In a message dated 97-11-28 00:52:29 EST, boballen@sky.net writes:
karim.marouf@cancom.com wrote:
> > Another question: if you're running your motor on the freeway at 4500
rpm,
> > are you causing a lot more wear than if you had an overdrive and were
only
> > using 2500 rpm?
To which Bob Allen replied:
> You'll get some argument here. Running at the torque peak is the best
> way to make an engine live. But, like every other moving part, the more
> it spins the faster it arrives at its demise. Every motor only has so
> many revolutions in it. But there are extinuating circumstances (check
> with the 'A' owners on spelling) as mentioned in your first query.
To which I now reply:
Bob and Karim:
If it's true that 90% of engine wear occurs at start-up, as has been
reported, then you will wear out the engine from starting it long before you
wear it out from driving it!
In the flatlands of Kansas, driving at 2500 in OD might not be a problem, but
here in the hills of East Tennessee, you might find yourself shifting out of
OD fairly often to avoid lugging the engine.
As for improved gas mileage, in my simple mind I can't see how putting the
transmission into OD will reduce the energy required to move the car down the
road, and, since an engine is most efficient at its torque peak RPM, the
mechanical energy required to move the car can most efficiently be converted
from the energy content of the gasoline if the engine is operated near that
torque peak, not at a relatively ineffecient 2500 RPM.
Being that there are no electrons involved, I have no idea if any of the
above is true or not, so I'm ready to be set straight. Until such a time as I
am set straight, I refuse to spend the money and my energy swapping in an OD
unit. A couple of years ago, I drove my MGBGT to Canada and back at a steady
80 MPH, with no problems (at least that I know of - it may have been worn out
from that drive to the point that it quits on me next week!)
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
|