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Decreasing throttle pedal pressure instead of letting it go and feathering it back

Discussion in 'Gen 3 Prius Fuel Economy' started by vahrn, Sep 5, 2010.

  1. vahrn

    vahrn New Member

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    Last night traffic conditions weren't ideal for Pulse and Glide... I usually do it the same, but I wasn't in the mood to annoy the guy behind me nor my passengers. So I tried some other tricks to get good mileage.

    The speed limit was 43 mph (70 km/h). This is a really tricky speed to keep. If you turn off the engine, it's okay you can glide it as much as you can, or you can max the blue part of HSI and draw power from the battery. In either case the slightest uphill will decrease your speed dramatically. If, on the other hand you keep the engine running, the instantaneous consumption reads some pretty bad figures for that speed (47 mpg). So I tried to keep a speed of 50 mph and instead of letting go the pedal off completely and feathering it back I tried to reduce pressure on the pedal and even if I fell back into the blue area of HSI the engine was still running. Instantaneous consumption decreased somewhat but not that much.

    Later on the speed limit increased to 56 mph (90 km/h). I did the same trick. Instead of keeping enough foot pressure to avoid to loose speed I simply kept it in the very first two lines of pixels of the white part of HSI (so the blue part was maxed out). The first let's say 5 minutes or so, consumption was about 44 MPG. Then as soon the battery charged itself up consumption went down to 75 - 60 oscillating. I was loosing some speed but at a far slower rate that when doing hyperstealth (which is also tricky to achieve if the battery is low). I ended my trip with an average of 65 MPG. Most likely I would have done better with Pulse and Glide, but how much? Not enough to be worth the annoyance, IMHO. And I would have annoyed more drivers...

    My point is that P&G really shines when your speeds are lower than 43 mph or near; above that speed keeping the ICE running at very low RPM (don't have a scangauge yet, sorry) is probably as much as rewarding as P&G and you can also manage to keep up with traffic.
    At 43 - 50 speeds keeping the ICE on is actually bad for mileage since I couldn't find a proper foot pressure to attain the "happy state" I achieved at 56 mph.

    Anyone with similar experiences?
     
  2. Flaninacupboard

    Flaninacupboard Senior Member

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    Yes, i see the 50mph at only 40mpg thing most days. It seems to be about the SOC though, as once it's up to six bars i'll see 80-100mpg at 50mph.

    I've still not managed to use pulse and glide to any great effect, but i do have to go over 45mph everywhere. i tend to ride hills manually, but the rest of the time use cruise control and just let the prius decide whether the engine should be on or off.
     
  3. bisco

    bisco cookie crumbler

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    i agree, above 40-45, i keep trying p&g with much less success, but better than a steady foot on the throttle.
     
  4. ken1784

    ken1784 SuperMID designer

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    On Gen3 Prius, the magic threshold of speed is 46 mph.

    Ken@Japan
     
  5. dcscm1

    dcscm1 New Member

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    Yes, I'm seeing the same thing. Above the 46mph limit that Ken mentions, I find Pulse and Glide a lot less effective. (At these speeds the 'glide' state still has the engine on but not using fuel, so I'm not even sure if the purists would call this 'gliding'.) Anyway, due to increased wind resistance at higher speeds, and likely due to the engine turning, I find that the 'glide' portion to be a lot shorter relative to the pulse portion than occurs at lower speeds.

    So, like you, I find that keeping the HSI just a bit above the midpoint (called warp stealth mode?) gives me very good fuel efficiency at those speeds that I haven't been able to substantially beat with P&G.