Recently, someone claimed higher mileage using pulse and glide with a speed range of 45 to 60 mph than cruise control managed 55 mph. This seemed counter intuitive since as Ken@Japan pointed out, the threshold between engine off, hybrid operation is 46 mph. P&G assumes the engine goes off, no fuel burn, so a range of speeds 45-60 mph would ordinarily result in little or no performance improvement. Regardless, it is a testable hypothesis. Early this morning, I drove to a new test route, highway 72/20, and the GPS reports a 9.7 mile segment between traffic lights and with a speed limit of 65 mph between these two points:34.619052 N 87.051419 W 34.649002 N 87.213184 W altitude range: 174-194 m The temperature ranged 64-68F. This was just a survey to find a stretch to do some informal, field testing: 45-60 mph - average speed 53 mph, 59.5 MPG 60-60 mph - average speed 60 mph, 58.7 MPG So obviously, I need to go back and retest with the temperatures above 80F and use 53 mph for the cruise control, equivalent speed of the 45-60 mph P&G. Also, I need to do runs in both directions to normalize any wind effects. In order to generate reproducible results, I use cruise control to resume speed, the pulse, and "N" to coast. But this begs the question of the poll. Bob Wilson
We bought are 2010 Prius so we would consistently get good gas mileage without coasting and driving slowly and upsetting other drivers. So far we have been averaging a little over 50 MPG with 5,500 miles on our car. My wife and I are very pleased with our Prius. You may get a mile or two to a gallon more by pulse and gliding but whats the point when you are so fixed on that and not being able to attend to your driving and upset other drivers as well. Just my opinion. Alfon
In fact the SAE paper and I both agree on this principle ... it needs to be done away from traffic. My early morning tests were between 4:30AM and 5:30AM and the P&G testing abandoned as soon as early morning commuting traffic showed up ... not even rush hour but the leading edge. Bob Wilson
Wouldn't 45-60mph be P&S? Pulse & Stealth. 45-60mph got higher MPG than 60-60mph because of the lower average speed. 45-60mph strain the HV battery more as well.
I'll be shifting into "N". Can you define "Stealth" say using the power display? In the initial test, I'll use "N" but if there is an agreed upon definition of "stealth," I'm willing to give it a try once I've also measured the equivalent, steady speed. I agree on the first but haven't measured the second. Bob Wilson
I do this all the time. Sweet-spot burn on the up terrain, warp-stealth glide on the down. It can return 70+ MPG segments. . _H*
Sorry, I really meant Warp Stealth to glide. Both would show only one arrow from the HV battery. Stealth = 0 ICE RPM powered by HV battery. I believe 2010 raised this speed to 45 MPH from 41 MPH. Warp Stealth = ~990 ICE RPM powered by HV battery. This can be done at any speed above 46 MPH.
So it needs hills? The reason I ask is the route is 9.7 mi. (15.52 km) with a maximum altitude change of 20 m. These are GPS reported values so realize each minor altitude unit, 1 meter, is 1/1000 of the horizontal units, 1 km. Drawn to true scale, this looks about as flat as the Tennessee River. I'm pretty sure only the very end is steep enough that the Prius would roll on its own. So what is the velocity profile or model for Pulse and Stealth on river bottom land? Bob Wilson
Actually, P&G works even on non-hybrid cars. It just happens to work a lot better on hybrids such as the Prius due to regenerative breaking. I know this may be counter-intuitive, but it's true.
Hi Hobbit, Which is equivalent to 53 mph on level terrain in SHM .. conclusion P&G at highway speeds give little if any advantage.
I am not sure how regenerative braking factors in to Pulse and Glide, since there is no braking in the glide. A Hybrid is in esence a way to do pulse and glide the engine, without changing speed. That said, the Prius Atkinson being much more efficient at low outputs than an Otto Engine in standard cars returns less of a benefit for Pulse and Glide.
