Waiting for initial warm-up cycle to drive?

Don't wait, and don't drive in stealth mode, except in parking lots and such. It's more efficient to move while warming up, except you don't want to floor the gas in the first stages as the system tries to baby the engine, by drawing more from the battery, which may mean more idling later.

The more you draw from the battery like in stealth around (not gliding) the worse your mileage will be.

 

Counter productive. Will not increase mpg.

 

I found an icrease in MPG by hitting the EV button on startup when the engine is cold as I live on a hill and regen/glide down the hill through a set of side streets (all down hill) to a set of stop lights about a mile away... I have about 50% (indicated) SOC on the MFD and when I go through the lights the traffic speeds up to beyond EV speeds. So I'm affectively delaying the onset of the engine warm up until I'm actually using the ICE at normal speeds. No ICE idle warming..

 

Someone has probably made a chart of this, but use your engine while it is working anyway. You MPG can actually INCREASE by driving while going through the warmup cycle. Try it out. My MPG increases at specific speeds during the warmup cycle. The increase isn't much, but the engine is running to produce heat -- why not use the mechanical energy being produced to move the car along?

 

Its so easy to lose bars while warming up, so I ease Prius along (like 5-10 mph) until its warm enough for stealth mode.
By the time I've reversed out, shut the garage door, travelled 300 yds or so then I'm ready for stealth mode with no drain on the battery.
Now that its getting colder though I've found that a change by as little as 1C adds 50yds or so to my warm up routine.

 

I seemed to notice an increase in the initial 5-minute-drive MPG by warming up at idle vs not. Does the MPG calculator factor in fuel used during idle?

 

That is an advantage of living in the UK. The US models have a much higher temperature requirement to enter EV mode, so this isn't an option for most of us most of the year.

Yes, it counts all fuel used, moving or not. As it should.

 

Hi All,

For battery longevity, I think its a good idea to wait one minute after powering up the car, only if you need to drive up-hill imediately thereafter.

If your route is on level terrain, or downhill, start the car, and drive off.

 

Bottom line is when the ICE is running, you should be moving for best mpg's. I hate to hear it running while I'm waiting for my gate to open (going to work) or waiting at the first stop light (going home), because I know it detracts from my mpg's.

 

I remember a very enthusiastic poster (Bwilson4web) once made a measurement, and starting with a ICE warm up on N showed less consumption than P or D itself, even if not moving at all.
But I rather do start moving immediately, and spare another kick in of the ICE 1/2 mile away, it means ICE is already spinning when needed. If to make hard throttle few meters away, I wait.

 

I've been using EV mode on initial startup, to avoid the warm up cycle until I am out of the parking lot, etc, to delay using the ICE until I would need it anyway on the actual roadway. The way I look at it, anytime the ICE is running and not providing thrust is a waste.

 

Although this does sound logical, there is the fact that while in warm-up mode, the engine runs really rich with delayed timing to warm the cat, which also really hurts fuel economy.

I've only tested my car once, and I saw significantly less fuel usage on my MFD during that first 5 minutes of driving the time that I let it idle to warm up for a couple of minutes vs. driving right away. (Just my observation so far)

 

I think it's pretty tough to do worse than 0mpg - idling at a stop. Gotta be better if you're in motion but not putting much demand on the ICE during the warm up.
Without some data it'd be tough to say where the crossover is - how much ICE demand at what stage of warmup and rate of travel is more or less efficient?

- D

 

This has been covered in other threads. The bottom line is that the ICE does not provide drive power during warm up but it dose charge the HV battery if the car is still in park. Therefore the best MPG is achieved by warming up while the car is still in park.

 

How is that possible? While in Park, the ICE is running but you are recording no miles, therefore getting 0 mpg, which is calculated in your average mpg for that tank. Even if you only get 5 mpg during warm-up if you drive off immediately, your mileage will be better than just letting it idle in Park.

 

I am not sure its correct, but it is Possible. Because unlike other cars, the Prius can fill its electric gas tank (battery) while the car is stationary. And then use the electric gas tank later.

Here is one scenario - although I am in no way saying that the mileage is better allowing the car to be stationary during warmup:

There are extra transmission gearing losses between the engine and the wheels in the 1st and 2nd Gen Prius. When the transmission fluid is cold, these losses are larger. And the engine power flows through those losses.

The transmission gearing losses from MG2 to the wheels is less, so the cold transmission fluid has less impact.

So, using the engine to charge the battery through MG1, rather than provide motive power to the wheels (all the way through a cold transmission), may be more efficient.

Argonne made a big stink about this extra gear set in 1st and 2nd Gen Prius. The third Gen Prius has the extra gearing between the MG2 and the PSD, now. And there is less gearing loss between the engine and the wheels....

 

This has been covered in many other threads, but that's not the conclusion that was drawn. It's not that simple. It all depends on initial driving conditions:

1) Low power requirement (flat or downhill, little traffic, low speed): Start driving immediately, but avoid heavy use of the accelerator.

2) High power requirement (uphill or lots of fast traffic): Use a short stationary warm up period.

It all comes down to power requirements. You are correct that the ICE does charge the battery during warm up, even when standing still in Park, but it's more efficient to drive slowly and use that charge to directly move the car. Otherwise you lose a lot through the battery charge/discharge cycle.

On the other hand, if you have to drive hard, the ICE runs at an inefficient setting until it gets warmed up. Pick the method that works best for your situation.

Tom

 

I beg to differ. I believe the ICE provides no power to the hybrid system during S1 unless the car is in park. (Just take a look at the MFD and listen to the inverter screaming.) So there would be no (extra) "charge" available to "directly move the car". As such the only way to recoup some energy back from the burned fuel during S1 is to stay in park and allow the HV battery to receive charge.

When there are conflicting opinions I resort to whoever holds the highest practical achievement. In this case no one beats the Japanese hypermilers - one of them maintains the world record of 84 MPG over the lifetime of 113K miles - and the rumor has it that they recommend leaving the car in park during S1.

 

See the previous post and yes consider long term average not just short term effects.