My fuel economy master equation

[EddieWinslow]

Just wanted to point out, my daily communte is on that exact same stretch of highway(litterally, I exit on french line,and I enter from the same entrance from Dougal). I set my cruise for 108-110km/h and get the results that i have so far in my Fuelly.

Still new with the car. so Driving habits are still adjusting.

[majorleeslow]

 

I don't think the radio would have much impact. Based on my testing with the ScanGauge the radio draws less than .5 amps. Granted, I don't have the volume set very loudly, if the volume is cranked it would draw more power.

Hmm the Amps in my limited electrical knowledge do not give much info. unless I know the voltage that's associated with it. If its running on 12v which means the stereo is only consuming 6 watts. However if its running on 300v then its 150 watts. Does it show the voltage?

[majorleeslow]

Just wanted to point out, my daily communte is on that exact same stretch of highway(litterally, I exit on french line,and I enter from the same entrance from Dougal). I set my cruise for 108-110km/h and get the results that i have so far in my Fuelly.

Still new with the car. so Driving habits are still adjusting.

Try a few times to set it at 90km/h for the same trip. I think you'll see an improvement. Edited September 18, 2013 by majorleeslow

[milleron]

I believe AC takes under 2Kw. but Even 1 kw could offset the SOC during non driving time when it's sitting in the lot under the sun.

You might get a 100 W panel on the roof of a car -- enough to drive the fan in the Toyota. I don't think there's any technology currently available that could power an AC and fit on a car's roof.

[alpha754293]

Just wanted to point out, my daily communte is on that exact same stretch of highway(litterally, I exit on french line,and I enter from the same entrance from Dougal). I set my cruise for 108-110km/h and get the results that i have so far in my Fuelly.

 

Still new with the car. so Driving habits are still adjusting.

 

I only run the test to the on/offramps. I'm assuming that you probably drive a little further to get to your destinations, which being city/county roads, means that you can use the EV mode more.

 

And I use that stretch of highway cuz it's super flat (for the most part) and quite straight. It's as close as I can get to a "test track".

 

I haven't ran it recently (since the PCM update), but I suspect that it should be higher now.

 

Try a few times to set it at 90km/h for the same trip. I think you'll see an improvement.

 

Not recommended. The maximum speed on 401 is 100 km/h, so you should always drive AT the maximum permissible to avoid being rear ended.

 

You might get a 100 W panel on the roof of a car -- enough to drive the fan in the Toyota. I don't think there's any technology currently available that could power an AC and fit on a car's roof.

 

Uhh....there are. But they're not cheap. And the A/C could be as high as 5 kW (if it's a really hot day). I've hit it a few times when I have leaving from work in the afternoons.

[hybridbear]

Hmm the Amps in my limited electrical knowledge do not give much info. unless I know the voltage that's associated with it. If its running on 12v which means the stereo is only consuming 6 watts. However if its running on 300v then its 150 watts. Does it show the voltage?

My estimate at amps is based on the ScanGauge reading of current flow from the HVB. In my ScanGauge thread I talked about the amps at idle, etc. I need to test further with the radio before I make any more statements because I don't want to say it wrong based on a faulty memory...

[acdii]

The radio draws off the 12V battery, not the HVB, but the battery charger would show as a draw, so the real question is, how much does the charger draw when under minimal load?

[milleron]

 

Uhh....there are. But they're not cheap. And the A/C could be as high as 5 kW (if it's a really hot day). I've hit it a few times when I have leaving from work in the afternoons.

 

Would love to see the reference to the panel sufficient to power an atuomobile AC that would fit on the roof of a car. I wouldn't use it for that purpose, but if there's one with that capacity at that size, I might rethink putting them on the roof of my house.

[alpha754293]

 

Would love to see the reference to the panel sufficient to power an atuomobile AC that would fit on the roof of a car. I wouldn't use it for that purpose, but if there's one with that capacity at that size, I might rethink putting them on the roof of my house.

 

http://www.technologyreview.com/news/410454/does-car-mounted-solar-make-sense/

 

That uses "old school" crystalline Si cells. They have like the newer flexible thin film polymer solar cells that some of them also tout greater photovoltaic energy conversion efficiencies, but those are probably still cooking in labs (like MIT labs or some of the US National Labs like Sandia or something).

 

And residential A/C systems take more than a few kW to run.

 

If you're thinking of deploying it at home, it'd more than likely that the solar cells is used to charge an array of batteries and ultra capacitors (for quick discharge on AC startup) as opposed to the solar array powering the AC directly. To do that, it'd be a decent sized farm field, probably with parabolic solar concentration dishes arranged in an array formation.

