How to properly test modifications (AKA: don't believe every MPG claim you read)

[RedDevil]

The fact that your commute is so short makes the results even more impressive.
I don't come anything near those figures on my 22 mile commute, never mind the temperature.
But my Insight is still breaking in, and so is its steering wheelnut. Who knows, MMMV.

So ambient temperature does play a big role in the first 10 miles of a trip.
Before doing any ABA testing one should warm up the car for at least 10 miles, and probably much longer if the temperature is anything less than 24C / 75F (as your graph seems to bend at that point); otherwise the first A measurement would have relatively low MPG.

[PaleMelanesian]

Originally Posted by RedDevil

So ambient temperature does play a big role in the first 10 miles of a trip.
Before doing any ABA testing one should warm up the car for at least 10 miles, and probably much longer if the temperature is anything less than 24C / 75F (as your graph seems to bend at that point); otherwise the first A measurement would have relatively low MPG.

Absolutely! In fact, probably even longer as the transmission warms up more slowly than the engine.

[sjc123456789]

Just read the thread -

Anyone come across this before

"Lies, damned lies, and statistics"

I'm always 100% correct in everything I say and do (sample size = 1, ie me!)

JOKE!


Did I see any mention of different fuels ? Winter / summer / manufacturers blends).


It's all good fun!

[superchow]

Originally Posted by Nerys

?? you see a TWENTY mpg difference with a 75 degree change in temperature?? WOW.

So far that confirms my somewhat unscientific hypothesis that the best mileage comes with the temperature comfort range of people too. My best tanks have been between 65 and 75 degrees ambient air temperature. But that can be attributed to many other factors, such as tires being not too hot (sticky/slippery) or too cold (too hard), or the driver just not having to use headlights (it's dark here in the Pacific NW in the winter) or A/C in the warmer months.

Looking forward to spring - that's for sure!

[Swordsmith]

Not much of an Eco-modder at heart, I converted my Sonic to run Flexfuel. Driven as I normally do, I've logged dozens of tanks of E85, and got a fairly consistent 22-23mpg. Recently though as part of an experiment, I did one tank driving reasonably; not hypermile style, not granny style, but accelerating gently, shifting early, keeping the RPM's down under 2K and staying at or barely above the speed limit. I got a little over 31mpg.

So it is very much not unreasonable to say that driver style can influence mpg, and it is also not unreasonable to say that experimental bias could, even subconciously, cause someone to drive more economically when testing a mod out, and less economically when doing the "A" portions of the test.

To eliminate this, I could for example give someone else the keys and tell them to go fill up my tank with either 87 octane gasoline or E85, but not tell me which, go drive a tank using "there and back again", and repeat the exercise several times, never knowing which fuel was being used each run.

I would not, however, be able to test things like this 'driving style" exercise, or the effects of pulse/glide, or the effects of coasting with clutch in vs in gear for injector shutoff; those strategies require someone actively pursuing them. Many of these would also preclude testing using CC, because varying speed is in fact the point of some strategies.

[aerohead]

Originally Posted by RedDevil

The fact that your commute is so short makes the results even more impressive.
I don't come anything near those figures on my 22 mile commute, never mind the temperature.
But my Insight is still breaking in, and so is its steering wheelnut. Who knows, MMMV.

So ambient temperature does play a big role in the first 10 miles of a trip.
Before doing any ABA testing one should warm up the car for at least 10 miles, and probably much longer if the temperature is anything less than 24C / 75F (as your graph seems to bend at that point); otherwise the first A measurement would have relatively low MPG.

SAE recommends a minimum of 22-miles at 50-mph to stabilize all hyrodynamic loads at equilibrium for whatever ambient temp you testing at.

[ssnsvibe09]

With my instrumentation, OBD interface (in the mail) and GPS, I am hoping to collect data that shows the impact of atleast some of these variables. I travel 120 miles everyday for work. I intend to take delivery of the all the electronics shortly and set them up before I start travelling for work in the new year. I believe that I will easily have 7200 samples per day, if not more. It would be great to turn some of these variables into linear constants that could be calculated out. I know... Did you see that unicorn....?

[P-hack]

problem w/obd interfaces is that they aren't always that accurate. They look at airflow and fuel trim via "polling", the don't measure the actual fuel injected, so engine mods are more likely to be thrown off by OBD monitoring, as are short duration tests. And they are more likely to hide inadvertent changes in driving style/conditions between tests.

[Swordsmith]

Is there a way to look at fuel usage directly, some sort of gauge in the line perhaps? I've noticed that my car's DIC, my UG, and my OBDII/Torque app are all fairly inaccurate (usually in different directions), and the only really reliable measure of fuel usage is still the old hand calculated method... but that seems crazy when the car should "know" how much it's using, instead of calculating it based on other factors.

[MetroMPG]

Originally Posted by Swordsmith

Is there a way to look at fuel usage directly, some sort of gauge in the line perhaps?

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