warming up the engine?

Since the 80's, Toyota has been asking recommending that owners warm up a newly started engine by letting it idle for 10 seconds and then driving the car gently until the engine is warm. They haven't advocated letting the engine warm up by idling, citing increased pollutants, increased fuel emissions, and little to no engine protection beyond what is offered by 10 seconds of idling (to let the oil circulate through the engine) and gentle driving till the engine is fully warmed.

The Prius uses the hybrid system to help do this for us. Watch the energy display carefully and you'll see how it babies a cold engine. When you first start the engine, the car will draw from the battery for even very mild acceleration. Even though the engine is running, it doesn't put a significant load on it unless you demand more acceleration than the battery can easily provide. As long as you are relatively easy on the accelerator while the engine is cold, the hybrid system can do a great job protecting the engine.

Now if I lived in Minnesota, a quarter mile from a highway where I had to quickly accelerate, then I might think of letting the engine idle with the car parked when the weather was frigid. That not being the case, I just drive gently while the engine is cold.

Unfortunately Toyota gives no display of engine temperature beyond a light for overheating. Fortunately, I have a ScanGauge.

 

The Prius Owner's manual says that "when starting or backing up, etc., the vehicle runs on electric power from the hybrid battery, because the gasoline engine efficiency is low. During normal driving, the vehicle runs mainly on gasoline power." (See pages 10-11)

This indicates that even if the ambient temperatures and the engine were relatively warm, that the Prius would STILL use more battery power when emerging from a standing start... not necessarily as a strategy to "baby" a cold engine... but as a strategy to use power more efficiently.

 

I've been wondering about this sort of thing in another thread...I still think that there are situations where the engine management software will allow the engine to give maximum power before it's really ready to do so.

 

<div class='quotetop'>QUOTE(cbs4 @ Dec 21 2006, 01:51 PM) [snapback]365220[/snapback]</div>

I'm not sure, without context, if that excerpt is referring to starting the car with a cold engine or starting from a stop (with a warm engine). They may be referring to starting from a stop and that inefficiency may be due to the way the PSD functions as a transmission and the inefficiency of the engine at low RPMs and possibly the inefficiency of the PSD to use engine power at very low speeds or in reverse.

Some expert posters responded to the observation that the Prius does use battery power to protect the engine in this earlier thread: http://priuschat.com/index.php?showtopic=21810

 

<div class='quotetop'>QUOTE(Pinto Girl @ Dec 21 2006, 02:20 PM) [snapback]365234[/snapback]</div>

And worse, since the throttle pedal doesn't directly connect to the throttle, we don't really have control over this. A bummer in my opinion.

 

I'm not an expert by any means, but I don't view the Prius as a spaceship either.

The uniqueness of the Prius is the "synergy" , as Toyota puts it, of a combination of traditional motive forces. I don't subscribe to the idea that one of those motive forces, the ICE, is somehow so "different" from the ICE's of other cars that don't have the synergy of other motive forces to combine with it.

The Prius's gasoline internal combustion engine is a gasoline internal combustion engine, period. Unlike diesel motors, gasoline motors develop peak torque at much higher rpms. To motivate 3400 lbs from a standstill to a running start takes torque. Electric motors can deliver more of this torque at lower energy consumption levels than a gasoline motor. The electric motor in the Prius relieves the gasoline motor from having to rev to 1900 rpm in first gear (or in the fluid drive of a torque converter) to move the car across the intersection.

By comparison, diesel motors deliver peak torque much earlier in their powerband, and at much lower rpms, which is why they are used in trucks and tractors that have to motivate a lot of weight from a standstill. Freight trains and some Navy Submarines use the torque advantages of diesel and electric motors combined... so hybridizing a combination of power sources, and using the most efficient for the task, doesn't seem so unique to the Prius.

The pages in the Owner's Manual for 2006 are 10 thru 12, in Section 1-2. The context will be self-evident, once seen, and covers what Toyota delineates as six stages of synergistic car operation.

All that being said, from reading the posts in the link provided of the Prius experts that have CANView data logging (synergistcally combined with a lot of intellgence), it does appear that on cold start, the electrical energy is called upon even more to motivate the load from a standstill.

My wife informs me that when she presses the accelerator quickly from a standstill (rare, but it has happened) the ICE will rev up high and inefficiently provide the power demanded. It would be better for the ICE if it was warm first before such a hard demand was made.

 

For my 05, about 7 seconds after the car is in READY, ICE will start to warm up and charge the battery. If extra heat is not required, it usually stops in about a min.

If I decided to drive during that 1 min warm up period, I can see that large amount of current is drawn from the battery and ICE RPM never go above 2000, given that you don't floor it. Meaning during that warm up period, most of the motive force is coming from the battery.

 

<div class='quotetop'>QUOTE(ScottY @ Dec 21 2006, 03:18 PM) [snapback]365286[/snapback]</div>

Agreed. But that means that the ICE isn't being used enough to really warm the oil and internal parts...which (in turn) means that when I accelerate onto the freeway in the morning and significant power is required, unless the software is specifically designed to limit RPM and WOT operation, it IS possible to run the engine harder than we should.

 

But you have to try though. When it's in stage 1, there's a definite "dead-band" in the throttle response. You can keep gradually lowering the pedal, and not a lot happens, as it's maxed out the power it can get from just the battery with the engine idling. Then when you've pressed far enough, it gives up and starts revving the engine, as you clearly are demanding more acceleration.

Alternatively, if you hold it in that dead-band, you'll later get a surge of acceleration as it enters stage 2, and moves the engine out of its warm-up idle, so it can now give the requested acceleration.

 

<div class='quotetop'>QUOTE(KMO @ Dec 21 2006, 05:02 PM) [snapback]365382[/snapback]</div>

I think I see what you're saying; this is beginning to make more sense now. I think I'm just beginning to learn how to 'read' what the car is doing, as I'd learned/been taught with conventional automobiles so many years ago.

Maybe I do need one of those CANview thingies; the car seems just too smart and has too many operational options built into the software for me to simply corrolate an action on my part with a given response...at least, in the way to which I'm accustomed.

It's feeling more and more like the process of learning the shift points of an automatic transmission...for instance, at what point I could floor the throttle and avoid a downshift to passing gear by getting MPH above a certain number...

A bit work-aroundy, perhaps, but rather interesting in its own way.