Re: [FWDLK] lugging an engine

[David Homstad <dhomstad@xxxxxxxxxxx>]

I was told that at very low rpms the fuel charge has more time to burn
before the piston reaches top dead center. This creates a larger volume of
gas, which is then compressed at TDC, creating extra stresses on the
bearings. This is not a problem at idle, but at low rpm with throttle
applied much more fuel/air is present.

This issue is supposed to be part of the poor reputation that Lincoln V12
engines had with their bearings. Because of the smooth power flow of 12
cylinders, owners would run them at low rpm when cornering or accelerating
after a slow down.

Dave Homstad
56 Dodge D500

-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of Mike Apfelbeck
Sent: Monday, February 21, 2005 2:03 PM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] lugging an engine

At 09:49 AM 2/21/2005, David Gedraitis wrote:
>While I'm aware that lugging an engine is bad and puts
>it under a load, I'm asking why this is bad?

Lugging the engine at low rpms puts the crank bearings under a lot of extra
load while at the same time the oil pump is turning slower, delivering less
oil to cool those bearings.

>  What does
>this do that ctually hurts the engine? Does it
>overheat?

The combustion chambers are putting out more heat, and at the same time the
water pump will be turning slower, minimizing its ability to circulate
coolant and cool the engine.

>Wear out the clutch faster?

Nope.

>I laboring for
>an engine isn't good, but I also know it does happen
>(think steep hills at high speed), so does anyone know
>anything more definite? I don't see why low vacuum
>would hurt, and while I know power isn't optimum,
>that's not technically harmful, either....

Theoretically, the brake specific horsepower rating (pounds of fuel per
horsepower per hour) would be more efficient under lower intake manifold
vacuum, but in practice the lower vacuum signal will open the power valve
in the carb, dumping more gas into the manifold.

Mike


>~dave
>
>
>
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