Quote:

Originally Posted by indnchf

The white AVG mpg bar on the NAV display is only for the last 15minute avg. When you shut your vehicle down it will retain your previous 15min history avg on that white bar, then when you drive it replaces the data with your current driving avg.
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In my opinion - this is virtually useless data as I would rather have a full tank or multiple tanks worth of average shown on the screen.

About the only thing the data is useful for is estimating your current miles to empty display since it shows how your current 15min average.

To each his own - but the Manual reads:
Average Fuel Economy (AFE): The AFE is displayed on the white bar across the graph. The AFE will be retained when the key is turned OFF, and will continue averaging when driving resumes. Pressing RESET will reset the AFE to zero.

Plus those using a ScanGuage have shown that the avg shown in the white bar is an accurate mesure of your overall MPG since you last pressed the RESET button. It could be to see what you might be getting for say a 10 mile drive at 60MPH on the expressway, your roundtrip to work and back etc., average for a single tank (reset at fill-up) or your avg on a 1K trip since you last pressed the RESET button.

Not Just my thoughts but from your Owner's Manual and many other long time users of the system.

 

Yes, the manual does state this but it does not state what average is saved. I'm saying it is a 15min average that is retained. It adds up when you look at the information that others have posted such as the 2000 data points saved and 2 pages of data saved.

Also manual computations seem to bear this out. I've had one mpg deducted by accelerating up a short hill.

Lets say you are 400 miles into a tank at 32.5mpg you accelerate up hill and now your 15min avg reads 31.5mpg

400/32.5 = 12.3 gal used
401/31.5 = 12.7 gal used

I find it imposible to use .4gal to go up a one mile hill no matter how hard you are accelerating.

Now lets convert this to my hypothis of a 15min average shown on the white bar

For ease of computation sake:
Assumption you are traveling a constant 60mph = 1mile per minute
Going up hill you press your accelerator to keep 60mph

15 min avg shows 32.5mpg so in 15 minutes you have traveled 15 miles.
15miles/32.5mpg = .461 gallons of fuel used during the last 15miles
You now go up hill and after one mile your avg on the NAV show 31.5mpg

15miles/31.5mpg = .476 galloons used in the last 15 miles of driving. (remember the previous 1 mile at 32.5mpg has been thrown away in the NAV computation)

Therefore to go that one mile up hill cost you an additional .015 gallons of fuel. This is a very reasonable amount to keep your speed up hill.

I'm just saying the nav computer changes to much to be anything greater than a 15min avg!

Now must people on this list state they are close to their avg shown by the nav on a tank which makes sense because they are trying to increase their mpg, and if you drive consistantly an average is an average. I'm just saying it's not a tank average.

Gary

 

So how would you explain my driving for more than 20 minutes and the entire green portion of the graph is BELOW the average displayed? or above? I've seen both many times. The math doesn't work for that very well....

Also the graph fluctuates wildly for the first few miles but near the end of a tank its much more steady?

 

i only reset my average mpg when i get my oil changed. in the begging when i drive my average changes rather quickly (1 mpg going up the hill by my house), but now with just under 10,000 miles, my average it is harder to change (dropping only .2 mpg going up the same hill). so the white bar must be the average mpg between resets and the green graph is over that last 15 min.

 

Now, Now Gary

This is why I use GaryG! Look down at my MTE, and tell these people you know better than I about how to drive, read the gauges and understand the data of the NAVI. You have seven post here, and your telling Phillip how to read his Navi. How disrespectful can you be? Please take a picture of your MTE at fill up so I can respect your opinion!

You better take another look at Phillip's post and review his data when you learn more about the Navi and the FEH. It's not that simple and I made those mistakes also.

GaryG

 

Hi Gary,
I'm trying to be disrespectful of anyone on this list, as everyone else does I am trying to learn the system in the FEH and how to maximize the system.