 

And saying that it's "roof mounted" doesn't necessarily imply that it actually had to fit the footprint of the roof. I was thinking more like strapping a giant sheet of plywood to your roof-style/size of a solar roof for your car. (Not very practical, but think outside the box.) :D

[hybridbear]

The radio draws off the 12V battery, not the HVB, but the battery charger would show as a draw, so the real question is, how much does the charger draw when under minimal load?

You're right, but changes to accessories that run off the 12V battery (such as turning on the headlights) immediately causes in increase in current out of the HVB. This makes me think that the current flow changes give us a pretty accurate measure of how much current is being drawn by that accessory.

[milleron]

 

http://www.technologyreview.com/news/410454/does-car-mounted-solar-make-sense/

 

That uses "old school" crystalline Si cells. They have like the newer flexible thin film polymer solar cells that some of them also tout greater photovoltaic energy conversion efficiencies, but those are probably still cooking in labs (like MIT labs or some of the US National Labs like Sandia or something).

 

And residential A/C systems take more than a few kW to run.

 

If you're thinking of deploying it at home, it'd more than likely that the solar cells is used to charge an array of batteries and ultra capacitors (for quick discharge on AC startup) as opposed to the solar array powering the AC directly. To do that, it'd be a decent sized farm field, probably with parabolic solar concentration dishes arranged in an array formation.

 

And saying that it's "roof mounted" doesn't necessarily imply that it actually had to fit the footprint of the roof. I was thinking more like strapping a giant sheet of plywood to your roof-style/size of a solar roof for your car. (Not very practical, but think outside the box.) :D

 

Like I said, the best that even the experimental system mentioned in your linked article could muster was 165 watts, and all the ones actually deployed commercially put out less than 100 W.

BTW, when mentioning deploying solar at home, I was NOT thinking of trying to run my residential AC, just a system like some of my neighbors have that lessens the electricity bill a little and feeds into the grid when home use is less than the array's output. The problem is that the break-even point on those things can be measured in decades rather than years. A 5kw panel small enough to fit on an automobile roof, might change that equation, but I still believe that nothing like that exists, and probably nothing remotely like that.

[majorleeslow]

All this solar panel talk wants me too experiment with the one I have. A 12v solar battery maintainer with reverse blocking diode.

 

I'm thinking if the accesory batt is kept topped off using solar power while not driving, It would draw less from the hvb and gas which should improve mpg a bit. And I wouldn't have to worry about jumping it when leaving it parked for a extended periods.

[majorleeslow]

 

 

http://www.amazon.com/gp/aw/d/B0006JO0KG/ref=mp_s_a_1_6?qid=1379594400&sr=8-6&pi=AC_SX110_SY165

 

Its only 1.8W so in full sun it should only pump18 watts in 10 hrs. not sure how much that will help. just want to try it.

Edited September 19, 2013 by majorleeslow

[alpha754293]

 

Like I said, the best that even the experimental system mentioned in your linked article could muster was 165 watts, and all the ones actually deployed commercially put out less than 100 W.

BTW, when mentioning deploying solar at home, I was NOT thinking of trying to run my residential AC, just a system like some of my neighbors have that lessens the electricity bill a little and feeds into the grid when home use is less than the array's output. The problem is that the break-even point on those things can be measured in decades rather than years. A 5kw panel small enough to fit on an automobile roof, might change that equation, but I still believe that nothing like that exists, and probably nothing remotely like that.

 

Like I said, that was only with crystalline Si cells. I know that they have other types of cells available (http://upload.wikimedia.org/wikipedia/commons/8/88/PVeff%28rev130919%29a.jpg

) and you can see the different technologies have different photovoltaic energy conversion efficiencies, so beyond that, it's just a matter of tying all the cells together to make your "panel". And at that point, it's "make it as big as it will fit/as big as you can afford".

 

And those are the ones where the efficiencies has been published. Doesn't include the stuff that's still cooking in the labs. I said they were available, I never said anything about it being commercially available and/or viable. lol.. ;)

 

http://www.amazon.com/gp/aw/d/B0006JO0KG/ref=mp_s_a_1_6?qid=1379594400&sr=8-6&pi=AC_SX110_SY165

 

Its only 1.8W so in full sun it should only pump18 watts in 10 hrs. not sure how much that will help. just want to try it.

 

I remember a REALLY long time ago, when my dad had his '88 Corolla, he had a little solar panel that was supposed to charge the 12V battery. Not sure how well it worked, but I remember it being there though (as a kid).

