[Shotimes] towing and fuel economy

[Ron Porter]

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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