fuel consumption on a diesel engine

**Aberk** · 05-26-2009, 08:59 PM

I have sniffed SCIIs requested PIDs when it is set in diesel mode. IIRC they poll MAP, EL, IAT, RPM, Speed.

**Aberk** · 05-26-2009, 09:02 PM

Originally Posted by Gilbo

Here in Australia, there are several members of an internet community for Toyota 4WD owners that are operating ScanGaugeII trip computers that seem to be getting accurate figures for fuel consumption in diesel engines. This seems to be evidenced when they fill their tanks there is less than 2 litres difference (over about a 150L fill) than what the ScanGauge indicates. I assume the gauge accumulates the instantaneous fuel figures to work out how much fuel has been used. This also must be the same way to calculate the average fuel consumption between fills.

When they do this, how many times have they logged previous fills? The SCII is designed to become more accurate with time and user input. This is great for enthusiasts, but not so great for you average consumer.

I question the accuracy of the fuel consumed after the first couple of fills with little other data to go by.

**Aberk** · 05-26-2009, 09:03 PM

Originally Posted by rodweb

Gilbo, I am a diesel Toyota owner in Australia and am interested in this too. The problem is the standard OBDII data does not include anything which can be used to estimate diesel fuel consumption.

I have seen some discusions on a technical OBDII forum somewhere and it was indicated that in all probablity, Scanguage was pulling up some Toyota Specific Manufacturers PID codes that provides some insight into Diesel fuel consumption. From memory, it was likely that the fuel consumption was deduced from injector timing which could be used to measure fuel useage but my memory is a bit rusty. Me? I just log each tank full at the servo and caclulate consumption that way. See my build up for info.

One of these days, I will add OBDII to my car PC, but not for a while yet.

SCII does not use manufacturer specific PIDs. I met with them at SEMA and asked. Plus I have never sniffed any such PIDs.

**pwb** · 05-27-2009, 12:31 AM

Originally Posted by Aberk

When they do this, how many times have they logged previous fills? The SCII is designed to become more accurate with time and user input. This is great for enthusiasts, but not so great for you average consumer.

I question the accuracy of the fuel consumed after the first couple of fills with little other data to go by.

he he, the product is a crap. If it cant read correct before some fills and userinput, what the fu**, does anybody buy that? If there is 2-3 users of a car in the family then every person must use the car the same % of the time every filling so that crapy product still can show correct reading. If this is correct then i hope all that have bougth SCII and have it on a diesel engine returns it to the seller and get there mony back.

/PWB

**firstorbit84** · 11-19-2009, 08:11 PM

I use ScanGaugeII on my TDI (Diesel) and I love it, and it is VERY ACCURATE when properly adjusted...

Yes, you do have to fill your tank every time you refuel and tell it that you filled up...
Yes, it will take some calibration (i.e. telling it how much fuel you put in) on the first few tanks to be really accurate..

However, once you do those things, it becomes frighteningly accurate down to the tenth of a gallon and tenth of a mile, so all you have to do after a while is just hit the "Fill up" button.. Besides, would you ever buy a new watch and expect it to be perfectly correct right out of the box?? Probably not, because you'd have to set it! The same thing with SGII.

Plus on top of being a great trip computer, it shows 4 live gauge readings which can cycle through a huge number of choices and even program your own. It can also read engine codes, and tell you all the gauge readings when the code was thrown, as well as clear the code on the fly.

**PhilG** · 11-21-2009, 07:31 AM

Three of my past Ford F250/F350 diesel trucks (a 1999, 2003, 2004) all had trip computers in them that showed miles per gallon or L/100km and miles/km to empty. The mileage numbers seemed reasonable (I never verified) but the miles to empty was scary accurate. I used to fill up an my local station, run 400km to a place to pick up a trailer and them 400km back. As I returned to the same station the computer would show 10 or 20km to empty and I would stuff 150L into a 135L rated tank so it was empty. If I started and stopped the truck several times on the way back, it would loose it's accuracy for some reason. So this accurate data must be coming from somwhere. I'm hoping to be able to set up something this accurate in my carputer when I finally get it installed.

**firstorbit84** · 11-21-2009, 01:44 PM

the other thing worth mentioning about the scangaugeII is that when you set it up initially with your engine size and tank size, the tank sizes are only to the FULL gallon and they suggest that you pick the full gallon lower than your actual tank capacity.

For example: on my TDI I've got a 14.5 Gal tank, so I set my scangauge to a 14 Gal tank, which means that the miles and fuel remaining are only counting down from 14 Gal, which would actually leave me with 0.5 Gal of fuel if I drove them all the way to zero. I try not to do this, as my fuel light comes on with about 50-60 miles remaining on the SGII