Pulse and Glide technique

[jmeagher]

I have a couple of very basic questions. My apologies if I this means rehashing a bunch of stuff y'all already know. I found a bunch of stuff in the forums that addresses this stuff tangentially but I'm looking for a couple really basic pointers and a way to force rank techniques for best FE.

Pulse phase
(In my case it's all with the ICE on (AT, won't allow FAS > 5mph))

Is it more-efficient to slowly accelerate (≤1.2 GPH in my case) or rapidly accelerate (from 3 to 9 GPH). Assume same end speed (~40 MPH), at which point there's a coast in N to ~20 (which happens at .18 GPH).

It seems like the slow acceleration is best intuitively, but I wonder if by dramatically reducing the acceleration time period, even at high gas consumption, means longer coasts and therefore better overall economics?

Stop sign/light starts
How does one go about figuring out what the optimal acceleration rate is for one's particular vehicle? What techniques are people using for acceleration? (for the purposes of this, assume we don't have to stop, and there's nobody breathing down our necks, the goal is just to get to 35 mph and maintain).

Overall technique ranking
If you had to teach the following techniques, assuming that a driver will adopt them at close to 100% efficiency for the technique in all regular driving, in what order would you teach them? Assume a generic mix of driving conditions in a non-hybrid vehicle. Obviously all is better and I’m sure everyone here does all these and more, but I'm interested in each technique's impact on real-world MPG for non-hypermilers. I realize some things (like DWB and idle coast are linked, but just humor me if you would; pretend they aren't and that the person will learn a certain maximum number of things and then stop - the overall goal is to increase FE).

• FAS at stoplights
• DWB
• Idle coast (ICE on)
• Sidewall max pressure tires
DRL off
Radio off
• Weight savings (assume we can ditch 30 pounds)
• AC off
Highway speed of 60 versus 70
Pulse and glide (mix of both high and low speed P&G
DWL

Also if I’m missing any biggies, please LMK.

jm

[ksstathead]

DWB/anticipatory focus
DWL
Lower highway speed
Max sidewall
Pulse & glide

Above are major, core techniques, the order of which depends on what kind of driving you are doing.

Stoplight FAS
AC off
Face out parking
Potential parking
Grill blocking

[chilimac02]

You've got the ideas. I'm wondering what you consider the difference to be between Pulse and Glide and Idle coast (ICE on). When I do a Pulse and Glide it is always with the engine off during the glide.

I think the best advice will be to keep it near 60 on the highway. Different cars like different acceleration patterns. You don't list your car, so I don't know what you have. You could always try one technique for a whole tank, then a different one for a whole tank and compare results.

[Socal Monster]

Originally Posted by jmeagher

I have a couple of very basic questions. My apologies if I this means rehashing a bunch of stuff y'all already know. I found a bunch of stuff in the forums that addresses this stuff tangentially but I'm looking for a couple really basic pointers and a way to force rank techniques for best FE.

Pulse phase
(In my case it's all with the ICE on (AT, won't allow FAS > 5mph))

Is it more-efficient to slowly accelerate (≤1.2 GPH in my case) or rapidly accelerate (from 3 to 9 GPH). Assume same end speed (~40 MPH), at which point there's a coast in N to ~20 (which happens at .18 GPH).

It seems like the slow acceleration is best intuitively, but I wonder if by dramatically reducing the acceleration time period, even at high gas consumption, means longer coasts and therefore better overall economics?

Stop sign/light starts
How does one go about figuring out what the optimal acceleration rate is for one's particular vehicle? What techniques are people using for acceleration? (for the purposes of this, assume we don't have to stop, and there's nobody breathing down our necks, the goal is just to get to 35 mph and maintain).

Overall technique ranking
If you had to teach the following techniques, assuming that a driver will adopt them at close to 100% efficiency for the technique in all regular driving, in what order would you teach them? Assume a generic mix of driving conditions in a non-hybrid vehicle. Obviously all is better and I’m sure everyone here does all these and more, but I'm interested in each technique's impact on real-world MPG for non-hypermilers. I realize some things (like DWB and idle coast are linked, but just humor me if you would; pretend they aren't and that the person will learn a certain maximum number of things and then stop - the overall goal is to increase FE).

• FAS at stoplights
• DWB
• Idle coast (ICE on)
• Sidewall max pressure tires
DRL off
Radio off
• Weight savings (assume we can ditch 30 pounds)
• AC off
Highway speed of 60 versus 70
Pulse and glide (mix of both high and low speed P&G
DWL

Also if I’m missing any biggies, please LMK.

jm

Have you tested either of the methods? It seems like some cars could handle the methods differently.

[PaleMelanesian]

I'm assuming you're in the CX-5 (nice car!). Find the lowest rpm it will shift at very light and gentle acceleration. Say that's 2200 rpm or so. Your best acceleration will be faster than that, but keeping the rpm below that mark. You can get on it a little harder after each shift and let up as it gets closer to the next shift point.