[majorleeslow]

So I did see a trend when I mapped the Temp to MPG over the same random trip data. Seems logical that above a certain temp the AC is working harder and harder to cool the interior even if its kept at the same interior temp. And it has a downward slope as it gets hotter.

 

Temps just started getting cooler so as they dip it should be interesting in next few months, but here's Summer chart.

 

 

[majorleeslow]

To add to above the dipped temps may be the only times the AC was ON.

[corncobs]

To add to above the dipped temps may be the only times the AC was ON.

Very nice graph could you make a parallel graph that shows the MPG vs. trip length? Maybe we would see that some of the higher MPG # while temps being are related to either short or longer trips compared to the one right next to it.

[majorleeslow]

I just wanted to share some of my observations on how different loads affect my fuel milage on City and hwy. I did not record the SOC before each tip. But the data is pretty insightful (in my opinion). the number in brackets is ppl travelling total. no number = just driver.

 

F= Fan, R = Radio, D = Defrost etc see the key on some of the entries.

 

Questions welcome.

 

 

 

This one shows how trip distance affects the mpg.

 

Thanks Corncobs. Did you want to see this chart? the blue line chart is trip dist vs mpg. Edited September 22, 2013 by majorleeslow

[alpha754293]

So I did see a trend when I mapped the Temp to MPG over the same random trip data. Seems logical that above a certain temp the AC is working harder and harder to cool the interior even if its kept at the same interior temp. And it has a downward slope as it gets hotter.

 

Temps just started getting cooler so as they dip it should be interesting in next few months, but here's Summer chart.

 

 

 

Excellent work, my friend. So....why AREN'T you working at Ford on the fuel economy team? lol.

 

What it really comes down to is power and energy. (Seems kinda silly for me saying that, but bear with me) - what I mean by that is W and Wh.

 

Gawd, I'm such an engineer. lol...cuz I look at that graph and think (first law of thermo) to figure out what your refrigeration cycle is "costing" you, and then the next thing that immediately pops into my head is power, energy, and efficiency.

 

And you can do that calculation in really simple ways that's not really quite that accurate or you can do it full out, but it takes a LOT longer to run all the numbers, but gives you a better, more accurate answer - one that's probably closer to the real world answer.

 

Great work though. Makes sense. 100 F - wow...

 

I actually don't know if the FFH has an electric heater or if it uses "conventional" heating (i.e. via the hot engine via a heater core). Hmmm...I should find out.

 

I DO think (if I remember correctly) that a lot of the EPA/SAE test are usually performed at 25 C, so it wouldn't surprise me if you might end up with a bit of a Gaussian distribution centered around that.

[corncobs]

Thanks Corncobs. Did you want to see this chart? the blue line chart is trip dist vs mpg.

Yes kinda I thought you had done this chart already. I still have a question are the MPG points they same as once one the temp chart? That's kinda what I was looking for but since the graph layout is different its hard to tell if that's is the case.

[majorleeslow]

The mpg points are same. But the mpg is actual mpg calculated (for the temp or trip distance data point which gives the real value) by figuring the sum of gallons used divided by the sum of trip distance for say 100 F or 5 miles on chart.

Actual gallons = trip summary distance / mpg number from trip summary

 

(which is always higher that the trip summare gallons used as Ford cleverly tricks the owners by truncating the last digit.)

 

Let me try to play with the numbers and see what comes out of it. I think I understand what you're looking for.

Edited September 23, 2013 by majorleeslow

[alpha754293]

The mpg points are same. But the mpg is actual mpg calculated (for the temp or trip distance data point which gives the real value) by figuring the sum of gallons used divided by the sum of trip distance for say 100 F or 5 miles on chart.

Actual gallons = trip summary distance / mpg number from trip summary

 

(which is always higher that the trip summare gallons used as Ford cleverly tricks the owners by truncating the last digit.)

 

Let me try to play with the numbers and see what comes out of it. I think I understand what you're looking for.

 

Well...I don't know if we're "tricking" you per se. There's probably nothing that really prevents us from displaying/showing all of the digits (to the precision of the data type). But eventually, you run into either practical or functional limits (most of which probably has to do with the text being too small for most people to read).

 

Measuring the fuel consumption is probably more difficult unless you're reading a fuel flow meter off the engine (or your weigh the tank, statically); but then you'd also have to figure out the density of the fuel that you're using, which of course, takes even more effort (since the density of gasoline DOES change with formulation, depending on who makes it (the specific refinery and the specific batch from that refinery (which production shift), etc. - so it all depends on how accurate you want to get.

