gijoecam wrote:
brulaz wrote:
carringb wrote:
...
I do like the new Ford transmissions which had a true gear selection, which will lock top gear and let the speed drop a few MPH on hills, instead of downshifting hold the exact set speed no matter what.
Yes, but when you go from auto to manually setting the gear, doesn't it start pumping more fuel trying to maintain speed? That's what my car with the manual tranny does anyway, and I doubt that it's more fuel efficient. Being able to set a relatively constant throttle would be better I think.
It has to do with the efficiency of the Persian. For a particular load at a particular speed, it takes a certain amount of power to do that work. The question is: at what gear and, therefore rpm will will the engine produce that power most efficiently? Every combination of tire vehicle and trailer will have a slightly different answer that question. There are no generalizations that can be drawn across all makes, models, or powertrains. This thread will go on ad nauseam...
Just to carry this on "ad nauseum"... no, wait I'm kidding... ;)
My best "achieved" diesel towing economy was found holding a steady throttle, which is really a fuel supply level since diesels don't have "air throttles". This method seems quite useful on multi-lane highways with low-to-moderate traffic since faster traffic merely goes around just one more slow camper rig. They really have no idea that your speed is varying unless they choose to follow for a bit. On 2-lane roadways, it would take constant attention to keep from blocking other traffic although their fuel economy would probably benefit, at least the first "follower". One can readily see that distant followers would be out of sync will speed vs hill location. With railroad equipment, part of a long train is generally going downhill while another part is climbing, which averages out. Such hills are officially called "undulating grade" and the train operator need only worry about uneven slack causing dangerous train forces to some segments.
Actually, I found that my best gasoline hybrid economy was a situation
near steady throttle instead of actual steady throttle. The hybrid car of which I speak ('07 Prius), has an instant screen-graph readout of mpg at the same time as it reads a 5-minute segmented average history going back 25 minutes. Although this sounds complicated, it provides a rather simple method to "nurse" the mileage along by watching the instant readout and receiving an improved average-over-5-minute reward for doing so.
Like many instant readouts, I found that going down a steep downhill yields a 100 mpg plus situation at steady throttle. It is possible to take advantage of this nearly "infinite mileage" by very slightly increasing throttle to purposely over-accelerate downhill thereby dropping the instant mpg to only 60 mpg, and then subsequently reducing throttle on the uphill to prevent a
sustained natural drop below 60 mpg. With intense diligence, the result is that one can regularily secure plus-60 mpg 5 minute segments, provided there is no wind. (I suppose it could be called hyper-miling.) Ideally, it seems such a car/method would have a computer setting that would allow setting the best possible minimum mpg while sacrificing steady speed. Finally, a steady throttle seems the next best thing and a lot simpler to achieve. In reality this would cause a traffic hazard as mentioned, since I topped some hills at 25 mph and hit close to 70 on some downhills.
TRIVIA:
I've mentioned this before, but in the interest of comparing frontal areas, drag coefficients and improved tech, my wife once owned a '95 Corvette with a six-speed manual tranny and LT1 350 cubic inch V8. With 3:42 axle gearing, the maximum speed of this model Corvette is near 170 mph in 5th gear (1st overdrive) at redline. This Corvette looked sleek, but was less slippery than her current Prius. The Corvette mpg readout normally checked spot-on with hand calculation, so... I once watched her sustain 22 mpg (instant readout) at exactly 100 mph on nearly level interstate (in cold January) for about a seven mile stretch... and I assume that was accurate. My first car was Ford's first OHV, a 1953 Ford with a three-speed manual, an auxilary overdrive and a 215 cu. in. "Mileage Maker 6" cylinder engine. It was a dog and couldn't make 22 mpg at any speed on it's best day.
Joe, just what do you mean,
"efficiency of the Persian"? Does this have to do with the Persian Gulf, or did you mean to say, "efficiency of the
Person"? Inquiring minds want to know. :)
Wes
...
