Short Tripping or "mini-tank" mileage

[DaveinOlyWA]

a lot has been discussed over the merits of the "average speed" verses MPG over various time periods. it has become pretty clear to me that the average speed over an entire tank of gas simply covers so much time as to be really useless. so i decided to track mileage over a well used route (work commute) to see how well the Pri handles short trips.

background: trip about 7 miles on way. relatively flat. some hills and valleys but start and end point elevations not a lot of difference. 11 traffic lights, 2 stop signs going, 3 coming. 58% 40 mph, 33 % 35 mph, 9 % 25 mph. Trip B reset for each leg.



morning commute; 5.30 AM very little traffic, lights on. cold but heat not used at this point.

afternoon commute; 4.30 PM. heavy traffic with high possibilty of stop and crawl traffic. daylight (will be dark after time change and will repost additional data for winter)

data points

miles; MPG; average speed; OAT; Delta SOC

edits; added stats after grill blocking. this is last set of numbers using summer formula gas

EDIT : winter is here. an obviouse drop in mileage seen. some symbols on lines for additional notes concerning conditions

*= wet roads or light rain
**= heavy rain and/or standing water on roads
D = extended defrost or ice scraping usually in morning only this early in the year

morning

7.1; 56.1; 32; 61; 0
6.9; 54.2; 29; 62; +1
7.0; 53.5; 30; 66; +2
7.1; 57.1; 31; 65; 0
6.9; 53.9; 29; 57; +1
6.9; 55.3; 32; 57; 0
6.9; 50.1; 32; 46; +4
7.2; 56.3; 30; 44; 0
7.1; 52.2; 28; 45; +3
7.1; 54.3; 27; 45; 0
7.0; 53.3; 31; 51; +2

7.3; 55.1; 26; 43; 0
7.1; 51.3; 28; 45; +1
7.1; 58.8; 31; 50; +1
6.9; 52.3; 33; 39; 0
6.9; 48.8; 028; 36; 0 ** windows iced up, had to run defrost a few before driving
7.1; 54.3; 26; 42; 0
7.1; 51.9; 26; 42; 0
7.1; 48.2; 28; 32; +1
6.9; 51.3; 26; 43; +1

7.1; 53.8; 28; 51; +1
6.9 ; 55.9; 31; 52; +2
7.1 ; 54.6; 28; 54; 0
7.1; 51.9; 27; 54; 0 ...**
6.9; 53.2; 29; 50; 0 ....*
6.9; 49.6; 29; 36; 0 ...D
6.9; 54.6; 30; 54; 0
6.9; 49.4; 27; 36; 0 ...D
7.0; 53.5; 28; 57; 0 ...*

Afternoon;

6.9; 65.1; 21; 69; 0
6.9; 68.1; 23; 72; -2
6.9; 72.1; 20; 75; -2
7.0; 63.7; 27; 70; 0
7.0; 64.1; 26; 69; 0
6.9; 63.2; 25; 70; 0
7.0; 63.2; 20; 64; 0
6.9; 64.0; 28; 66; -1
6.9; 63.1; 23; 74; 0
7.6; 71.0; 23; 82; -2
7.0; 62.7; 23; 76; 0

7.0; 59.6; 23; 59; 0
7.0; 63.4; 25; 63; 0
7.0; 60.7; 25; 61; 0 ** opposite direction**
7.0; 61.1; 24; 63; 0
7.0; 64.9; 27; 66; -1
7.0; 60.6; 18; 66; 0
7.2; 62.7; 25; 57; -1

7.0; 56.2; 23; 60; 0
7.0; 60.0; 27; 60; -2
6.9; 57.3; 19; 57; 0
7.0; 55.8; 16; 57; -1
7.0; 59.5; 20; 60; 0
7.0; 56.1; 26; 56; 0
7.2; 54.7; 15; 50; -1

ok. so there it is... kinda started this late so the dont yet have the temperature range i was hoping for, but then again, it doesn't really seem to matter.

what does matter is the SOC. there is a major penalty for short trips when SOC is below 6. because of road construction (which is happening on that short north-south jaunt on Yelm Hwy) i frequently have to detour which lengthens the percentage of the 25 mph commute. this basically runs my SOC down. i actually discarded some of those because they were way out of the data range. some detours took me to nearly 8½ miles and involved sitting on the road while construction equipment cleared up to 15 minutes at a time.

will continue this latter to see what effect temps have in winter with and without grill blocking

http://maps.google.com/maps/ms?ie=UT...27595&t=p&z=15

**edit** fricking Google!! ok. i guess we try something else for maps

[bwilson4web]

I take a screen snapshot of the Google Map and then load it into PowerPoint. Using PowerPoint, I then add the lines and other indicators to show exactly my route:


Just a suggestion.

Bob Wilson

[DaveinOlyWA]

show off!!

