MFD tricks

I'd like to discuss: (1) getting 99.9 MPG for non-trivial distances, and (2) getting a display with solid, 100 MPG bars.


Ok, let's start with getting the consumption numbers right. This will take about two hours, not counting the vehicle preparation and route:

• Vehicle Preparation

• high energy gas - in North Alabama, Shell, 87 is the highest followed by Exxon and Chevron (as of last summer.)
• change lubricants - fresh engine oil, filter and transaxle oil but let them 'age' for about 30 days. Be sure the ICE level is no more than 3/4ths full.
• clean air filter - need we say more?
• tires - maximum side wall pressure
• wheels - recent alignment including rear wheels if you know how to adjust using shims
• either have your radiator blocks or a thermistor hack (a system that allows lower ICE temperatures to appear to be at 70C)

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• Route Research

• find a flat parking lot you can maintain 15-20 mph without having to come to a stop
• map a route to the lot from the nearest limited access road

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• Driving protocol

• look for a windless day or evening at 75F or more degrees ... bring good music
• drive at a speed of 50-60 mph for at least 30 minutes to fully warm up the car, tires and charge the battery
• take the exit and drive to parking lot and stop
• put in the radiator blocks and/or enable the thermistor hack
• optional: do a forced charge on battery and then turn it off and back on
• reset the MFD and do a practice lap at 18-20 mph
• without stopping, reset the MFD after the first lap and try to hold 18-20 mph for as long as it takes to get as many miles on the display as you want at 99.9 MPG

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This will take about 40 minutes and relies on a latent defect of the MFD display: a single 100 MPG instantaneous display bar becomes the 5 minute average.

• wait for a 5 minute display bar to update
• in electric mode - slowly accelerate to 6 mph for one, 100 MPG display bar
• coast to a stop and wait for 5 minute display
• repeat until all bars show 100 mpg

Shortcut: force charge the battery then turn off the car and start it up again for this trick. However, you'll have a small mileage number, like mine.

Bob Wilson

 

Which one is true?

The top one clearly shows 99.9 MPG for 10 miles yet the 5 minute bars show something else. The bottom one clearly shows six, 5 minute bars of 100 MPG and because it was done all electric, the actual mileage was much higher. I've simply documented how to achieve either result including the preparation.

Bob Wilson

 

The tricks are vehicle preparation, route planning, operation and weather, which I've listed. Once individuals have achieved their "personal best" the pressure is off and we can enjoy our wonderful vehicles.

Bob Wilson

 

At these levels, it is a question of being practical. It is the degree of each step with all of them combined. For example, driving 18 mph or ignoring the warm-up and forced charge fuel burn may not be practical for everyone. Often knowing you have maxed the MFD is enough to take this off the table but we are also headed into summer.

In the northern hemisphere, we are two months away from August, perfect hot weather for a driving test. In the USA, the July 4th Independence and September 1st, three day, weekends are opportunities for mileage driving tests. For example, an average speed of 20 mph would require 50 hours of driving:

• 8 hrs - Friday evening
• 16 hrs - Saturday
• 16 hrs - Sunday
• 10 hrs - Monday

An average of 90 MPG would let our ~11.2 gallon usable fuel, North American Prius drive 1,000 miles and join the 1k mile club ... without having to run out of gas (carry a spare 1 gal. container on Monday.) But we don't have to go that far. Just take enough time to demonstrate the vehicle capabilities and take a photo for an avitar ... then enjoy.

Bob Wilson

 

Actually it is basic engineering testing. There are two parts to the 'tricks' ... those that demonstrate how the display, the bars, work and those that demonstrate Prius performance.

The MFD bar trick came from investigating my 2003 Prius MFD accuracy and one happy accident when I was in a drive-in food line and saw the 100 MPG bars propagate. The ragged bars even with 99.9 MPG consumption shows a latent defect in the bar logic that hopefully has been corrected in the NHW20. In contrast, the consumption numbers are quite accurate. Knowing the MFD bars in an NHW11 are inaccurate makes it a lot easier to pay attention to the consumption numbers.

The performance characteristics of my hybrid have never been as well documented as the performance characteristics of my old Cherokee 140 airplane. So I've become a Prius 'test pilot' and conducted a number of tests that hold as many elements constant as possible and vary just one at a time. This data allows me to make informed decisions that tradeoff speed for performance and identify problem areas. It also has a practical application, vehicle diagnostics.

Recently someone came to this forum complaining about a loss of mileage. Many folks listed the most likely failure modes and the user continued to report, "nope, still broke." So I asked them to do two simple, fixed speed, 20-30 minute driving tests around flat loops. If their numbers came within the range of my MPG vs MPH plot, the diagnosis is simple, "Your vehicle is performing as expected." It is really hard to fix a vehicle that is not broken.

I think the real difference is to compare and contrast instructive MFD displays with instructive text with just MFD displays lacking enough information to replicate the results. Even if the text is as obvious as "coast down a hill," at least there is enough information that anyone can replicate the experiment. That is the engineering way.

Bob Wilson

 

Hi Larry,

There is nothing to take offense at. We're discussing a technique, a technology. Nothing more or less.

I have demonstrated that the NHW11 Prius MFD display has at least two flaws in the bars:

• actual 99.9 mpg mileage may not show up as solid 100 MPG bars
• the bars appear to use some 'sampling' every 5 minutes and a single 100 mpg value fills for the whole interval

It is my hope that these flaws have been corrected in the NHW20 MFD and the data I've seen suggests they have.

I'm listing the steps any Prius driver can go through to achieve 100 MPG on just about any warm day of the week (or with a thermistor hack, in 50F weather.) This is reproducible and requires no more or less skill than the items already listed.

It is purely instructional ... a cookbook that allows anyone who feels the need to demonstrate high mileage to "max out their display." Usually, having achieved some personal best, they can then relax and not be quite so "driven."

Sounds like a fine product.

Bob Wilson

 

The "Nice display" is reward enough and fortunately, the scripts I've described do not take a lot of time or fuel. But I am curious, does your opinion also extend to the Prius and Insight marathon drives?

Do you also condemn the marathon drives that were 100 times longer as "... wasted a bunch of fuel, and ... something that is totally against the whole ethos of an environmentally friendly car?"

Bob Wilson