HCH-II --Miles after fuel light?

Discussion in 'Honda Hybrids' started by xcel, Jun 30, 2008.

  1. LL3

    LL3 Well-Known Member

    But if your gas tank was empty, you would not be able to get that, right? You could not just use the EV.

    How would that work anyhow? If you were going the right speeds, and with light pressure feathering or pulsing the throttle, with no assist or regen, the valves are shut, right? But there is still an RPM so isn't gas still being used to turn over the ICE?

    TIA,
    LL3
     
  2. msantos

    msantos Eco Accelerometrist

    Actually, we've had a couple of HCH-II owners claiming that they have done so.

    Personally, I think it is not the brightest idea to let it run dry just to see if you can ride the pack for a while longer on the HCH-II... just like I think it is a fundamentally bad thing to do so on a Prius II under the same circumstances.

    At first thought, I don't see why that cannot happen in principle as long as the car is not keyed off after it ran out of fuel. But if it runs out of fuel after the ICE has warmed up at least up to the point that EV glide can be evoked and sustained then it would appear to be doable.

    Obviously, how far you would travel depends on your initial state of charge, but speaking from my own regular experience I can sustain a EV powered glide for the entire duration of my neighborhood at 4-5 pips of EV assist.
    As usual, I do so as yet another reward for managing my SoC properly but... on a relatively flat terrain I can squeeze up to 10-15 HP of motive pack power to cover a good distance. The less aggressive the assist and the higher the initial speed, the longer the covered distance.

    Cheers;

    MSantos
     
  3. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Thanks for clarifying, Manuel -- that was the situation I was thinking of. If you are driving along at highway speeds with a high SOC and you run out, you should be able to extend the coast down substantially.
     
  4. LL3

    LL3 Well-Known Member

    Thanks for the info MS and RLC. I learn more and more on this site each day. I just hope I never have to be the one to test that theory.:D

    LL3
     
  5. Soybean

    Soybean Nintendork

    On my HCHII, the light usually means about 3 gallons left. Zero bars means about 2 gallons left. I get nervous after that, though, so I try to fill up quickly.

    The most dangerous I've lived was to get to a point where I filled it up 11.8 gallons. Will I ever try for the big 12.0? We'll see...
     
  6. ml2007hchII

    ml2007hchII Active Member

    I decided to push my previous limit a bit in an attempt to get a 700mile tank for the first time. It worked! The gas light came on at 650miles, second-to-last bar disappeared at 654 miles, last bar disappeared at 675miles, and my final tank distance was 713miles @ 63.1mpg.

    What I don't fully understand is why when I filled-up at the gas station (my practice is to stop filling when it clicks off), the amount was 10.66 gallons, but 713 / 63.1 is 11.29 gallons. Which is the right amount of gas consumed for that tank?

    Mark
     
  7. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Mark, you should always use the miles from the odometer divided by the gallons actually pumped.
     
  8. ml2007hchII

    ml2007hchII Active Member

    Sean-
    Odometer miles divided by gallons of gas pumped makes sense.... unfortunately, my entire log on this site (12 months worth) reflects odometer miles divided by mpg calculated by my car. If that is the case, then on my last tank, instead of 713miles / 11.29 = 63.1mpg per the car, it should be 713miles / 10.66gal pumped = 66.88mpg. Is this how you calculate and log your mileage? For this tank of mine, it is a 6% difference! Is this a normal discrepancy?

    I guess it leaves me wondering how I should log my mileage now... 1.) continue to log as what my HCHII tells me it is, 2.) leave previously logged tanks as-is and log future tanks as tank miles / gallons pumped, or 3.) edit all previous tanks to log as tank miles / gallons pumped and continue to document this way from now on. I actually could do option three, as I have all gas receipts reflecting actual gallons pumped.

    I appreciate your feedback,
    Mark
     
  9. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Hi, Mark! I would go with #3 -- the pump is always the official last word in authority. ;)

    Personally, I've been including the FCD readout in the notes section for my tanks so that I can track the difference between what the car tells me and what I really accomplish. Most FCDs are slightly optimistic so don't be surprised if your next fill comes in higher than you expect (indicating an underfill this time around).
     
  10. ml2007hchII

    ml2007hchII Active Member

    Sean-
    I updated my log.... on average (last 12 months), I found my iFCD to underestimate my mileage (compared with calculating using total distance/gallons gas pumped) by 3.7%. Thanks,
    Mark
     
  11. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Hey, that's a nice improvement! It's also interesting to see that your FCD is not optimistic -- what type of terrain do you normally drive and what is the average trip length?
     
