Warmup: what a Prius wants...

I have experimented with this on my drive home from work. I use EV to get me out of the parking lot and disengage EV when turning on to the road. At that point I have tried two different approaches. The easy does it approach is light accelleration up to 40 MPH and hold her steady until I am out of stage 1. That method usually relies on MG2 to accelerate the car and results in my SOC dropping to the low 50's before it begins building up again. The second method is to accellerate hard enough to make the ICE do all of the work with little participation from MG2. My SOC stays at about 60%. For me, the latter yields much better results than the former. By the time I make it about 3 miles to get on the interstate I am at 60 MPG at 60% SOC. Using the easy does it approach, I am lucky to be at 50 MPG and my SOC is at 58%. Which approach do yo think I ended up using?

 

I believe that what we're seeing here is the emissions vs economy trade-off that was made. With a cold engine and catalytic converter, the Prius uses the electric motor to reduce emissions at the expense of fuel economy.

 

Will you explain? I don't understand what your saying.

 

Ok I will admit my ignorance. Can you point me to what these acronyms mean.
SOC
MG2

60MPG at warmup. I usually get my worst mpg at startup, granted I have only had for 3 days. I am struggling with the best approach on acceleration on to highway(65), mid-speed roads(45) and then of course in-town(30). Do you just get there and level off, hence the lower MPG upfront or do you become a nuicance and put, put to final operating speed staying in the ECO zone the whole way. I tried the ECO method today as there was no one behind me. It took a long ways to get to operating speeds of 45 and above.

Sorry for the the newbie mentality. I hope this may address some of newness questions out there.

--Mickey

 

SOC = State of charge, of the main traction battery
MG2 = Motor/generator #2.

The Hybrid Synergy Drive (HSD) combines an engine and two electric motors/generators (MG1 and MG2) into a planetary gear (the power split device). Engine is the planets. MG1 (the sun gear) mostly act as a generator to generate current. MG2 (ring gear) mostly act as a motor to drive the car (it also act as a generator in regenerative breaking).

For your other questions, do a search here on PriusChat and you will probably find all the newbie answers and then some.

 

Maybe there is a FAQ sitting around somewhere. I am always hesitant about asking questions of the like as they probably have been answered numerous times and of numerous opinions. Searches are good but sometimes with the questions aren't so specific, they are quite difficult to hone in on that keyword or two. And then sometimes you just overwhelmed with too much information.

Then sometimes in the effort to not spend hours and hours of valuable time, you simply just ask the question in hope of someone offering an answer, a link or sharing their valuable opinion.

Thanks for the answers to the acronyms. They do make sense.

--Mickey

 

Regardless of what vehicle I'm driving, it is my habit to drive gently while the ICE is warming up, to avoid undue wear and tear on the cold engine. I don't think the Prius will change my thinking is this regard?

 

It hasn't mine. I even allow the engine to warm itself before I drive off and regularly average 60ish on the MPG on the consumption readout, but it's warm weather here too.
And I'm the guy that never goes into the power portion of the HSI on four lane roads, but I'm almost always in the right lane too though.

 

The Prius is designed to use more battery power at warmup to keep the rpm's lower while warming up. It is best to let the engine warmup at slow speeds especially the type that allows you to basically creep around at near idle speed. Basically my rule is to stay under 35 mph for the first few minutes. You also want to be able to have a 6 second stop somewhere early in your trip to force the engine further along in its warmup cycle, but that's another trick all together.

 

To add to what I just posted. If you get up on the pedal right away without being easy during warmup you will have 2 consecutive segments (5 minute bars) that are around 25 MPG or less, the first one would be from the warmup cycle and the second one being from the battery charging.
I hope this helps.

 

Just a note for the 3rd Gen Prius: When you stop the car during warm up, the engine will turn off after just a moment. This is different from the previous generation.

 

Actually it's the same, just the engine temperature where the warm-up shutoff occurs is lower so it happens sooner.

Wayne

 

Thanks for the tip. I so lucked out. I live .4 mile from the gate in our community - a 35mph speed limit with two stop signs. Sounds perfect for the warmup - and I'm in FL so even in winter...

OK I'll stop, don't want to make you folks jealous.

 

You don't have to make a stop for the Stage 4 transition in the Gen III.

Wayne

 

What krousdb was describing is the observation that driving more briskly forces the ICE do more work during warm up.

The Prius is programmed to reduce emissions while the engine is still cold. It does so by driving mostly on electric while giving the ICE a chance to warm up under a light load.

But when you press the accelerator firmly, it has no option but to obey you, and abandon the careful ICE warming up. The ICE will warm up faster and the battery depletion will be reduced. As we all know, using the battery too much will harm FE (hence, the P & G method was invented). But the Toyota engineers have still opted to do so, since it helps to reduce emissions.

 

So,
What may have been considered a fuel efficiency hit by not driving the vehicle during it's short warm up phase, may if fact not be so bad after all? Call it a bad habit, but my upbringing as a mechanic will not let me drive off immedately in a cold engine, so I will give the engine a minute or so to idle before I drive off, and yet I still average mid 60's fuel consumption by the FCD anyway, I haven't actually computed it.

 

In the Prius that doesn't seem to be necessary, the electric motor will help you with that.

I know that you have to be easy on a cold engine, but never found it necessary to stand still with a stationary engine to warm up. Driving off nice and slow is just fine. All my cars explicitly stated in the manual that this was the preferred way of warming up, not standing still with an idling engine.

I also do not do that out of consideration for my neighbours. I have developed an allergy for idling engines about 15 years ago. There was this guy living in the same appartment block as I was. He had a diesel that he always parked right below my bedroom window. Every morning when he drove off at 5:30 am, hew woke me up with his warming up show, gassing and revving the engine for a good 2 minutes. Spreading around a lot of noise and toxic fumes and basically ruining a good night's sleep. I once talked to him about it, that it was not necessary and that he would not kill his car by driving off immediately and slowly. But he was adamant that it was necessary and so I was forced to sleep in the back bedroom.

 

Wow, that's annoying...just think if he had a Prius how quiet it would have been...

 

I'm afraid that if I had a neighbor doing that, the flower pot on my window sill may be shaken loose from the noise and fall on his car