The best efficiency is at low rpm and high load, a combination that most automatics don't allow. You're trying to get as close as you can to that. Aim for low rpm, and within that aim for high(er) load while still keeping the rpm low.

The real magic happens in the glide. Plan WAY ahead and try to never need your brakes. If you come in to a stop or intersection too fast, by all means use the brakes for safety. Just make a note of that and plan farther ahead next time so you don't have to.

[SentraSE-R]

As Andrew said, ATs are usually programmed with shift logic that doesn't allow best fuel consumption. They downshift and slip their torque converters well before their engines' best BSFC.

Originally Posted by jmeagher

• FAS at stoplights
• DWB
• Idle coast (ICE on)
• Sidewall max pressure tires
DRL off
Radio off
• Weight savings (assume we can ditch 30 pounds)
• AC off
Highway speed of 60 versus 70
Pulse and glide (mix of both high and low speed P&G
DWL

• Highway speed of 60 versus 70The best thing the average driver can do for fuel economy is slow down. 50 mph v. 60 mph v. 70 mph is 50 mpg v. 41 mpg v. 32 mpg in my Scion xB. In my Nissan Sentra SE-R, it was ~ 40 mpg v. 33 mpg v. 26 mpg. In my wife's Hyundai Elantra, it's ~50 mpg v. 45 mpg v. 39 mpg

• DWB
• Idle coast (ICE on)
• Sidewall max pressure tiresConserving momentum goes hand-in-hand with lower speeds. Braking simply turns momentum/inertia/kinetic energy into heat and brake dust.

• FAS at stoplightsThe EPA (at fueleconomy.gov) says drivers waste $,17 of every fuel dollar idling

• AC offA proven power robber & fuel waster, costing ~ 5 mpg. I usually can get away with cracking the windows down an inch and turning the fan on. If I have to run AC, I close the windows, recirculate the air, and turn the fan on high speed. I try to only run the AC compressor under low load conditions (on downhills, coasting to lights), and not at all when stopped.

• DWL
• Pulse and glide (mix of both high and low speed P&G
• DRL off
• Radio off
• Weight savings (assume we can ditch 30 pounds)This is the mouse milk category for ATs. DWL and P&G do help measurably, but the others probably can't be quantified, since they're lost in the white noise. Do them, but don't expect much for your efforts.

[WriConsult]

It seems like the slow acceleration is best intuitively, but I wonder if by dramatically reducing the acceleration time period, even at high gas consumption, means longer coasts and therefore better overall economics?

I think most people do intuitively think grandma-like acceleration is best, but that thinking is often wrong. It can be true with hybrids (which may have smaller engines and start digging into their battery packs unless you go really light), but is emphatically NOT always the case with ICE cars.

You really want to get through those first couple of gears very quickly, because those short gear ratios are extremely inefficient no matter where the engine is on its BSFC map. Not that you want to floor it, mind you: as with most things in life, the optimum is somewhere in the middle. With an automatic, the optimal rate of acceleration is extremely easy to figure out: just push it as hard as the transmission will let you while still shifting by 2200rpm or so. Put another way, those short pulses of power do use more gas per second but use less gas overall, and allow you to spend a larger share of the time gliding.

For local driving, here's my ranking of things that are worth doing:

• DWB. Local driving is ALL about DWB, low speed P&G and coasting, and they go hand in hand. It's all about avoiding having to throw away precious momentum into the brakes any more than you have to. Let everyone else hamster-race up to the next red light, dodging around you as they move their foot directly from the gas to the brake once they get close.
• Pulse and Glide (low speed) -- I completely agree with Andrew above that the magic is in the glide. In local driving, I'm probably coasting 75-80% of the time my vehicle is moving.
• Idle coast -- yes, while you're moving and not pulsing, you should be spending a very large percentage of the time doing this.
• AC off -- IF/when you can manage it. If I'm by myself in the car driving around town, I will usually put up with the heat and almost never use AC. My Hyundai is a very inefficient idler, and AC makes it considerably worse. However, my family is less tolerant of a car that's 90 degrees inside. But of course FASing kills the AC, and I still sometimes try to force them to live with that.
• Fas at stoplights -- at least at longer lights, definitely worth doing.
• Weight savings (assume we can ditch 30 pounds) -- this might only save a tenth of a mpg or so, but that can still add up. It's not worth pulling out necessities, but definitely avoid carrying around genuinely unneeded weight.
• DWL -- there are times you may use this, such as when you're going uphill and P&G isn't feasible.
• Sidewall max pressure tires -- much less important than on the highway, but still worth doing.

For highway driving my ranking would be different:

• Highway speed of 60 versus 70. This is absolutely #1. 70mph generates 60% more wind resistance than 60mph, and there's only one way to pay for that.
• DWL. If your vehicle has decently tall gearing (as a CX-5 does) this is the main thing other than keeping the speed down. My main highway technique in my reasonably tall-geared TDI.
• Pulse and Glide (high speed) -- for my short geared Hyundai this is HUGE, saving 30% or more, and is my main highway technique.
• Idle coast (ICE on) -- yes, on hills that are big enough to allow it. In fact, going up and down moderate hills is a natural form of P&G, and many of us find ourselves getting better mpg on rolling rather than flat terrain.
• Sidewall max pressure tires -- also very important on the highway.
• AC off -- again, IF/when you can manage it. I find on my new Hyundai that the penalty is pretty minimal on the highway, so I don't mind turning it on if my family demands it out on the road.

