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Quantitative Pulse and Glide

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Posted by bwilson4web on February 2, 2011, 7:12 am
Good testing is based upon holding as many variables constant and only
changing the one under question. Certainly it is important to document
the methodology to so others can replicate THE RESULT. Sad to say, we
get a lot of "Pulse and Glide" methodology and too little test results
where everything is kept constant except the use of "Pulse and Glide"
versus say "constant equivalent speed."

On a single day I conducted a series of runs over the same course,
both ways, only changing:

o pulse and glide
o constant speed


Pulse was handled by using "resume" on the cruise control stalk. Glide
was handled by shifting into "N". This limited the speed range to
25-42 mph due to the 23 mph lower limit of cruise control memory and
upper limit of 41 mph on hybrid mode.

Constant speed was handle by setting cruise control to the equivalent,
speed over the course of the pulse and glide protocol.  Entry to the
course was at the constant speed equivalent. Exit was at a fixed
location at least six pulse and glide cycles later.


constant - PnG
70 - 78
74 - 85
76 - 90
85 - 93
90 - 94
- - - - - -
79 - 88 MPG average

PnG = 11.4% improvement

So for the pleasures of changing the speed from 25 mph to 42 mph,
mileage improved 11.4%. Sad to say, I've only found one other similar
report, SAE 2009-01-1322. However, it looks like they allowed the
traction battery SOC to decrease during some of their tests. Still, we
have two documented tests comparing PnG to constant speed.

. . . Anyone else?

Bob Wilson

Posted by News on February 2, 2011, 1:42 pm
On 2/2/2011 2:12 AM, bwilson4web wrote:

With respect, what effect do you think this sort of repeated, wide speed
variation (+68% to -41%) has on surrounding drivers and traffic?

Posted by bwilson4web on February 2, 2011, 2:38 pm
I think it is nuts with other traffic around. It leads to unnecessary
tailgating at both ends of the speed range . . . depending upon the
posted maximum speed.

Both the SAE paper and my own testing confirm these should only be
done isolated from other traffic. So in my case, it was a Saturday
morning on a straight, flat road at Redstone Arsenal that connects the
river side recreational areas and the main base. If other traffic
showed up, I aborted the test by pulling on to the shoulder and
parking. After traffic cleared, I proceeded to the next start point
and set it up again. But I believe low-traffic roads and parking lots
exists that can be used for such tests and this is why I'm looking for
others who might measure their Pulse and Glide performance versus
constant speed.

Likely places to find under utilized roads and parking lots include:
sports stadiums and recreational areas at dawn or non-weekend days.
Roads near rivers are often fairly flat, especially if on flood
planes. Higher speeds can often be tested safely between 2:00 and 5:00
AM. The key is to find roadways at times they have very little traffic
and if there are multiple lanes, use the emergency "flashers" to
signal following traffic should pass.

From my standpoint, I'm interested in the physics, the engineering
aspects that let us know how much pulse and glide improves mileage.
Too often I see only one number posted:

"I got <wonderful> MPG using pulse and glide at <Y> elapsed speed."

Without the control:

"I repeated the same route at a constant <Y> speed and got <something
else> MPG."

This second statement is too often missing so no one can really tell
what pulse and glide accomplished.

Bob Wilson

Posted by News on February 2, 2011, 3:26 pm
 On 2/2/2011 9:38 AM, bwilson4web wrote:

<Note to "Bruce Richmond">

<Note to "Bruce Richmond">

Agreed.  Experimental design is important.  As is limiting experiments
to the lab.

Posted by Bruce Richmond on February 3, 2011, 5:46 am
<Note to News, learn to read.>


"The down side is that it will annoy anyone stuck behind you when you
are doing it.  I know that and make it a point not to play that game
when someone is stuck behind me."

Did you not understand the above statement?

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