Maxed out my own efforts, what is next?

Discussion in 'Gen 3 Prius Fuel Economy' started by Brett., Jun 27, 2012.

  1. Brett.

    Brett. Junior Member

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    That is how I discovered the benefit of using N. The first time I switched into N I felt the "I'm free" feeling you describe here, and no amount of fancy footwork blanking out the HSI display can duplicate that.

    If anybody needs proof of that, here is a simple test for you to make note of.

    1.) Approach a downhill slope at a predetermined speed. Using a starting reference mile marker, or other marker keep the selector in D and Glide your best to the bottom, record your speed at a predetermined point, or mile marker.

    2.) Go back, and approach the hill at the same predetermined speed. Shift into N and N coast your way to the same point or mile marker, and record your speed.

    The results will be that using N you obtain a higher speed 100% of the time unless driver error in starting the glide, or shifting into N is counted as a variable. Less friction, less drag, higher exit speed, maintain maximum speed longer during N coast which in turn translates to higher mpg based on the increased distance of the coast, and the fact that no pedal error will take power from the HV battery when and if you hit a bump or get a tired / heavy foot. The split second that your foot creates illumination on the battery side of the HSI display is the same moment your speed decreases and more energy is wasted.

    If a stop, or turn is at the end of your N coast, by switching into D you can maximize regenerative braking by pressing the brake pedal enough to fill the charge indicator but not apply the friction brakes. Doing this you can easily make up for the lack of regen effect in N, or D glide for that matter. Since your maximum speed is always going to be higher in N coast, you may end up with several opportunities down your long hills to switch into D and regen brake to scrub a few mph, switching back into N for the duration and reaping the benefit of the stored energy you would not otherwise have had provided you descended the same long hill in a D Glide. IF you were to regen brake in the middle of that, gliding wouldn't take you back up to speed as quickly, or at all depending on the hill. "Experts" welcome to challenge this theory.

    So far I've found no valid argument to say that N coasting is in any way inferior to D glide, and I've just given from my perspective a reason why N coasting may in fact harness the potential for more energy regeneration over D glide.

    That's all for now, I'm currently at 60.5 on my CONS display using these techniques after 70 miles of the exact same driving I do any other day which has previously left me stuck around 51.5 on CONS. This too, using my AC since it's been hotter than usual out.

    Next test will be to determine if in D glide the HV battery has a draw on it and how much, compared to if there is a draw on it in N coast at all, and how much.
     
  2. F8L

    F8L Protecting Habitat & AG Lands

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    I have started monitoring the GPH when in neutral vs. gliding and sometimes neutral decreases GPH vs. a glide and other times it is higher. It seems to really depend on engine temp, warmup phase etc.. On a cold engine neutral may be better than trying to glide but will it affect warm up time?
     
  3. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Just curious, but why would you want to put it in N when the engine is on? Wouldn't you lose any battery charging that the engine might be doing?
     
  4. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Have you ever considered the safety issues being in N compared D? The valuable split seconds it may take to put it in D before making evasive maneuvers might be worthy of some consideration.
     
  5. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

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    Because of the lower drag. You are correct, while in neutral it cannot charge the battery, but more drag means more use of the engine. The trade-off is obviously not going to be as clear as a conventional car, but there may still be a crossover point.

    Can't speak for the OP, but yes. I'm also aware that the vehicles I drive (a Prius and Civic) are inherently less safe than a minivan. They're also less safe than a more powerful car that could accelerate out of danger more rapidly. As a rule, I don't mind trading a slightly increased risk of an accident due to failing to anticipate danger and a delay in being able to accelerate to avoid a car, in order to improve fuel economy.
     
  6. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    So you draft semi trucks about 10-20 feet behind them?
     
  7. F8L

    F8L Protecting Habitat & AG Lands

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    This was usually during the warm up phase and SOC was already around 60%. I played around with neutral when I realized I could not enact a glide. GPH was approx. .28 in the failed glide but in neutral it dropped to .17 or so. In a case where I know I am going to have plenty of regen and warm up opportunities ahead I could see using neutral to drop consumption. It is not a technique I plan to employ regularly, however.
     
  8. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Justin, I'd be interested to hear your take on all the above. Do you think it is wise to constantly switch to N instead of doing a glide via your foot, once the ICE is off?
     
  9. F8L

    F8L Protecting Habitat & AG Lands

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    Wise? Probably not from a total safety standpoint. From an fuel economy standpoint I bet using neutral over a glide could have advantages although they may be limited to specific situations and may ultimately depend on how much energy is used while in neutral vs. a warp stealth situation.

    If for example you have a very long steep hill than you are descending and you know your SOC is starting to drop below the charge threshold then I would think that using neutral before the SOC drops below that threshold, and the engine is still off, would be more fuel efficient than trying to maintain a warp stealth glide. In warp stealth you still use a small amount of energy but it is enough energy that on a long hill you can drop quite a bit of SOC. At least this was the case in the GenII. So if you use neutral would you use even less energy than warp stealth? If so then this is the more fuel efficient technique. Trust me when I say that trying to maintain warp stealth on my downhill commute can be quite difficult in the winter when the engine is subject to quick cool down and SOC is close to the threshold.
     
  10. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    ^^^This.

    I too could also concede that there are a FEW instances where a N glide is better, but definitely not safer.

    So Brett, looks like we are meeting in the middle on this issue, if that's cool with you. ;)
     
  11. ES44AC

    ES44AC C.A.U.S

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    Couldn't agree with you more! He's really annoying to the max makes you wonder how he ever got so 'famous'? They should cast him as Mad Max in a 'Return to Thunderdome The Prius Chronicles' he'd be an instant hit! Move over Mel here comes Wayne!
     
  12. F8L

    F8L Protecting Habitat & AG Lands

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    Some of you will just never get it.
     
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  13. Brett.

    Brett. Junior Member

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    Hey everyone, I'm home.

    To Mark, yes I consider split second maneuvers and I'm not saying that I am bionic, but for a decade I've driven nothing but stick cars. Shifting to drive, shifting to race etc has led to me having a keen ability to execute gear changes faster than the average driver. With this car being auto and my hand constantly on the lever it's just as easy, if not easier.

    As an extra safety measure, I do not play follow the leader on the streets. From motorcycle riding I've adapted my field of view from riding the bikes to driving my cars. Look ahead, way ahead. Unless it's an animal, or someone speeding running a red light that I have no control over I have been fortunate enough to have plenty of time to stab brake and avoid close calls.

    The first day I bought this prius, I hit a deer for the first timee in my life. I was in D going about 45 in 50 zone and my best maneuver was no match for the deer who stopped, watched my reaction and ran directly into the front end of my car. I drive more cautiously than ever before on that stretch of road for that reason.

    As for an update, here is where I am at after almost half a tank. I would have reported sooner, but short tanks aren't proof of anything. This is the real deal, 300+ miles is enough miles I feel to demonstrate that what I'm doing is legitimately working. 70+ club on the display

    [​IMG]
     
  14. Brett.

    Brett. Junior Member

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    And yes, I am ok with meeting in the middle, as I do both D glide and N coast so there are advantages to both as mentioned it is really situation specific. I've found a way to use it to my advantage and I'm just exploiting that, I hope to encourage everyone to always strive to break their previous records.
     
  15. F8L

    F8L Protecting Habitat & AG Lands

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    Very nice! Especially for a Prius newb! ;) Thanks for trying new stuff and convincing me to do the same.
     
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