[bwilson4web]

Actually you have given me an idea when I start the Oct 1 to Dec 31, 2009 mileage collection and recording. I was planning on just tank records but the mini-records are exactly what is needed for an accurate "mph vs MPG" set of charts. So I'll make sure the workbook has two data entry spreadsheets and graphs that reflect the different sources.

Thanks!
Bob Wilson

[DaveinOlyWA]

well this chart was a restart because of the large discrepancies in mileage. i even did a couple reverse trips where i drove to work on my day off in the afternoon to see if direction made a difference (it didnt) and it took me a bit to realize how much of an impact SOC had on the short trips.

but then i noticed the difference in SOC which was aggravated by the construction. because of it, i was detouring either on 54 th ave coming into my development which basically meant over a mile at 25 mph which meant a pretty low SOC at end of trip but high mileage which i lose the next day. the other detour option was turning at college/rainer to ballustrade then a cut over which used EV since balustrade is all 25 mph as well.

a couple of times when bombing around town on errands, i did a reset to see what short trip mileage is with no warmup. seens like i am settling around 80 mpg...not bad

[bwilson4web]

Originally Posted by DaveinOlyWA

. . .
but then i noticed the difference in SOC which was aggravated by the construction. because of it, i was detouring either on 54 th ave coming into my development which basically meant over a mile at 25 mph which meant a pretty low SOC at end of trip but high mileage which i lose the next day. the other detour option was turning at college/rainer to ballustrade then a cut over which used EV since balustrade is all 25 mph as well.
. . .

You and a couple of others had mentioned the same thing and I really noticed it this morning. Last night, my wife and I made a midnight trip to the grocery store driving through the neighborhood. This ran the traction battery pretty low but I didn't notice it until this morning.

I drove up to a regular intersection and instead of shutting down, the engine kept running. Then I noticed my traction battery SOC was down to two bars and it made sense. Once I got on the Parkway, 50 mph, it took about 6-7 miles before the traction battery SOC was back to normal. Thereafter, mileage was normal.

What this suggests is a 'mini-plugin' system might be 'low hanging fruit.' Day dreaming, this is what I'm thinking:

• smart curb - with 'whisker' wires that contact underbody bus bars to transfer power at 48 VDC. At 48 V., there is little risk of electrocuting small critters or clumsy people. The smart curb would test before application of power.
• in-vehicle tickle charger - using the temperature and voltage, a smart charger, NiMH aware, would bring the traction battery SOC to a reasonably high level, say 78%, enough that the traction battery ECU won't throw a code but plenty of energy to handle warm-up driving.
• block and transaxle warmer - at say 6:00 AM or upon hitting a switch, start block heating for the ICE and transaxle. For good measure, see if inductive heating can be used on the steel belted tires to bring the tread temperature up say +5C. Actually, I'd like it to have a smart 'warm-up' based upon past driving practices as well as a wireless "leaving soon, git 'er ready."

I need to implement the prototype on my NHW11 and if it works, use the lessons learned for the ZVW30.

Bob Wilson

[DaveinOlyWA]

LOL!! oh man, WOW really have time on our hands.

ya, if you look, the 50 mpg trip was the next morning after the 70 mpg trip. i did the detour thru Balustrade. my SOC parked and the next morning was 2 bars. with that short of a trip, it took something like 5-7 minutes to get into good mileage when normally it takes 2-4 minutes. doesnt sound like much, but on a trip that is only around 13-14 minutes in length, it makes a big difference.

[Indyking]

Originally Posted by DaveinOlyWA

a lot has been discussed over the merits of the "average speed" verses MPG over various time periods. it has become pretty clear to me that the average speed over an entire tank of gas simply covers so much time as to be really useless. so i decided to track mileage over a well used route (work commute) to see how well the Pri handles short trips.

I have exactly the opposite opinion. Short trip MPGs are really cool for things like personal satisfaction, short experiments, or even to play around with the Prius HSD in different situations, but for real measurement of FE to inform prospective buyers or current interested owners, it is pretty much hopeless. Lifetime or at least "whole tank" MPG is a lot more useful for that purpose.

I fill up my tank in a gas station that is 6 miles away from my house, and the way home from that gas station is a slight downhill. In that stretch I get 80+ MPG all the time (have got 90+ a couple of times) but what's the point of doing that? Does that reflect what the Prius FE is? NO, not even close!

[DaveinOlyWA]

for a real understanding of what affects your mileage, it might be hard to evaluate a tank the consists of several dozen trips of varying lengths, traffic densities and weather conditions stretching over several days or weeks.

any error you make will be magnified. i do not advocate not keeping LT stats. in fact, i greatly encourage it and post mine in my signature in order to encourage others to do so.

also, when it gets right down to it, its simply more knowledge. now gathering knowledge does require work and a question of evaluating the worth of the data verses the time it took to gather it is a question i am not going to address

[Indyking]

Originally Posted by DaveinOlyWA

now gathering knowledge does require work and a question of evaluating the worth of the data verses the time it took to gather it is a question i am not going to address

... because it is very personal. Myself, for instance, don't think it worth it. Others may think differently....