Anybody else have this problem with their Gryphon or Edge? The Average Economy PID is WAY off, like 3mpg off. The first tank I ran through the truck with it it was a couple MPG lower than what it was, and all the subsequent tanks of fuel (5 or so, with a few towing) the Gryphon has been 3MPG high. Like it will say I'm getting 16.5-17mpg, and I'll fill up and only have gotten 13.5. It hasn't been correct once.
And yes, I reset the Gryphon's econ each time I fill up, and yes I reset the Gryphon for my tire size, and double checked it versus a GPS.
So anybody else have this problem?
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__________________ 2007 F-150 FX4 SCREW 1999 Long Travel 4x4 Ranger
Just a thought but you may be resetting it too often. I've never reset my Edge and it's always within half a gallon. I think it takes awhile for them to calculate correctly. Is the mpg erratic after you reset it?
I'm going to agree with mx here. I have never once reset my average econ, and mine is always fairly accurate. Within 1 mpg or so of my calculations almost every time.
At first, it was way off, it settled down a bit after I put some miles on it. Just a guess though, really not sure. Not very familiar with this yet.
Last edited by MercedesTech; 03-03-2009 at 04:01 PM.
An average is an average though... it shouldn't matter how long its run for. If I want it to average the fuel consumption of 10minutes of driving it should be doing that, or if I want an average of each tank or an average of a years worth of driving. The amount driven shouldn't make any difference in the average economy.
__________________ 2007 F-150 FX4 SCREW 1999 Long Travel 4x4 Ranger
An average is an average though... it shouldn't matter how long its run for. If I want it to average the fuel consumption of 10minutes of driving it should be doing that, or if I want an average of each tank or an average of a years worth of driving. The amount driven shouldn't make any difference in the average economy.
I have to disagree. Your mpg varies drastically while driving. If you're stopped at a red light your mpg drops drastically. Why? You're not moving. For example program the tuner to show the INSTANT mpg. You'll see that it's all over the place. The average needs time to calculate. And it doesn't sound like one tank full of gas is long enough for it to be as accurate as it can get. Actually only being off 3 mpg isn't bad in that short of distance. Now just think if you did an average over 3 tank fulls of gas. Think it would be closer yet? I do.
I have only put two tanks of gas in mine since I received my Gryphon but it read 2.5 mpg higher than I actually got. No big deal, the instant MPG still helps you see what you need to do to drive more economically.
Location: Among javelinas and scorpions near Tucson, AZ
Vehicle: 2005 Ford F150
Posts: 3,124
Interesting to see the different responses here. The average MPG on my Gryphon is off by about 2 MPG too. Usually too high. From watching it, I'm guessing it shows you the average MPG in a previous 10-minute "window". I base that on how quickly it will change while stopped at a light as mxracer pointed out or how rapidly it increases if you coast down a long hill.
My truck also has an information center that shows average MPG, and it changes much more slowly, sort of like its window is the last hour of driving. And the info center's MPG is usually quite close to what I get doing a hand calculation at fillup.
yea, mine is off to... but i reset it everytime i fill up... i will stop doing that now...
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2006 f-150 super cab, XLT, 5.4, 4x4, 6.5' bed, stainless tube steps, ford bed liner with tractor supply rubber mat for traction, Gryphon programmer with 87 performance tune, 255/70/17 general grabber AT2's
Bill at PHP explained it all to me when I was up there for a live tune. He said it really wasn't close to dead on until you ran about 3 full tanks through it. He explained to me about the sitting at a stop light thing, it may look like it drops early but it eventually compensates itself out, I'd try to explain more but I was half driving/half listening to him when he was explaining it. Would hate to get some facts wrong, but nonetheless, mine's a little off too on a highway trip. I usually get better gas mileage than the gryphon indicates on a long highway trip, as for my daily commute to/from work, it's pretty dead nuts.
An average is an average though... it shouldn't matter how long its run for. If I want it to average the fuel consumption of 10minutes of driving it should be doing that, or if I want an average of each tank or an average of a years worth of driving. The amount driven shouldn't make any difference in the average economy.
The more data collected the better your accuracy will be. If you reset it you are throwing away data points.
The more data collected the better your accuracy will be. If you reset it you are throwing away data points.
I definitely have to agree with this...My average did not get close until I had stopped reseting it. When I was reseting it each time it was showing about 2.5-3 mpg higher.
We covered this in other threads before but I'll go over it again.
The Average Economy function uses a cumulative average of 100,000 samples. When you reset, the sample count goes to zero and moves up from there. Something like this
((Current Average * Sample Count) + Current MPG) / (Sample Count + 1)
...and so on. Samples occur about once a second. Once it hits the 100,000 mark, it then runs off a stabilized average value. The calculated number of samples is clamped at 100,000 and the latest MPG value is figured in and divided back out. Without having to store every single sample value, this is the most efficient and accurate way calculating the average.
When you consider that 100,000 samples (at 1 per second) comes to almost 28 hours of run time and 60 MPH at 15 MPG equals 4 GPH, you would have to use 112 gallons of fuel to fill the "Average Buffer", or roughly 4 tanks which is why the longer you go between resets the more accurate the readings are.
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One final though as well is that all the calculation for fuel economy are based on the specific density of gasoline. Anything that changes this density and the resulting mass of fuel being injected is going to change the calculations for fuel economy. Ethanol and "Winter Blend" or oxygenated fuels will all have an adverse effect on fuel economy ratings and is not taken into consideration by the programmer.
Take care.
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Bill Cohron - (678) 963-9913 - Gryphon & Evo Specialist
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