Best Techniques to Drive the Prime

If the engine is cold at the top of the hill, I would put it into HV mode rather than CHG mode. The engine will go into its warm up cycle which will slightly charge the battery without putting any load on the engine while it is still cold.

 

My head hurts just reading that.

 

I think Pizza Driver was referring to engine life, not mpg. Avoiding putting too much load on an engine until it reaches operating temperature. Some of us are old-fashioned that way.

 

Not so much whether to start driving immediately but about putting load on the engine while it is cold. I just remember that was always the advice back in the old days with cars, a lot of people thought they needed to warm up the engine to operating temperature before they started driving, but the advice was no, wait a few seconds to get oil pressure but then start driving, drive normally, but avoid hard acceleration for the first mile or so. Now in an HV a lot of that acceleration is coming from the electric motor so it's probably not as critical, maybe not enough to worry about anymore. But hard to break old habits which is why I said some of us are old-fashioned about it. Coming out of my house I have an immediate uphill stretch of about 1/8 mile, on cold days I tend to baby it up that hill unless someone is behind me. Maybe I don't need to but I do it anyway.

But one habit I had no problem breaking was waiting for oil pressure. When I got my first Prius I remember it seemed like such a luxury to push the button and immediately start pulling out of the driveway even before the ICE starts.

 

When the ICE is on but the throttle position is lower than the half way point in the ECO section of the hybrid system monitor, then it will actually be charging the battery. This is why I recommended not going into HV mode until reaching the top of the hill. Use the battery to climb the hill, then when you get to the top of the hill, go into HV mode and the engine will kick in to start warming up even if it is not needed to drive the car. This will allow all of its energy to be used to charge the battery giving you more EV range for later in the trip.

 

Thanks for clarifying. Okay so I guess there is only one old-fashioned person (me) who still worries about putting a heavy load on a cold engine.

 

From my experience in the Prius C, Toyota's software already accounts for mitigating the load on a cold engine. When I would start up with a cold engine you would see an incredible amount of drain on the battery even with low to moderate acceleration. I assume this was to take some of the load off the engine. I have not really seen this same behaviour in the Prime, but it would be harder to notice with its much large battery.

 

I agree with you. I don't drive the car very hard either until the engine warms up.

 

That's good to know. I guess then the only time you would even think about it in regular Prius is if for some reason you didn't want to overly drain the HV charge in the first mile, so you would drive a little easier while the engine is still reaching full temperature. Of course in the Prime you are most likely starting out in EV mode anyway, which would seem at first to make this a moot issue, but actually it's just kicking the can down the road, because say 25 miles into your trip the cold ICE is going to start up. Do you want that to happen while you are climbing a hill? Maybe not, and I guess you could plan ahead about switching earlier to HV. But then again maybe it's not worth worrying about if we're only talking about a small inefficiency during a very brief period, as opposed to cumulative engine wear which is what I was thinking about. But even engine wear is probably not the worry it used to be, since with Prius it seems the engine will far outlast the car in most cases. Which I suspect will be even more true with PHEV.

 

I have never driven a Prime but I have always driven an EV.

Every EV I have ever driven it's always more efficient to drive in ev at the lowest speeds possible, regardless of terreign.
My volt is no exception, having a gas engine adds a dynamic especially in cold but it's still slow = ev fast= gas
See my attachment below on my 2013 of what's possible if you optimize your route for low speed.
It's a trip that's 1/3 low speed country, 1/3 high speed freeway and 1/3 medium speed country.
With a gas engine on board it's a good idea to keep a small amount of electric range for high speed downhill (low load) situations but generally , especially in cold you want to keep heat off and engine off during ev, then isolate gas usage to occur all in one stretch.

Aka you want to minimize longer gas engine on off events because efficiency drops a lot as your motor cools below 180 and falls off a cliff below 150.

If you can provide the distances, speed and terreign of each "leg" of your trip I can give you a itinerary of when where and what.
You need to pay close attention to your instaneous kw and remaining battery so you don't come home with more than a mile or so in the tank.

Best thing you can do is set a kwhr/ mile goal and hold your instantaneous usage there as much as possible.

Good luck

 

I don't think the hill really factors in as much as you think.

If roadway speeds are low or if traffic is so light you can do whatever you feel like I would just drive electrically up and down the hill setting a kw/mile goal and include that stretch in your ev run and let the car turn on the gas burner when it wants

The key is to know your route, optimize it then map it out into segments so you don't need to on off the engine as much.
You will find on a predictable route you can approach the trip more analytically and adjust behavior to match the mode your in for that stretch.

On my once weekly long trip I only have 3 sections even though it's a 100 mile trip, gas burn is on the middle 3rd and I focus my effort less on engine control and more on hypermiling technique

 

The Prime runs a loop of engine coolant to suck heat off the catalytic converter. The catalytic converter gets HOT in seconds, so this will help to warm the engine faster but they have to limit it so the catalytic converter can maintain the temperature it needs to work correctly. I do not know if the Gen 4's have this feature.

Remember the 2004 generation Prius when it would store heated coolant in a thermos bottle and return it to the engine when you powered up? My 2006 had that but parking all day outside on freezing cold days cooled it to the point where it never helped much.

 

Inferno, what is your mpg for the trip if you just switch the car into EV Eco mode and drive it? Do nothing fancy, just drive it? The only manual action will be to switch into B mode if there's a steep downgrade, and back to D mode at the bottom.