  12. msantos

    msantos Eco Accelerometrist

    Hi Sean;

    Unlike most (if not all) other hybrids, the HCH-II almost always underestimates the FE 99.0% of the time.

    Cheers;

    MSantos
     
  13. Right Lane Cruiser

    Right Lane Cruiser Penguin of Notagascar

    Really? I wasn't aware of that! My Insight seems to wander around an average that is pretty much right on...
     
  14. msantos

    msantos Eco Accelerometrist

    Yes, it is true.

    In fact, I found it almost unbelievable when my 2006 actually over-estimated the FE for the very first time after some highway driving during this summer.

    I guess it depends mostly on the driver and driving regimen but for the average HCH-II this under-estimation is quite normal and a good piece of HCH-II trivia. ;)

    Cheers;

    MSantos
     
  15. ml2007hchII

    ml2007hchII Active Member

    I drive with rush-hour traffic 37miles each way to work. First 4 miles are 40mph rds to the expressway, then ~30 miles expressway (I usually drive 55-60mph), then ~3 miles 40mph surface streets again. On the way to work, there is a slight downward slope overall, and upward on the way home.

    I admit that I am pleased to have learned that my iFCD underestimates my overall FE. I felt like I was really using all techniques I had seen and learned on this site, but not achieving the results that many others have been. I got an engine block heater right around New Years, which helped significantly in the colder weather. Another driving change that I made only this spring that significantly bumped up my FE was to NOT use cruise control (which in retrospect I had lazily been using from Sept 07), in favor of DWL and monitoring the iFCD like a hawk, backing off to hold my mpg in the 80-100mpg range as much as possible. At first, my foot/lower leg got pretty tired of this, but have gotten used to this, and can't see myself getting lazy again, given the FE increase I experienced! I am always scouring this site to try and find any HCHII FE tricks that I haven't yet come-across, but admit it's getting harder. Notably, I have not purchased a scangauge. I have been thinking about it, for my wife, who dries an 08 Odyssey. I'm not sure how much additional FE benefit I would get from it. What do you think?

    Mark
     
  16. LL3

    LL3 Well-Known Member

    Hi Mark,
    I came to the same conclusion, and our mpg on the same year/make of car looks about the same. I am working on raising it into the 60's...a lot of hard and sometimes frustrating work. The only thing I do not like is using the EPA average that was assigned for our cars in 2007. Even they admitted later that these numbers were off. I think they are somewhere between 42/45 instead of 49/51. Any way you look at it though, we are kicking butt!

    LL3
     
  17. ml2007hchII

    ml2007hchII Active Member

  18. bear15

    bear15 Well-Known Member

    This is absolutely correct. Our HCH-II underestimates while our Prius usually overestimates.

    Regarding more tricks for high MPG, I suggest looking at some of Msantos discussions. In the summer months,
    70's and 80's are very possible.

    Cheers!!

     
  19. guzmania

    guzmania Active Member

    I have run the '08 HCH to no lights twice and on one of those occasions ran 20 miles before the fill up. I have never taken more than slightly over 11 gallons. I wonder why there are reporting discrepancies between individual cars of the same type.

    The car says that the overall MPG since first birthday is 51 mpg. But on the reported miles and gallons here I'm over 53. I do not mind the under-reporting but at first I got anxious when I had a "bad" tank.
     
  20. jmelson

    jmelson Well-Known Member

    No. When you go down a hill, and ease up on the gas pedal, you will see the instantaneous fuel consumption gauge (I always leave that display up, if the engine were to overheat, I'm sure that the computer would let me know) start to climb. At some point, there is a tiny "bump" and the bars zoom up to 100 MPG. That bump is the engine turning off all fuel, and switching the intake valve timing to minimize pneumatic losses. At that point, it is using ZERO gasoline, until you press harder on the pedal. The engine is still spinning, it has to, because, unlike the Prius, the traction motor/generator is built into the engine flywheel. But, it can run with no fuel consumption when going down hills, coasting to a light, etc. When going down gradual hills, you may need to press very lightly on the gas to keep the normal regenerative braking from slowing you down. You can even apply electric power only, with VERY light pedal pressure, to make it over the top of a hill, and do a series of hills with a general downward trend, without starting the engine at all.

    Jon
     

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