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I'm not sure if other Prius pilots have noticed this, but the Scangauge can not give accurate FE values while in stealth (EV) mode. Even though the instantaneous FE indicated is 9999, and GPH is 0.0, the scangauge still records some amount of fuel used.

A good example is when I leave the parking lot at work. I use the EVb immediately after powering up and drive about 1/2 mile thru the parking lot (15 MPH) and out to the main road. When doing so, I watch the current MPG climb quickly to about 3000. If I drive slower, I notice that the FE stops climbing and actually starts to drop!:eek:

The ICE has not started yet!

You can also reset the MFD and compare the two. During ICE-on conditions, the two agree, but as soon as the ICE drops off, the divergence begins. The MFD always shows higher FE because it assumes correctly that no amount of fuel is used.

If you stop to think about this, in order for the SG to report a value at all, it has to assume a small value for fuel consumption as to avoid dividing by zero.

So here is the crux of the problem.... Proper calibration depends on how much ICE-Off is used during a tank. One can calibrate for a particular route, but any other route, assuming ICE-off is used, will not be accurate. So for someone hoping to use the SG for a 100+ FE marathon attempt, you won't know how to calibrate it until after the marathon is over.

Wayne, could you contact the SG guy and find out what fuel rate is used for his calculations during EEV mode? With that data, one could conceiveably change calibration based on expected driving conditions. I know, this may sound ridiculous to some, but for those who want accurate feedback to be used to improve driving technique, this info would be very valuable.

Hi Dan:

___We know about this. It happens in all vehicles that I have driven ICE-Off. I can boot up the Accord or Ranger and glide down the drive for a 1/3 of a mile and record FE in the 500 – 2,000 mpg range when it should be pegged at 9999 mpg. The ICE has not even turned over yet so it is quite easy to pick it out … You will find the same under warp stealth, regen and EV in the Prius I or II as well. The gph use under EV is below the SG-II’s display resolution (less then .1 gph) but it is recording something > 0. Even with warp stealth showing 150 +, or regen around the same depending on speed in the Prius-I or II, you are recording fuel use when none is being consumed. At 150 + (regen or warp stealth w/ the ICE still spinning over) or 500 + mpg’s while tooling along under EV or regen below 41 mph, the modes do not skew the overall as much as you might think. The SG-II is calculating FE in a manner involving air flow, not injector pulses like the SuperMid and that is about the best thing we have given the OBD-II protocol does not spell out the proper data stream to calculate fuel consumption directly. Maybe OBD-III will but it is not in the cards for OBD-II that I know of?

___Either way, once you have calibrated the distance/speed and the gallons offset at each and every fill (this also calibrates to your driving habits and temperature compensates throughout the 4 seasons), the SG-II readout will come a lot closer to your actuals then the OEM MFD by a long shot. As an example, the Prius-I’s last tank came in at 79.13 top off to top off and the SG-II displayed 79.1 after some 392.5 miles. The MFD was showing 83.4 after the same. At 0% mph/distance offset and a + 2.3% gallonage offset from the previous tank, I could not expect much better then that given how FE is measured via OBD-II in the first place?

___Good Luck

___Wayne

I agree, for normal driving, the SG is more accurate than the MFD. But when driving in the 100+ MPG range, the ICE is off 3/4 - 4/5 of the time. The SG will be wayyyyy off. When we calibrated the SG at HF 2006 for the mileage challenge, we took a small sub 100 MPG segment and calibrated it to the MFD. I think it was +5%. But since the calibration was done on a sub 100 run, it had less ICE off time and will not be completely accurate either. If the SG guy will tell us what the assumed fuel rate is during ICE-off, we can calculate what the calibration should be.

While we are on the subject, why didn't we use a SG during the Insight marathon? I know it wouldnt have been accurate but it would have given us more granular feedback then the ICD. We might have known if our 1.2 l/100 km segments were closer to 1.1 or 1.3.

Hi Dan:

___Same reason as you hypothesized. Unless it is calibrated for those maximum FE runs, you are off by some margin. Nobody drives like that for days and days and if they are, they have calibration numbers to help bring her back into cal.

___I will speak with Ron next week about the 0 RPM condition and forcing FE to 9999 or GPH to 0.000. That should suffice? It would not help the Prius I or II during Warp stealth or Regen above 41 mph but it would for EV.

___Good Luck

___Wayne

Wayne,
While you are at it, for the Hybridfest MPG Chalenge this year we will be using Scangauges for certain vehicles (ie Prius' that think they will be achieving over 99.9 mpg).

