Biggest MPG error you've seen on your uncalibrated gauge? (Nissan X-trail SG/UG)

[wdb]

My SG reports 9999mpg when I am in DFCO and actually getting [infinity]mpg. That is by far the largest error I've seen.

IIRC the SG in the Fit was optimistic but no more than 10%. I played with adjusting it and drove myself nuts for a while. Finally decided to set it, forget it, and use it as a relative measure.

[MetroMPG]

wdb: funny. I LOL'd.

---

Originally Posted by YeahPete

My scan guage turns off when I try EOC. . So I really don't know much better my mileage is if I tried EOC.

Do you have your fuel type set to "Hybrid"? That's what you need to do for EOC (it doesn't mean your car's a hybrid, only that the gauge should stay active while the engine is off but the key is still ON.

[MetroMPG]

I double-checked the gauge settings: engine size was correct.

With the accurate numbers from his gas receipt, I entered a +30% offset for fuel use (not 40% as previously mentioned, but still waaaay off). We'll see next week if that works.

[MetroMPG]

Update: after several tanks, the fuel offset is set at 41.1%

I've never seen one that far off. Crazy.

[Miller88]

For some reason my ELM327 bluetooth scanner keeps identifying my parents Focuscape 2.0 EB as a 1.6L engine. Throws the figures off a bit.

[ever_green]

When I changed the headers on my Subaru, my offset jumped to +15% from +7%. This I later found out was because the car was running richer than before. Scangauge II does not take AFR into equation, it always assumes a 14.7:1 AFR and i think ~12:1 for open loop.
Apps like torque pro have the ability to take AFR into consideration but they are not very accurate from my experience. SG2 is so far the most reliable and practical device I have used.

[gone-ot]

...assumed stoichiometric 14.7:1 AFR is *why* almost ALL mpg meters are seldom 100% accurate...especially, coupled with those times (short trips, cold weather, wot) when the engine is running in "open-loop" rather than "closed-loop" operation.

[MetroMPG]

Yessir.

But 41% off? That should win some kind of prize!

Actually, I think I'll contact Linear Logic and ask them about it. Will post back.

[MetroMPG]

Linear Logic says not only is it normal, but the developer's own car has a 30% offset:

Hi Darin,

There is nothing wrong with numbers that high, each vehicle is different. The only important part is that it is accurate from one tank to the next.

Depending on what sensors are available for the ScanGauge to calculate fuel use, it has to assume certain values for information that isn't there.

If the assumed values are off too much it can make the calibration % higher or lower. My car is about 31% usually, our F150 is at 1% or less most of the time.

Regards,

[darcane]

Originally Posted by MetroMPG

How about 40%?

I loaned him my ScanGauge and set the engine size. We were really impressed with the early numbers he was getting, but became progressively more skeptical as the gas gauge approached E.

What all do you calibrate on the SGII?

On an Ultragauge, it needs engine size, and you calibrate distance and fuel consumption. If I have it set for one car that is on one end of the ranges and move it to a car that would be on the opposite end of each range I could see it maybe being that far off, even if I change the engine displacement.