[slowmover]

“Steady state” is all to the good in figuring HP draw. The problem is
maximizing steady state.

1). Few are the trips when towing where accel/decel events aren’t the definitory problem.

2). Whether traffic congestion or terrain, the amount of time spent opened-throttle is where the fuel reserves disappear. The only time weight matters. But IT MATTERS A GREAT DEAL,
(why empty car stunt driving has nothing to do with fuel economy despite general belief).

How to get the load to speed

How to maintain steady-state

How to minimize braking

And to do it all in a way which MAXIMIZES safety (never otherwise), will be the big difference between otherwise comparable rigs.

In commercial work, where the ONLY difference is the driver, it’s as much as a One-Third penalty between best & worst drivers. Completely about accel/decel.

The amount of time spent steady-state (engine Hours) is surprisingly lower than expected no matter the day’s total miles.

(Whine) “It’s too much work”.

“I be gettin’ runned over!!”

Etc

Half the trip — even Interstate — can be other than steady state (cruise control as definition).

Where aero REALLY matters is in handling crosswinds. These are natural AND man-made. They can be constant. Which means yet more juice to maintain headway.

But, who is the operator? Is he towing something to make his living? That’s both incentive and disincentive to maximize aero qualities. They aren’t “qualities” for a contractor covering a large metro area if “aero” reduces on-site efficiency.

As I’ve posted before — and will continue — an empty vehicle MPG is just noise. Tells us nothing worth knowing. Until proficiency in moving a FULLY loaded vehicle comprises a high proportion of annual miles, HOW to estimate, calculate towing fuel use is in the dark.

1970 or 2020 the baseline starting point for travel trailer towing is a 40% penalty. This is constant. No matter how “good” one is with the tow vehicle loaded 80%+, 40% is a fair minimum.

It’s a good deal higher (increases rapidly) with road problems of climate, terrain and congestion.

Be clear about use.

Tractor-trailers APPEAR to be a model. But how many of you expect that electric vehicle towing will be from one large metro to another, nation-wide.

Optimized conditions with experienced, motivated operator doesn’t come about motoring to & from a single metro region. One must be a minimum of 75-miles from city center before traffic spaces out.

How many miles will you cover past that point, or returning is where aero FINALLY reaches potential. And that’s assuming no adverse weather.

I see that the argument there’s no difference in power-plants. I’d recommend you read those who are towing with Tesla sedans. Electric can get penalized by virtue of what it is. Where comparative power draw is simply higher. Demand creates resistance.

The theoretical load isn’t higher, so that’s the point here. Better more carefully check the hypothetical underpinnings. Assumptions.

With diesel versus gasoline, towing MPG comes down to cylinder pressure. Highest = Winner. Every time. As it’s those transitions (degree & duration) that tell the black box story.

In ancient days — besides adding tachometer, vacuum gauge & fuel flow meter — the savvy added an airspeed indicator to modify throttle inputs versus travel set speed.

Towing an aero-inefficient load, weight & winds both matter. A CAT Scale ticket, and knowing prevailing winds foot-by-foot are the only way past NOT having a turbocharged diesel.

The only RELEVANT practice while solo is with a load factor of 85%. Aero matters little without the trailer. It’s fixed. Knowing how to maintain the glide, is the thing, and can’t be done empty.

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