Above 45mph, the ICE has to spin, and we observe fuel injection during "N" coasting at that speed. That is wasteful driving and never reflect a real world fuel economy experiment, I think. Anyway, my opinion for the true glide is only done by the ICE stop situation below 45mph. Ken@Japan
i contend that at highway speeds, it takes too much gas to accelerate so a steady speed ON FLAT ROUTES is the best way to get the best mileage. now as Hobbit alluded to, if there are hills, then let gravity work for you. build up speed on the down slopes and slowly bleed it off going back up the other side. that would help...but flat routes... keep it at a steady speed is best i think
I'm with Ken on Pulse and Glide and it is fairly easy to test on this flat route using cruise control acceleration and "N" glide. Once that is 'off the table,' there may be merit in looking again at "Pulse and Stealth." Speculation but if we can get a good BSFC chart and map the transition between normal and energy re-circulation (aka. 'heretical mode'), it may be there is an operational line, actually a type of hysteresis loop that might be exploited: acceleration - high BSFC, normal mode, pumping up the kinetic energy stealth - highest BSFC, energy re-circulation, extending the duration by making up any energy deficit from a fraction of the kinetic energy My NHW11 has a Graham scanner and I have historical data. It may be as simple as mapping out BSFC data in normal and energy re-circulate mode and seeing if a closed, operational curve might provide a high efficiency, high speed advantage. For example: Acceleration along the upper blue dots followed by extended operation in the red dot area at peak BSFC. "Steath" might be as simple as having an energy re-circulate indicator and driving a profile based upon it and ICE rpm. But we don't have enough information about the ZVW30 to map out these states and I haven't seen energy re-circulate in the SAE papers, yet. What I'll do is run the classical Pulse and Glide experiment Saturday morning with my wife's ZVW30. I'll try to add a battery current reading and record the data with a digital recorder including: speed (mph) instanious MPG ECO power bar traction battery current This may give us insight to refine Ken@Japan's power bar map ... a rough approximation of power bar to wheel efficiency. Bob Wilson
Steady 50-55 is one thing, where steady-state to maintain is basically running right at the bottom RPM/load of the efficient range. But note that terrain is rarely *dead* level, even in the bottom-lands ... even very slight rises can cause speed to drop off and suggest a slight increase in push, and a slight fall afterward is perfect territory for a warp-stealth glide even if it doesn't wind up being incredibly long. And if you're on the secondary highways with limits of 50 or 55 and a few traffic lights, that forces glide-downs and re-accelerates ... and more states are starting to put in those "signal ahead" warning things that actually *tell* you what state it's likely to be in when you reach it which allows much better planning. . Where you've got like a 45 mph speed limit, minimal-pulse may actually be just a little too much power which would eventually take you too fast, thus mid-speed P&G does make sense for those scenarios. And working it into the terrain you come to is a pretty obvious extension of the techniques. . _H*
Good point. I've also been wondering at the experiment's use of cruise control for the pulse phase. Is that really an efficient ICE use mode ? Wayne Gerde's recommended 'driving with load' (DWL) instead of cruise control in hilly areas suggests otherwise.
I'm new to my Prius, but I'm pretty sure the MFD shows energy going back into the battery even without braking. There is still friction and etc causing the car to slow down, so I believe some of that lost energy is captured by the battery somehow... Someone correct me if I'm wrong. I don't know a lot about it yet.
Muhaha... When people here say 'glide' they imply that the gas pedal is being pushed down just enough to prevent the regenerative braking you mention. On a G2 Prius the MFD has no arrows.
Preliminary Results (more coming) Protocol Pulse - at 45 mph (72 kph), the gear is shifted into "D" and cruise control "resume" activated to accelerate to 60 mph (96 kph) Glide - upon reaching 60 mph (96 kph) the car is shifted into "N" No air conditioner but windows on one side rolled down Running start into each measured segment Route Alabama 72/20 - 14 miles (22.4 km) Eastern end - mile marker 63 just west of Rocket Road Western end - mile marker 49 just east of County Road 150 Column 1 Column 2 Column 3 Column 4 0 End Latitude Longitude Altitude 1 East 34 37' 24.48" N 87 04' 53.74" W 195 m 2 West 34 41' 03.33" N 87 18' 20.47" W 196 m This divided, four lane highway is posted 65 mph (104 kph.) Whether running pulse and glide 45-60 mph (72-96 kph) or the equivalent 53 mph (85 kph), we are always slower and in the right hand lane. With one exception, traffic flowed smoothly and passed without causing any backup or consternation. That one exception was the first P&G run that started late due to setup problems and had to end early due to unexpected, local congestion. Results Temperature: 90F (32 C) Wind: 10-12 mph (16-19 kph,) winds from WSW or W Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7 0 model direction method MPG miles time mph 1 NHW11 East cruise 62.0 14 15:35.7 53.86 2 NHW11 East P & G 60.5 12 13:32.9 * 53.14 3 NHW11 West cruise 58.7 14 16:07.7 52.09 4 NHW11 West P & G 55.0 14 15:42.3 53.49 I'll have to borrow my wife's car for the ZVW30 data. This may have to wait until Sunday. (*) short segment, due to traffic, driving and recording screw-ups, this segment started late and came in 13:32.9 sec from mile 50 to 62. Notes There are other methods for handling what has been called pulse and glide or pulse and stealth or terrain driving. Understand that I have no problem with such claims except I don't have a way to replicate them. Without a quantified or mechanical or automated way to replicate these alternate approaches, test and validation remains a problem ... good luck! But the ZVW30 ECO power bar may provide a measurable power scale. Ken@Japan has posted an ECO power bar with a scale. His first posting looked to be a 4 part scale although I think a 5 part scale might work even better. Regardless of the divisions, a scale on the ECO power bar would provide a way to define reproducible power levels. It would then be a trivial task to measure the acceleration and fuel burn of the different settings, a relative BSFC measurement. This would provide a quantifiable alternative to using cruise control for the 'pulse.' But let's address that in another thread. Bob Wilson
