Tested: MPG/fuel economy VS. speed, 2000 Honda Insight, 1.0L lean burn, 5-spd

[Smokingwheels]

Had a look at the figures, you tests is roughly 10% increase in speed is a increase in fuel by 10% based on what I ive been told so good news on my info.

[trooper Tdiesel]

are you using the 128 oz or 160oz gal

[Blue Angel]

Originally Posted by trooper Tdiesel

are you using the 128 oz or 160oz gal

If you look at the legend on the graph you will see he is reporting in both US and Imperial Gallons, as well as L/100km.

BTW, ~153.7 oz = 1 Imperial Gallon

[IamIan]

Just for fun ... interesting to see the difference between the real world data you collected and the all theoretical graph I came up with attached bellow



Assumptions I had used:
Gen-1 Insight CdA and Weight
Assumed Tire Crr of 0.01
Including 200 Lbs of fuel and driver
On Flat Level Ground
No Head or Tail Wind
Cool / comfortable day ( low 60's )
Average Humidity & pressure
Assuming average E10 mix of ~35 kwh / gallon energy content
Used Stock tire rolling circumference and gear ratios to get MPH to RPMs
Used BSFC to estimate ICE peak Possible Lean Burn Efficiency at calculated ICE RPMs.

The known other variables that I didn't think of a good way to account for are:
Vehicle electrical loads
Transmission efficiency losses
Real world Operating efficiency vs the ideal peak BSFC point at that RPM

I'm sure I missed a few as well.

[IamIan]

In an effort to try and refine my crude theoretical model to make better sense / match the real world data collected.

In watching the 12V system load I regularly see it around ~300W. It goes up and down of course. It depends on what the instantaneous 12V load is. But ~300W from IMA to DCDC would still be about ~326W of ICE parasitic load, if it had to cycle through the IMA battery maybe as much as ~362W of ICE load.

I also tried to narrow down the ICE air pumping losses a bit. The best tool I have is to watch the IMA Volts and Amps while using MIMA to force the ICE to hold certain RPMs ( all while in fuel cut / FAS stationary in neutral ). From the IMA battery side it seems like about ~1 kw of electrical power per 1,000 ICE RPMs. The Actual Air Pumping losses would be less than this as the IMA system is not 100% efficient from battery to shaft. But I've seen studies showing the IMA system ( Motor + Inverter ) combined up to 92% efficient from DC battery load to shaft output. So the actual Air Pumping losses might be around ~0.92 kw per 1,000 ICE RPMs. At 31MPH in 5th gear that's about ~1,058 RPMs and about ~973W of parasitic air pumping losses.

The other interesting thing that came out of that was a better quantification of the air pumping losses ( and IMA Battery electrical consumption ) for running in MIMA-EV-Mode at low speeds. ie. MIMA up to ~10kw IMA assist to move combined with FAS to not use any fuel while doing so. Normally not much use outside of the worst stop and go traffic.

[sheepdog 44]

As a purely academic exercise, i decided to see if i could determine the engine efficiency of Lean Burn in a Honda Insight engine from MetroMPG's real world testing. Well, the Former UFO is not stock, so the one constant i had to approximate was the CD. Stock cd is .25, UFO is under .25cd. So take this approximation with a grain of salt. Also the MPG calculator neglects certain km/h values, since the primary values are in mpg. For example, you can not find mpg at 70km/h!

MetroMPG's real world numbers were compared to a theoretical Honda Insight using the Aero/RR/MPG calculator, which was really informative, since any unknown variables are accurately expressed in the real world mpg he got.
[QUOTE=MetroMPG;326520]

Raw numbers: (All values are for Lean burn in 5th gear)
Speed ........... AVG ..........

km/h . mph . MPG (US) ENG EFF% .....%MPG Gain vs non LB

50 ... 31.1 ..... 130.9 ...... 18.7% ................00%
60 ... 37.3 ..... 121.5....... 22.4% ................12%
70 ... 43.5 ..... 113.9 ...... 24.7% ................24%
80 ... 49.7 ..... 98.0 ........ 25.2% ................27%
90 ... 55.9 ..... 88.5 ........ 26.5% ................34%
100 .. 62.1 .... 81.3 ........ 28.1% ................42%
110 .. 68.4 .... 67.1 ........ 25.9% ................39%


You can see engine efficiency goes up with speed, as the engine experiences higher loads and rpm drops. Those are pretty good numbers for an engine experiencing low load on a steady flat road. Lean Burn nearly approaches the engine efficiency of high load in a pulse and glide regimen. Which would be the condition where an engine experiences peak efficiency. And corroborates the story that Lean Burn gives more or less the same mpg as Pulse and Glide at certain speeds.