Scangauge Accuracy

I've used my Scangauge for about 5 or 6 fillups now and I noticed that the mph is off by about 2 mph (the Scangauge being lower). But, the odometer is dead on.

I'm probably missing something, but this doesn't seem logical. If the speedo is off, wouldn't the odometer be off?

GA

 

I know my mpg for a tank is off from the excel file i use to log my fillups etc. Other than that it is fairly accurate. The gallons used is right on when I fill up.

 

It's not a mechanical connection between the speedo and the odometer like the good old days. It's usual for the speedometer to read different (Higher) than your real speed. Your scanguage miles driven matches the odometer perfectly because it's geting the same information the odometer is from the trucks sensors. Mine also matches and it's MPH reading is very close to what my GPS shows for speed.

 

X2
My the scangauge matches the GPS. However, the needle on the dash is about 2mph off. It's probably due to the 'needle' not being set precisely to the dash -but the data its receiving is accurate.

 

I think this is the key - same station, same pump, and LET IT SHUT ITSELF OFF THEN STOP !!. Mine was pretty darn close until I started trying to top off the tank, which seems to vary depending on temperature, filling station etc. I believe the gas foams up or something, kinda like a bottle of pop, and sometimes you can't full the tank all the way to the top, but other times you can. Basically if you follow their instructions, it will be pretty close. I think I'm gonna start doing that gain.

 

It seems to me, and I say this having run only two tanks thru my scangauge, that any time you change your routine significantly: ie, pull a trailer then not, haul around a bunch of sand for traction or whatever, work tools then not; that you need to re-calibrate the SG.
Remember how you were to fill the tank the first time but not hit the refill button; then refill and hit refill and adjust the gallons on the guage to match? That was telling the guage to enter a fudge factor for your tank and filling technique, a factor that it constantly refines to the smallest correction factor possible.

If you do something that throws off your milage, which SG remembers and constantly updates, Then I think you need to re-do the calibation procedure to reset the SG memory, sort of.

SG only knows, and can only compute, based on past history.

 

my scanguage seemed to read mpg accurately on the first tank i ran on it, which was an avg of 19mpg. now it is reading that im getting like 10mpg. can someone possibly tell me what im doing wrong? i have a big roadtrip in 2 days and i need to fix this

 

Do you enter the gallons you fill with on every fillup? You're supposed to do that as a calibration. If so, you can try resetting it and going through the setup again:
http://www.tacomaworld.com/forum/2nd-gen-tacomas/23461-scangauge-accuracy.html#post324615

 

another thing that bought my accuracy down to with in 0.1 or 0.2 gallons each tine i have filled up is to set the cutoff point a lot lowerr then the default.

If you watch , when you take your foot off the gas the mpg goes to 9999; this means the computer is no longer measuring anything, consequently all your coasting time is not part of any calculation.

I set my cutoff at idle throttle position (TPS) +2 or , on my truck, +16 as my idle position is 16, the book says +4 or more , but I found that to really thro off the observed results.

I have found that if I maintain a TPS of 20 to 23 I tend to get maximum MPG for whatever situation lI am in at the moment; cosequently I can pick the right gear for that particular driving situation (with an auto I dont know how this all works out , you just have to experiment).

Totally stock with a Leer topper (180 # or so) and maybe 150 pounds of tools in the back; I typically get 19.4 to 20.6 in in town stop and go and on flat ground no wind interstate 65 speed control I can reliably expect 21.4 to 24.8 (instanteanous) and 21.+ average. You go 70+ and all bets are off; you need to hit the bank before a trip like that. You bought a big motor so there you go; sure glad I didnt get the 270 HP Nisson (lot of other reasons too, but . . . .)

I display Speed, TPS, MPG and Instaneous MPG.
My tank milage and odometer mailage are always dead on. truck spedo reads 2-3 high (seems to be endemic), but odo always right there.

I dont baby it; but I am not a 20 something idiot either.

 

i just got my scanguage and installed it on a full tank. soooo...

1. will it throw off the calculations if i fill up just a half a tank. and...

2. how can i change the tire size in it. i think the stock tires are 245/75/16 and now i have 265/70/16 mickey thompson mtz so i would think that would make a difference

 

Both of those topics are covered in depth either in the scan gauge manual or on their website, or both.

 

I check mine with every fill up before i drive off. Most of the time I too am within .1-.3 of what I took to refill. No problems so far...