$70 OBD2 MPG Meter

[QuickLTD]

Which one did you guy that was inacurate?

[mazade]

I'm assuming that he's talking about the Kiwi MPG... and I'm betting that he's referring to the Instantaneous MPG mode. If you're not too steady with your pedal foot that thing can/does jump around a good bit.... not to mention in stop & go city-driving.

[QuickLTD]

That's what I was thinking because the AutoMeter gauge isn't out yet to my knowledge. They are generally accepted as one of the best in the industry for automotive/racing instrumentation. I cant imagine putting their premier brand name on something that didnt function as promised instead of one of their lesser brands. I guess we will see.

[tom43571]

I was referring to the KIWI MPG. The inaccuracy was not due to my foot adjusting on the pedal. I have set the cruise on the highway and at no time did it read over 27mpg (even down hill). When I got off the highway, I filled up and did the math, 41mpg average for the fill up. Either I75 through Ohio is horrible on gas mileage or the gauge is inaccurate.

[mazade]

How very interesting... well as I already did in the case of my Kiwi MPG, it got sent back for an issue with its/the CANBUS protocol... it stopped working for my 09 aveo, but still worked in other vehicles, and the aveo is just fine, and the guy at PLX said they discovered such an error with the KiwiMPG.
First generation of the device, bugs can usually be expected. Don't hesitate to get in touch with them, they should be more than happy that these bugs are being discovered and are able to be worked out 'sooner' rather than 'later'.
Sorry to hear about your troubles though; I hope things work out for you there.

[gone-ot]

Originally Posted by tom43571

I bought one and it is wildly inaccurate. It is more of a random number generator than an MPG gauge.

...I just installed an AutoMeter 9100 ecometer (MPG gauge) in my '09 Vibe and encountered similar results: (a) only the MPG-average display is usable; (b) the three other displays (MPG-instantaneous, MPH and RPM) never seem to settle-down on a single number, even at constant freeway speed with cruise control engaged...you'd expect the MPH and RPM numbers to be stable under these conditions.

...I can somewhat rationalize the fluctuations in MPG-inst. because every wind-gust, bump in the road and incline/decline are being "adjusted" via fuel-squirt volume and duration by the ECU, so swings coinciding with road conditions makes sense, however, this doesn't seem to hold for the ecometer.

...and, unless I did something wrong (which has a high probability), the first gauge reading was 38.2 mpg vs. actual tank-fillup of 34.4 mph...or 0.89 "tweeking" factor. Am on second tank now to get a "second opinion" before I attempt their "efficiency number = 100" recalibration process.

...stay tuned.

[The Atomic Ass]

Originally Posted by tom43571

I was referring to the KIWI MPG. The inaccuracy was not due to my foot adjusting on the pedal. I have set the cruise on the highway and at no time did it read over 27mpg (even down hill). When I got off the highway, I filled up and did the math, 41mpg average for the fill up. Either I75 through Ohio is horrible on gas mileage or the gauge is inaccurate.

Originally Posted by Old Tele man

...I just installed an AutoMeter 9100 ecometer (MPG gauge) in my '09 Vibe and encountered similar results: (a) only the MPG-average display is usable; (b) the three other displays (MPG-instantaneous, MPH and RPM) never seem to settle-down on a single number, even at constant freeway speed with cruise control engaged...you'd expect the MPH and RPM numbers to be stable under these conditions.

Digital meters do this. Unlike analog gauges there's nothing dampening the reading, so it changes as fast as it recalculates. The factory gauge in my father's Bravada will move around on the instant setting at a steady speed/level ground as well.

It was also my assumption that these gauges had to be calibrated to the specific vehicle.

[gone-ot]

Originally Posted by The Atomic Ass

It was also my assumption that these gauges had to be calibrated to the specific vehicle.

...yes...and, no.

According to the AutoMeter "Installation Instructions" (p/n 2650-1424-00): "...In some cases (primarily with MAP brand vehicles) you may need to fine tune the math formula used by the ecometer to calculate your vehicle's MPG."

...where: "...some engine/vehicle types (most Chrysler vehicles, diesel engines, etc.) you will be required to input a value for the engine size of the vehicle. These vehicles utilize a MAP (manifold air pressure) sensor and the ecometer needs a little more information in order to calculate fuel economy accurately." To my knowledge, the Pontiac Vibe (nee' Toyota Matrix) isn't a MAP vehicle.

However, after a second tank-fillup comparison, a common "tweeking" ratio of between 0.889-0.886 seems to exist. So, I'll crank in a "tweek" number 89 (factory setting is 100, adjustment range is 60-to-140) and see what happens. I'll also check the DSP (displacement in Liters) value which *should* have automatically been set to 1.8, if not, then I'll manually set it too.

As for the other displays, the RPM and MPH displays seem to constantly "cycle" (above, correct, below) by 0.6K rpm/mph, over and over. Maybe it's useful to others, but my wife will never understand it!

However, the MPG-instantaneous display is totally worthless! Random swings between 12mpg to 114mpg while driving with cruise control on don't really *tell* you much, and it NEVER seems to settle down or settle around a common value.

One VERY interesting bit of information is how the MPG-average value clicks down in value -- ie: XX.9...XX.8...XX.7...XX.6, etc. -- as you sit at a stoplight; it really makes you painfully aware that you're "eating" gasoline without gaining milage! And, the numbers click down pretty quickly!

Lastly, the 15 colored LEDS around the circumference of the gauge face act just like a "colorful" vacuum gauge, but a vacuum gauge is much cheaper than the ecometer, ie: red(left) = BAD, orange(central) = poor, green(right) = good.

P.S. -- list price $69.99, got mine for $60.66+S/H.

[loulan]

it sounds good.