Engine/transaxle preheat yields 25% better FE in short commute.
 

Using a 1500 watt circulation tank heater starting at 5˚C It reached 70˚C engine coolant temperature, in the garage in 40 minutes. This is the temperature that a Prius can enter stage 4 in which the engine shuts off after warming up allowing EV mode and automatic EOC.

I got a record commute: 4.3 L/100Km (54.7 mpg) My average without preheat was 5.8 (40.5 mpg)

25+% FE :cool:

Well done! I see you reached 70 deg c in 40 minutes. Thats fast. I'm currently using 1kw but it takes 2 hours to get to 50 deg c. I'm thinking i should change over the heater to 2 kw as the rate of heat loss seems to be high from my engine. Maybe the extra heat input will overcome the heat loss more?

ollie

In the Prius 70˚ is the magic number at which point FE savings are largest because once you reach that the engine doesn't run when it's not needed.

I also have sealed off my engine compartment with a grille block and foam weather stripping to keep all that heat in.

Nice boost, Marcus!

It's another example of how modding a hybrid (or vehicle with technology associated with hybrids) can yield even greater savings than the equivalent mod on a conventional car.

(Other examples: mods that enable lean burn to be entered/held longer, aero mods that enable a CVT equipped car to automatically lower engine RPM at cruise vs. a fixed gear transmission).

Fun, fun.

Not to take it too far away from topic, but I find that this is why CVT may be the desirable drivetrain for OE's looking to increase fuel efficiency in their new(er) models.

Sure, CVT is only ~80% efficient (discussed numbers, not concrete information), but I think the efficiency of the unit as a whole is overcome by the ability to constantly and consistently keep the engine in it's most efficient RPM area for the desired reaction (acceleration, etc.).

So, it may be prudent to start with a lesser (or efficiency-inferior) unit, and build upon it, rather than touting the old, already efficient equipment, at least in this case.

We now return to your regularly scheduled thread.

...even though I live in "...the desert..." with 105-117°F summers, I've been contemplating getting a Engine-block Heater element from Toyota/Canada to use pretty much year-around.

...should drastically reduce the typical "...half-hour..." engine-running time needed before the engine slowly climbs UP to its best FE.

Very nice!

I have a 400w block heater and stick on 150w heaters on my oil and trans pans. I let them run for 45-60min. before I drive. I don't track temps, but I've seen 5-8mpg difference over the first two miles and as much as 4mpg at then end of my 40 mile commute.