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Old 05-02-2013, 08:19 PM   #41 (permalink)
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stewie:
you don't actually need to drive the car as you can change the #'s is on the fly.
meaning they will recalculate the existing tracked info, I have done this many times, once in a while the mpguino will freeze up entirely but simply unplug it and plug it in again, it will retain the stored info but lose the tracked info.

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Old 05-02-2013, 11:33 PM   #42 (permalink)
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Great. Thanks for that info. I didn't know that. I reset my tank by mistake already twice so i can't use my stats on this tank unless i pump up soon and start over. May do that after i get VSS right. Ok so 2 and mini 2.5 test is done. I will test 3 time tommorow.
To recap. Here is what i did.

Speedo test. Pre-test. I checked GPS speed and got closest i got few times was 8086 and 8090 and i settle on 8090 for testing.

1st test drive of 8090
11.80m guino x 8090vss = 95,462 / 11.794m gps = 8094 VSSP/M

changed vssp/m to 8094

2nd 14.53m x 8094 = 117,605.82 / 14.543m gps = 8086.764. Note close to my eye test on speed gps

changed changed vssp/m to 8087 ( rounded up as it's closest)

2.5 mini test 3.37m guino x 8087 = 27253.19 / 3.372m gps = 8082
Guino not having third digit it may mach here at 8087. I will ignore 8082 as distance was too small. Will test 3rd one tomorrow and post here.

Weird that our numbers differ. Could be GPS discreptencies between our units? Mine says it connects to 9-12 sats. That's crazy accurate if indeed app is accurate. Thing is if done on full tank 3 times you will get to accurate result anyway so it's just a matter of time. I don't mind waiting for precise number but would like to get very close soon if we can work with each other on those numbers. Let me know your thought whey you think mine is going down and yours is going up Our tire pressure is different but i can't believe that would be the difference? BTW i would not change your usec/gall data until you confirm few times your VSSPM is correct per link below.

"MicroSec/Gallon - use this to adjust displayed fuel consumption. You may want to readjust this initially to get a ballpark MPG reading (after VSS Pulses/Mile is deemed accurate), then calibrate it with a couple fillups. If the mpguino displayed MPG is high or the displayed tank gallons is low at fillup then reduce MicroSec/Gallon by the percentage that the gallons are low or the displayed mpg is high. Like the vss pulses, this would benefit from user contributions about what values work for what specific cars."
MPGuino - Combustory

Let me know what you come up with both VSSPM and usec/gal. I won't be changing usec until i get VSSPM right first after few tests.

Last edited by stewie; 05-03-2013 at 02:41 AM..
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Old 05-03-2013, 12:06 PM   #43 (permalink)
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3rd test

Speedo test. Pre-test. I checked GPS speed and got closest i got few times was 8086 and 8090 and i settle on 8090 for testing.

1st test drive of 8090
11.80m guino x 8090vss = 95,462 / 11.794m gps = 8094 VSSP/M

2nd test. Changed vssp/m to 8094

2nd 14.53m x 8094 = 117,605.82 / 14.543m gps = 8086.764. Note close to my eye test on speed gps

2.5 mini test. Changed changed vssp/m to 8087 ( rounded up as it's closest)

3.37m guino x 8087 = 27253.19 / 3.372m gps = 8082
I will ignore this figure as 3.4 miles is not long enough distance.

3rd test with VSSP/M @ 8087

11.80m guino x 8087 = 95,426.6 / 11.795m gps = 8090

8094 was too high and 8090 was too low. To lower guino mil VSSPM needs to be bumped. Correct value is between 8090-8094. Will try 8092. I will then try usec number from wiki. Fill her up and reset all stats and test further. If and when i get some 50m+ trip i will retest both parameters again.

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Old 05-03-2013, 03:43 PM   #44 (permalink)
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4th mini test @ 8092

6.630m guino x 8092 / 6.636 gps ..right on to .xx digit. Will try 8091 to force it to .xxx closest match. Then will fill her up to top, zero out start testing default usec and do long distance test for both.

