Scangauge II wildly inaccurate - Resolved

Excellerator · #1 02-04-2007, 06:21 PM

I went and finally filled up the tank for the first time after buying the Scangauge II. I've filled up and gone through one whole tank with it, and so I was finally able to calibrate the device.

According to the Scangauge II, my average gas consumption was 14 MPG... however, through my manual calculations, 242 miles on 11.571 US gallons equals 21 MPG. In order to make it show that I actually burned that amount, I had to adjust it by -25%.

All this time the Scangauge II has been off by 25%?! How is that even possible? Is it due to the rate at which the Scangauge II can update the display? I got it set to "Fast" and to me at least it looks like it's working fine. How would I be able to tell if the setting is not right?

brick · #2 02-04-2007, 08:52 PM

Interesting. I would say double check your base settings (engine size, etc.) and see what happens on the next fill. Part of this may be a bit of variability from one fill to the next on the part of the pump. You shouldn't have to put up with anything as crazy as a Prius tank bladder but even my Accord was off by +/- 5% or more on a regular basis. Even so, my calibration factor with that car was only 4-6% at the very most.

Excellerator · #3 02-05-2007, 11:19 AM

I just went out and checked it, and for some reason it was all on default settings... yet I'm poitive I had it all set up right from day one. It thought the Camry had a 3.0L engine and a 15.0 US gal. tank (though it's actually 2.2L and 18.5, respectively). So yeah, hopefully this should help.

I wish it could calibrate itself.

Fredness · #4 03-10-2008, 07:41 PM

http://www.scangauge.com/support/pdfs/SGMan5_0.pdf

Covered completely in the directions. The MPG is based off injector time, and distance travelled. Since distance can be off due to tire pressure, all these little things need tweaking, and there is NO way to have it "pre-calibrated"...

Probably the best directions I've seen on a mobile device - the directions sold me on the part. Now that I have my WideBand O2, I can start saving up for my ScanGuageII.

Dan · #5 03-10-2008, 09:44 PM

I have an obscenely complicated and obtuse spreadsheet to calibrate to the nearest thousandth of a gallon

holler if you want it.

11011011

Shrek · #6 03-11-2008, 04:59 AM

Quote:

Originally Posted by Excellerator

I went and finally filled up the tank for the first time after buying the Scangauge II. I've filled up and gone through one whole tank with it, and so I was finally able to calibrate the device.

According to the Scangauge II, my average gas consumption was 14 MPG... however, through my manual calculations, 242 miles on 11.571 US gallons equals 21 MPG. In order to make it show that I actually burned that amount, I had to adjust it by -25%.

All this time the Scangauge II has been off by 25%?! How is that even possible? Is it due to the rate at which the Scangauge II can update the display? I got it set to "Fast" and to me at least it looks like it's working fine. How would I be able to tell if the setting is not right?

Be sure to set the fuel-cut setting correctly. For a Toyota you most certainly have dfco in your engine. Without this value being set correctly you will appear to use more fuel than reality. The value should be your idle throttle position plus one (Use the TPS gauge)

Then be sure to fill the tank correctly so that there are no air pockets.

I calibrated mine against the car's native computer. That was much easier.

Maxx · #7 03-11-2008, 08:02 AM

I never set my fuel cut-off, but I KNOW that my car has it... of course idle throttle is 0, I guess that would do it. All that being said, I've gotten consistant results (winter/summer)with a 2.5% offset. But right now the SG2 is in my girlfriends 2000 jetta TDI which I was recently doing work on (timing belt, MAF sensor).

rweatherford · #8 03-11-2008, 09:16 PM

My first fill was off 10.5% today. Hopefully that will be my only calibration needed that is so large.

worthywads · #9 03-11-2008, 11:50 PM

Quote:

Originally Posted by rweatherford

My first fill was off 10.5% today. Hopefully that will be my only calibration needed that is so large.

Don't be surprised if you see a big jump when going from E-10 to straight gas or vice versa.

rmcmast · #10 03-12-2008, 11:20 AM

Quote:

Originally Posted by worthywads

Don't be surprised if you see a big jump when going from E-10 to straight gas or vice versa.

I'm up around 10% now and have been on E10 since at least the first of the year. Before that, I was usually around 7-8%. So E10 makes a difference in the SGII calibration?

Thanks,

Rick