I am currently a Prius "window shopper"... Still learning the ins & outs. Have been reading the threads on this forum, very very informative. Question: I am having trouble internalizing the apparent On Demand cold start & run aspect for the gas engine. It seems to go against everything I ever learned back in the old days... The reason I ask is that my commute begins on two small, residential streets ( ~10-15 MPH), and then turns onto a main road that goes uphill and requires immediate acceleration. On a typical cold ( 0-5 F) January morning, I presume that the gas engine would have its initial start as I push to accelerate up the hill. Is there any long term impact to a gas engine by cranking it up ice cold and immediately subjecting it to a load like that? Has there been any unique adaptations to the design of the engine to allow for that, or does it use any new or exotic lubrication to accommodate that kind of use? Thanks for any insight you might be able to provide on this subject.
I like your question. I have heard, and perhaps some of the "experts" can verify this, that the engine does not have ignition and fuel applied until it is turning over and has oil pressure, this may only take a few hundred milliseconds so is not noticeable. The engine does run to warm its self up also to provide heat and keep the catalytic converter warm. This reduces fuel mileage in cold weather by a few MPG. Prius engines seem to have a very long life in both cold and warm climates so whatever is done seems effective. Some posters on this site have been using 0W-20 synthetic oil in the winter even though it is not one of the recommended weights. Others, like me, just use the recommended 5W-30. When you first start out in the morning the engine will be running to warm its self up but the car may run on the battery if there is sufficient charge available. The Prius engine is very lightly stressed and I think the circumstances you state will not be a problem for it.
<div class='quotetop'>QUOTE(P=EI @ Apr 7 2007, 01:22 PM) [snapback]419446[/snapback]</div> Yes. Once the special startup process concludes (which in itself is designed to reduce stress), you'll discover that the electric motor is favored more in the winter than in the summer. I've been a witness of this for years, since there is a hill just outside my home I routinely climb. The difference between the seasonal extremes here in Minnesota is easy to notice. The system takes advantage of having that powerful motor to lighten the load (even more so than usual) on the engine while it is still warming up. That's pretty sweet.
the gas engine starts about 7 seconds after you turn on the car. so unless you push it out to the hill, it'll be running anyway. the start/stop is actually pretty well designed. as tumbleweed described, the engine is spun to (i forget the exact number) rpm with oil pressure by the electric motor (no starter) before applying spark. the car is pretty gentle on the gas engine overall.
<div class='quotetop'>QUOTE(P=EI @ Apr 7 2007, 02:22 PM) [snapback]419446[/snapback]</div> No. The engine will be on right away, and you'll be on both gas and electric right away. The gas engine will start within a few seconds of the car coming to Ready, in order to heat up the catalytic converter and the passenger compartment (in that order of importance). As is stated above, the system treats this engine a little differently. The electric motors spin the engine up to around 800 or 1000 rpm first, get some oil pressure going, then turn on the spark and fuel. The Prius engine is, relatively speaking, babied during normal use. The software is incredibly complex and the whole system works great.
There is a stainless steel thermos that will fill with the engine coolant when you shut the car down and will be pumped back into the engine upon startup , thereby allowing it to have a warm start. If you doubt this, please get and read the owners manual and research this forum for more info.
<div class='quotetop'>QUOTE(galaxee @ Apr 7 2007, 01:57 PM) [snapback]419528[/snapback]</div> 1000 rpm
<div class='quotetop'>QUOTE(P=EI @ Apr 7 2007, 01:22 PM) [snapback]419446[/snapback]</div> Last thing I heard, the idea that you have to pre-warm your engine by letting it idle for 10+ minutes on cold mornings doesn't hold true for ANY modern engines anymore. The only reason people 'need' to pre-warm the engine is for a comfortable temperature INSIDE the car. But supposedly it affects the engine only very little. We live in Alaska and have blockheaters on all of our non-Prius vehicles (which, BTW, would be a solution to your problem), but whenever we forget to plug them in the night before, we often simply drive the vehicles immediately after starting. And so far I haven't noticed any kind of negative effect from this, other than freezing my butt off while the cabin is slowly warming up.
