Can starting in EV mode be dangerous?

I noticed my 06 gives that pop-down window whenever outside temp. changes.

 

your mfd for my instrument cluster? sure. :lol:

 

Thanks for the welcome, windstrings.

Your point about using EV to "pre-warm" the ICE is something I've never thought of. I didn't think that pump started until the ICE started. So it is always good to learn something new.

 

I guess the original worry is about oil not being up in the engine? Since the prius does not have a starter.. it has a huge electric motor that spins it up to speed. (people have mentioned this).. since it's turning before it fires.. ( about 1400rpms ) everything has the oil it needs.

 

I thought about that for awhile and happened to read about the work of a fellow Prius owner, hobbit, and the website http://techno-fandom.org/~hobbit/cars/ect/.

He made a temperature guage to monitor the engine temperature. He said, "One of the most fun things about this is watching the head temperature bounce upward as the stored coolant is pumped back in from the thermosbottle at startup. If the engine is prevented from starting [by shiftingto Neutral or hitting the EV button], it is obvious that the recovered heat rapidly dissipates into the rest of the block. So it is actually best to let the engine start when it wants to, right after the pump cycle when the *cylinders* are maximally preheated -- emissions are likely to be lower as a result. Continued warmup will heat the rest of the block anyway."

So I would say that it is important to start EV mode immediately and stop the "hot coolant" from the previous time being pumped into the engine. (I'm not 100% sure that EV immediately stops that pump though). I didn't think about how the coolant immediately heats the area around the cylinders, and then as time goes on that heat is dissipated into the rest of the block. I thought it would continue to heat, but apparently there isn't enough residual heat stored to do this.

 

Said fellow owner is right here, hi. The hot stuff from the bottle
is pumped in immediately upon power-up to READY mode, giving no
opportunity to switch to EV before that happens. So a downside
of EV is that you *lose* the bottle contents' heat unless you let
the ICE take advantage of that pre-warm condition about ten seconds
later. Trying to prevent normal ICE startup by waiting longer lets
the heat dissipate away, effectively giving you a colder startup
when you finally let it ... so really, it's better to let the car
do it on its own timeframe because that really is at peak heat
where it counts.
.
What I haven't tried yet, I don't think, is going to IG-ON, invoking
EV, and then going to READY. I'm not sure it would even work. Now
that I've said this and I'm not planning to drive anywhere today,
someone else may beat me to the experiment.
.
_H*

 

There's a relatively small amount of hot coolant stored in the thermos, and a cold engine block is going to absorb and dissipate that heat relatively fast.

I still say you are better off letting the engine start immediately (unless you are going to be moving the car a very short distance - which is one of the few Toyota-approved uses of the EV switch in countries where it is standard), and then, once the engine is warm enough to permit EV use, use it the same way the car would do if it was warm (slow speeds when the SOC is high) or to draw down the SOC before a long downhill which will recharge the battery.

I never use EV to draw the battery down below 4 bars, which seems to be around where the car itself likes to keep it. I.e., I use the EV to help the car do what it normally does itself, and I assert that this is the wisest use of the switch.

You will probably get worse mileage if you try to drive long distances in EV or you think of the Prius as an EV that you can coax more distance out of before the engine comes on.

Even when I draw down the battery (to 4 bars) at the end of a trip, I do it by forcing EV mode only at slow, steady speeds. I use the engine to accelerate after a stop, then go back to EV. You can go a goodly distance this way, letting the engine do the hard work, and using EV to maintain speed on the steadies. This is what the Prius was designed to do, and it saddens me to see people coming up with far-fetched schemes, like driving the first mile entirely in EV and then letting the engine start when the battery is at a minimum. Doing this you are working against the car, not with it.

 

I finally got to try the above-detailed experiment [variants of
EV-before-READY]. Doesn't work. The EV button is completely
ignored until you're in READY mode, by which time the coolant is
already pumping [if it's going to at all, that is] and you've lost
that little bit of storage unless you let the ICE fire up fairly
soon thereafter.
.
Now, why it *doesn't* pump at all in really cold weather remains
a mystery. I *know* it's got something greater than ambient
stashed away in there, and for normal non-EVB startups I wouldn't
mind having whatever it can give me around the cylinders instead of
thrashing the poor engine from dead-cold. This seems like sort of
a design flaw... various attempts to squeeze hoses and move warmer
bottle contents closer to the outlet thermistor haven't worked to,
um, "stimulate" it, either.
.
_H*

 

I'm wondering it would be worth it to put a switch so somebody in EV mode could postpone the coolant pumping from the thermos.

Also, how warm does that thermos actually get the engine, and how quickly does it cool back down to where it was? It seems hobbit has done the research, so hopefully he can post that information. Is the thermos really that big of a deal?

 

I'm pretty sure if you put a switch in the pump circuit to stop it till you were ready to kick it out of EV that it would set the CEL or possibly the MIL. The computer keeps pretty good track of temps and time, and the delay on start up is so the pump can charge the head with hot coolant from the thermos. If it didn't see the rise in temp vs what it sees in the thermos, it would complain. Probably the code for no coolant transfer what ever it is.
Edit: I said "what ever it is" so I don't have to look it up in the ESM.

 

Depending on how long it's been shut down and how cold the weather
is [and how windy], I've occasionally seen coolant temp go from
below freezing up to 50 C from the bottle, and then the engine
fires up. That's an ideal scenario. Gain will naturally be less
the longer the whole system sits in the cold -- and apparently if
it sits long enough, it's not worth pumping coolant at all.
.
If I prevent the ICE from starting after the pump cycle, by EVing
or shifting to neutral or whatever, that recovered temp rapidly
drops -- in my ideal example, from 50 C down to 20 C in maybe a
minute or so. The coolant comes past the temp sensor and is sent
right in around the cylinders and head -- but then the rest of
the still-cold block immediately starts to rob that heat away.
The crank bearings, for example, aren't going to benefit at all
from this -- it's really to reduce emissions by starting with
higher cylinder wall temps. Everything else will warm up eventually
from the heat of burning fuel. It'll just take longer in cold
weather.
.
_H*

 

Nothing new here.
A wise use of EV switch prevents a loss of some fuel.
An excess use will lose some fuel.

We don't have the CARB requirement.
The battery warranty is as same as engine, 5 years or 100,000 km.

I believe it not a Toyota's decision, but the US government (EPA?) does not allow the EV switch for the EPA testing.

Ken@Japan

 

Are you saying you know more about Prius than Toyota engineers?

Please understand there is no place of market where both the thermo and EV switch are equiped.
Also, the primary purpose of the thermo is to improve the emission data, not for reduce the the warming up time.

Anyway, have you seen following presentation and the start condition of pump?
http://john1701a.com/prius/presentations/2...entation_38.htm

Ken@Japan

 

Ken - Am I reading this correctly? Are you saying the Japan and Euro models equiped with EV Mode from the factory do not have the coolant pump?

 

and no bladder