Ugh, I am really dreading the winter now. I am guessing I will have to keep the Prius in the garage and move the other car outside. This way I at least maintain some heat from the house, and thus lower the warmup time needed.

Bob, please keep us posted on your results.

Also, what is the "ms" in ms/sec?

 

A garage certainly helps in winter.
Also:
1) Block most of the grill vents in front of the car (see other threads on this site) - only cost a few $ of pipe insulation
2) Keep climate control system off for the first few minutes (better than having cold air blow at you anyway).
3) Avoid short trips
4) Use block heater (I haven't installed that)

And. it would seem an EV mode switch would really help for really short trips in cold weather ....but I have an EV mode switch, but I've found that in really cold weather (significantly below freezing), the Prius won't let you engage EV when starting the car, even with heat off

PS. I believe ms is Milliseconds, as in millisecond per second that fuel is injected.

 

I really want to install a block heater, but I'm concerned about voiding my warranty. I just bought it in July and the last thing I want is to void my warranty [plus the extension I purchased]. Are there any risks to voiding the warranty in installing the block heater? Also, I am guessing it needs to be detached, and re-attached every night?

As for the blocking of air-intake, what is the theory behind this? The cooler outside air makes the fluid temps lower?

 

Hi,

I'll try to cover all of the questions and comments:

1. "P","D" vs. "N" - I don't have the battery energy data. The question we're trying to find out is which gets the ICE warmed up so the car will operate in 'hybrid mode' sooner. I'll have data tomorrow with more details.
2. Block heater vs warranty - we don't think it is a problem because Toyota CA sells and installs the part and the engine block is cast with a receiver for the block heater. I don't have it handy but apparently there is a Toyota USA part number but it is not available in the SouthEast (or so it is reported.) I believe there is a group buy being organized in PriusChat.
3. "Karkus" pretty well laid out the rest. It is "ms of fuel injection" per "second of operation." I've switched to an easier fuel measurement, air flow in grams per second. This avoids having to use the ICE rpm times the injector timing and a constant to handle the four stroke, four cylinder engine (the constant is 2.)
4. I'm committed to sharing what I've learned although I usually don't publish here, first. Typically I publish in the technical groups and then repost here . . . which reminds me.

Bob Wilson

 

Thanks for the clarification, Bob.

 

The engine is least efficient when cold, but the only thing worse than driving on a cold engine is NOT driving on a cold engine and letting it run while sitting idle and providing no useful work for the energy it's burning and emissions it's creating.

The best strategy is to drive it right away. It's not as efficient, but it will warm up faster if it's being used. I don't recommend jack-rabbit starts and running the engine hard in an effort to make it warm up faster anymore than I recommend that after it's warmed up. Drive it reasonably... but do drive it.

As for engine block heaters... yes it's true that if you can warm the engine block you'll improve your initial fuel economy by shorting the amount of time needed to warm up. While this is good for the "car" fuel economy and emissions, it's actually NOT good for the environment as a whole. The question you need to ask yourself is... where are you getting that "heat"?

In the case of an engine block heater, it comes from electricity. And quite a LOT of electricity. This is sort of like saying you want to reduce how much natural gas or fuel oil your furnace burns to heat up your home in the morning, so you'll turn all your electric hair-dryers on at full-blast (at 1500+ watts each) and leave them running for 3-4 hours!

There's a LOT of mass in an engine block. It takes a lot of energy to heat it up. Most of the electricity we have still comes from fossil fuels (by far).

It's more environmentally friendly to forget the engine block heater and just let the car warm up normally from driving. If only there were a way to guarantee that the electricity you consume could only come from renewable sources then it might be different, but the reality is that we're all on one big grid and MOST of that grid (by far) gets it's energy by burning fossil fuels.

If you own a garage then you can help by making sure you park in it. That will help shorten the warm up time and at least it doesn't burn any energy to use the garage.

Regards,
Tim

 

I have to test it but my block and transaxle heaters are rated at 525W, less than the air conditioners, 1,800W or gas furnace blower, 700W. At 525W for a couple of hours, this is a fairly modest expense.

In the Tennessee Vally, power comes from coal, hydro and nuclear plants. The coal and nuclear plants are operating at high thermodynamic efficiencies, much higher than a cold Prius ICE. Wiki reports coal plants at 36-48% thermodynamic efficiency depending upon the cycle. Coal, fuel rods and the rain water comes from USA sources but half of our gasoline is imported.

The fuel savings is dependent upon the morning commute. In my case, the first week suggested a solid, reproducible improvement, 54->60 MPG, with morning temperatures of 70-80F. Our Japanese friends have calculated the heater is less expensive than the extra gasoline burned to heat the ICE. I'll be doing my own studies.

Last winter, I tested a thermistor hack and achieved significant fuel savings by avoiding 'heat only', ICE operation. I was able to get the car into hybrid mode in less than 3 minutes instead of 5+ minutes. For a 20 minute commute, this turns out to be a significant savings:


As for warming up the car before tacking a significant power demand, it is a complex equation. If I lived at the bottom of a valley or had to drive on a high speed highway, I would do everything practical to get my car to an efficient temperature before the heavy load. In my case, I weave a mile through my neighborhood at 25 mph while it warms up.

Bob Wilson

 

Thanks for the thoughts guys.

Bob, I would be curious to see the study of electricity used on the engine block heater versus fuel burned during ICE warmup. Particularly if it can be made in dollars and cents. The only unknown, and maybe someone has this information, is how much emissions are actually being created by the power company while you are using the electricity to run the engine block.

I am definitely one of those people who is interested in hypermiling for both FE and environmental sake. I want to contribute to the C02 emissions in every way I can. Fortunately, I can justify my hypermiling addiction with the environment as my reason.

 

This is what Ken@Japan reported in message 15394 in the Prius Technical Stuff group:
Using Ken@Japan's numbers, 100 ml would be about .0264 gallons which at $3/gallon would be $.08. Two hours of 400W block heater would be 0.8kW hour and the Huntsville rate is 5.5 cents per kW hour. This would be about $.04 cents. This is a gasoline avoidance.

Bob Wilson

 

Interesting. So there is a net savings of about $0.04 for each time you use the engine block to heat up your car during the colder months.

I've seen you research on the engine block heater suggesting that it has benefit even during the warmer months, so the next question would be how much is the savings during the warmer months? I am guessing it is less visible than in the winter.