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Old 08-03-2009, 02:06 PM   #1 (permalink)
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Hi,

I figure you' all might get a kick of this:

July 25, 2009

Thanks to Ken@Japan sharing a proposal to use a series of power bands for pulse and glide ... something like this:

I have a mile long, flat stretch that I have used for maximum speed testing with my NHW11. What I propose to do is accelerate from a standing start with a fully warmed up and highway charged ZVW30 at each of these power settings:
  • 25% - sets the maximum speed that can be reached on the test track. Three runs recording the mileage to reach the track limit speed should be enough. For good measure, I'll try to record traction battery current and record the time to speed. If I reach 50 mph before the end of the track, I'll sustain 50 mph to the end point. This will allow me to factor out the speed effects from the acceleration.
  • 50% - again to the newly established maximum speed
  • 75% - same thing
  • 100% - same thing
  • 1xx% - maximum power acceleration to maximum speed or 50 mph, which ever comes first.

So here is the followup:

July 26, 2009

Part of the scientific method is to run a test, even it the results are unexpected. In this case, I was able to get some 'lessons learned' that I'll use to refine the methodology:
  • 25% - the first pass was all electric and the others had a mix but mostly electric. The maximum speed was 25, 25 and 23 mph and took 1:48.5 in one measured test.
  • 50% - three passes came up with 40, 41, and 41 mph. It took 51.4 seconds, twice, to reach the maximum speed. The mileage came in 51.4 and 45.3 mpg.
  • 75% - reached 54 mph and took 1:15.0 and 1:01.8 to reach. The mileage appeared to be 43.6 and 45.6 MPG.
  • 100% - easily reached 50 mph and setting the cruise control worked. It took 0:37.5 to reach so most of the run was on cruise control. Mileage came in a 46.8, 54.1, and 51.0 MPG over the 0.8 mile course.

I have the GPS data and will see to what extent it can replace manual record keeping. However, I think it makes sense to polish the protocol and then as I approach the end, brake to a stop and at that instant record the MPG and average speed, a snapshot at the end.

The other alternative is to accelerate to peak MPG speed and then brake and repeat the cycle multiple times. This may also provide a way to quantify the power bar.

LATE NOTE:

I didn't run the Garmin GPS until the end of the 50% power settings and then on through the 75% and 100% runs:


This was practice but several things jump out:
  • Garmin nuvi is coarse - the polling intervals in the trace data are too large to get enough points at the different speeds. However, I have a GPS mouse that reports 1 second GPS intervals.
  • First order approximation is possible - the data points culled from the Garmin data may be enough to get a first order approximation of the power at each setting.

I'll have to convert everything into standard units and hopefully get some rough, initial numbers. The way the 50% and 75% tapered off as they approached their maximum speed gives confidence in this procedure. Better still, solving a quadratic equation can give a clue about the rolling and aerodynamic drag.

NOTE2: Approximate power from first runs.

___%| _kW| hp
_50%|_5.8|_7.8
_75%|_9.5|12.8
100%|17.2|23.1


Not unexpected, it appears to be a non-linear scale. The usable data is the up slope in the acceleration graphs up to ~30 mph. However, I really need to repeat this testing with the GPS mouse for improved accuracy.

Bob Wilson

ps. We don't have "tables" here or is some special separation character needed? I used "|" like I do at PriusChat and MyHybridCar.com.

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Old 08-03-2009, 02:51 PM   #2 (permalink)
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Interesting testing Bob. I know I've asked around about the best way to accelerate with my 04 Prius. The general consensus is that it doesn't matter too much. Try to keep rpms low is the only general rule I've heard.
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Old 08-03-2009, 03:47 PM   #3 (permalink)
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Quote:
Originally Posted by Daox View Post
Interesting testing Bob. I know I've asked around about the best way to accelerate with my 04 Prius. The general consensus is that it doesn't matter too much. Try to keep rpms low is the only general rule I've heard.
I'm going to suggest:
  • =< 2,600 rpm - my data indicates excellent efficiency here. Hobbit prefers 2,200 rpm so we're in the same ball park.
  • 2,600-3,200 - good, not as great but OK.
  • 3,200-3,900 - starting to feel the fuel burn
  • 3,900-4,500 (rpm limit of NHW11) - feel the fuel burn
Still, whatever works.

As a general rule, rpm is a rough 1st order indication of power setting. If you have a portable GPS, you could calculate the power vs. rpm settings. Just a fun thing to do and with the fuel burn at a constant power setting, get a rough idea of how much fuel to reach a given speed at any arbitrary power setting. ... and then your head explodes. <GRINS>

Bob Wilson

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