Scangauge accuracy/calibration issue

[Lucias_D]

I wanted to share my scanguage issue as of late and see of others have had this happen.

I just went through almost a complete tank of fuel using P&G techniques. During this my mpg averages (via scanguage) climbed much higher than expected. 70-80mpg averages seemed too good to be true (51 normally w/o P&G). When I finally filled the tank (near empty), my readings were waaaaay off. I averaged approx 55mpg and scanguage said I was at 62+ and had another 100+ miles left in the tank

Up until this point, my scanguage was accurate to within .1 gallon during full ups and had no issues. I did have my refresh rate on high which Scanguage does say can be inaccurate on some vehicles. I wonder if the P&G messed with my readings due the fast refresh, because ormally (before this tank) I just set the cruise and go. I changed it back to normal on this fill up.

Have any of you experienced a sudden loss of calibration and/or weird experiences on the fast refresh time?

2002 golf tdi 5spd

 

[SFHGolfTDI]

I really don't think refresh rate is the issue, but I could be wrong. It is, however, well documented that changes in driving style from one tank to the next, or in driving conditions (city vs. highway) WILL alter your SGII readings. So my guess is, your use of P&G techniques you hadn't used before was what caused the change in SGII estimates.

Also, I noticed your in Sacramento. You should try this fuel and report back. Since you seem to be interested in fuel efficiency, run a tank and tell us what happens. You may want to be careful if you have an original IP and have run any blends of bio in the past though.

 

[meerschm]

If you are altering the fill process, you are effectively changing the capacity of the tank, and need to re-calibrate the scangauge.

http://www.scangauge.com/wp-content/plugins/download-monitor/download.php?id=1

see page 20

 

[SFHGolfTDI]

If you are altering the fill process, you are effectively changing the capacity of the tank, and need to re-calibrate the scangauge.

http://www.scangauge.com/wp-content/plugins/download-monitor/download.php?id=1

see page 20

I didn't see that he said anything about a different fill process ??

 

[meerschm]

I may have misread the P&G for some kind of pump manipulation to get more fuel into the tank.

 

[SFHGolfTDI]

I may have misread the P&G for some kind of pump manipulation to get more fuel into the tank.

P&G = Pulse & Glide, a hypermiling driving technique. You are probably thinking of a ventectomy.

 

[meerschm]

Sounds like some kinky driving technique. reminds me of a joke i will not share here.


anyway, on second read, if the scangauge folks warn that a high refresh rate can cause inaccuracies, seems not much of a need to look further.

 

[Ike T]

It is, however, well documented that changes in driving style from one tank to the next, or in driving conditions (city vs. highway) WILL alter your SGII readings.

This is my experience. I had mine calibrated to 0.1 gal accuracy against actual usage for over a year. Then my driving conditions changed from a consistent route to inconsistent routes. Hasn't been "accurate" or even "consistently inaccurate" since the change in driving.

 

[VeeDubTDI]

I experience wild fluctuations of the ScanGauge's accuracy based on my driving style. If I'm consistent, then it is consistent. If I mix it up, then all bets are off.

It's because of this that I gave up on trying to use the ScanGauge for MPG tracking. I just monitor tank-to-tank with good old hand calculations. I can pretty much tell what I'm going to get based on the odometer reading and the fuel gauge position anyway.

 

[meerschm]

I actually like the SG for GPH. seems about right, and I like how it goes to 0 when slowing down in gear or down a hill.

can also see differences from warming up vs up to temp.

 

[Lucias_D]

Hmmm, thanks for the replies. I didn't know my change in driving style could alter the readings that much. Seems to me that if you calibrate something, it shouldn't change unless you change fuel delivery, timing...or something like that.

It's been 200ish miles since I filled up and 1.) changed my refresh rate, and 2.) Recalibrated. The irregularity is still occurring with P&G. Normal/cruise control driving shows low 40s which I know is closer to 50, while P&G still is showing 65 instead of the 70's it was before. While the recalibration did improve my accuracy with P&G, my reading are way off when driving normally.

I haven't changed my fill process either. I've done a ventectomy and every time I fill up, I take my time and fill to the top of the filler neck.

I feel pretty confident now that this issue is because of my driving style changes. Since I don't feel like doing P&G on the regular, I think I'll keep my calibration for steady driving. The car is new to me so I'll still need more seat time reconcile fuel gauge/trip readings. Then ill be able to better estimate FE, and "until empty" figures.

Thanks for the help and I'll have to check out that fuel