[Shotimes] towing and fuel economy

[Robert Bruce]

It really boils down to simple physics.  It takes X amount of energy to move
a mass Y distance.  If you double the mass and all else being equal, it will
take twice as much energy to do the job.  In your case, your engine is
converting the btu's in the gasoline to move the mass.  Doubling the mass
requires doubling the fuel requirement.  Of course the frictional drags
don't double, so the fuel consumed isn't entirely double the amount.

That's the basic principals tha Smokey Yunick used for many years trying to
produce a better internal combustion engine.  He knew that if you figure out
how to burn the gasoline at a lower temperature, then more of the released
btu's would convert to flywheel horsepower instead of thermal energy losses
(heat).

Sorry if the s[elling in this e-mail is poor.  I just had Lasik surgery
yesterday and my near vision is still quite blurry.  Hopefully the
spellchecker will do a good job.

Robert Bruce
92 w/3.2
http://www.cardomain.com/memberpage/810875


-----Original Message-----
From: shotimes-admin@autox.team.net
[mailto:shotimes-admin@autox.team.net]On Behalf Of Ron Porter
Sent: Friday, May 27, 2005 6:43 PM
To: 'van Oss'; shotimes@autox.team.net
Subject: RE: [Shotimes] towing and fuel economy


With more weight to pull, you have a greater throttle opening with more air
and then fuel to maintain the same speed/rpm.

Let's use two gross examples. In one, you gut the interior and a total of
1,000 #s of weight. Second example is the same car with 2,000 #s of scrap
iron in the trunk at stock weight, plus five passengers.

Both run the same rpm for a given speed......which gets the better gas
mileage?

Ron Porter

-----Original Message-----
From: shotimes-admin@autox.team.net [mailto:shotimes-admin@autox.team.net]
On Behalf Of van Oss
Sent: Friday, May 27, 2005 6:27 PM
To: shotimes@autox.team.net
Subject: [Shotimes] towing and fuel economy

Today I used the Crown Vic to haul away two trailer loads.  While driving I
got to wondering about something.

When I'm towing a load, part of the load is mass (affecting acceleration and

braking), some is friction (trailer tires and axles), and some is air
resistence.  Overall, fuel economy is lower than when the car operates with
a trailer.  Okay.

But could someone please explain exactly how that plays out in an EFI
engine?  Let's say that the car, versus car and trailer, are driving down a
level road at, oh, 25 MPH.  At a given speed in a given gear, the engine
revs should be the same, yes?  Or am I wrong?

So granting that the engine has to "work harder" under tow, exactly what is
it doing differently?  Does the computer change the air/fuel ratio? What's
going on in there?!?!?!

TIA for the education.

VO
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