I'm just trying to present info as I currently see it. I'm sure it's never as simple as first presented, but without discussion and info from many, we can't figure it out.

Your mileage on the MTE is wow, and I'm sure for most people difficult to obtain. I would be happy if I can get a combined avg of city/hwy above 36.

Our questions could be answered quickly if only the radio mfg would state how much and what data the NAV retains. Until that time we have to make observations which can vary wildly from driver to driver and FEH to FEH.

A good example, the previous post regarding green bars halfway down from the avg for a full screen, in my assumption this should have evened out after 15min or maybe it's 30min that needs to be counted? I can't explain this behavior with my theory, so what's the next theory?

For me in the meantime I will keep track of my gallons used at fill ups to odometer readings and get a 10 tank avg to avg the differerences in tank fillups. And write down what the NAV says per tank and compare both, and also avg the NAV reading over the 10tanks for a comparison.

From reading most posts, the two numbers NAV, and tank avg's get closer the more miles on the FEH?

Just asking questions not attacking anyone here........

Gary

 

Thanks for the support GaryG – we all have made ‘Stupid’ mistakes and will keep on doing so – we are just human. Take a look at GaryG’s post of his driving style and what he swore to a year ago and some of the things he preached then he swears off of now. That is one of the things I really like about this particular forum – the banter back and forth but also give and take – and I take a lot from the guys that REALLY know not just about the FEH but driving in general, whether it be a Hybrid or Excel and his ’03 Ranger pickup with an average of a 37.1MPG and all the others others. Most of the time I just sit back and read (listen), soak in their knowledge and experiences and try and put them to work for me.

Not trying to start anything but working off your last post and doing it in a different way.

I think you said “The white AVG mpg bar on the NAV display is only for the last 15minute avg. When you shut your vehicle down it will retain your previous 15min history avg on that white bar, then when you drive it replaces the data with your current driving avg.”

OK – my trip meter reads 400 mile with an average of 35 MPG (11.43 gals) on the white line.

Heck - I just ran into a 7.5 mile backup on the freeway – total stop and go. It takes me 45 minutes (3 – 15 min intervals) to make that 7.5 miles. For general purposes – say I had a ScanGuage - ‘Reset’ it when I got to the backup. Now I was reading 35 MPG on the NAV screen when we stopped - and turned the ignition off - it takes me 15 mins to go 2.5 miles and the average on the SG (because of EV) shows 65 MPG – I turn the ignition off. OK so now I guess my White Bar Average must be showing 50 MPG. We travel on another 2.5 miles – same scenario – now the White Bar must be showing 57.5. We go the last 2.5 miles – same scenario – my White Bar must then be showing 61 MPG!! A gain on the Avg MPG White Bar of 26 MPG in just 7.5 miles.

In reality we probably would have used about 0.12 Gal of gas for the 7.5 miles. Ok that means 407.5 mile on 11.54 gals or just 35.3 MPG, which is just about what the NAV avg would be reading.

Wish I could hit 61 MPG – Would be pushing GaryG

This is just an example but I think pretty close to what you were saying.

 

I'm not sure what the real answer is... I'm sure its not the last 15 minutes... We could verify that easily, all we'd do is RESET the average, drive 1/2 a tank or so.... park the car in a lot with MAX A/C on for 15minutes. If its the average of the last 15 it should read 0MPG at the end.

Incidentally I verified my all points below the line hypothesis just now when I was out driving (I broke all of Garys good driving tips to do it...I think I heard him sobbing). I have picture but and can post but its from a cell phone so its pretty hard to look at. There were two points just above and two points WAY below... The area above didn't equal the area below.

The truth is it SHOULD be the average since a reset. Its not like it takes any memory to do so. You don't have to remember every point to do that... you just keep the average and the number of miles traveled. Then when you add in a new point you "weight" the old average by the number of miles traveled before averaging in the new point. You only have to keep two numbers.....not the entire timeline

As to what they really do.... I'm not sure.

