Is pumping the gas the best for mileage in the c?

Discussion in 'Prius c Main Forum' started by clokwise, Jun 9, 2012.

  1. clokwise

    clokwise Member

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    After watching some reviews online it seems some people mention sorting of pumping the gas pedal to stay within the range of the battery power and not getting your meter up into then gas (red) side. Is this the best technique? It seems opposite of how you would drive a gas car but then again this isn't a typical gas car :)

    Thanks
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I missed the links to what you are talking about, but I suspect they are doing the opposite. Feathering the gas pedal to find the absolute minimum pressure needed to maintain speed.

    Beyond that, I would need to see the ' some reviews online' that you saw. No idea what you saw.

    [Edit;] Perhaps you saw Pulse and Glide instructions and are confused that they were saving gas by pulsing, they weren't. They were saving gas by gliding. Below some speed (41 MPH in the Gen 2, 45 in the G 3, no idea in the v or c but near 40 MPH) when you do not apply gas the engine shuts down, using no gas at all. If you can apply just the right amount of accelerator, you also get no regenerating braking, just coast. When you feel your speed is too low, you speed back up, trying not to use any battery power.

    I decline to Pulse and Glide much as it annoys other drivers, so try it out when you cannot see any other cars anywhere.
     
  3. clokwise

    clokwise Member

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    No one particular really. Just seems like they use. Technique of pushing down to build up some speed, using only battery power, then coast and pump the gas pedal to maintain that speed while keeping the "pumps" out of the red. I may be totally wrong which is why I'm asking.
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Yes now that you mention coasting, they may well be demonstrating Pulse and Glide. And yes in a 'normal' car it would not work as well. Normal cars do not shut the engine down when coasting, so they are still using gas, normal cars have 'too much' Horsepower so it is hard to avoid pumping losses.

    If you have 300 HP and your car uses 20 of them at 60 the throttle is almost completely closed and the pistons are trying WAY too hard to suck air passed that (almost) closed throttle plate. If you have 73 HP and the car uses 20 of them to go 60 MPH, the throttle is quite a bit more open, and the pistons are sucking air passed it easily. A large part of the Prius good gas mileage is that the engine is sized to cruise, not accelerate rapidly, they add the Motor/Generatorss for that.

    [​IMG]

    You would waste a lot of energy trying to pull air through that.
     
  5. secondspassed

    secondspassed Member

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    I find if accelerating from a stop to more than around 25mph, it is beneficial to pulse as the OP describes. Under 25 it's better to do it in one go. It keeps the revs from getting too high and is sort of like changing gears in other cars. When you back off sharply and very quickly push back down more lightly you are telling the car to chill because you don't need as much power to keep accelerating at that stage. I usually will pull back sharply on the gas like that 2 times if I'm getting up to 45-55mph. Don't be afraid to go into the red, though, just keep it quick and use it as one last thrust before easing up.
     
  6. F8L

    F8L Protecting Habitat & AG Lands

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    You shouldn't be pulsing and backing off then pulsing again to get up to speed. Do it in one pulse the back off to maintain a desired speed level. The idea of "pumping the gas pedal" is not what you are trying to achieve here.

    Pulse and glide is simply accelerating up to 41-42mph then backing off the throttle enough to enter glide mode which cuts fuel AND avoids regeneration so you can coast for a long distance. In order for this to be effective you want to be able to glide for over twice the distance covered while pulsing otherwise you can only hope to break even. Once your speed drops below 30mph or so you can pulse again. This can also be used to drive between stop signs in residential areas except you glide to a stop instead of a specific speed.
     
  7. secondspassed

    secondspassed Member

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    I respectfully disagree, but it may have to do with distance between lights. I think if you've got a good amount of ground to cover then it's good to make the early and heavy fuel investment to do it in one go. It would help with warming the engine for efficient cruising if nothing else. Many times my pulsing during acceleration is due to a strong possibility of stopping soon. There is also the issue of meshing with the other cars on the road. I'd have to let the people in front of me get a good lead to be able to pulse in one go. So as not to piss off people behind me I find the mini pulses to be a good balance. It's usually much more efficient than accelerating too slowly. It also helps mesh with the flow of traffic since it helps match your movement with cars that have to change gears. To each his own, I find I get good results averaging about 53mpg calculated in a very hilly area.
     
  8. Oldwolf

    Oldwolf Prius Enthusiast

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    The Atkinson Cycle that our engines are designed with is what reduces the pumping loss the most I think.
     
  9. F8L

    F8L Protecting Habitat & AG Lands

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    Your driving conditions may differ and your technique may yield different results but the typical pulse and glide technique has been proven most effective and is the technique used to create and break world records. You should try to master those techniques first and then see if yours works better. If you are able to get 80+mpg with your techniques then you may be on to something that could help others who have to drive in similar situations. Otherwise, 52mpg is nothing special for a c or even a GenIII. Since my commute is 98% freeway I don't get to P&G much but when I can stay off the freeway or at least keep my speed at 60mph or lower I see between 64mpg and 58mpg (indicated). Maybe your technique will pan out and help me too. :)
     
  10. secondspassed

    secondspassed Member

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    53mpg is nothing special, yes. I don't hyper mile and pretty much anywhere I go on a regular basis there are big hills. I don't know what to tell you, especially since you don't drive the same car, but I've tried accelerating to 50mph in one go many times and my mileage is always worse. This has nothing to do with "pulse and glide" because my goal is not to glide, it's to get to a cruising speed. Every time I ease up on the pedal and come back down I'm telling the car to let itself use some of the momentum I've just given it to help ease the demand on the engine. The difference in efficiency is very clear, both audibly and according to the gauges. Driving on flat land it's absolutely no problem to get above 60 or even 70mpg, I just rarely have that luxury.
     
  11. vinnie97

    vinnie97 Whatever Works

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    ^Sounds more complicated, but the terrain may play a role in your results. The hills in my area are generally of the longer distance variety, so I have become pretty dependent on cruise control.
     
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