Extreme hypermiling attempts

I did no special treatment.
Actually, the 188km trip was done from the tank full.
The spare wheel and rear seat are in place.
And so on...

I think Bridgestone ECOPIA EP100 summer tires are very good.
In Japan, we can get better one called EP100S than the EP100.

You don' have to be so sensitive about the HSI 100%.
I think HSI 110% is acceptable.

Ken@Japan

 

Thanks, Ken!

 

Dear instrumented Gen III owners,

Full HSI bar corresponds to what numbers in any of the following? kW, hp, RPM, IGN, etc...

And Ken, one problem I've not been totally satisfied with are slight uphills while pulsing and gliding. Do you like to be at speed before them so you can glide partially up? Do you prefer to always pulse on an uphill? Do you just go constantly from 50 to 35 km/h regardless of terrain, even when it means the glide will be very short (like on an uphill)?

I have dreams about these questions, your insight will be much appreciated

 

None of the above. It is more complex than that.

 

I, myself, do not know these numbers and I do not care about these numbers.

I don't like slight uphills either.
I try to avoid the slight uphills route as much as possible.
There are too many environment variables on everyone's slight uphills, such as terrain, length, traffic speed, battery SOC and others.
Therefore, there will be 100 way to attack the hills on 100 different drivers, no single answer.
I think it is everyone's homework on their own environment.

Ken@Japan

 

To elaborate on the complexity a bit, it's hugely dependent on the battery SoC (if it's lower than about 58% or so, the engine will work harder for a given throttle input and charge the battery; if it's higher than say 62% or thereabouts, the engine will relax a bit and let the car draw power from the battery to drain it back to the preferred 60% level.

It's also dependent on warmup, of course; for the first minute, the car will try to provide almost all power from the battery (you get maybe 6 amps of charging if you're stopped, which would be about 1.2 kW).

But under normal circumstances (SoC at 60% and car is warm), I'd expect it to be around 1800 rpm or so with the HSI full, give or take a couple hundred.

 

To extend the Glide period on a P&G cycle using a 2010 Prius on a flat road

1) the SOC needs to stay over 45% (3-4 bars, if you don't have a ScanguageII) so that the ICE will not attempt to recharge the batteries. When a 2010 Prius goes into a traction battery recharge cycle you loose about 3mpg to 6 mpg.

2) the engine coolant which warms the the emission system needs to stay over 160 degrees Farenheit ( >= 160 if you have a ScangaugeII FwT Xgauge). P&G is impossible to do from a cold start because during the first several minutes of the trip because the Prius ICE needs to warmed up the catalytic converter. When the 2010 Prius ICE goes into a warm up cycle you loose from 7mpg to 15 mpg in the winter time. Grill blocking is helpful in the winter time in an urban/suburban P&G cycle when speeds are under 45 mph. Because the ICE is running harder and is on more often than not when driving on the highway (both winter and summer) - grill blocking is not as useful for highway driving. If you exclude the fuel cost of the warmup phase of the ICE - your mpgs will be higher. If you include the warmup phase of the ICE - your mpgs will be lower.

3) You need to be using Low Rolling Resistant (LRR) Tires and/or the tire pressure needs to be atleast at the maximum sidewall air pressure, e.g. Yokohama Avid S33 maximum side wall air pressure is 44psi. When the road surface is dry and smooth, higher tire pressures, e.g. 50psi/48psi, can sometimes deliever even lower rolling resistance. When the road surface is rough and uneven, lower tire pressure (e.g. 40psi/38psi) gives better traction and thus fuel effiency than higher tire pressures(e.g. 50/48 psi). A tire's rolling resistance decreases as the tread wears out. New tire rolling resistance can be over 10% higher than the older tires they replace.

4) The best road for gliding have to be smooth black asphalt with no road/speed bumps or rumble stripes. Having a slight incline, e.g. 6 feet downhill over 300 feet, can helps too. Any dip or downhill section of a road can be used to improve FE. Synchronizing acceleration/application of power while moving downhill will increase FE ( more kinetic energy is created per unit of energy when the energy is applied while the vehicle is moving downhil than if applied when the vehicle is moving on a flat or uphill road )

5) With respect to the Pulsing subcycle - I believe the best metric for how hard the ICE is working on the 2010 Prius is the Gallons per Hour (GPH) Xguage on the ScangaugeII. Regardless of whether the 2010 Prius is in Eco, Normal, or Power mode, the most fuel efficient gasoline burn rate for the 2010 Prius is somewhere between .80 to 1.3 gallons per hour (pulsing speed <=45 mph) with my current guess to be about 1.0 gallon per hour.

6) To minimize the energy load - the AC should be off unless the car is moving over 45 mph. If you can handle it --the windows should be rolled up to minimize air drag/resistance.

