Wayne Gerdes - CleanMPG.com
- June 21, 2006
Pulse and Glide
Let me take this opportunity to thank Dan Kroushl (Krousdb) who taught me the Pulse and Glide technique for Prius II’s last year. I also want to credit my “Prius Marathon” friend and co-driver Dave Bassage and Internet friend Bill G. for their help in making P&G one of the most important tools in my own hypermiling toolbox. Both Hobbit and Graham Davies should be credited for discovering/describing “Warp Stealth”. Doug Schaefer for taking the time to clean up and brigten some of my less then spectacular pics. And finally Carl H. for both his time and the use of his Prius II for many of the pictures below.
First 100 mpg Prius II segment
Krousdb’s first ever recorded 100 mpg + sustained segment in a Prius II
A friend of mine from work, Carl H., used to receive the upper 40’s/lower 50 mpg’s in his 2005 Prius II from the time he drove it off the lot through late spring/early summer of last year. With what I was taught in regards to P&G via E-Mail from Dan, Dave, and Bill, I passed along the technique as I understood it to Carl and his FE went from that higher 40’s/low 50’s mpg mark to the low to mid 60 mpg mark seemingly overnight! As his Prius II has broken in, temps have warmed in Illinois again, his Prius II’s setup is almost perfect, and he has become more adept at using the P&G technique in situations where it would be applicable, he is now punching out 70 and 80 mpg tanks over his own 25 + mile commute! His use of an alternate route paralleling the Interstate has allowed the ability to run within the P&G constraints for much more of his commuting distance allowing him to almost but not quite double his FE from Day 1 until today! With these real world results, I hope you can both learn and use the technique(s) when and wherever applicable in your Prius II as well.
Carl H. and his Prius II on the Alternate - Warm up Pulse and Glide Route.
Without further fanfare, here is the P&G and “Warp Stealth” technique(s) in both explanation and with pictures so you can learn from and use them while driving through your daily grind as well.
“Pulse” is any acceleration from a lower speed target at a rate to keep from drawing off the pack while also filling the pack (Green Arrow from the MGSet to the Pack on the Energy Monitor screen). You do not want to see Orange arrows from the MGSet to the Wheels on the Energy Monitor screen. Our intent during the “Pulse” phase is to get up to a top target speed less then 41 mph in which you can quickly and smoothly transition to the “Glide” phase. Any top speed target will work to fit a given traffic condition as long as you maintain less then 41 mph for the highest FE. That was the explanation but how do you actually “Pulse”?
Using a 30 mph to 40 mph band as an example, when you are cruising along at 30 mph, you step into the accelerator just enough so as to not see assist from the pack (as described above) and fast enough to maintain an average “Pulse” rate of your choosing. You can control your “Pulse” rate of acceleration but you do not need to maintain an exact rate as seen in the pics below. A 20 mpg average “Pulse” rate may include an initial 17 mpg rate when you first start the “Pulse” and maybe 23 mpg “Pulse” rate when you hit your top target speed before you transition to “Glide”. For a 40 mpg average “Pulse” rate, you might see a 36 mpg “Pulse” rate when you begin your “Pulse” and a 44 mpg “Pulse” rate just before you enter your “Glide”. To recap, you gently step on the accelerator enough to get the ICE to spin up and provide propulsion with the energy screen showing ICE power to the wheels and power through the depicted MGSet to the pack while the digital iFCD readout is showing anywhere between 15 and 55 mpg for the acceleration back up to 40 mph or less.
Example of a 16 mpg Pulse rate.
Example of a 23 mpg Pulse rate.
Example of a 32 mpg Pulse rate.
Example of a 40 mpg Pulse rate.
“Glide” is the coast down mode that can be a bit tricky. What you want to see in your Energy Monitor screen is the ICE-Off and no arrows from anywhere or too anywhere (Black Screen) while you are coasting down from the top “Pulse” target speed to the lower target speed for a given traffic condition. This allows little to no loss of momentum via Regen or providing “Electric Only” propulsion to the wheels. The way the “Glide” technique is implemented is that you hit the maximum target speed below 41 mph during your “Pulse”, let off the accelerator just a touch for a fraction of a second to shut down the ICE and induce a touch of Regen (best if you can skip Regen altogether), then press down on the accelerator ever so slightly to achieve and then maintain blacked out arrows all around with the ICE shut down, no regen to the pack, and no pack to MGSet to wheels propulsion down to the lower speed target. The blacked out arrows on the energy screen tell you that you are in or very close to being in this almost coast free state. You will need to practice this in your Prius II as it is not intuitive. I am sure most have probably been told by whomever that Regen is a hybrid’s real technological advance. It can be in circumstances when you must come to a stop before you had planned without the ability to “Glide” much of that distance. Many hypermilers evoke Regen for SoC management, when confronted with an uncontrollable slow down during a heavily congested traffic situation, or when a blown light timing forces an abrupt stop. Just remember that a pure “Glide” from 40 mph and below as well as “Warp Stealth” as described later on in the article from much higher speeds works. With a little practice, you will be able to enter into and out of “Glide” mode at will while just using your right foot on the accelerator.
