How To Do A Steep Uphill When The Engine Is Cold

My suggestions:

(1) Move to the top of the hill ;
(2) Don't bother adding an extra loop, it just wastes fuel. Does the hill have any other traffic? If not, start out slowly uphill until the engine gets some warmth. If traffic demands quickly getting up to speed, then further discussion is called for.

 

I also have a hill just outside the driveway, but no other way, but uphill. If engine is cold, fast climb can totally deplete the battery, as ICE refuses to help. There are 2 solutions to the problem:
1. slow climb at the middle of HSI scale. That creates smaller loss of charge.
2. idling ICE before driving, so ICE can handle the hill.

I'm actually doing a study to see what is more fuel efficient (see my separate thread on that), and the results are encouraging to suggest that #2 is maybe better and clearly not worse, at least in hot summer (as initial warmup till ICE stops is very short).

 

Can you climb the hill by setting the cruise control to 20 mph? or maybe 15

By the way, there is another reason why you should move to the top of the hill or at least out of the bottom of the hill. Flood.

 

I don't think you can set the cruise under 25 mph.

 

The only benefit of living down hill is that the last mile of driving is all downhill and EV only.

 

No technical data to backup my view but i personally let the car idle for a few seconds before pulling away and heading up a hill depending on how cold it is outside. I dislike forcing the cold engine to rev if it is reluctant to do so, keeping it out of the pwr zone as long as its favoring battery use on the warm up cycle. From parked to start of hill how far is it, 30 seconds drive or less?
I face a similar situation on my daily commute, it is mostly all downhill for me but there is a short steep uphill section 30 seconds from my driveway before the downhill portion. I find on a summers day like today if i drive off right after startup the ICE generally will take 30 secs to warm up enough that it will start to assist the electric motor, so when i reach and start the uphill portion the ICE will rev freely and assist in propulsion. I don't believe it has completed the warmup cycle fully but it is enough that the computer decides the ICE is allowed to work. And from my observations that generally takes 30 seconds to reach in the warmup stage.
I suppose you could always test yourself either of your methods by resetting the trip computer on each route and see which returns the best mpg.

 

If your quarter mile loop takes you up the same route that you'd take if you just head straight up the hill, don't bother. If it saves you a quarter mile later, then it might be a good option.

In this case, I would probably suggest idling at the bottom; not long though. The engine will produce power as needed about a minute after you power the car on. Depending on how your car is parked, this might be just enough time to get you out of the driveway. You'll know it's ready because you can hear the engine rev when you press on the gas pedal. If you pay close attention, you may also hear the engine's sound change slightly when it goes from the inital warmup stage (~1300 RPMs putting about 6 Amps into the battery) to the second stage (~1300 RPMs putting about 20 Amps into the battery).

You can also chug along slowly, using the small amount of power that the engine is producing; but this is a speed and acceleration that is barely suitable for use in a parking lot, much less normal driving. Going up a hill, it's probably not enough to even keep you moving without draining extra power from the battery. So best to hit that ~1 minute mark before you start up the hill.

 

If the hill is right smack bang out of the driveway right away, better to sit idle for a little over a minute until you hear a change in engine note (if you don't have a way of determining if it's past stage 1a). If you have a Scangauge or Torque, once the temp gauge reads 104F, then you're good to go to tackle the hill.

Another good indicator is ignition timing. If it's negative, then the car is still warming up. If it's already positive (start of stage 1b, then you can start driving off). Also a good indicator is BTA (amps in/out). If it's negative, then the system now accepts charging from ICE. If positive, it's still using energy to propel the vehicle while the ICE warms up.

If you have about half a mile of flat road or slight downhill before the road start to go uphill, and there's no traffic, then it's more efficient to just let the car crawl with just a slight pedal pressure (5-10%). That way you're already starting to cover ground while the engine warms up and using just enough juice from the traction battery.

I can relate because that's how my morning commute is like.

 

Let me suggest:

• reset trip meter
• READY car
• run tests with and without the morning, idle until it stops, ~1 minute
• set cruise control speed 25 mph
• record MPG at the crest

In a perfect world, run three tests in each mode or five tests and drop the best and worst, average the three.

I look forward to your results.

Bob Wilson

 

If I had to choose, I'd rather go down a hill in the morning so that the car would warm up while it's moving with gravity. Going up a hill at the end of the day put less stress on the car since it is already in full operating temperature.

 

I forgot to mention the best solution:
3. Get a plug-in block heater.

This is on my to do list when warranty expires. I hate to do any mods under warranty.

 

I don't think it will void the warranty if you put in an OEM heater like i did to mine. The dealer knew about it and they didn't say anything about voiding the warranty.

 

Walt,
Welcome to the club of PriusChat members who live at the bottom of a hill. My driveway is one, and I have three more significant uphill slopes in the first four miles.
I may also try the warm-up first technique folks are suggesting.

 

Cold start your Prius. Put it in Drive and go to the downhill route. Once you you get up to 15 mph set the transmission into Neutral and glide allowing the engine to warm up during the quarter mile loop - about 300 feet before the steep uphill climb put the car back into Drive and accelerate to 40 mph at the foot of the steep hill. Hold your accelerator so the HSI display is smack in the center (right under the eco capsule) . Maintain acceleration pressure and allow the car to lose speed as it climbs up the hill (e.g. 30 mph) . At the crest of the hill - let ease up on the accelerator but don't let it go into braking regenerative mode. After passing the crest of the hill - accelerate back to your desired speed.

 

There is no problem. It's suppose to do that.

The system will intentionally protect the engine from strain. That's a fundamental part of the design. It reduces emissions.

Living near the bottom of a valley and having owned each of the generations of Prius, I know the hill climb extremely well. In the dead of winter (very cold here in Minnesota), the battery-assist is quite pronounced too. I just start the Prius and begin the climb. It has never been an issue.

Now, I have the plug-in model. So, I'm even more familiar how the system automatically goes out of its way to limit RPM initially.

Just drive it.

 

There is a problem, by "protecting" the ICE, the system puts wear and tear on the battery. There is a finite number of discharge cycles in any battery, even more so in lithium.

Do you have a problem with any of the 3 solutions I provided?

 

On the subject of the first warmup stage S1a, I'm not sure if this stage a fixed time period based on coolant temperature or other factors are involved? Reason I say so is on my commute when i start in the morning and by the time i get to the start of my short hill climb there is a stop sign which takes me generally 30-45 seconds to reach. Every time i come to a stop here and then start to climb the hill my v seems to be in stage S1b. Is it a coincidence that the coolant has warmed up enough just as i reach the stop sign to enter stage S1b or does it enter this next stage because i came to a complete stop? seems odd. It is very convenient though, as the hill is a steep enough grade i think the battery would be quickly depleted trying to climb it, the ICE would eventually have to help whether it wanted to or not. On that note, I believe the ICE can be forced to rev even right after startup if you floor it, correct? Not that i'd ever want to do that.