Re: [A/S] Fw: Airstream Pullers

["Harvey Barlow" <harveybarlow@xxxxxxxxxxxxx>]

Jim,

Thanks for the discussion, all good info.

When I buy one, it will almost certainly be equipped with a six speed
close-ratio manual transmission so shift points whether upshifting or
downshifting to pull a long steep grade or up to the discretion of the
driver.  Of course diesel engines have very different torque curves and I
hear the "big boys", the over-the-road truckers, speak from time to time of
operating at a certain rpm or mention avoiding lugging the engine.

I guess my question is, when towing with a manual transmission diesel
powered truck do you wind the engine up against the governor with each shift
or is it preferable to "short shift" them say at 1800-2200 rpm.  Does it
matter for fuel economy, engine longevity, etc?

I know about gas engines.  I know from experience that a small block light
truck engine like a 350 Chevy doesn't develop maximum torque until around
3500 rpm so to pull a hard grade with a small block, you have to downshift
and rev the engine.  On the other hand, my 460 Ford will pull hard at as low
as 1400 rpm and develops maximum torque at 2200 rpm.  It is not necessary or
desirable to wind the Ford engine.

How about the diesel?  I'd like to find a book written by a knowledgeable
diesel truck engine user which discusses those concepts.  I know that a
diesel begins developing near maximum torque just above idle so do you allow
it to lug at low rpm or is it recommended to rev it higher?

Harvey