MPG study driving with HSI display vs without

There should be a distinction between driving techniques so the data is actually useful.

If you drive without a care for efficiency then I doubt the HSIANG makes any difference. Conversely, driving for efficiency may benefit from the HSI depending on how nerdy the driver is. LOL

 

Probably also depends how much experience the driver has. Not having HSI will probably make less difference for a driver that has driven with HSI a lot, knows the car and the methods better.

 

True that.

 

Driving slower makes your mileage go way up. Driving faster makes your mileage go way down.

Staring at HSI makes you drive slower. Sometimes much slower.

 

I find the HSI is helpful, especially for a pair of items

1) It helps me dial in my glide (trying to hit the line between regen braking bar and the lower EV bar.

2) It helps me get/maintain the bar in the lower quarter of the gas powered range bar.

It helps me avoid driving with the lower band nearly full but not going into the gas powered band, which would quickly drain the HV battery and screw up my mileage.

 

Most of the time, optimizing the Prius' fuel efficiency depends on keeping tabs on the changing road conditions, e.g. the grade of the road, traffic lights and other things you are sharing the road with. The key factors to optimizing a Prius' fuel efficiency are its top speed, its current speed, knowing if and when the Prius needs to slowdown and/or brake. The meters are useful for occasionally validating how you are doing.

Currently I use the HSI to gauge how much work my electric motors are doing
either as forward traction motors (which I try to optimize to avoid draining the battery) or as regenerative brakes (which I try to maximize to optimize the SoC of the HV battery).

I am also using two ScangaugeII with the following xgauges...
( .70>=GPH=1.30, RPM>1100, M1c/I1C=?, M2c/I2C =?) and
( AVG>60, FwT<=200, SoC>=.50, Flv > 0.5 )

where ...
During a pulse phase of a P&G cycle,
GPH can be from 1.30 to 3.0 in an uphill- mountanious terrain. Normally, on flat or downhill road, for a P&G cycle during a pulse phase, the GPH is from .80 to 1.20.
RPM =0 , GPH < .02 then the ICE is off, i.e. the Prius is *gliding*
.70 <= GPH <= .90, RPM <1200 then ICE is on at lowest possible loading factor when doing mini-pulses in a mini-P&G on a flat or downhill grade. I use mini-P&G during the first 5 minutes after a cold start or while crawling along in an extended traffic jam.


1100 <= RPM <= 1800 then ICE is in its most energy efficient *sweet spot*

SoC <= .50 then ICE may run to auto recharge the HV battery which will make your MPG go south. When SoC < .55 , I try run the ICE rather than use the electric motors until SoC > .55

FwT < 103(from a cold start), 110(after Stage 1 warmup) then the ICE will automatically run to heat up coolant/emission system - this causes the MPG to dip especially in the winter time if the Prius is stuck in a traffic jam. When FwT < 140 especially in the wintertime , I try to run the ICE exclusively (GPH>1.0) when pulsing rather than use the electric motors. I use this xgauge to also monitor coolant level when grill blocking. When FwT > 200 (especially for superhighway driving and the summertime), any lower grill blocking comes off.

M1c and M2c are the motor temperatures its used for grill blocking. When too high then upper grill blocking comes off ( sometimes swapped with I1c,I2c which monitor the motor inverter temperatures instead... not sure which is more important).

AVG >= X where X mpg, the trip's goal fuel efficiency

Flv = fuel tank level in gallons > .5 gallons ( I'm not sure what's the safest min level)

hope this helps

Walter Lee
aka "HyperDrive 1" at Cleanmpg.com mileage log
2010 Toyota Prius III Blue Ribbon/Dark Grey oem floormats
Yokohama Avid S33D (rainy weather set to 44 psi front/42 psi rear)
grill blocking ( 0% upper, 100% lower)
ScangaugeII (2)
odeometer +23000, overall +59 mpg

 

Great info Walter, thanks! I plan to use it when I get my ScanGauge.