that. 5 watts is a parking light, not a DRL. You're off by a
factor of about five there at a minimum. Also I think you are being
conservative on your conversion of gasoline to electricity. However, I
don't know if 35 MPH is a good average or not, so I'd have to say you're
at least within an order of magnitude.

nate

 

Turn signal bulbs are 27 watts, not 5 watts. Plug that into your formula.

You are low by a factor of a little over 5 and a little under 6 due to
your wattage estimate error.

True.

 

http://www.nytimes.com/2004/01/31/p...tml?ex=1091505600&en=742832fab995bee9&ei=5070
http://www.eagleforum.org/column/2004/july04/04-07-21.html


BTW, I think Edwards is basically a well meaning and decent human being
who has taken advantage of a flawed legal system to make himself rich,
while helping a few of the many thousands of people who suffer from
misfortune.

Ed

 

Dan, are they wasting gas in Northern Europe or are they saving lives there?

Richard.

 

I stand corrected. Never thought of it that way. However, I would
still question the amount of extra drag on the motor. They don't
really show a calculation in the How Stuff Works page, more of a total
amount, so we never really see the impact on average MPG per car. I
would suspect that properly inflated tires would affect MPG much more
than DRLs.

 

It's not an "either/or" question. There are perfectly good, inexpensive
DRLs that use a total (for BOTH DRLs!) of 12 whole watts. These are
fairly common in Europe. I have a set of them -- made by Hella -- on my
shelf, waiting for me to have time to put them on my truck.

 

So you *still* don't get it.

Why, my goodness! Your ignorant little guess is *certainly* much more
scientific than the valid mathematical calculation under discussion here!
Thanks for sharing it.

 

I'm an engineer. I didn't write it, but I don't see any mistake, nor do
I see any assumption that could be off by more than a factor of 2 either
direction.

I'm still waiting for some mathematics that support YOUR "belief" that
it isn't significant....

 

Just because one waste is bigger than another doesn't imply to me that
we shouldn't try to eliminate the waste wherever possible. We've often
pointed out on this newsgroup that carmakers will skimp on components
(eg. brake rotors) to save a few ounces per vehicle in order to improve
mileage, yet GM is lobbying to throw away all the fuel it takes to run
DRLs, which have questionable benefit at best.

And many computers these days have pretty sophisticated power management
systems that reduce the power they burn when not in use quite a bit. Of
course it often depends on your settings, but they're getting better.

 

Larry Bud wrote:

When you turn on an electrical load, for example DRLs, the voltage in
the car's electrical system drops slightly. The voltage regulator senses
this drop, and in response it increases the flow of current to the
"field" (or "rotor") coil of the alternator. The increased current
flowing through the field coil of the alternator creates a stronger
magnetic field rotating with the rotor, which has a stronger interaction
with the fixed, or "stator" coils of the alternator, which causes a
larger current to flow in them. The larger current is rectified and fed
to the output terminal of the alternator, thus stabilizing the voltage
and providing power to the load you just switched on. A byproduct of
this is that with the larger magnetic field generated by the rotor, and
its stronger interaction with the fixed stator coils, is that there is
increased DRAG on the rotor, which must be made up for by an increased
torque supplied to the alternator pulley by the gasoline engine. The
increased load on the gasoline engine is sensed by the Engine Management
System, which slightly opens the idle-air control valve, allowing more
air to enter the intake manifold. The mass air-flow sensor or MAP
sensor, depending on design of the engine, detects the increased air
flow and the ECM then increases fuel flow to the injectors, supplying
the added power needed to turn the alternator when it becomes harder to
turn because of the increased field current due to the voltage regulator
detecting a drop in voltage because you TURNED ON YOUR FRICKING DRLs.

Any questions??

Absolutely wrong. See above.

 

Uh, Matt? That IS a big part of the emissions claim.

Misfire = greater emissions, false misfire detection= emission system
"false alarms." By using an automatic transmission, the emission system
"false alarm rate" can be reduced, so that it can operate at a higher
"probability of detection" for a real misfire, thus producing a fleet of
cars with lower emissions.