So far when I've checked by normal math with a fillup, my Nav has been +/-1 or 2 MPG and not too bad.

 

OK – Last post on this subject and I apologize for the last one – don’t know what got into me – just old and cranky I guess.

Why don’t we go with the K.I.S.S. (Keep it simple stupid)

The Nav computer gets the same data as the ScanGuage or any other measuring instrument. The data sent to it – the same data that goes to the OBDII – right? Well just as Tim said -

Quote:

Originally Posted by TeeSter

I'm not sure what the real answer is... The truth is it SHOULD be the average since a reset. Its not like it takes any memory to do so. You don't have to remember every point to do that... you just keep the average and the number of miles traveled.

The unit has to only keep up with 2 numbers and they are sent to the OBD and the NAV unit. The fuel consumed and the miles driven, which are both saved until you hit the 'RESET' button. Have the computer divide those two and display them on the screen. You don’t have to keep up with 2,000 points at all – just those two to get the average.

Or to throw in another theory if that is OK – How about the computer taking these stored figures – total gas consumed so far and miles traveled since last ‘RESET’ – have another computation based on what is being used at that instant, or whatever interval they came up with, and the effect it would be having on that set number for a single tank, (13.5 – 15.5 whatever they might use), and average BOTH of these numbers together. If you used the last scenario of 'On Board Data' of Miles/Fuel consumed, that would kind of explain the deep drops in MPG even deep into the tank or after several thousand miles.

There could be an error in both the electronic calc and the manual calc. Both could be contributed to the actual miles driven. I have checked my odometer several times and by several different ways and it always came out that it was incorrect and if you use that factor on my manual calc of MPG against the NAV reading – they came out to be almost the same.

I have done what you suggested and kept up with the NAV average and manual average over a long period and it is almost a wash. Yes I know there are big swings - usually down and it takes a long time to get them back - and I don't have an answer for that - but in the end all is well.

Again – Sorry about the outburst – If you have read any of my post that is one of my pet peeves.

 

Gary, sorry for getting smart, and it is true the information given on the Navi and most of the systems on the FEH is limited. The battles here and other sites have gone on for almost two years trying to figure out how the FEH works. An example of what Phillip said about me changing my opinion and techniques is the “Fake Shift”. I came up with that term when I first bought my FEH in Feb. ‘05 to reduce high RPM’s. Now, I never increase RPM’s to a point I need to FS to keep control. Later, I figured out the FS in “L” was a battery charging gold mine that brought me to MPG in the 70's on short 20 mile RT.

Those here that have and understand the scangauge, understand a lot more about the running averages of the Navi and the information center on the dash (deleted with the Navi). When you know how the instant MPG can impact your averages, you will find out how going up hill can drop your average real fast. Did you know that when the ICE is cold, charging a very low battery and slowly accelerating, your getting below 10mpg. It’s so bad that the traction motor has to assist the ICE to accelerate. There will be times the ICE is guzzling gas and your average will tank.

The scangauge measures every 10th of a gallon you use throughout an entire tank, or more than one tank if you don’t reset it. The scangauge can confirm at what point the Navi average drops data and I can assure you, it’s much longer than 15 min. I reset the trip OD, Navi average and tank average at fill up every time. Most driver’s reporting 400 mile to a tank will not have any or very little data dropped if they reset at fill up. All of my tanks since I got the SG in Dec.’05, have been over 600 miles or would have been if I didn’t fill up before. I’ve made it a point to determine the point in mileage that the navi drops this information, and concluded it drops the data after so many hours of running, not miles. It is possible that the 2000 data points are minutes because I may have use the scangauge hours incorrectly. I was looking at the navi data dropping at around 20 hours on the scangauge, but I don’t know that when your in EV at a stop or moving, the scangauge clock stops but the navi continues.

If you use the gas pumped at fill up to determine your tank MPG, you will never know what you got on a single tank.

GaryG