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Old 06-04-2008, 12:34 PM   #1 (permalink)
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Pulse and Glide with hills

What is the most efficient when PnGing through rolling countryside:
Pulse up the hills and glide down, or
Pulse down the hills and glide up?

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Old 06-04-2008, 12:42 PM   #2 (permalink)
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Pulse up, glide down. Average speed should be about the same but your peak speed will be less.
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Old 06-04-2008, 12:49 PM   #3 (permalink)
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Hill or no hill I just pulse when I get to the lower speed limit I wish to hit and glide when I hit my max speed. I have yet to hear why it would be more efficient to do it one way versus another, but am open to hearing any that you guys have.
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Old 06-04-2008, 01:33 PM   #4 (permalink)
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It's just one more way to keep the engine running at the best BSFC. You can "pulse" at that optimal rpm/throttle position, without changing speed. You get the same benefits, but without the air drag of the higher peak speed, or the crazy speed variations. Instead of building kinetic energy, you're building potential energy.

Seat-of-the-pants testing I've done shows this to be the better choice, for my car, in my area with the hills we have. My best highway run - 75mpg for 150 miles - was using this technique. Pulse from the bottom at ~45mph to just before the peak at ~60mph, glide up and over and down.

It seems to work better for manual than for automatic, though. I think DWL is better on hills for automatic.
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Old 06-04-2008, 01:36 PM   #5 (permalink)
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Quote:
Originally Posted by dcb View Post
Pulse up, glide down. Average speed should be about the same but your peak speed will be less.
I'm inclined (sorry ) to agree with you, but let me play the devil's advocate, for the sake of argument. 'Pulsing up' contradicts the 'ride like a cyclist' mantra. It puts more of a load on the engine, further decreasing efficiency. Is the 'glide down' enough to compensate?
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Old 06-04-2008, 01:40 PM   #6 (permalink)
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I'd say DWL / bicycle / roller coaster driving would be the intermediate level technique, and maybe the best for an automatic that likes to downshift with high load. Pulse up, glide down would be the next level, and better suited to manual transmissions.
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Old 06-05-2008, 12:45 AM   #7 (permalink)
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I agree with PaleMelanesian.

You're right that some of the tips on the big list are contradictory. The differences are mostly related to whether you're doing mild, medium or hard core.

When the list was produced, we also tagged each tip with ratings for difficulty/skill level (but I haven't incorporated into the output yet). They would show that the contradictory tips are in different categories.
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Old 06-05-2008, 02:39 AM   #8 (permalink)
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A higher peak speed (pulse down) would mean more of an aerodynamic penalty, right?
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Old 06-05-2008, 05:26 AM   #9 (permalink)
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I've been struggling with the same question about p&g vs. hills. My commute has quite a few of them. I don't have the definitive answer due to a lack of testing instrumentation, but I've been experimenting with the technique. I approach each hill a little differently based on it's steepness. If it's shallow I just pulse up the hill and glide down, initiating my pulse well before the hill so I can gain most of my momentum before I get to it. There are a couple areas where I shorten my glides and initiate my pulse early on the downhill to make the most of gravity and cheaply grab some extra momentum. For steeper hills, I will initiate my pulse early, grab momentum and let it bleed off as I climb the hill. I maintain the same throttle pressure for the pulse throughout the climb, gearing down if necessary. When I crest the hill, I continue the pulse, using gravity help regain my momentum and initiate a coast once I'm up to speed. It makes for a longer pulse and sometimes a shorter glide, but usually I can make up for it later in the trip. My favorite sections involve long downhill runs where I can kill my engine and coast for a little over a mile.

This is all seat of my pants type of stuff, so I can't really tell you if I'm on the right track with this technique, especially because I'm very new to the concept of p&g driving and I definitely need some more practice to get it right. On the other hand, I did get about 25mpg out of the last tank. Given that the updated EPA combined rating on my truck is 16mpg, I must be doing something right.
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Old 06-05-2008, 09:00 AM   #10 (permalink)
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[QUOTE=Twerp;31598]I've been struggling with the same question about p&g vs. hills. My commute has quite a few of them. I don't have the definitive answer due to a lack of testing instrumentation,
Right. I'm in the same situation. Haven't installed the vacuum gauge in my '88 Accord, but encounter several miles worth of rolling terrain on my daily commute. With back-to-back hills, there's opportunity to use either strategy, so it's not just a philosophical exercise.

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