We are open to suggestions from you and others on the best calibration settings to enter.

___I will speak with Ron next week about the 0 RPM condition and forcing FE to 9999 or GPH to 0.000. That should suffice?


Yes, that will suffice. Thanks!

Wayne,
While you are at it, for the Hybridfest MPG Chalenge this year we will be using Scangauges for certain vehicles (ie Prius' that think they will be achieving over 99.9 mpg).

We are open to suggestions from you and others on the best calibration settings to enter.

Eric,
I would recommend the following:
Reset both the MFD and SG. Leave the SG calibration at 0%. Have Wayne drive the MPG challenge route. THen force charge the battery until the MFD drops below 99.9. Compare the MFD to the SG and calculate the calibration setting. Repeat for each type of car and set all SG's similarly for each type of car.

Too bad I can't make it this year. I would volunteer to do calibration runs.:(

Hi Eric:

___I met with Jerad today to go over the Clinic course and add some extras. Very very productive day indeed and the students are going to receive yet another bonus (2 in fact) from what we came up with. Anyway, Jerad should be running a whole tank through for calibration numbers in very short order. There are only 4 or 5 guys you can get the calibration numbers from as a heavy P&G’er throughout an entire tank would be needed. Jerad, Marc, Chris, Dan and Jim do not really have any full tank - P&G calibration numbers that I know of but Jerad will work on it. His short 20 miles per day is going to take him a while and I do not know if there is time. I will not have a Prius II to run through a tank until at least next week at the earliest myself darnit :(

___Dan, always serving to please ;)

___What I would like to do is run the course (or our Clinic course?) for an entire day over maybe 300 miles (tank top off to top off) and really lock down those calibration numbers. I have the Prius-I’s Speed/Distance - 0% (actually a negative .8% but you cannot input that small an offset) and total Gallons needs a positive 2.3% offset. This is not a Prius II however :(

___The good thing is that even with a slightly offset + or – 1.5%, everybody will have the same handicap other then comparing against other non-Prius hybrids w/ a % above EPA combined or some other such thing?

___Good Luck

___Wayne

Hi Eric:

___I met with Jerad today to go over the Clinic course and add some extras. Very very productive day indeed and the students are going to receive yet another bonus (2 in fact) from what we came up with. Anyway, Jerad should be running a whole tank through for calibration numbers in very short order. There are only 4 or 5 guys you can get the calibration numbers from as a heavy P&G’er throughout an entire tank would be needed. Jerad, Marc, Chris, Dan and Jim do not really have any full tank - P&G calibration numbers that I know of but Jerad will work on it. His short 20 miles per day is going to take him a while and I do not know if there is time. I will not have a Prius II to run through a tank until at least next week at the earliest myself darnit :(

___Dan, always serving to please ;)

___What I would like to do is run the course (or our Clinic course?) for an entire day over maybe 300 miles (tank top off to top off) and really lock down those calibration numbers. I have the Prius-I’s Speed/Distance - 0% (actually a negative .8% but you cannot input that small an offset) and total Gallons needs a positive 2.3% offset. This is not a Prius II however :(

___The good thing is that even with a slightly offset + or – 1.5%, everybody will have the same handicap other then comparing against other non-Prius hybrids w/ a % above EPA combined or some other such thing?

___Good Luck

___Wayne

I am in the middle of a tank now and I've never used the tank fillup feature of the SG-II. I will try to remember to reset it tomorrow morning, but that still means by next sunday I will only have about 75 miles (my 23 mile route is only twice a week and in this weather I'm biking to work most if not every day, plus some tooling around on the weekend). I can compare this to change in MFD to see if it's still within the range but that doesn't help a whole lot, and it's still not comparing to actual fillup. I know my MFD has averaged about 2.5% optimistic vs real world so that could be factored in.

I tend to agree about not worrying too much about whether we can get an exact calibration, as long as it's the same for everyone. I can think of only a few people that might care if the SG were to report 100 vs an "actual" of say 102. ;)

___The good thing is that even with a slightly offset + or – 1.5%, everybody will have the same handicap other then comparing against other non-Prius hybrids w/ a % above EPA combined or some other such thing?

___Good Luck

___Wayne
Agreed, as long as everyone uses the same calibration on Prius II's, all will be fair. My concern about accuracy will come into play when several of the Prius pilots knock off the top Insight pilot. I just don't want disputes about SG calibration to diminish the feat.:D