Updated MPG vs MPH chart

As others pointed out, their data includes the least efficient driving modes and in particular the first two miles. These short trips are likely to include the engine warm-up overhead and really hit the mileage hard. It may also include times when the car was left "ON" but "parked."

To really understand their data, we need the raw data file. But my own testing suggests:

• 0->~45 seconds - during the catalytic converter light-off, the car will draw heavily from the traction battery. By shifting between "D" and "N" one can reach ~40 mph and coast with excellent fuel efficiency.
• ~45 -> ~300 seconds - during this time the engine is warming up the coolant and burning fuel heavily.
• ~300 seconds+ - fully warmed up, the engine and hybrid rules apply. Now the car will be efficient like mine and other graphs show.

I have long felt there is 'low hanging fruit' in our Prius:

1. More EV in the 45->300 second warm-up - Toyota already turns off the ICE soon but only when stopped. During this warm-up phase, the Prius control laws should continue to more heavily tap traction battery power. Then handle charge replacement when the car is cruising or regeneration. IMHO, there is 5% potentially lurking with this change.
   • Several times I've asked PIP and Volt owners if they have the option of switching to some sort of 'engine in idle' mode while using stored traction battery for motive power (i.e., in ordinary EV mode.)

I see this potential fuel-saving pattern in the recorded data. It is simply an extension of EV mode into the second, engine warm-up period. But pending a change in the control-laws, there is an approach that works:

• First, cold-soak, start - drive 1.5-2 miles, neighborhood, 25 mph speed, flipping from "D" to "N" and coasting as much as possible. Let the engine continue to warm-up at 'idle' during coasts, no use of heater. Once the coolant reaches 70C, let the car go into normal hybrid mode (some changes with the ZVW30), and drive normally. Don't worry about the traction battery charge as normal intra-urban speeds, 40-50 mph, will easily supply the missing charge efficiently.

I do applaud their improved metrics BUT they need to share the raw data for a 'Bob' look. <grins>

Bob Wilson

 

I still remember a day shortly after getting our first Prius nearly eight years ago when I realized I had become a Prius gear-head. I started reading SAE papers (yippie April, new SAE papers!), subscribe to AutoWeek, and the only people at work whom I could even discuss car technology using the right terms were the Corvette and Ford enthusiasts.

You are in for a treat as somethings have gotten way better. Warm-up is much improved but there is room for improvement. The cooling drag is still higher than it needs to be and once the transaxle reaches operating temperature, it is a low-drag rolling beast with good, high-pressure tires. Handing is improved over the NHW11 although this means 'Prius handling'.

My 'boy toy':

I had just towed ~1,700 lbs of trailer and airplane, 600 miles, ~53-54 mph, ~28 MPG, through a NorEasterner. Yes that is my tow vehicle (need to get air-bags for the rear springs next time.) But around town:


There is one other airplane owner at work and two flyers. Everyone else has learned not to mention either 'Prius' or 'airplane' around me unless they have time for a Bob-talk on my latest work. <GRINS> . . .

I had just gotten up from a nap to work on a CAD program designing the next engine mount. I've already shipped off the original carbed, VW engine, 60hp @3200 rpm, 172.3 lbs. I am replacing it with a fuel injection, oil injection, liquid cooled Hirth 3502, 60hp @2400 rpm (prop), 112 lbs. Instead of a fixed pitch, wooden prop, it will use an electrically controlled, variable pitch, 3-blade composite prop . . . required by the slower turning prop.

The plane is going through a major refit that should reduces the empty weight, improve the electronics, and speed-brakes to steepen the final approach. I am also looking at (testing required) a tri-gear design of my own making to improve landing. I'm not expecting faster as much as quicker takeoff, faster climb, similar range, higher reliability, quieter, and lower maintenance.

Oh did I mention, don't use the word 'airplane' around me? <GRINS>

Welcome back to the world of efficient cars!

Bob Wilson

 

Comments inserted.

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. . . I don't know if it is good to coast in neutral during initial warmup?

Run your Scangauge II showing 'GPH' and you soon find that there is about a 2x difference in the first 2-3 minutes between "D" and "N". Although warm-up is much improved, it still accounts for the bulk of the fuel burn in the first 5-10 minutes. These are not 'hard rules' as I just got a data recording OBD scanner, call these anecdotal observations:

• ~45-55 sec catalytic converter warm-up - running open loop, the car will accelerate nicely using the ICE to speeds above 40 mph. Shifting into "N" puts the engine in minimum fuel burn rate and the instant MPG goes through the roof.
• ~50-~120 sec coolant warm-up - thankfully the engine shuts down when the car is stopped. However, at a constant speed, shifting into "N" cuts the gallons per hour significantly. Sorry, I don't have hard numbers but it looks like once the coolant reaches a little over 50C, fuel consumption becomes closed loop, very efficient, and shifting to "N" is no longer helpful.

I don't know why the pips flash so early. I think I should be able to use what I understand to be 1-2 gallons after it flashes. It seems to agree with fuel used on the scan gage that I have 1-2 gallons left. Does the gen 3 stop when out if fuel or will it still move like when a gen 2 is out of gas?

I have only found one indication with our ZVW30 that it has finally burned the last of the gas . . . the arrows in the 'power flow' display disappear. It silently goes into traction battery mode and you can easily discharge it low enough until it suddenly shows a power steering fault, "PS", and becomes an inertial mass. When driving on 'flash', I switch to 'power flow' and monitor the power flow arrows. When they go away, I use the remaining traction battery power to find a safe place to park and add the spare gallon.

My six fuel exhaustion experiments found from "flash" to "out of gas" there was 2.1 gallons with our car. I recommend checking your own car's "flash" to "out of gas" (carry a spare 1 gallon container.) In our case, I reset "B" trip meter when "flash" begins and use the MPG and miles to calculate how much fuel is burned. Since I'm running over 50 MPG, our 2.1 gallons is good for 100-130 miles to schedule a fuel stop when it works for me . . . the owner.
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GOOD LUCK!
Bob Wilson

 

Excellent!

This is how we should approach experimentation. Now about "c", this happens during the catalytic converter warm-up. Once you reach speed, shift into "N" and you'll turn off the traction battery drain. This reduces the battery drain until the catalytic converter begins operating in about 45-50 seconds. Thereafter, using "N" doesn't really buy much and the traction battery needs the replacement charge.

Bob Wilson