One thing I try to do cruising on the highway is to always re-step on the gas pedal. It seems that if you are cruising along at a certain speed, if you re-step on the gas pedal and go back to that same exact spot on the display (same MPH), your instantaneous MPGs will increase. Just an observation! I am also using an Ultra-Gauge which supports this with actual numbers rather than the stacked bar chart on the display. Has anyone else tried this?
What is this doing to your trip average MPG? Temporary high instantaneous MPG is of little use if the temporary low MPG before or after consumes all the 'saved' fuel.
Here is a quote from F8L from the 600 Mile thread which is where I first wrote the info above and was asked to start a thread on it: I believe this seeming gain in iMPG is based on the likelihood that most drivers accelerate to a desired speed then reduce pedal pressure to try and maintain that speed but they still apply too much throttle and they are actually still accelerating albeit very very slowly. This why it is always recommended to lift off the throttle completely upon reaching your desired speed then applying pressure to maintain speed. Simply backing off the throttle a little wastes time while you try to find the right amount of pressure. This time spent hunting adds up and mpg drops. I think he is accurate in his assessment. Read more: http://priuschat.com/threads/600-mile-club.112285/page-5#ixzz22VOGGZdX
For me...not much or even any at all, since I will look right away at the iMPG when I start cruising a certain set speed, so I catch it right away. If you don't pay attention you might be iMPG at lets say 55-60 when you could be iMPG 75 for multiple stretches on the highway which would add up on a single trip depending on distance of a flat or a very slight decline terrain.
I disagree. The same effect happens when using the cruise control resume to accelerate up to a set speed and the cruise control resume should reach the set speed and maintain it. Canceling and resuming cruise control gets it back to EV only. Furthermore, you can observe that you accelerate up to then maintain speed, the engine is running even though the HSI indicator is below the midline which normally indicates that the car should be in EV. It is pretty clear to me that once the engine is on, their is a slight affinity for the engine to stay on which must be overcome by letting off the accelerator.
I don't think we are discussing the same thing. We are concerned with one's ability to properly judge how much throttle input is required to maintain a set speed and do it quickly. There are many time that I think I am applying enough throttle only to find out that I am applying too much throttle. I realize this because my iMPG appears lower than it should for the given conditions. If I continue with the same throttle input I eventually gain 1mph above my desired speed. This tells me that I just wasted a bunch of energy by accelerating very very slowly and that my iMPG may have been compromised for the last 20seconds or even more. While hypermiling, that is a long time to drive at -10mpg (random number). The idea presented by jsfabb forces the driver to be more aware of throttle position and speed as well as iMPG. Sure someone with excellent foot control could accomplish the same thing without lifting off the throttle so far but it seems to help those of us with less finesse. FWIW I have covered almost 180,000 miles on my Prii and I have always observed the same thing jsfabb did. Lifting off the throttle upon reaching your desired speed then reapplying pressure to maintain that speed always seems to get my iMPG stabilized faster than if I just gradually reduce throttle input. Driving with no shoes on helps too! LOL
the engine makes a completely different sound after you settle in to the new throttle setting to hold speed. sounds like the rpm's are lower?
Now I see what you are doing. I sometimes do that below 45 mph when the SGII RPM shows that the ICE has not shut down. But I haven't been doing anything above 45, and usually don't watch the iMPG gauge anyway, so cannot directly address your question. My concern was about something different, with a rumored mpg improvement method involving releasing and re-stepping on the pedal repeatedly, at a high rate. Someone who followed the description thought it worked, but I felt that it was just triggering a quirk/bug in the mpg calculation with no demonstrated improvement. By doing this just once, you are not delving into that unproved method.
Hobbit covered this a LONG time ago, and in fact the DVD that comes with the gen3 in the UK tells you to do this. I don't have a scangauge so cannot tell you -what- is different, whether it is engine timing, or ICE:MG1 speed or what, but -something- is different. From some cursory reading of the predictive algorithms the HSD uses to try and anticipate driver behaviour it seems after getting up to speed the car is "expecting" you to accelerate more so is in a state ready to accelerate. Releasing the accelerator will drop you into stealth or warp stealth, and the slow application of the small power required to maintain speed sees the engine stay in whatever high efficiency/low consumption mode it's in (I think Hobbit called it Super Highway Mode or SHM for short)
Might seem like a dumb question, but what is iMPG? Is it that stacked bar MPG gauge next to the speedometer?
