Auto Meter 9100 ecometer MPG gauge
 

http://www.pfyc.com/mm5/graphics/new/gn2120.jpg

OK, I've had my ecometer since 24-June-09 and have now gone through four tank-fillups, so it's time for a review.

1) of its four operating modes (MPG-inst, MPG-avg, MPH, RPM), only the MPG-avg seems truly useful (displayed values on the other three modes "jump" around too much to be really usefull).

2) it has a single calibration setting (EFF=XXX) which seemingly affects only the MPG-inst and MPG-avg readings. It comes preset with EFF=100, but can be adjusted anywhere between 60-and-140...and, although the EFF-number entered/displayed is an integer, I'm suspecting that it actually represents a decimal-place efficiency value, ie: 100 = 100% = 1.00, etc.

3) the OEM preset EFF=100 produced MPG-avg readings that were too high:

tank#1 0.893 = (1.00)*(34.1mpg/38.2MPG)

tank#2 0.861 = (1.00)*(32.1mpg/37.3MPG)

tank#3 0.935 = (1.00)*(34.5mpg/36.9MPG)

...so, I tweeked the setting down to EFF=90, which yielded a closer correlation between the tank-fillup mpg value and the ecometers' MPG value:

tank#4 0.887 = (0.90)*(33.8mpg/34.3MPG)

...so-o-o-o-o, apparently, the Pontiac (Toyota) 1.8L (2ZR-FE) engine needs an EFF=0.88-0.90 setting. Next tank-fillup should confirm this.

...although not provided in the owners/instruction manual, here's the basic "calibration" formula:

EFF(new)/EFF(old) = mpg(tank)/MPG(meter)

...so:

EFF(new) = EFF(old)*[ mpg(tank)/MPG(meter) ]

where:
EFF(new) = new calibration number derived from tank-fillup vs. MPG-avg value and old EFF nuimber.
EFF(old) = the calibration number the ecometer had during the test period.
mpg(tank) = value from tank-fillup, ie: mpg = miles/gallons.
MPG(meter) = value from ecomoter MPG-avg display.

4) there are no corrections for distance (MPH) or fuel (GALLONS) values, just the single EFF=XXX value; simple, but not easily "correctable" for multiple changes (tires/wheel sizes, etc.).

5) both the RPM and MPH readings are 3-digits: (a) in 1,000's of rpms, ie: 1.42, so accuracy only to 10's of rpms; and, (b) 64.9 mph...but, both constantly "jump" around by 3 values in the last place, making it a guessing game as to what the actual value is.

...more to come.

Sounds interesting. I wonder where yo got it from.

I'm looking for a cheaper alternative to the Scangauge but I don't want to get into soldering and wiring. It would be much nicer to just plug into the ODB-II port. I really don't want anything other than average MPG.

edit:
I can already plug my Vagcom cable in with my laptop and get some readings, but I can't find anything giving me mpg readings. (cheap vagcom ebay cable, not the real thing)

...ordered it on-line from Big Boys Custom Toys LLC, Enfield, CT...cost $74.50 USD including shipping & handling.

...I'm almost at the point of NOT recommending this device, because, so far, only the MPG-avg mode seems to work acceptably. The other three modes (MPG-inst, MPH and RPM) all "jump" around continuously, never settlling down on a fixed number, almost regardless of what the car/engine is doing.

...I don't know if the problem is with the unit or the car interface (2009 Pontiac Vibe 1.8L with CAN-OBD-II) and little help comes from Auto Meter (they were VERY prompt in responding before the sale, but are now disturbingly silent after the sale). I'm trying to find out if others are having similar problems either with the unit of with the unit installed on Pontiac Vibes and Toyota Matrixs and Corollas.

...the good news, however, is that once "calibrated" the MPG-avg reading displayed at the end of a tankfull of gas is quite close to the actual tank-fillup value.

...what vehicle are you thinking about installing it on?

Old Tele man -

I can see the MPG jumping all over the place, but the RPM and MPH should reflect what's happening on your dashboard.

It's too bad. A pretty product that doesn't seem to deliver the goods.

CarloSW2

...while driving with cruise-control set at 65 mph, on flat/smooth highway, both the RPM and MPH displays continuously "jump/drift" up/down, ie:

65 mph (speedometer) = 64.4 - 65.0 - 65.6 mph on meter
2700 rpm (tachometer) = 2.68 - 2.70 - 2.72 rpm on meter

...the road is perfectly flat, there were no other cars either in front or beside me (I drive to work VERY early in the morning). And, I cannot detect ANY actual up/down changes in either speed or engine rpm (seat-of-pants or dash gauges), but the ecometer continuously cycles up/down by about 0.6 mph and 0.2 rpm.

...only the MPG-avg display is "constant," with understandable periodic changes resulting from traffic (truck windstreams), wind, road grade/slope, stoplights, etc.

...and, the MPG-inst display is even worse, with values randomly swinging between 99+mpg and 2mpg popping up under same conditions as for RPM and MPH.

...I'm on my fourth e-mail to Auto Meter asking "what gives?" But since the last two weren't answered, I'm not "...holding my breath...".

Old Tele man -

That sucks. Last year I was doing some data logging with a different OBDII gizmo, and I got pretty regular data :

This data was sampled between 1 and 5 seconds. The sampling depends on how quickly the ECU/PCM returns the request for data. The above boils down to :

HOWEVER, the above data was not gathered with an eye on your observation. It's not continuous, I sorted it for you to see.

If I get the chance, I will attempt to replicate your test conditions, albeit at a lower speed, and see what I get.

CarloSW2

...I work with digital "instrumentation" and am aware there are three obvious areas where problems can arise: (1) sample-rate, or how fast the data are gathered by the cars' mpu, (2) output-rate, how fast the resultant data from the car's mpu are placed onto the CAN-bus, and (3) read-rate, or how fast the ecometer attempts to "read" the data from the CAN-bus...however, the CAN-bus itself is synchronous.

...and, since the "delta" in MPH readings seem to be a 'constant' 0.6-mph value, it could also be a problem with "how" the ecometer 'chip' translates the data that it's gotten from the CAN-bus.

Hi, I have the autometer 9100 and I'm not seeing the jumping around that you are reporting, so you may have a bad one. I have mine on my 08 Ranger.

John

dyerjg -- "Thanks," for the input...so far, you're the only 'user' to report that what I'm seeing isn't "normal." Knowing that it shouldn't be vs. proving it are two different things.

...now, if I can just find someone using one on a 2009 Vibe for specific confirmation (positive or negative). ...again, very little response from Auto Meter, so I'm making sure I've gathered all the facts that I can.

...just did my seventh tank-fillup(s):

tank#5 0.890= (0.90)*(34.3mpg/34.7MPG)
tank#6 0.905= (0.90)*(35.5mpg/35.3MPG)
tank#7 0.930= (0.90)*(36.9mpg/35.7MPG)

which (surprise, surprise) are all well within my acceptable 'tolerance.'

...I really, REALLY, would like to be able to recommend this thing, but just can't get enthused when only 1/4th of the functions work acceptably...although, for 'driver re-training' it's doing a darn good job...just wish the "other" 3/4ths would work well.

do you have a picture of it in your car thinking about buying it but would like to see how it looks in a car/suv/truck