RobertSmalls' Prius C

[RobertSmalls]

Unexpectedly, I got 62.5mpg on the way to work, and 66.0mpg on the way home. I'm impressed, especially for a 45°F day, and driving home with the headlights on. These are numbers that would be only slightly disappointing on an Insight, and there are a few important ecomods left to do on the Prius C.

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Perhaps some Prius veterans can chime in here, but this is what I've figured out about the Eco Meter. The Eco Meter is a bit like a tachometer, in that it indicates how hard various parts of the powertrain are working, and how much power the driver has requested.



The blue region is regenerative braking. Braking is bad, for obvious reasons.

The first half of the green region is where EV mode is possible. Electricty isn't cheap, so I use it sparingly. If I can extend an engine-off coast in traffic without drawing much power, I'll do it, but the combustion engine should be the primary source of propulsion.

In the first half of the green region with the engine on, the engine isn't heavily loaded enough to be efficient. This is the vertical part of the BSFC curve at 1000RPM. Stay out of this region.

The second half of the green region is where the engine operates efficiently. This is where I keep it during cruise and acceleration.

The last segment is colored red and labeled "PWR". I'm not sure exactly what happens here, but it sounds like trouble.

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Biggest peeve: once the car is warm, it will let you accelerate up to 45mph or so without turning on the engine. It has a 1KWh battery, which should be good for at least a mile or two. But I have to resort to trickery to even back out of my driveway without it turning on the engine. That's especially sad because the combustion engine is only a hindrance to rearward progress.

The car is programed to try to get its catalytic converter hot within a certain number of minutes of being turned on. So instead of waiting until I'm on the main road to fire up the ICE, it does it three seconds after you power up the car. For now, I've exposed the shift interlock override so I can park the car in Neutral and pull it out of the garage by hand. Then I start the car, and I have three seconds to get the car rolling backward before I have to be in Neutral. It won't start the engine until I shift to D. I really want the ICE to stay off until I get out of my neighborhood and out to the main road, where it can warm up quickly.

The long-term solution is to trick the car into allowing me to use EV mode right off the bat. I wonder if a coolant temperature hack would do the trick. It would be amusing to repurpose the presently-useless "EV Mode" button for the task.

[MetroMPG]

Originally Posted by RobertSmalls

I have to resort to trickery to even back out of my driveway without it turning on the engine. That's especially sad because the combustion engine is only a hindrance to rearward progress.

I'm sure I don't need to ask if there's a good reason why you don't back into your driveway.

Makes more sense to do this when the car is warm and willing to shut off its engine so you can EV mode yourself into your parking space going backwards. Also makes human-assisted launches possibly more efficient going forward (because you don't need to then stop & change direction) ... or, hey - you could reverse your rear tires up a pair of ramps for "launch assist" when it's time to leave!

I wonder if a coolant temperature hack would do the trick. It would be amusing to repurpose the presently-useless "EV Mode" button for the task.

Tim (Daox) has been working on a coolant sensor hack. I don't know the details, but maybe he'll chime in.

[Xringer]

I wonder if a 144vdc battery charger could be used to top-off the pack after you parked in the evening?

So, if you tricked your C into cool-ICE EV-mode, you would have enough juice to get up to main street.?.

[Daox]

The coolant hack I have worked on (presently not installed nor working) is not going to do what you want it to. The EV mode is not based on coolant temperature I do not believe (unless you turn the heat on). It is based on pack temperature.

Also, good luck with even getting 1 mile out of your battery pack. Max SOC is 80% and max discharge is 55% on my 2nd gen. That means you get to use a whole 25% of that 1kWh pack. Believe me, you'll pay for it when the engine kicks back on too. It really is best to stay out of it IMO.

[RobertSmalls]

Originally Posted by MetroMPG

I'm sure I don't need to ask if there's a good reason why you don't back intoyour driveway.

Conservation of momentum! I roll onto my street at 15mph, bounce into the driveway at 10mph, and coast to a stop in front of the garage.

Originally Posted by Xringer

I wonder if a 144vdc battery charger could be used to top-off the pack after you parked in the evening?

It's a NiMH pack, same as the Insight's. I don't see any reason why I can't use the Insight's battery charger to charge it. I'll look in to it later.

Daox, I'll try it with a warm engine some time and see what the SG SoC indicator says. The first leg of my commute is 0.3mi, has a top speed of 25mph, and has five complete stops and a red light. I understand why EV mode in a gas-fueled car is generally a terrible idea, but it could work well in this case. One step better would be an ICE kill switch, though. If such a thing does not exist, it needs to.

Good news: I found a copy of the FSM.
More good news: The section on "Hybrid Vehicle Control" is 572 pages.
The ECU has 110 terminals.

[Cobb]

The way I got 15 more mpg was to save ev use for maintaining and coasting. I also rode the brakes to a stop hard enough to fully lite up the brake part of the indicator. I also fully inflated the tires to sidewall psi.

Ive gotten a lot of nasty emails about my rip of the useless ev switch too on a youtube video I made of my test drive. Infact during the test drive Ive pressed the button several times and got one message after another as to why it couldnt go into it. Then, looking at the screen, half the time it appears the ICE was off and it was on battery and that was even at highway speeds.

I never let the idling bother me at low speeds. It was explained to me the drivetrain is geared too high for the ICE to drive the car below 10 mph and it was better for it to spin using mg1 to top off the pack and mg2 to move the vehicle and the coolant heating up, blah, blah, blah.

[Xringer]

When I go downtown, my first stop light is 1.3 miles down the hill.
When I take off, the C is running first in EV mode, then in mixed mode.
So it seems to be warming up fast.

We've parked downtown (3 miles from the house), picked up items at a store,
get back in the C a few minutes later, hit the EV button and drive about a quarter mile
to the bowling alley on the battery. The EV button works if the car is warmed up
and the SOC is up..

[bwilson4web]

Originally Posted by RobertSmalls

. . .
The car is programed to try to get its catalytic converter hot within a certain number of minutes of being turned on. . . .

The catalytic converter "light off" is about 45-55 seconds and common to our 2003 and 2010 Prius. One of the best metrics is MG1 torque but you can also see this by watching the mass-flow (or gallons per hour Scangauge II.) The catalytic warm-up phase is an "EV with engine idle" so my strategy is:

• Mentally start a 45-50 second 'clock' to accelerate to a coasting speed.
• Accelerate modestly, use your instruments to keep engine in 'idle' mode. I typically reach 35-40 mph when I am able to shift into "N".
• Park near exit, this allows you to maximize acceleration in this brief phase.

I know 'common wisdom' is drawing on traction battery charge is expensive to replace. In my case, I'm finding the charge is replaced within 2-3 miles and at 45-55 mph, I can't find a significant hit. This is not in any way an endorsement of trying to maximize regeneration which is fuel inefficient. Rather this brief interval is available and can be exploited.

Bob Wilson

[SwamiSalami]

Originally Posted by RobertSmalls

Cool front wheel covers on the insight. what'd you use or do you have a link in which they're discussed? (they don't look like pizza pans)

[MetroMPG]

I'm not sure if Mr Smalls did a write-up on his wheel covers. But he showed them to me at GGP a few years back. They're fiberglass cloth, laid up on the wheel (which has only small openings, stock). He attached them to the center caps, so they can be popped on/off relatively easily.