Shifting RPMS

LMFAO, welcome to the club!

 

least I'm not the only goof ball to try it.

 

I average 7.29 mpg, running 79900 between Victorville and Sacramento, loaded both ways. I generally shift at 1500 on level roads or downgrades. climbing hills I use a gear that will let me pull the hill staying around 1500 to 1700. Where ou upshift absolutely has a affect on your mileage, there is no advantage to running your engine "Tight" your are just wasting fuel. Only a company driver that does not pay for the fuel would not understand how too shift to save fuel, in the lower half I shft 11 - 1300 and as speed picks up I will run my rpms a 1000 or so higher in each gear to about 500 to 1600. The target for shifting is to come into the next gear at the botom of the torque curve to keep it pulling.

If I run the engine hard and shift at 1700 and up my mileage drops to the low 6 or high 5's. At 4.00 per gallon your tossing dollars up in smoke.

 

First I should explain "tight" is the upper range of HP curve where torque takes a significant dive... Most engines see this in 1600-1800 range.

In our OTR fleet of 2012 D-13 Volvo's there was no difference in MPG w/ progressive shifting vs unrestricted, just made a bunch of grumpy old men grumpier. In fact we seen a brief loss in fuel economy for first 1-2 weeks <--can attribute that to learning curve w/ missed shift point and such. (its hard to teach old dogs new tricks LOL)
Please, don't misunderstand what I said in original post. We watched it real time, and did see avg of 1.2mpg immediate loss @ the upper end vs lower. But ultimately in every 200 gal measure, it was not noticeable. The amount of time spent running through gears was insignificant to the overall performance. I've been itching to get my hands on city/daycab fleet details, but no success yet.

What may, or may not be surprising?, is a 1.0 mpg gain w/ drivers over 10yrs experience vs 2-9yrs. I'm a bit skeptical of this number due to routes and weights, but it is also obvious the highest performing drivers have some background in mechanics, or O/op.

 

You shift whenever you have enough power available in the next gear to continue smoothly accelerating. It isn't a set rpm, it could be upshift at 950 from 4th to 5th when light, and 1450 from 8th to 9th when heavy. And it'll change from there depending on uphill or downhill? headwind? etc?

 

Exactly. I do not understand why so many guys worry about what rpm to shift at. I've said it several times before but i'll say it again.

Shift by feel not by sight.

 

This article maybe a goog starting point for someone to study. http://www.overdriveonline.com/smart-driving-6/

 

An engine that's been detuned more than 10% from factory specs, a transmission that has been converted from a 13 to a 9, and tall gears...a flatlander...will be ran tighter than what it was designed to. Had an old Columbia that had a 430 Detroit that was detuned to 350 HP, a 9 speed top 2, and 3:48s that couldn't pull a hill deadheading. The truck never saw better than 4 mpg. Fueled up in Sioux Falls and used 3/4 tank running into the wind to Rapid City. The beancounters called me on the phone and told me that my fuel economy was atrocious. I told them that their truck was atrocious. They told me that I was shifting wrong and that I needed to drive slower. I told them that the best the truck could do in a headwind was 40 mph and any slower, I would have to get off of the interstate.

 

LMAO... sorry I know not funny.
Gotta lub the beancounters!