In a message dated 5/5/98 12:34:16 PM Eastern Daylight Time, ccrobins@ktc.com
writes:
> How anybody can't see that running the car in OD results in fewer
> engine revolutions per mile, and thus less wear, is beyond me.
Charley,
That's because engine revolutions per mile is but one factor in engine wear,
and a relatively minor one at that. It is quite possible to get MORE engine
wear with an OD than without it. To illustrate, consider driving up a steep
hill and then down the other side, in both cases with the car in fourth and OD
and the engine turning about 2500 rpm. On the up side, that engine is really
struggling to make it (if it will even make it at all), with a great deal of
wear taking place. On the down side of the hill, at the same rpm, the engine
is coasting, and virtually no wear is taking place. Engine revolutions per
mile is the same in both cases.
As I've said before, there is a much greater benefit to an OD in flat country
like Kansas, but here in the hills of East Tennesse, the opportunity to use
the OD is very limited. In fact, third gear gets a great deal of usage.
Remember the cardinal rule of scientific investigation: in order to evaluate
the effects of one parameter, ALL other parameters must remain the same. If
EVERYTHING else is the same, there will certainly be less wear with fewer
revolutions per mile, but in the real world, everthing else is not the same.
You may or you may not get less wear and greater economy with an OD.
When you put an OD in your car, you automatically add an additional horsepower
drain on your engine just to drive the additional gears, clutches, etc, to say
nothing of the high pressure oil pump that has to be driven to operate the OD.
I don't know how much extra HP all this consumes, but in an MG, you have very
little you can afford to waste. Just driving the car in straight fourth puts
extra wear on the engine just to power the extra load. Negligible, I'm sure,
but extra wear none-the-less.
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 - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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