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Pulse and Semi-glide on the Freeway?

Discussion in 'Gen 2 Prius Fuel Economy' started by Winston, Apr 7, 2008.

  1. Winston

    Winston Member

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    I was trying a slightly different technique on the freeway this weekend. I have read about the Warp stealth technique, but it causes me to decellerate too quickly. I was driving in some mild traffice and decided to keep my speed between about 58 and 65mph. This is what I tried this last weekend.

    I would accellerate up to 65mph while getting a mpg reading of about 30-35mpg on the MFD. Then I would back off on the accellerator and hold it in a position where I was getting above 90mpg, but still had the engine running. This would cause me to slowly decellerate down to 58mph. Then I would repeat the cycle. I was able to get some very nice mpg bars this way. Well above the 60mpg mark, while still averaging over 60mph.

    This is similar to some of the other techniques discussed (or maybe this was discussed previously, but I could not find it) but by keeping the engine running when decellerating it allows me to decellerate much slower than when I would be in "warp stealth". By "loading" the engine when accellerating up to 65, I think it keeps the engine operating in a more efficient power band.

    I think this simulates what happens when I get good mileage on rolling hills.

    Any comments. It this method discussed some where else?

    I like the "Pulse and Semi-glide" name.
     
    #1 Winston, Apr 7, 2008
  2. Winston

    Winston Member

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    #2 Winston, Apr 7, 2008
  3. JimboK

    JimboK One owner, low mileage

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    Here's more on SHM from where it was first described and the term first coined. It gets into some pretty heavy talk of using ScanGauge numbers, in particular ignition timing, as benchmarks. As I posted in that thread, I'm not convinced it's not just that those IGN readings happen to coincide with very low ICE speeds -- probably in the ballpark of what you've achieved with those high iMPG readings. Some are of the belief that the ICE is "loafing" inefficiently at such low RPM ranges, but it's hard to argue with some of the results.

    I let terrain and traffic conditions guide what highway technique I use. I really think constant fluctuations in speed are more annoying to drivers behind you than one that's slower than posted but consistent. So the heavier the traffic, the closer I get to steady-state. As you suggest, on level terrain or gently rolling hills, SHM is more consistent than higher RPM pulses alternating with warp stealth. With steeper hills where with WS I lose minimal speed, maintain it, or gain it, I'll use that.
     
    #3 JimboK, Apr 7, 2008
  4. Winston

    Winston Member

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    I guess I will just post again in my nearly personal thread. Maybe I am :deadhorse: but I feel it is OK to discuss old subjects again, since new members rarely read through all the old stuff.

    Anyway, I played around with my technique on my way home yesterday and this morning. It seems to work really well to alternate between the SHM and and instantaneous mpg reading of around 30mpg. The 30mpg number gives me a slow accelleration on level ground and gets me up most rolling hills. The SHM allows me to hold speed if there is a slight downgrade or it causes me to decellerate slowly on level ground. I got quite a few bars over 75mpg on the MFD.

    In conclusion, I think SHM is much more usefull than warp stealth. It is also pretty easy to find SHM with just the impg gauge. I might not be getting the exact ignition timing numbers that are mentioned in the other thread, but I am getting between 70-99mpg on the mfd. Even in some traffic I am able to avoid bothering the cars behind me. I stay within a 5mph band if there are cars near me. That is about as good as everyone else does on the highway.
     
    #4 Winston, Apr 8, 2008
  5. kocho

    kocho Member

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    That's my thinking as well - more "useful" in terms of real life traffic on the highway. Deceleration on level ground at 60 mph is pretty quick when the ICE is off and the batteries do not help, so I have to pulse way too often just to keep-up with traffic.

    I "feel" (I can see the ignition timings and some other data on my "live" scanner but not as good as ona ScanGauge) that pulsing too often is less efficient than just doing what you are doing. I have been doing it with similar results myself. Only that in my '02 I can't seem to reach the same #s as you guys are getting in the '04+ model. If I get to 52-55mpg on the highway I feel happy (my city is usually a bit lower when traffic is heavy) ;)
     
    #5 kocho, Apr 8, 2008
  6. ServoScanMan

    ServoScanMan Member

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    This sounds like what I do on the interstate. I-35 thru central Texas has gently rolling hills. I gently accelerate up the hills and glide down the with MPGs in the 90s (instantanteous). I can even do this at 75-80mph. Pretty cools stuff!
     
    #6 ServoScanMan, Apr 8, 2008
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