7) Any weight in the rear cargo area increases the rolling resistance/ friction on the rear tire. The 2010 Prius rear tires are especially sensitive to the weight on the rear tire. A full fuel tank represents about 77 pounds and a fuel tank that is almost empty is about 7 pounds. When the fuel tank has less than 1/4 full, the Prius with over inflated tire can glide a bit further on a flat road surface. One of the reasons the Aptera is has only 1 wheel in the rear is that the engineers wanted to reduce the drag from the rear wheel so the reduced the rear axle from two wheels to only one. The reason why the rear tire pressure is lower for the Prius is to increase the rear traction for the rear axle.

8) IIRC Ken1984 optimum P&G speed range was 40mph for the top speed and 20mph for bottom speed. ISTN wind resistance/ drag drops off during a glide cycle after the Prius' speed drops below 33 mph - at which point rate of speed loss during the glide phase of the cycle decreases. To extend the glide phase - one only needs to lower the the bottom speed of the glide phase to something as low as 15 mph before returning to the pulse phase of the P&G cycle.

9) 100% real gas gives better MPGs than ethanol gasoline mixtures (E10,E15).

hope this helps

Walter Lee
2010 Toyota Prius III , Blue Ribbon/Dark Grey, Oem floormats
Yokohama Avid S33 ( 50 psi / 48 psi)
ScangaugeII (AVG, Fwt, SoC, GPH)
odeo 14700 miles/ +59 mpg overall,
md/dc area

 

To extend the Glide period on a P&G cycle using a 2010 Prius on a flat road

1) the SOC needs to stay over 45% (3-4 bars, if you don't have a ScanguageII) so that the ICE will not attempt to recharge the batteries. When a 2010 Prius goes into a traction battery recharge cycle you loose about 3mpg to 6 mpg.

2) the engine coolant which warms the the emission system needs to stay over 160 degrees Farenheit ( >= 160 if you have a ScangaugeII FwT Xgauge). P&G is impossible to do from a cold start because during the first several minutes of the trip because the Prius ICE needs to warmed up the catalytic converter. When the 2010 Prius ICE goes into a warm up cycle you can lose from 7mpg to 15 mpg in the winter time. Grill blocking is helpful in the winter time in an urban/suburban P&G cycle when speeds are under 45 mph. Because the ICE is running harder and is on more often than not when driving on the highway (both winter and summer) - grill blocking is not as useful for highway driving. If you exclude the fuel cost of the warmup phase of the ICE - your mpgs will be higher. If you include the warmup phase of the ICE - your mpgs will be lower.

3) You need to be using Low Rolling Resistant (LRR) Tires and/or the tire pressure needs to be atleast at the maximum sidewall air pressure, e.g. Yokohama Avid S33 maximum side wall air pressure is 44psi. When the road surface is dry and smooth, higher tire pressures, e.g. 50psi/48psi, can sometimes deliever even lower rolling resistance. When the road surface is rough and uneven, lower tire pressure (e.g. 40psi/38psi) gives better traction and thus fuel effiency than higher tire pressures(e.g. 50/48 psi). A tires rolling resistance decreases as the tread wears out. New tire rolling resistance can be over 10% higher than the
older tires they replace.

4) The best road for gliding have to be smooth black asphalt with no road/speed bumps or rumble strips. Having a slight incline, e.g. 6 feet downhill over 300 feet, can helps too. Any dip or downhill section of a road can be used to improve FE. Synchronizing acceleration/ application of power while moving downhill will increase FE ( more kinetic energy is created per unit of energy when the energy is applied while the vehicle is moving downhill than if applied when the vehicle is moving on a flat or uphill road )

5) With respect to the Pulsing subcycle - I believe the best metric for how hard the ICE is working on the 2010 Prius is the Gallons per Hour (GPH) Xguage on the ScangaugeII. Regardless of whether the 2010 Prius is in Eco, Normal, or Power mode, the most fuel efficient gasoline burn rate for the 2010 Prius is somewhere between .80 to 1.3 gallons per hour (pulsing speed <=45 mph) with my current guess to be about 1.0 gallon per hour.

6) To minimize the energy load - the AC should be off unless the car is moving over 45 mph. If you can handle it --the windows should be rolled up to minimize air drag/resistance.

7) Any weight in the rear cargo area increases the rolling resistance/friction on the rear tires. The 2010 Prius rear tires are especially sensitive to the weight on the rear tire. A full fuel tank represents about 77 pounds and a fuel tank that is almost empty is about 7 pounds. When the fuel tank has less than 1/4 full, the Prius with over inflated tire can glide a bit further on a flat road surface. The reason why the rear tire pressure is lower for the Prius is to increase the rear traction for the rear axle.

8) IIRC Ken1984 optimum P&G speed range was 40mph for the top speed and 20mph for bottom speed. The wind resistance/drag drops off during a glide cycle after the Prius' speed drops below 33 mph - at which point rate of speed loss during the glide phase of the cycle decreases. To extend the glide phase - one only needs to lower the the bottom speed of the glide phase to something as low as 15 mph before returning to the pulse phase of the P&G cycle.