 

YOU MIGHT be able to read some of that data off the CAN bus via the OpenXCPlatform,. but I haven't tried, so I dunno. (Because then you can develop your own Android app running off an Android tablet and you can display as many digits as you would like on a much larger (possibly) screen, which makes reading it much more easier.

 

Course, then you might say/think that we're "tricking you" with the sensors that we're using, so it's probably better if you replace the sensors as well with ones that are several thousand dollars lab-grade ones. ;)

[acdii]

Tip #1

Calibrate your speedometer/Odometer. There is a new pinned topic regarding this.

 

Tip #2

Calibrate your fuel fills. Also covered under the same topic.

 

Once you know how much gas it takes from the same pump after 3 fills, and know exactly the variance in your Odometer, then you can precisely calculate how much fuel you are actually using, and ignore the general purpose trip meters. They are there only to serve as a general guide to how the car is doing and are not accurate except in a general manner. Only precise instrumentation on the car will give you true results, and I dont think any of us want to hang $1000's in equipment on our cars just to find out how many actual MPG it gets.

 

Tip #3

Don't use MPG, but use gallons used instead. How many gallons of fuel did you consume this month in this car, that you would have used in your other car. Look at the bigger picture instead of the smaller one. Compare my Flex to the HyTi, Both go roughly the same distance on a tank, but the Flex holds nearly 5 more gallons of fuel. Go 1000 miles and see how many more gallons the one uses over the other, then you will get the bigger picture, wow it cost me XX more to drive this one vs the other one the same distance.

[hybridbear]

So I did see a trend when I mapped the Temp to MPG over the same random trip data. Seems logical that above a certain temp the AC is working harder and harder to cool the interior even if its kept at the same interior temp. And it has a downward slope as it gets hotter.

Very cool to see data to go with a theory that we've talked about for a long time. As we've said before and is shown in your chart, peak MPGs come at the highest ambient temperature where you are NOT using AC. I could often go as high as about 85 outside ambient temp when doing city driving without putting on AC during the summer and those were my best tanks on Fuelly. Once it got consistently above 90 during August we were using AC a lot more and it cost us about 5 MPG over an entire tank going from 55+ to only about 50-51 MPG.

[majorleeslow]

 

Well...I don't know if we're "tricking" you per se. There's probably nothing that really prevents us from displaying/showing all of the digits (precision of the data the type). But eventually, you run into either practical or functional limits (most of which probably has to do with the text being too small for most people to read).

 

Measuring the fuel consumption is probably more difficult unless you're reading a fuel flow meter off the engine (or your weigh the tank, statically); but then you'd also have to figure out the density of the fuel that you're using, which of course, takes even more effort (since the density of gasoline DOES change with formulation, depending on who makes it (the specific refinery and the specific batch from that refinery (which production shift), etc. - so it all depends on how accurate you want to get.y

 

YOU MIGHT be able to read some of that data off the CAN bus via the OpenXCPlatform,. but I haven't tried, so I dunno. (Because then you can develop your own Android app running off an Android tablet and you can display as many digits as you would like on a much larger (possibly) screen, which makes reading it much more easier.

 

Course, then you might say/think that we're "tricking you" with the sensors that we're using, so it's probably better if you replace the sensors as well with ones that are several thousand dollars lab-grade ones. ;)

Whoa firstly do you work for Ford? in that case Good for you.

 

And don't get me wrong when said it was a 'clever trick'. I meant that some owners are under impression that when it shows 0.0 g consumed rather that 0.09 g consumed. They assume its all electric no gas was used, and do not realize that they are seeing a 'truncated' number and not a 'rounded' number ( which would be more accurate representation) in this example would be 0.1 g. This issue threw my charts for a few days till it occured to me how to figure out actual gas consumption.

 

 

Wow great tips on measuring fuel consumption thanks to you and Acdii. Mine is poor-man's way take pics of trip summary and adjust each tank fill if there's variance. So it's more like mpg snapshot of my day to day commute.

 

I believe for summer numbers and relatively new guages its been very close. May be a slight bit off as my calculated gallons consumed vs actual fill is usually less by about +5 to +7% (about 0.7 g per 10 g fill) at the pump. Not sure if that's due to evaporation from the tank, pump calibration or gauge issue, or the mpg number not being accurate (truncated) like gallon number. I consider this as just a small factor.

 

I just saw the note about being on fuel economy team. Sure, if the pay/benefits are good why not. I'm open for being a consultant. I'll keep that in mind. Thanks.

Edited September 24, 2013 by majorleeslow