Extreme hypermiling attempts

lol. No worries. OK math,
log (x^2) is 2*log(x)

 

Oh ok right ... I forget them log identities

I checked your math and your math is correct.

Don't forget the MFD is usually optimistic by 5 to 6% as well. Ferls' 2.3 L/100km turns into 2.4 actual.

It seems that Ferls is very close to being the pulse & glide master, given the theoretical limits.

 

Very good point.

 

I'm an American. I have to blame something.

 

To me 22 mph/35 km/h to 31 mph/50 km/h already seems like quite the tight range, and it seems to produce very nice results, at least on flat ground. I remember the Japanese woman who got that 118 mpg (that was her, right?) would go down to 18 mph/29 km/h.

It is great you have good terrain to test this out. My area is riddled with stoplights or just large enough hills to disturb the process. Let us know how it goes with a lower target speed. If I find a good spot I'll give it a shot and let you know here. Your acceleration/SOC figures were a great help, grazie mille, Ferls.

 

Hi Sage,

I've used the formula for power of aerodynamic drag, P = (1/2)* rho * v^3 * A * Cd to calculate the aero work / mile and have come with the following values that differ from yours

Constants:
rho = 1.22521 kg / m^3 (density of air at STP)
A = 2.16 m^2 (frontal area of Gen II)
Cd = 0.26 (coefficient of drag of Gen II)

math:
40 mph = 17.8816 m/s
P = (0.5) * (1.22521 kg/m^3) * (17.8816 m/s)^3 * (2.16 m^2) * (0.26) = 1967.1 kg m^2 / s^3 = 1967.1 watts
work / distance = (1967.1 watts * 1 hour) / (40 miles) = 49.18 wh/mile

data set:
(mph, aero work/mile, non aero work/mile)
(40 mph, 49.18 wh/mile, 103.62 wh/mile)
(45, 62.24, 119.06)
(50, 76.84, 113.96)
(55, 92.98, 109.92)
(60, 110.65, 104.85)
(65, 129.86, 103.54)
(70, 150.61, 99.69)
(75, 172.89, 95.61)
(80, 196.71, 91.09)

Unless I've made a mistake. Then it seems non-aero work/distance decreases with speed. Perhaps you can graph it to determine if it's linear, 1/x, etc.

Another factor dominates around 40 mph data point to buck the trend. It could be an outlier, or something else.

 

Hi Sipnfuel,

Nice approach, and so far as my cursory look at the math can tell, no errors.

Your power equation for drag calculates out to 162.1 wh/mile at 75 mph, pretty spot on with Wayne's data point. The log-normal graph I made of Wayne's aero drag measurements is not *really* linear, it just wants to be
If the top of graph is taken as linear, extrapolating down to 40 mpg is much closer to your value, so I think you are right. Well, unless the power equation breaks down at lower speeds but I cannot explain why that would be the case.

Do non-aero energy losses really go down at higher speeds ? I doubt that is the case for tyre-on-road, but maybe it is true for lubricated moving parts as they get warmer. Feris could test this by first heating the joints up with say 30 minutes of highway driving, and then staging a P&G test.

Enjoyable exercise, thanks for joining in!

 

I've calculated aero work at 75 mph to be 172.89 wh/mile

Where do you get the value ~160 wh/mile. Is that calculated or a figure given by Wayne?

The constant power portion of the vehicle (computer, displays, pumps, relays, actuators, etc.), I assume is very insignificant.

Rolling resistance force increases with speed linearly, but higher temperatures decreases rolling resistance force by an inverse relationship. Still the overall force should increase with speed.

Rolling resistance force

Also if the Prius experiences higher downforce at higher speeds, then the rolling resistance force will increase as well. I'm doubtful this happens.

 

I calculated air resistance at 75 mph as (75/40)^2*49.18 = 172.9 wh/mile. I don't know why I wrote 162 earlier.

Sorry about that

 

SipNfuel,

Feris' best result was a an average speed of 37 kph. This calculates out to 28 wh/mile aero drag starting from the 49.18 wh/mile at 40 mph you obtained using the power calculation.

 

You are correct!
Following is my best for 188.5 km (117.2 miles) trip.

I did pulse up to 50km/h and glide down to 35km/h on speedometer reading, between 45km/h and 30km/h on actual speed.
The average speed shows 34km/h including some signal stops.

I do not care about engine rpm, but I pulse at HSI 100% in normal mode, then glide at HSI 0-10% or N range.
My JP Prius has Bridgestone ECOPIA EP25 summer tires (factory standard) and the pressure is 270kPa(38psi) front and 250kPa(36psi) rear.
Probably, I did 20% of pulse distance at 10km/L(10L/100km 23.5mpg) fuel consumption and 80% of glide distance with no fuel consumption.
The result was 50km/L(2.0L/100km 117.6mpg).

Ken@Japan

 

^^ It's a beautiful result Ken.
I can just imagine how annoying 49.9 km/L would have been

 

Ken is the man!!!

That is what draining the battery is for :rockon:

 

Thanks Ken.

Did you take any extreme measures? like:
Starting the trip with gas tank 3/4 empty...
Taking out the spare wheel and rear seat...
Going through 2 months diet before the test...lol

Giora.

 

With all of this work being put into trying to attain the highest MPG numbers I am curious if you guys have also researched the best LRR tires for this sort of thing. Ken states he is on factory tires.

In the performance world we are always searching for the parts to give us the most HP and the stickiest tires for traction. I would think that we would be doing the same thing with the Prius and hypermiling but we would choose the best tires for fuel economy.

 

I have a question in regards to ken1784's method above. When pulsing to HSI 100%, does that mean filling up the HSI section to the right, but excluding the power section at the end?

 

+1

 

The first post from the OP indicates they are reading SOC from a SG II on a 2010. I hadn't seen the x-gauge codes for this parameter on the spreadsheet posted by another OP on PC. Where did you get the codes from for SOC?

 

See post 281 here:
http://priuschat.com/forums/gen-iii...scussion/64406-scangaugeii-work-2010-a-8.html