why does the ICE come on after 25 minutes?

After 25 minutes of sitting the ICE & the cat isn't warm enough, hence the start up procedure.

 

i pulled my wife's hycam out of the 75 degree garage, it hadn't run since the day before. the ice fired as i backed out, and shut down as soon as i shifted from reverse to drive.

 

Why ask why ?
It certainly ran several times on the way to the store, right ??

 

Spoof the gas tank sensor to show empty
(or did that only work on gen ii? )

Then you could control EV mode to a point.

 

OK.
While that sounds reasonable on the surface...........

Several MILLION things happen with your home computer every second.
Do you feel compelled to know why each one of them happens ?

The car is controlled by a computer.

 

I work in IT, so yes... I feel compelled to know what's going on with my computer...

Why do you care why he cares?

 

The engine was probably still warm, but the catalytic converter will cool much faster because there's less mass.

 

Our regular 3rd gen Prius behaves similarly. Very occasionally it'll stay in electric-only at restart, but typically only with a minute or two of off-time. The programming is conservative I guess.

4th gen is much more willing to run engine off. Time will tell how that pans out.

 

Because asking a question that very likely NOBODY present has a real answer for (just guesses) is a waste of everybody's time.
But then so is complaining about that.

 

True, we may not know the answer, but someone might. That's a chance to learn and receive edification. In that instance, everyone who reads this thread will have learned something, making the community greater.

But yeah, this is one of those, the computer told it to do that, and without the programmer we'll never know "why" it is that way.

 

G'day,

I too would agree with JimN's assessment.

It's winter here and I've noticed my c starting its petrol engine more noticeably which confirms to me it needs more time to warm up and then cools down more quickly once 'at rest' between longish stops (and shops).

I suspect the ICE has a set operating temperature, not summer and winter settings, so the seasonal change of about 10 degrees or so means more heating at start-up in winter. One reason for fuel consumption to increase a bit during winter as well. Also the car heater is needed in winter, whereas in summer, it's only the air-con (which runs off the battery I believe?).

Maybe priustexasbob could mentally keep a rough check on how long his ICE runs after a short stop compared to the first start in the morning? If our hypothesis is right, then it's shorter once the car has had its first morning run. And the hypothesis could be confirmed to a theory .

David S.

 

+2, catalytic converters don't start working properly until they reach 400-600C.

That's hotter than Texas

 

Lets just answer his question. After 25 minutes, it will go through the warm-up stages even though it is already warm. That is why short trips are tough on mileage. It appears that the Gen4's firmware is better configured to maximize mileage.