Prime cold starts @ W.O.T.

The topic has been beaten to death over the past decade, overwhelmingly proven a non-issue.

Basically, the plug-in system saves some capacity to allow the engine to warm-up prior to fully engaging. With an OBD-II device, you can see RPM held back during that period. The hybrid system itself also has stress prevention built into it. The pistons are lighter weight and the camshaft is offset. Also, startup (fuel & spark) doesn’t take place until oil pressure is established.

For example, this video I captured from long ago you can see the cold engine fire up (just before the 5-minute mark) and be held to 1500 rpm.

 

Prius Prime is no different than any other car in this respect—do not race a cold engine.

When I am driving in the EV mode on the freeway with an ice-cold engine and want to switch to the HV mode, I take my foot off the gas pedal before I press the HV button, and then I drive as gentle as I can with the vehicle speed at 57 mph on the speedometer until the ICE warms up and stops, which should take about a mile or two. From that point on, I drive normally.

Using the recommended SAE 0W-16 engine oil also helps.

 

It's not 1950 anymore.

Engines, fuels and lubricants have all advanced considerably.

And the proof is in the pudding: people have been driving these PHEVs in low temperatures for years. Toyota hasn't gone broke on warranty fixes and there hasn't been apocalyptic wave of engine failures.

You don't have to trust everything modern, but this one has been safe for a while now.

 

With our 2010 hybrid, for the first few blocks after cold-start, the engine runs at a moderately high idle, and giving gas has no effect on rpm; the motive power is from the hybrid battery. That changes to more normal throttle response, presumably after coolant achieves a certain temp.

 

That' s the main thing. You might do a "cold start at W.O.G.P." (wide open go pedal), but the go pedal in a Prius is not the throttle. It's not connected to the throttle. It's not even connected to the computer that controls the throttle.

The computer it is connected to has a nice conversation with the one that controls the throttle, and if they agree it might be nice to start the engine, the one in control of the engine does that, and decides how much throttle to use.

 

It also isn't like it's just sat in the car cold in the engine bay. The motor, inverter, and transaxle have been running for miles at that point. Some of that heat does transfer to the engine.

 

Good to note! I forgot about the much lighter weight oil.

 

Was that the only one you watched? There are many others where the engine simply fired up during the course of the commute. I simply did haven't time to look through that collection to find exactly what you wanted.

Watching 0-60 tests is a different scenario. Basically, if you are dropping the pedal to the floor from a dead stop with SOC almost gone, you are making the choice to risk engine stress. It is easy enough to fire up the engine prior.

 

In addition to not adding load immediately, these hybrid designs also spin up the ICE and its oil pump BEFORE adding fuel/spark.

 

Well if the book says don't race the engine...

And if you don't race yours...

But your comments are based on a youtuber who did race it...

...then that's kind of a weird strawman argument. I wouldn't worry about it unless you're actually trying to launch a youtube channel here.

 

At CAN rates of a megabit per second, they can have quite a friendly chat in the 13 ms you might need to notice you noticed anything.

 

I had a Volt for some time between Prius Primes. Being I’m sensitive to cold engine starts, sometimes when going on a trip I would let the engine run gently through a warm up cycle to lessen the shock of an engine not run for two weeks being asked suddenly to perform hard. I don’t think they start gently if power is requested going up a hill, etc. Speed doesn’t drop off. The engine revs it’s … out from cold as far as I can tell.
On the first Prime, a 2020 LE, I would hear a little start up rattle after the engine didn’t run for a week or three. The new to me 2020 Limited so far seems tighter, no rattle, but need more time to tell. The new one is a better car I think, no dash rattles, no steering squeak squeak at times like the other one. The Volt had start up rattle too, but none after I switched the filter to one with an anti drain valve. The original came without. I would let it not run for six weeks sometimes.
With the power outages this winter I was aware of many neighbor generators. These sit for even years, then start and run at full throttle and load. No one seems concerned and they don’t fail.

 

You’re thinking it would act differently? If the engine kicked in, I suspect it’d go to fast idle, and hold steady rpm regardless of what the driver does with gas pedal. Until coolant warms some.