5th test @ 8091

11.860m guino x 8091 = ........ /11.873m gps = 8082.14

WTF!!!!! ....8091 is under and 8090 is over...over large distance this will widen by a lot. Is this margin of error in GPS reading? Must me and math give wide variety of different numbers. Either margino of errors or phone gps is fruther back from VSS sensor of the car so over longer distance this will throw off numbers.

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Old 05-03-2013, 10:47 PM   #45 (permalink)
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WD40 how are you doing bud. My numbers are inconclusive and closest seems 8090 for me still. 8094 was under so anything higher for my car will widen the guino margin further. Andrzej any thoughts there?
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Old 05-04-2013, 12:52 AM   #46 (permalink)
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stewie:
wanna blow your mind try setting mpguino to metric for more accurate #'s to deal with,
I did a 78 mile trip today and the errors are way bigger, now it shows that maybe my #'s should be 7575 if miles and 7579 if kilometers..
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Old 05-04-2013, 01:43 AM   #47 (permalink)
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I don't know what to say, so by that logic on 400 mile tank you one will get to 6700 number....lol....that's nuts man. Also then that would mean short term mileage would be off by large amount. See where I'm going with this? Something is very wrong here. Calculations alone and 5 test i did should yield same number and those number vary. I see you're dedicated! 78m just to test this device? Bro what bugs me there is plenty of people here with VX and guino i suspect and its just two of us figuring this out. That ain't right!!! ...lol. Here is a good question. This device has been out for 3 yrs now and we know wiki numbers are off so that means in 3 yrs NO ONE got the number correct!!! Does that mean device a faulty? I dunno but again something here is very wrong. I will change usec number to wiki default just to test it out on that number but that should not matter. It seem like there is variable missing from Guino and its guessing. I must admit i do not understand everything fully but that's what this forum is for so people can chime in and help out. Not sure why that's not happening.

Is VSS on our VX so damn accurate that guino just reads incorrect values all the time? Dunno again. Something is messed up here.

Does VSS on VS needs to be adjusted for 2.5% difference in tire size? I do not think this is possible to adjust for in guino. I'm all guessing here.

Last edited by stewie; 05-04-2013 at 02:04 AM..
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Old 05-04-2013, 02:46 AM   #48 (permalink)
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WD40 check this out, bold print especially. Hmmm.....

"To measure the VSS counts per mile get on the highway and find a mile marker and reset you VSS counts to zero. Drive ten miles as marked by the mile markers and note your VSS counts. Divide by ten to get your VSS counts per mile. Take an average of this process if you really want to nail it down, but I do not feel that is necessary. You may need to test this count every 6-12 months to readjust this number."

VSS - Vehicle Speed Sensor

The VSS count is fairly straight forward. There is a device on your car that rotates and creates a certain number of pulses per revolution. The sensor is usually attached to your transmission and it has a direct gear ratio to your tires that I will call the rolling ratio. This sensor is used to feed the vehicle computer the speed and distance data. The actual gear ratio has only one main variation, and that is the tire diameter. For the MPGuino to calculate the the MPG, this input is critical for determining the distance traveled. The VSS count is typically measured in counts per mile.


Theory vs. Reality

As with any engineering of a product you will have fudge factors. The important thing to realize is that you always design to get the fundamentals close and then expect to calibrate to meet the accuracy needed for the function. For this product we will evaluate the best way to calibrate and adjust to improve the accuracy of the numbers. This may not be necessary at all if your goal is to get feedback on your driving habits, then the accuracy does not matter, as long as you realize that the MPGuino is changing your driving habits to conserve gas AND best of all save you money.
So first let's discuss the factors that will affect your accuracy.

