Scan gauge accuracy??

[Jazz]

Has anyone done any testing to check the accuracy of the scan gauge??

I ask this as my SG was showing an average of about 10.5 LPHK. But when I did a 110km test and refueled it showed I had used 15 litres, therefore about 13.5 LPHK. The driving was at 100 kmh on the hume highway. I intent to do further testing but I have noticed some owners posting what seems like incredible fuel economy. Just wondering if they are taking the SG readout as 100% accurate.

I also find the average LPHK just doesnt seem to work out right when compared to the litres used and Km's travelled. I realise "average" figures from the SG are somewhat open to interpretation.

I wish the SG was right but i have my doubts.

(Vehicle is a 2007 D40 auto)

 

[Old.Tony]

A number of factors are involved. Krafty has provided a bit of info about his experiences elsewhere and will probably come past here later - he's got one, and has figured out ways to make it inaccurate or to help it out.

The unit relies on the ECU's information. The ECU would know fairly accurately what the injector durations are and therefore the fuel usage rates would be available. Injector duration and fuel rail pressure with power strokes per minute can be used in a formula to work out the exact current fuel consumption figures. These depend on the injectors actually delivering that fuel rate - new injectors will, old injectors will start to have margins of error.

Vehicle speed is also an important factor and tyre sizes affect the car's knowledge of this. It relies on an aggregate of the ABS sensor information to determine vehicle movement, so if you change tyre size, the car will move a different distance to what the computer thinks, further affecting the ScanGauge.

The best measure is to use your trip meter (accounting for errors introduced by different tyre sizes) and always fill the tank to the same point. You can't assume the bowsers are accurate either - they're allowed something like a 3% error, I think.

In the long run that ScanGauge ought to settle down, but I think things like partial fills will disturb it. It'd be hopeless for me on a long run, because we take jerry cans with us and will stop to whack another 20L in every now and again. I'd have the thing hopelessly confused all the time!

 

[Krankin]

I don't use my SG for fuel economy figures,
I rely on fuel consumed v distance travelled.

Too much buggarising around try to us the SG.

I would rather like a dedicated factory built in econ/fuel use/trip meter system
like the one on my missus' Territory.






.

 

[KraftyPg]

SG is not a real time fuel calculator despite the figures changing like they are real time, it works or a series of averages taken every 4 seconds (or thereabouts) and then averages it's reading out for your trip. The readings are more than likely based on the number of squirts each cylinder gets, your ECU knows how much fuel is in each squirt and SG more than likely just reads this figure uses it against the distance measurements to work out averages.

The reading you get for any single trip may or may not accurately take into account actual economy because there will be times in any trip where your peak economy heads north of 40 LPH (take off and up hill etc) and there will be times where it can register 0 LPH for the opposite reason. If these peaks coincide with one of the readings SG takes it's easy to see how an average figure can get out of whack, over the whole tank all things being ideal you should get a fairly accurate reading which means the "real time" figures should only be used as a guide not as gospel.

One of the biggest factors in producing errors is not setting it up correctly. If you don't set it up with engine size, etc right your readings will be blown out, I tried it once with a tank size of 15 litres when I was stuffing around and it came back with a 400% error and something ridiculous like 250LPH. That's an extreme error but you will also get an error if you set the tank size to 80 litres and fill the tank to overflowing each time, the error will be nowhere near the above example but the pipe holds about 1.5 litres which means SG is calculating 81.5 litres as 80 litres.

You can also create the error by not entering the details correctly at each fill (price doesn't matter unless you are working out costs). SG pretty much reads the exact information that a manufacturers econ meter would read the difference is you program SG whereas the cars that get them factory fitted are pre-programmed for you.

I haven't tested how much difference using the same pump and allowing it to switch off automatically without any further topping up actually does but they make the suggestion in the book so obviously they do it for a reason. I think it's a bit airy fairy to suggest such a thing one because we don't all use the same pump at every fill but also because there are still varying factors even with the same pump. I actually have mine set at 82 liters and I top it up to the very top each time and my tank figures come out within 0.1 or 0.2 of the self calculated figures and my remaining fuel figures are never more than 0.5 of a litre out.

