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Pulsing and gliding your way to better fuel economy
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02-13-2008, 08:15 PM
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Senior Member
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Join Date: Nov 2007
Vehicles: 99 Honda HX MT, 93 Mazda MX6 LS V6 MT, 99 Dodge Grand Caravan Sport 3.3L
Posts: 620
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Re: Pulsing and gliding your way to better fuel economy
From the article -
Since you are your transmission's brain, it can't try to downshift when you put the pedal to the metal. That's right, go ahead and mash it ... this is momentary, right? (Unless you're driving a Lamborghini, you accelerated briskly, but did not get airborne.)
Ok, I guess I'll enjoy pedal to metal accelerations on my HX! Couldn't belive my last short tank of 4.1 gals was 43.8 mpg! - With fun acceleration!
__________________
1999 Honda Civic HX MT
1993 Mazda MX6LS V6 MT
1999 Dodge Grand Caravan Sport
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02-13-2008, 08:35 PM
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Member
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Join Date: Jan 2008
Vehicles: 2008 Toyota Yaris Sdn AT
Location: Pittsburgh
Posts: 69
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Re: Pulsing and gliding your way to better fuel economy
Man, I'm having a hard time coming to grips with that part. I have no idea at what point I've gotten enough glide to justify dumping as much gas into the engine as I just did during the pulse. In most cases, I just don't feel like I've gone far enough in the distance it takes to drop the target MPH. I live in a very hilly environment. My downhill FAS are great, but the P&G still eludes me. Also, I know to shut the ICE off for moderate to long idling times (red lights, etc), but should I really be restarting my engine with the ignition so often as I am trying to P&G (I have an AT)?
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02-14-2008, 02:39 AM
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Kaizen Driver
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Join Date: Dec 2007
Vehicles: 2002 Toyota Corolla Verso 1.6 VVT-i Manual
Location: Norway
Posts: 377
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Re: Pulsing and gliding your way to better fuel economy
"First, in some states like Colorado, coasting in neutral (at least downhill) is illegal. Also, when in neutral you are at a safety disadvantage because of the delay of shifting back into gear."
This is wrong,wrong and utter wrong! For a typical 'european' car which is generally low-powered and manual shift, you are usually cruising in a low gear with low rpm. If you floor the pedal to get away from danger, the engine will only say 'oomph!', and nothing will happen other than a 0.1 g acceleration anyway.
If you are in neutral, you will have an easier task to select proper low gear, floor the pedal and drop the clutch. Zoom!
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02-14-2008, 08:07 AM
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Beat The System
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Join Date: Jan 2007
Vehicles: 2009 Fit, 2004 Odyssey, 96 Civic retired
Location: Longview, TX
Posts: 12,782
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Re: Pulsing and gliding your way to better fuel economy
Just stay away from absolute full throttle. At some point, the car's computer starts ignoring the fuel/air ratio and just dumps a bunch of fuel in there. With a scangauge, you can see this by watching the Loop gauge. If it goes Open Loop, you've gone too far. Anything less is golden.
For an auto, you'll have to go easier on the throttle. You want the most throttle that will avoid a kickdown shift. The lower the rpm, the better.
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Andrew
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100 mpg commute / 90.2 mpg tank = 1191 miles
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02-14-2008, 08:17 AM
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Senior Member
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Join Date: Feb 2007
Vehicles: 1997 HONDA CIVIC HX Manual (M5), ScanGauge
Location: CT
Posts: 502
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Re: Pulsing and gliding your way to better fuel economy
Quote:
Originally Posted by PaleMelanesian
... For an auto, you'll have to go easier on the throttle. You want the most throttle that will avoid a kickdown shift. The lower the rpm, the better.
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Probably the best advice that I've seen that's specific to auto-tranny driving.
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1997 HONDA CIVIC HX Manual (M5) ScanGauge, MPGuino, running 54 psi. Currently ~ 47 mpg avg (summer).
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02-14-2008, 08:48 AM
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Member
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Join Date: Jan 2008
Vehicles: 2008 Toyota Yaris Sdn AT
Location: Pittsburgh
Posts: 69
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Re: Pulsing and gliding your way to better fuel economy
Quote:
Originally Posted by PaleMelanesian
For an auto, you'll have to go easier on the throttle. You want the most throttle that will avoid a kickdown shift. The lower the rpm, the better.
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Cool. Thanks. That's the first time I've seen it addressed that way.
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02-14-2008, 04:54 PM
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Veteran
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Join Date: May 2006
Vehicles: 04 prius
Location: Bahstahn
Posts: 2,691
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Re: Pulsing and gliding your way to better fuel economy
High-torque but low RPM is sort of counterintuitive, just
because most people associate opening the throttle with a big
vrooom. So the way to keep that in check is with gears.
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Can someone with an automatic and a scangauge actually *check*
and tell us about how high you can push LOD before your tranny
downshifts itself, per the gentle-application advice given
above? I think the commuity at large, observers of the Prius,
and the various BSFC charts and such we've found kicking around
generally agree on 75 or 80% as low-RPM optimal to stay on the
efficiency hump.
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I'm not exactly sure how to account for idling in some of those
charts, since it looks like very low load at low RPM would be
down in the inefficient regions. Maybe it is, just not happening
frequently enough to make significant enough fuel consumption
relative to the rest of the chart?
.
_H* |
02-15-2008, 07:06 AM
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Veteran
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Join Date: Dec 2006
Vehicles: 2001 Corolla, 2008 Sienna
Location: Richmond, VA
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Re: Pulsing and gliding your way to better fuel economy
I'll try to remember to check that out when I get the chance, hobbit. On flat surfaces, I think I can get up to about 60 LOD before it downshifts, but that is just a guess. It might be higher. I usually watch GPH. 1.7 GPH is about equal to 50 LOD. If I remember I'll look today on the way home. But that's 8 hours from now, so it could easily be forgotten.
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Skwyre7
(aka Michael)
 
 
New to hypermiling?
Want a clinic in central VA? PM me.
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02-15-2008, 04:23 PM
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Veteran
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Join Date: Dec 2006
Vehicles: 2001 Corolla, 2008 Sienna
Location: Richmond, VA
Posts: 1,602
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Re: Pulsing and gliding your way to better fuel economy
Going about 45 mph up a slight hill, the transmission would downshift between 65-67 LOD. This was reproduced three times (on the same hill). This was on a warm ICE.
__________________
Skwyre7
(aka Michael)
New to hypermiling?
Want a clinic in central VA? PM me.
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02-15-2008, 10:55 PM
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Veteran
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Join Date: May 2006
Vehicles: 04 prius
Location: Bahstahn
Posts: 2,691
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Re: Pulsing and gliding your way to better fuel economy
So you could safely push to, say, 60% to stay in high gear?
Sigh, I was sort of hoping it would be a little more than
that, but that's still not *too* bad on the BSFC charts and
I guess they have to leave themselves a little headroom.
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Thanx, that's useful. I should log more time in someone's A/T
car just to get a better idea of how it feels..
.
_H*
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