HCH-II - SAHM "Super Highway Mode" (70-90 MPG)

Discussion in 'Honda Hybrids' started by msantos, Jul 27, 2008.

  1. bear15

    bear15 Well-Known Member


    Awesome thread!!! Thanks for sharing this very important technique with us. We hope you are enjoying your vacation. I know for us, part of the fun on a vacation trip is what you illustrated-- going after high mpg!!
  2. brother

    brother Well-Known Member

    I read this thread with great interest, as it appears that this mode is not unique to hybrids. I accidentally "discovered" 55-65 MPG at ~43 IGN the other day. Like you say, the mode is attained by gently backing off the gas from about 60 mph. Unfortunately, my terrain is too variable to stay in the SAHM for long, so extensive testing is difficult (hint: anyone with a car like mine want to test this on flat terrain?).

    I have also seen the 75+ mpg low-speed sweet spot Wayne mentioned at ~23 (IIRC) IGN. Again, due to the terrain bugbear, I'll need quite a bit more time for testing; there is not much low-speed level roadway in my commute.

    Way to go! :flag:

    EDIT: BTW, thanks to 70_West for bringing this to my attention. :)
  3. hunter44102

    hunter44102 Well-Known Member

    Is the SAHM a Pulse and Glide technique? Without looking at the scangauge, is the car essentially slowing down, and when exactly do you speed back up?

    I will be driving about 900 miles this labor day weekend so I have lots of time to try techniques.

    I would like to go an average of 60MPH the whole trip, so in this case, would I start off at like 65MPH and slowly go down to like 55MPH to get the mileage. After this, how quickly should I get back up to 65MPH? I'm guessing I should avoid assist to get back to 65

  4. msantos

    msantos Eco Accelerometrist

    Hi Hunter

    It is definitely not a pulse and glide variant. It is a stable, steady-state pattern that leverages the gas-engine's low cam mode features, and the PCM's control of the CVT.

    In reality you'll want to use this on a highway where a steady state of speed is possible. You can retain the mode when climbing small hills and as long as the loss in speed is bearable to you. You can also use it mild descents as long as the upper speed is safe as well. I've had it in mild descents sometimes reaching 80+ MPH (kind of scary if you are not accustomed to these speeds).

    While you can do it without a scangauge, the SG is instrumental for locking it in with your accelerator pedal and keeping it on for as long as possible. 75+ MPG (@ 55-62 MPH) is quite achievable - even with a somewhat loaded car. ;)


  5. hunter44102

    hunter44102 Well-Known Member

    Thanks for the quick reply Msantos - I am driving from Cleveland to Chicago (rnd trip) which is really flat as there are no mountains or even large hills.

    I -do- have a scangauge and will give it a shot. I just wanted a perspective of what the vehicle itself was doing speed-wise and you answered that.
  6. psyshack

    psyshack He who posts articles

    SAHM the heck out of it hunter! :)

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