Turning DRLs off can enable longer FASing, but since you're in an automatic and won't be FASing except at lights, I wouldn't recommend bothering with it.

The only benefit you're going to get from turning the Radio off is less distraction. Some cleanmpgers swear by it, but doing without the radio makes my head want to explode from boredom. If you find that the radio distracts you from your hypermiling mission, then by all means turn it off. Personally, I've never found that to be a problem.

[waltermlee]

1) Driving without Brakes (DWB) - anticipatory braking is probably the most useful and easiest concept to adapt for a conventional gas vehicle.
2) lower Highway speeds, limiting your speed to a top speed of 60 mph and bottom speed of 50 mph will easily make your car more fuel efficient.
3) Driving with load (DWL) is needed on hilly roads.
4) Pulse and Glide (P&G) is for flat roads.
5) overinflating tires to max sidewall pressure reduces a tire's rolling resistance and supports the glide/coasting phase of 1) and 4).
6) FAS/NICE (if its legal in your state)

It's alway more fuel efficient to accelerate downhill than uphill or on a flat road.
It's alway more fuel efficient to accelerate on a smooth dry road surface than a rough or wet road surface.
It's always more fuel efficient to accelerate in a straight line than along a curved pathway

When you accelerating and speed over 50 mph, you start to lose energy from wind resistance

When a trip is shorter than 7 miles or 20 minutes, fuel efficiency takes a bigger thermal loss..

The ICE is always more fuel efficient after its fully warmed up.

If you have a six speed automatic Cx-5 mazda - the most efficient RPM and GPH for accelerations will be defined by the minumum rpm/speed/torque requirements of the transmission gear being used. Each gear will have its own the miniumum and optimum RPM (sweet point).
WriConsult is correct ... you need to observe at the minumum RPM and speed needed to shift upward from gear 1 to 2, from gear 2 to 3, and soforth. To get the best fuel efficiency you need to shift to the highest gear you can as quickly as you can and then stay there as long as you can.

The most fuel efficient speed is about 30mph because that the approximate highest speed where wind resistance is neligible for most vehicles which are moderately aerodynamic in form.

Find a flat road that is atleast 1 mile long where you can go 30 mph. Accelerated up to 30 mph and keep up that speed manually. Slowly ease up the accelerator allowing the RPMs and GPH to drop until the speed drops to 29 mph. Remember the RPM(1) and GPH(1) at this point. Raise the speed back to 30 mph, then slowly ease up the accelerator but donot allow the car to drop below RPM(1) and GPH(1) if the speed drops below 29 mph then remember this RPM(x) and GPH(x) and the speed up back to 30 mph. Repeat this process until you find the lowest possible RPM and GPH setting that will maintain the vehicle at 30mph. If you are doing an MPG marathlon those two numbers are useful to know when doing a pulse n glide.

[ItsNotAboutTheMoney]

I see kstat's anticipation and raise him buffering.

If it's the A to Z of hypermiling I'd go:

"Golden Rules"
Anticipatory focus
Buffering
Placard tire pressure

"Free Money"
NICE-on/hybrid glide
Partial DWB (coasting to stops with delays, avoid wasted acceleration, anti-wave)
Light timing/smart braking/threading the needle

"Trade-offs"
DWL
Parking: potential/face-out/distant
Slow down!
Full DWB
Grille-blocking
Sidewall tire pressure
Removing excess weight

"The Book"
P&G
FAS
Side drafting

That is:
I'd start with the anticipatory driving, buffering and maintaining placard tire pressure because those can be presented as improving safety, and they lead naturally to fuel economy gains without the driver consciously trying. In addition the on-road techniques can help make driving in traffic less stressful.

Then follow up with techniques that provide gains without requiring the driver to give up time.

Then introduce techniques that involve some trade-offs in terms of time in or out of the car. The driver can figure out which trade-offs they're willing to make.

Finally I'd introduce the more advanced techniques that are used to suck-squeeze(-bang)-blow the most miles out of each drop of gasoline (or diesel).

[RedylC94]

Originally Posted by WriConsult

I think most people do intuitively think grandma-like acceleration is best, but that thinking is often wrong. ...

The only benefit you're going to get from turning the Radio off is less distraction. Some cleanmpgers swear by it, but ... .

Yes to both those points. Very slow acceleration wastes time which can only be made up by cruising faster, which consumes more fuel than moderate acceleration and a slightly lower cruising speed, assuming equal overall trip time. In general, the way you manage your decelerations is more important than the way you accelerate.

Some grandmas I know have a heavy right foot.

About those radio swearers ... Such comments inspired me to measure the power my car radio takes. At a reasonable volume level, about one-fourth ampere, or less than 4 watts. That won't have much effect!