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I just filled up and the SGII vastly under reported the amount of gallons used - 1.25 gal or 8.4%! :confused: Thought I was getting a 34.1 mpg tank & actual was 31.56, an 8% difference. I've had the SGII since the first week this year (7 Tanks) and have been fluctuating between 3.0 - 5.0%. In fact over the last 4 tanks, I've used less gas than the SGII reported. This drastic change almost caused me to run out of gas. If I had chose to fill up at home rather than near work I'd have been stuck on the Tollway in 10F weather!!!:mad: And this is with a 0.9 gallon safeguard (SG tank size 16gal, actual 16.9 gal).

I'm wondering if it is common to have such a great fluctuation? Does anyone have similar experiences? The only explanation I can think of is that the gas pump calibration is off and I received much less gas than reported. Any suggestions or feedback would be appreciated.

Cheers,

Stephen

Hi Laker:

___In my experience, the colder it gets, the more offset after each tank fill has to be dialed in. The last two weeks in Chicago have been pretty miserable and 8% offset is what I have my Accord dialed back by in the winter if that helps. During the summer, I am at parity to + 2%. You are offsetting after each fill, right? With the offset, your actual and shown will be a lot closer as the offsets change with the seasons.

___Secondly, do you have a low fuel light in your vehicle? You should know the approximate gallons left from low fuel and use your SG-II’s current aFCD to gauge your distance before fuel starve. You have to take some responsibility for this as the SG-II can only pull so much data off the OBD-II bus and FE by direct ECU calc is not one of them.

___Good Luck

___Wayne

Wayne,

You are so right. The weather here in Chi-town has been down right Arctic and I'm a Canadian! Avg temp for that tank was 17F (2/9 - 2/18). Oddly enough the avg temp during a previous tank (1/27 - 2/1) was colder (14F) and the recal only increased from 3.9% to 5.0%??? That's why I thought this fill up was so odd. FYI - I recal the SGII at each fill up. I'll just chalk that up to the cold stealing the mpg's.

I've also learned my lesson and will pay heed to when the low fuel light. Thanks for the tip of using aFCD to gauge the amount of fuel remaining. Quite useful and overlooked. I think the light comes on with 2.5-3.5 gallons remaining.

As always, you are wealth of knowledge with a willingness to assist. :)

Oh yeah definitely pay more attention to the low fuel light than the scan gauge. I know for me my light comes no when there's about 2.3 gallons left. So even if somehow I only get 20mpg, I still have at least 40 miles range until I'm stranded.

I just filled up and the SGII vastly under reported the amount of gallons used - 1.25 gal or 8.4%! :confused: Thought I was getting a 34.1 mpg tank & actual was 31.56, an 8% difference. I've had the SGII since the first week this year (7 Tanks) and have been fluctuating between 3.0 - 5.0%. In fact over the last 4 tanks, I've used less gas than the SGII reported. This drastic change almost caused me to run out of gas. If I had chose to fill up at home rather than near work I'd have been stuck on the Tollway in 10F weather!!!:mad: And this is with a 0.9 gallon safeguard (SG tank size 16gal, actual 16.9 gal).

I'm wondering if it is common to have such a great fluctuation? Does anyone have similar experiences? The only explanation I can think of is that the gas pump calibration is off and I received much less gas than reported. Any suggestions or feedback would be appreciated.

Cheers,

Stephen


I had to spend some experimenting to get the SG well calibrated. Calibrating by using the fillup->dial-in amount of fuel procedure seems to be too coarse.

First of all, check that you do not have any fuel-cut setup causing problems. The newer SG has fuel-cut set as default, but this will usually cause SG to under-report rather than over-report consumption.

I calibrated by comparing against the car's internal consumption gauge, checking and resetting for each trip for some period.

What is your SG's offset in %? It seems to calculate very accurately, so if it is not close to 0% you should be suspicious.

I have actually considered bringing along a 2-3 inch wooden ramp to tilt the car while fuelling, to avoid air pockets at the top of the tank from spoiling the fillup accuracy.

Bomber991 - Thanks for the encouragement to not ignore that little yellow light! :D

Shrek - My current offsets are +7.4% gallons & +2% miles. Not certain of the fuel cut but believe it is set to a value of 15 but I can't be certain. Diamondlarry & I played around with that about 5 tanks ago and it seemed to be correct until this tank.

Sounds like you had a short fill on the previous tank. I have seen fill differences up to almost 10% by actuals. While I don't recommend doing this on a regular basis.... due to the EVAP system.... I'd fill it to the very top of the fuel fill pipe on 2 consecutive fills and set your default % adjustment. Since starting with the SG... I've gone from +1.6% to 0.3% to +1.1%.. and my latest calls for +1.8%. But, I've never seen a SG error of 1.25gals. At this point, I'm going to average over a few fills and set & forget it. Your choice.

From what I see, fuelcutoff should be set @ your idle TPS +1. If your TPS reads 14 @ idle, then 15 would be correct for you. You won't see much DFCO action on your automatic, its more a factor w/manuals.

Is your +2% mileage adjusted to your speedo or your odo? If speedo, adjust it to your odo instead. My Toyota speedos seem to read about 2MPH higher than the odo. At 0% SPEED, my ODO differences are less than 0.5%.

Bomber991 - Thanks for the encouragement to not ignore that little yellow light! :D

Shrek - My current offsets are +7.4% gallons & +2% miles. Not certain of the fuel cut but believe it is set to a value of 15 but I can't be certain. Diamondlarry & I played around with that about 5 tanks ago and it seemed to be correct until this tank.

Sounds familiar. I was at +10% or so before I realized something was completely off. Maybe just reset to +2 or so, and bring that piece of wood to the same gas-station, same pump twice. Drive the backwheel onto the wood so that the car is angled (no air pockets in the tank), or just fill it to the top at least twice with a very short drive in-between - for each new tank.

My SG is also at something between +1 and +2% - if I remember correctly.