Factors NOT in our control:
Is it possible to control or measure these factors? yes, is it practical? not in my opinion. So these factors will introduce errors that will need compensation in the fudging process. I feel it is a pretty safe assumption that over time these factors will average within a range that will permit fudging.

Injector Pressure - Your car has a pressure regulator to manage your fuel manifold pressure, and it will regulate to it's setting. You could measure your pressure, but then you would have to know how that affects the fuel flow through the injector. We also do not know how the pressure changes over time and this can affect your fuel flow.

Injector Efficiency - Well, since MPGuino is a device that was targeted to older cars, then you have to expect that injectors tend to clog and become less efficient over time. The only way to calibrate that problem is to measure the actual flow through each injector. Have fun if you want to tackle that project. `,~)

Rolling Ratio - The rolling ratio is a constant changing ratio that will affect your VSS counts per mile. The main reason it changes over time is due to tires. As a tire gets more worn your VSS counts per mile will increase. When you replace that old set of tires with new tires, you will have less counts per mile.

Fudging/Calibration process

There are two areas I want to focus on to get this system as accurate as possible. Let's consider fudging the fuel flow rate and measuring the VSS counts per mile. I am taking this approach, because measuring the VSS counts is a practical option and it can be done with some accuracy. In contrast the fuel flow rate used to calculate the total fuel usage is not very measurable and therefore should be fudged.
To measure the VSS counts per mile get on the highway and find a mile marker and reset you VSS counts to zero. Drive ten miles as marked by the mile markers and note your VSS counts. Divide by ten to get your VSS counts per mile. Take an average of this process if you really want to nail it down, but I do not feel that is necessary.
You may need to test this count every 6-12 months to readjust this number. You can compare your numbers to you odometer, but understand that the odometer does not take into account the tire diameter as accurately as your measurement, but it can be used as a verification that you are in the ball park. The best verification would be if you noticed that you have a fairly repeatable offset from the odometer and your calculation.

To measure the fuel is much more difficult. Really the best way to do measure the fuel would be to drain the tank and run the tank dry of fuel. Now weigh the amount of fuel and put it in the tank. Run the tank dry again and compare the actual fuel usage with the MPGuino. Again do this multiple times and take the average. Personally I would not do this at all, but it is the only real way to get acuracy. For a much more practical method, start a fuel usage log. Go to many different gas pumps and take an average over time. I have noticed that the cheapest gas stations tend to calibrate to the high side of the legal limit, if not actually outside the legal limit. Try to keep a standard procedure, like only filling to the first click off. Compare your fuel usage average to your MPGuino fuel usage average and look for a trend. Now fudge the fuel usage to match.

MPGuino - Combustory

Last edited by stewie; 05-04-2013 at 02:55 AM..
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Old 05-04-2013, 10:40 AM   #49 (permalink)
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stewie:
wow thats nuts
I assume that all cars that have this type of info built in are off as well, as there are way to many variables to take make them 100%, I would assume maybe 90% accurate.
I switched to metric yesterday as my car is in kilometers, that way I can calibrate MPH more accurately, it seems to be very accurate.
So I will test mpg next, close is all we can count on.
I mainly use the mpguino as an instant and trip MPG tool, the actual MPG is calculated from the gas pump and the odometer and now the 2.5% tire size difference.
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Old 05-04-2013, 11:34 AM   #50 (permalink)
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I think that mainly refers to tire wear tho. So the 7575 number you say you find accurate? You didn't test that one yet? Thing is if your odo on guino will be off by 20m by end of the tank your mpgs will be off too by much so i don't know. I will try this but i do not think vss will be changing on screen. That number is constant. This confused me here.

"To measure the VSS counts per mile get on the highway and find a mile marker and reset you VSS counts to zero. Drive ten miles as marked by the mile markers and note your VSS counts. Divide by ten to get your VSS counts per mile. Take an average of this process if you really want to nail it down, but I do not feel that is necessary. You may need to test this count every 6-12 months to readjust this number."

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