9) 100% real gas gives better MPGs than ethanol gasoline mixtures (E10,E15).


hope this helps

Walter Lee
2010 Toyota Prius III , Blue Ribbon/Dark Grey, Oem floormats
Yokohama Avid S33 ( 50 psi / 48 psi)
ScangaugeII (AVG, Fwt, SoC, GPH)
odeo 14700 miles/ +59 mpg overall,
md/dc area

 

Regarding #1, I often have trouble holding a glide on a steep downhill section of highway due to my SOC dropping to 57.5% which seems to be the threshold for the Genii at 60-70mph. The ICE turns on to charge the battery and mpg drops from 9999 to about 120-150. I experimented with putting the car in neutral to try and reduce drag so I could make it up the next rise with as little throttle input as possible and mpg went from 120 ish to mid 300mpg. Since I have to recover that energy at some point my question is; should I just let the engine run on the downhill and get 120mpg or put it in neutral for 350mpg and let the engine recharge the battery while I drive the rest of my 40 mile commute on the flat freeway? Speeds are 65mph the whole way.

 

It sounds like F8L situation is a very long downhill section of road where the Prius gen2 achieves +65 mph either with the ICE in Neutral or with the ICE in Drive but with the foot off the accelerator and the batteries are recharging. I have only experienced this twice on a Prius gen2 roadtrip (rental ) when I'm driving through the PA mountain side. If the Prius is gliding downhill goes over 40-45 mph then ICE wil automatically turn on -- burning gas at about .30 GPH. I've read that if the Prius is put in neutral while its going downhill that the ICE will not automatically turn on at over 40-46 mph and that a gliding speeds higher than 60mph can be achieved with this technique. Unfortunately, I havent tested this technique out. Learning how to do this is on my things to do list

Correct me if I am wrong but From what I understand, when the Prius is in neutral - the batteries will not recharge because both
MG1 and MG2 are not engaged.

As for F8L's situation, If the road is flat AFTER the downhill section of road - the Prius would probably get better MPG if it was allowed to stay in neutral until the Prius needed to pulse the ICE again - maximizing the time ICE is off and the tranny is in neutral getting most of the Prius's kinetic energy translated into distance travelled. However, if the road is uphill AFTER the downhill section of road and the Prius is in neutral - you'll have to put the Prius back into Drive as it nears the bottom of the hill and start up the ICE before the Prius has to climb uphill. Let's suppose that the downhill road section is very long AND the Prius can glide a great distance in neutral before there is a need to switch back to Drive mode when the downhill section gives way to an uphill road section on the highway. If the Prius must go uphill after going downhill then I recommend gaining additional speed shortly before going uphill -- pulsing to a speed about 10 to 15 mph more than the desired speed at the top of the next hill/crest. It's more energy efficient to gain this extra speed and momentum while the Prius is still going downhill than to do so when the Prius is going uphill. My recommendation is a combination of two hypermiling techniques: Driving With Load (DWL) and NICE technique -When at bottom half of a downhill section of road or near the bottom of the hill the Prius speed should be 10 mph to 15 mph higher than the speed of the Prius when it reaches the top of the hill. At the bottom of the hill, the driver's foot is pressing the accelerator but as the Prius goes uphill the pressure on the accelerator is gradually decreased until it reaches the top of the hill at which point the Prius speed would have dropped by 10 mph to 15 mph from the top speed at the bottom of the hill - with foot off the accelerator at the crown of the hill so that the Prius essentially gliding the desired speed for a few seconds as it goes over the hump of the top of the hill. If you have to go downhill again - when the Prius starts pointing downwards again pulse the ICE at the desired speed near the top of the downhill section of roadway and then glide for the rest of the downhill section until you reach the last 100 feet or so of the downhill section - at this junction if the car must go uphill again you must turn on the ICE and apply this technique again - if the road at the bottom of the hill is flat you have the option to continue the gliding phase.

BTW - the 2010 Prius MPG drops from about 68 mpg @50mph to about 50mpg @70mph (in a somewhat linear fashion) so the Prius can gains higher FE even with Cruise Control(CC) simply by lower the speed a notch down when traffic permits it.

 

That is almost how I tackle my commute but I do not usually accelerate to 10-15mph faster than I want to top the hill at unless I was traveling downhill in the first place. At which point just go as fast as the car will go while in glide or neutral. What you wrote makes sense so I will start using that method and see if it helps. I average 53-55mpg with my 15" wheels and 45-46mpg with my 17" wheels on this commute.

Here is a graph of my commute elevation and my average speed:

Total Distance: 76.81 km (47.7 mi)
Total Time: 58:23
Moving Time: 54:40
Average Speed: 78.92 km/h (49.0 mi/h)
Average Moving Speed: 84.28 km/h (52.4 mi/h)
Max Speed: 115.96 km/h (72.1 mi/h)
Min Elevation: -28 m (-91 ft)
Max Elevation: 396 m (1300 ft)
Elevation Gain: 87 m (284 ft)
Max Grade: 2 %
Min Grade: -10 %
Recorded: Fri Aug 12 15:00:31 PDT 2011

 

Very nice results, my friend. A big congratulations to you.

 

ben fatto!