MFD tricks

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05-26-2008, 12:15 PM

bwilson4web

Engineering first

Thread Starter

Join Date: Oct 2005

Location: Huntsville, AL

Posts: 5,613

MFD tricks

Hi,

There was a recent discussion of an entertaining TODAY show drive from Chicago to New York and someone asked a question. So I'd like to discuss: (1) getting 99.9 MPG for non-trivial distances, and (2) getting a display with solid, 100 MPG bars. These techniques works on both the NHW11 and NHW20 Prius:

Ok, let's start with getting the consumption numbers right. This will take about an hour, 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)

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

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

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. Again, drive the car for 30 minutes at highway speeds to warm the car, tires and charge the battery. Then drive to a parking lot:

wait for a 5 minute display bar to update
in electric mode - slowly accelerate to 6 mph for one, 100 MPG display bar
shift into "N" and roll to a stop
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. A force charge means you hold the brake with the left foot and hold the accelerator floored with the right. Testing has shown this to be a safe technique originally found in some Toyota maintenance documentation.

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.) Add an extra day, say all day Friday, and the daily drive becomes a much easier 10 hours per day. 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

ps. I got these displays with my $17,300 used, 2003 Prius. My mileage signature reflects over 55,000 miles combined highway and city driving. "Eat my shorts TDI Jetta." NOTE: Prius MSRP: $22,000.

Last edited by bwilson4web; 02-09-2009 at 04:48 PM.