As Tony said partial fills can upset the tank, but they wont effect things dramatically without user intervention. If you get near to empty and add a 20 litre Jerry can to get you another 200ks your LPH figures wont change dramatically, the SG will consider your tank as empty and read 0 for the remaining fuel but it's smart enough to realise that it's running so their must be fuel and therefore the LPH calculations will remain very close to what they were before the top up. Even if you constantly top up providing you don't use the "fillup" option and say you put 20 litres into the tank your LPH will remain very similar to what it was from the last top up. Doing this you might eventually see a large difference in your LPH readings but if all other settings are correct you'd have to do a fair few top ups before things changed that dramatically because not all of the LPH figures are based on what's left in the tank. Even if you do get it out of whack two or three full fills should get the calculations back to normal.

Using the "fillup" option and only putting 20 litres in means SG will try to calculate that it took 20 litres to fill and it thought there was 70 litres missing therefore the error is 50 litres and it will accommodate this in the LPH readings. So never use the fill up option unless you totally fill the tank.

There is a few other things I've noticed with SG but this post is already getting way too long. SG will should serve you are accurately as any other econ meter because it reads exactly the same info as other readers but there are things that a user can do which will influence the readings so it's not infallible.

 

[Krankin]

Thats why I dont use it for fuel figures.

 

[WoodyD40]

I'm finding that the SCII is pretty accurate with how much fuel i have left in the tank. So i'm pretty happy with it. Been a good investment i believe. And its another toy to have in the car to play with when i'm bored sitting at the traffic lights.

 

[merchant]

I have one of these things and question whether they are worth it or not. I guess they are good for accurate temperature readings when up north.

 

[KraftyPg]

It's worth is entirely dependent on what you use it for, even though the LPH might be out at times it can still be valuable for that alone but with something like 100 other functions (yes it's a pity on 4 can be visible at a time but then I'd rather not have another 7 inch screen in the cabin) there is many things you can discover/learn/or play with that may or may not change their worth.

 

[Aussie Frontier]

I use my Scangauge for economy and DTE and after a bit of mucking around its now pretty much spot on. If it says I have 16.5 litres left in the tank then when I fill up its pretty might right on the money.
The things to remember as the other guys have said is its only as accurate as how well you set it up. Changing tyre size and not adjusting it will throw it out .
If you have it set up correctly then its a god send . My low fuel light comes on with only 17 liters of fuel left so thats when I usually fill up anyway. However I have on a few occasions been coming back into town when the light comes on so I rely on Scangauge to tell me how much fuel I really have left.
So far best refill I think was 76 litres and that was exactly how much it was meant to be.

 

[KraftyPg]

You're right on there Aussie it's a godsend when set up right. I've deliberately ran my ute to almost nothing on the gauge twice, once wasn't an issue because it was around town and servos were everywhere but the first time I did it the car had less than 10K on it and I was driving from Eucla to Norseman, it was an edge of the seat ride after the light came on 180 odd ks from Norseman and I was constantly looking at the gauge and the SG to re-assure myself but when I got into Norseman with 4 litres to spare (SG said 3.7) atleast I knew just how much I could trust my ute and SG together

 

[mike1303]

Hey guys,
I've recently put a SGII In my truck and I'm yet to fill up for the first time, I'm wondering when you all filled up? I.e as soon as the light came on or when you think the truck is running on fumes??

 

[merchant]

Hey guys,
I've recently put a SGII In my truck and I'm yet to fill up for the first time, I'm wondering when you all filled up? I.e as soon as the light came on or when you think the truck is running on fumes??

MIke

Go by your manual. I think it says to fill up and use the fill up function. Then after about 1/4 of a tank fill up again using the same bowser and use the fill up function again (just to set the SC11 up properly).

I could be wrong. If i am i'm sure someone will point it out.

 

[Aussie Frontier]

Scangauge says to run down to less than a 1/4 of a tank. It will take a few tanks to get the gauge running accurately.Basically fill up the truck when the light comes on for instance then set the scangauge to the amount of fuel you put in.Try to use the same bowser for the first few tanks that way you stand a better chance of getting the same amount in the tank every time.
After initial setup my scangauge was accurate to a 10th of a litre.
Make sure your speed reading is as accurate as you can get. Setting it up from a GPS is best .Do not rely on any gauges in the truck.

 

[KraftyPg]

On the issue of accuracy once again in possibly one of the silliest places to test my SG I tested it. Border Village to Norseman, 740ks, Nav should do it easy but there is always some doubt and since I don't carry extra fuel the doubt is never too far away. Last fuel before Norseman is 186ks or thereabouts away at Belladonia but I'd done it once so I tried it again. SG was faultless, last year SG was also faultless but I was less confident with it because I hadn't tested it, but this year confidence was up and I let SG do the talking and by the time I got to Norseman I put 72.5 liters in and SG told me I'd used 72.7.