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Discussion Starter · #1 ·
Hello, I have a loop around my house where I often do some mpg tests. The loop is 4mi long, flat at first and then up a steep hill, and back. It typically has a red light followed by around 2000 feet at 35mph, and repeat. I make sure I start and finish with the same numbers of battery bars. 75°F, no a/c.

My first loop was me trying my very best at fuel economy with very slow accelerations and Eco mode. It returned 71.8mpg.

For a second loop I decided to floor it after each red light or stop (not going after the hard point on the pedal though). Basically, I try to reach the posted speed limit as fast as possible and then either cruise or slowly lose speed. Still in Eco mode. To by biggest surprise, it yielded 70.5mpg.

Note that the engine was already pretty warm at the first loop. It's a relatively small loop so the error might be a few mpgs, maybe 5, but even with that, I find it a very good surprise that the mpg is in the same ballpark. Meaning you can "have fun" for a very small toll on mpg. I also remember one of you saying that his girlfriend drives more aggressively and returns better mpg so that makes me think it's possible.

I don't think this "technique" works when red lights are close to one another though. I think you need some cruising distance to rip the benefits of a hard acceleration.

Thoughts?
 

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Yeah, you can do this in short burst without hurting fuel economy much. I do this sometimes at traffic lights to have some fun. Keep in mind this only works when the battery is at optimal temperature/battery level while it's warm outside.
 

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My first loop was me trying my very best at fuel economy with very slow accelerations and Eco mode. It returned 71.8mpg.
[...]
For a second loop I decided to floor it after each red light or stop (not going after the hard point on the pedal though). Basically, I try to reach the posted speed limit as fast as possible and then either cruise or slowly lose speed. Still in Eco mode. To by biggest surprise, it yielded 70.5mpg.
I think the 'mpg magic' result was close for both cases because the speed was kept <45 mph, and the car is primarily driven by the electric motor(s) in Honda's hybrid design for <45 mph speeds.

The Insight's max torque occurs at 3000 RPM and involves the electric motor (directly or via combined hybrid mode), instead of the gas engine alone. Since gas engine use is minimized, mpg results are maximized:
  • GAS ENGINE ONLY = 99 lb-ft torque @5000 RPM
  • ELECTRIC MOTOR = 197 lb-ft torque @0-3000 RPM
  • COMBINED HYBRID = 197 lb-ft torque @0-3000 RPM

From the Alex on Autos video for Honda hybrid design, "below 40-45 mph, only the electric traction motor drives the vehicle forward (with power from battery pack or from generator tied to engine). Only above 40-45 mph can the clutch between the two motor generators can close, to send power mechanically without involving either electric motor."
 

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Discussion Starter · #5 ·
I think the 'mpg magic' result was close for both cases because the speed was kept <45 mph, and the car is primarily driven by the electric motor(s) in Honda's hybrid design for <45 mph speeds.

The Insight's max torque occurs at 3000 RPM and involves the electric motor (directly or via combined hybrid mode), instead of the gas engine alone. Since gas engine use is minimized, mpg results are maximized:
  • GAS ENGINE ONLY = 99 lb-ft torque @5000 RPM
  • ELECTRIC MOTOR = 197 lb-ft torque @0-3000 RPM
  • COMBINED HYBRID = 197 lb-ft torque @0-3000 RPM
From the Alex on Autos video for Honda hybrid design, "below 40-45 mph, only the electric traction motor drives the vehicle forward (with power from battery pack or from generator tied to engine). Only above 40-45 mph can the clutch between the two motor generators can close, to send power mechanically without involving either electric motor."
Interesting video! At speed under 45 mph, the electricity still comes from the gas engine. The way I see it, if you floor it, you are getting close to the gas engine 5000 RPM peak torque and that's why it's still pretty efficient. The electric motor has a flat torque plateau at speed under 45mph so it can be taken out of the equation.
 

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Discussion Starter · #6 ·
I repeated the experience this week and it still holds true! Got 61.x mpg in my very controlled test loop for both cases.

Hard acceleration (flooring it in Eco mode, not past hard point) is equivalent to a slow acceleration in terms of mpg, provided that:

  • the engine is warm (160F or above)
  • there is some cruising at constant speed after you accelerate, like at least 10 seconds.

Basically you can have fun with 0 guilt, amazing! (OK maybe a little more wear and tear I suppose)
 

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Try it in normal mode. I’ve never used Eco mode for more than a very short period (its slow response annoyed me) and consistently average 55-61mpg depending on season. Even using Sport mode for 1/4 of a tank only dropped mileage to 53. I find that eco mode provides little improvement in mileage for its maddeningly slow response. This car truly allows you to have fun and still sips gas doing it!
 
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I feel the same about doing some strong accelerations in short burst even in sport mode doesn't appear to impact mpg by much.
 

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I’ve read similar tests where they confirm your optimal fuel efficiency “gliding” around 45 mph, so the longer you take accelerating up to 45 mph, it actually hurts your fuel efficiency.
Not that flooring it is good, but accelerate briskly to optimal speeds
 
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