What a Glide will look like on the Energy Monitor screen.
You may consider using a small amount of EV to maintain a slower speed and or crest a small peak so you can continue your glide down the back side. There are limits to EV so use it sparingly within the P&G technique and only where it can extend your Glide for even higher FE.
Why does P&G actually work? P&G is not just about a speed range nor is it about an acceleration rate. It is a combination of a given amount of fuel consumed and distance traveled in the “Pulse” phase vs. the distance traveled in the “Glide” phase. If you “Pulse” for .3 miles at 35 mpg, you need to “Glide” at least twice the distance covered during the “Pulse” (.6 miles) to achieve 105 mpg average over .9 miles. When “P&G” is broken down to its component parts and reassembled, you simply have to accelerate for a given distance at a given consumption rate (“Pulse”) and coast (“Glide”) for an extended distance to cover the Pulse’s fuel consumption to achieve a given FE. Here are a few examples:
The following equation will show you what you will need to achieve for a given target FE.
Pulse distance * [(Target FE mpg/Average Pulse Rate in mpg) – 1] = Glide distance needed to achieve target.
For a 100 mpg target goal, the following equation and examples of differing Pulse rates (Average FE during the Pulse) will give you your glide distances needed to achieve your 100 mpg goal!
Pulse Distance (miles) * [(100 mpg/20 mpg) – 1)] = Glide Distance (miles) needed to achieve target.
Pulse at a 20 mpg rate of acceleration over .2 miles:
.2 miles * [(100 mpg/20 mpg) – 1] = .8 miles of Glide to achieve 100 mpg over a total distance of 1 mile.
.2 miles of Pulse at a 20 mpg pulse rate with .8 miles of Glide will give you a 100 mpg.
Pulse at a 30 mpg rate of acceleration over .3 miles:
.3 miles * [(100 mpg/30 mpg) – 1] = .7 miles of Glide to achieve 100 mpg over a total distance of 1 mile.
.3 miles of Pulse at a 30 mpg pulse rate with .7 miles of Glide will give you 100 mpg.
Pulse at a 40 mpg rate of acceleration over .3 miles:
.3 miles * [(100 mpg/40 mpg) – 1] = .45 miles of Glide to achieve 100 mpg over a total distance of .75 miles.
.3 miles of Pulse at a 40 mpg pulse rate acceleration with .75 miles of Glide will give you 100 mpg.
Pulse at a 50 mpg rate of acceleration over .4 miles:
.4 miles * [(100 mpg/50 mpg) – 1] = .4 miles of Glide to achieve 100 mpg over a total distance of .8 miles.
.4 miles of Pulse at a 50 mpg pulse rate with .4 miles of Glide will give you 100 mpg.
Pulse and Glide sequence in the real world
Prius II “Pulse” Sequence #1: RR Crossing sign is ~ 1/3 mile ahead. Time is 11:38 AM. “Pulse” rate: ~ 24 mpg. Speed is ~ 33 mph and climbing when the picture was taken. Pulsed to ~ 35 mph due to (2) sharp turns after RR tracks ahead. Notice 3 Blue Bars on the SoC graph.
Prius II “Glide” Sequence #2: Notice RR Crossing sign a hundred + yards ahead. Time: 11:38 AM. Proper “Glide” showing no Arrows. ~ 33 mph and decelerating slowly in the “Glide”. Notice 4 Blue Bars on the SoC graph achieved during previous “Pulse”.
Prius II “Glide” Sequence #3: Just about to pass RR Crossing sign. Time: 11:39 AM. Proper “Glide” showing no Arrows. ~ 32 mph and still decelerating in the “Glide”. Notice we still have 4 Blue Bars on the SoC graph for a little EV later on in the “Glide”.
