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Old 05-01-2011, 11:36 PM   #1 (permalink)
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Pulse and Glide VS DWL

Driving with load says you should hold throttle constant going up and down hills.

Pulse and glide/BSFC charts suggest you should pulse up them in low gear at high throttle and coast down.

Both theories are pretty well accepted around here, but they appear contradictory to me in this area.


Explain/discuss.

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Old 05-02-2011, 06:11 AM   #2 (permalink)
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When you get your best MPG during constant load driving, the engine isn't working at its best BSFC.
That's the key to P&G.
The engine is only returning good MPG because it's hardly putting out any power.
It could make more power more efficiently, if only you'd let it.
But in normal driving, you can't let it as you'd always be accelerating because the engine would put out more power than what little you'd need.

Enter P&G.
The pulse is done near the best BSFC.
MPG are fairly high, but there's also a lot of power being generated very efficiently, for a short period of time.
Gliding engine-off consumes no power at all.
(Keeping the engine on uses only a little bit of gas - though in a highly inefficient way)
The catch is to stretch the glides to the maximum, i.e. reduce drag as much as possible.


The combination of bursts of highly efficient fuel use with no fuel use at all, is often better than driving with constant load at an inefficient power setting.
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Old 05-02-2011, 01:16 PM   #3 (permalink)
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^^^ That's why MT P&G beats AT DWL, because the P&Gers only run their engines when needed, while the DWLers have to run their engines all the time when moving
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Old 05-02-2011, 01:41 PM   #4 (permalink)
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So in your opinions DWL is more of a "stopgap" measure. Pulse and glide is the one true way.
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Old 05-02-2011, 02:56 PM   #5 (permalink)
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Pulse and glide can get cumbersome, with traffic, repeated starts and stops on a long journey. Most use a mix of the two. Pulsing and gliding where able, dwl where unable and driving "normal" where necessary.
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Old 05-02-2011, 03:07 PM   #6 (permalink)
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Quote:
Originally Posted by justjohn View Post
Driving with load says you should hold throttle constant going up and down hills.

Pulse and glide/BSFC charts suggest you should pulse up them in low gear at high throttle and coast down.

Both theories are pretty well accepted around here, but they appear contradictory to me in this area.


Explain/discuss.
I thought DWL was you selected an MPG level (min and max) or a LOD rating (still don't know what that is based on) and drive to that rather than a constant position. You may combine it with a min speed range.

I am happy to be wrong about this...
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Old 05-02-2011, 11:04 PM   #7 (permalink)
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Quote:
Originally Posted by Arragonis View Post
I thought DWL was you selected an MPG level (min and max) or a LOD rating (still don't know what that is based on) and drive to that rather than a constant position. You may combine it with a min speed range.

I am happy to be wrong about this...
This is my understanding of DWL as well.
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Old 05-02-2011, 11:38 PM   #8 (permalink)
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Quote:
Originally Posted by justjohn View Post
So in your opinions DWL is more of a "stopgap" measure. Pulse and glide is the one true way.
As Bestclimb said, most of us mix and match our driving to suit local conditions. P&G gets the best results, especially on level roads and downhills. DWL works well on short and moderate uphills.

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