To wrap up the tutorial on P&G, you want to accelerate up to a maximum of 40 mph in the “Pulse” phase, begin the “Glide” phase and coast down to a lower target speed. Once the lower target has been reached, you want to reinitiate the “Pulse” phase, re-accelerate back up to a maximum of 40 mph using the energy screen as displayed, and repeat when and where applicable. The Prius II is very flexible in terms of how to apply the P&G technique to a given traffic situation. You can “Pulse” at any rate between 15 and 55 mpg, “Pulse” to a target of 40 mph or any speed under that depending on what traffic allows, and “Glide” from the higher speed “Pulse” target to any lower speed including stopped! It only depends on traffic conditions around you. For most, a “Pulse” w/ a 17 - 23 mpg acceleration rate might be best to keep up with normal traffic acceleration rates and compress the P&G speed range to between 33 and 39 mph while driving on a 35 mph limited roadway or in traffic tie-ups and jams that allow it. While P&G’ing between a 33 and 39 mph range, a car behind on the 35 mph limited roadway can barely perceive you are driving any different then they might be themselves! P&G will push a Prius II’s average FE over a given distance through the roof when and where it can be implemented. The large band and lower target speeds may make the P&G technique un-usable under a multitude of traffic and or roadway conditions you may drive through on a daily basis. When in those non-P&G friendly conditions, drive as any hypermiler would with only a portion of the tools available and save the P&G technique for when and where it can be applied safely and correctly.
Normal Commute Result
Carl’s current tank at 81.5 mpg after 492 miles going back and forth to work.
Interesting 5 minute bar graphs above. First 5 minute bar: Country road transition to a short State Route jaunt. Second 5 minute bar: Short State Route and transition to country road. Third and fourth 5 minute bar’s: Country Road. Fifth and Sixth 5 minute bar’s: Heavily traveled city/suburban roads with ~ 90 mpg average over the 30 minutes. Carl's previous record tank may be bested by 8 mpg's and possibly more? Still at 1/2 tank too!
Warp Stealth or HS (High Speed) Glide
What is the “Warp Stealth” technique all about? Since I personally have < 20 miles in a Prius II at highway speeds, I can only describe what I saw on the Energy Consumption screen while exiting the Interstate multiple times early yesterday afternoon. Carl has been using this technique for a while to great advantage when under higher speed conditions. I was astounded seeing it for the first time with the ICE-Off under a type of EV mode while far above the 41 mph MG1 limits. Hobbit lightly touched upon the technique a few weeks ago in the thread entitled Throttle Control
. MG1 is spinning backwards at a very high RPM as it should in this condition. Warp Stealth is very similar to the HCH-II’s EV/Glide mode in which the ICE is spinning while in Fuel Cut. With a slight amount of EV, you can slow the deceleration somewhat but a HS “Glide” is where the Fuel savings will make this technique a good one for those traveling the highways and byways of America. The 2 pictures below should explain exactly what you will see while the Pack draw is minimal when coaxing the Prius II into this condition. For a more detailed description, please read Hobbit’s page on: “Warp Stealth: a Prius driver's guide.
Prius II Full Picture - We were decelerating through 48 mph at the time I snapped the picture while coasting down onto the off-ramp from a short highway jaunt. This is “Warp Stealth” or HS “Glide” while exiting I-55 in North Central Illinois.
Warp Stealth - Closeup
Close up of the Prius II’s Energy Screen during the “Warp Stealth” mode above. Although the cloth is covering up most of the Speedometer, you can just make out the side of the 4 and top of 8. This is the same image as above zoomed in to the area of interest taken while decelerating through 48 mph showing 99 mpg, ICE-Off, and running down on EV. This is what “Warp Stealth” or a HS “Glide” looks like close up.
To enter into “Warp Stealth” from a higher speed cruise, you drop back on the accelerator a small amount and enter into a slight slowdown with a very light amount of Regen for fuel cut. Skip the Regen just as you do when entering “Glide” if at all possible. The Energy Screen should show an ICE-Off condition. Slowly reapply the accelerator (exactly like you would to enter “Glide”) which eliminates any Regen if you did inadvertently evoke it. You should see the pack come online to keep the ICE (still in Fuel Cut) spinning yet off at a rate to protect MG1 and/or help push the car via MG2 a small amount.
How can “Warp Stealth” be exploited besides for a high speed “Glide” (41 mph and above) and transitioning to a std. “Glide” (below 41 mph) while coasting down to an arterial from a Highway Off-ramp? I have the distinct feeling “Warp Stealth” can be exploited similarly to P&G below 41 mph but at highway speeds? A HS P&G may be an area some Prius II owner would like to explore. I am positive it will not yield the same types of FE increases as a standard P&G below 41 mph will but you may see a nice increase over and above the Prius II’s standard higher speed cruise. This higher speed cruise is where the Prius II begins to consume fuel at a rate some may consider unacceptable and especially when compared to its capabilities below 41 mph? I will leave this question open until either Hobbit or another serious Prius II hypermiler can take the technique to its final conclusion.
Finally, please practice the technique(s) above on roads with little to no other drivers around until such time they are second nature. There is a risk you will be paying far too much attention to the Energy Monitor display while learning/practicing instead of the road ahead as you normally do! I am sure we all know what the consequences of this inattention could lead too so please for all our sakes, be very careful out there.