Gen3 warming up stages

Depends by what you mean by "not huge". At freezing the first five minute difference can be almost double or better your MPG's. Normal MPG would be 15 +/- without the block heater, with a proper 3 hour warm-up you can expect 25-35 MPG. At 50F a normal 25 MPG can be boosted to 35 MPG, I've seen up to 45 MPG. It makes a difference.

Wayne

It may be... but I don't understand why I have to drive like grandma for a few minutes to get in this mode. Maybe this has been fixed in 2010? Dunno.

HSD should tap into heretical mode whenever the ICE torque is greater than what the wheels need. Lowering torque output from ICE is not an option because it would result in partial power and pumping loss. There is net gain from getting more efficiency out of the ICE at lower RPM despite the conversion loss from energy recirculation.

I have been wanting to write a program to indicate heretical mode by calculating the MG1 RPM, MG1 current, MG2 RPM and MG2 current. I also want my program to show the BSFC map in real-time. I just need to read out ICE RPM and Torque output. That would be sweet I never got time!

We observe certain different behavior among Stage 1a and Stage 4 depends on coolant temperature threshold.
I have never heard any behavior changes after entering Stage 4 at above 70C coolant temperature on both Gen2 and Gen3.

Of course, we observe different behavior in the heretical mode, but it is another story.
Also, the transaxle oil becomes warmer and warmer as we drive long distance. I believe we see better mpg when the gear train temperature becomes warmer.

Ken@Japan

I would add to this tip:
If you suspect that coolant temp is above 60C (like after several hours stop in a summer day), you can:
Wait the 12 seconds in parking position, then, while still in parking, depress the gas pedal until engine fires up and release the pedal - if engin stops - you are in Stage 4 - drive normally, if however engine stays on - you are in Stage 1a.

(on second thought: you do not even need to wait the 12 seconds before depressing the pedal if you have no intention to go to EV mode!)

In trying to wrap my head around the stages, it helps me to put it in graphical form. I'm hoping it will help others too. This info comes primarily from ken1784 and then from ksstathead. I'm not attempting to add anything new to the discussion, other than to present the info in a more quickly accessible form. Still don't know when the Gen III will defend stage 4. The chart currently shows that at 60 C the car will run the engine (if gas pedal is depressed) until 70 C. Not sure about these numbers. Any corrections or suggestions for improvements are appreciated.

I think you could combine some elements and reduce the number of images:

• "WS>45", "25< Glide < 45", "IOFF = Yes" is common to 2 and 3
• logic between 1b and 2, can last two IFs be combined, last three?
• How is "Glide < 45" different from "25 < Glide < 45" ?
• Is "Ready 0" to "4" correct or does it ever go to "3" ?
• How is "4-" and "3" different?

Bob Wilson

yes, but I am trying to stay with the establish concept of 5 stages. OK, 5 1/2 if you count stage 4-.

I don't think so, as each covers a different starting range of temps and each concludes with a different temp.

In stage 4, you can start an ICE off glide at any speed below 45. In stages 2 and 3, you must be between 25 and 45 to start an ICE off glide.

Earlier in this thread, Ken says this about stage 4 "if the coolant temperature is above 60C on power up, Prius is already in this stage"

At the conclusion of stage 4- you are back in stage 4 without the need for an idle check. But, again, I'm not yet sure which are the right temps at which this occurs.

Very interesting info here.
I watched the energy screen closely when I started cold engine in the morning and while in the stage 1a, there was only battery propulsion under 10MPH, but ICE powered the wheels partially at speeds over 10MPH. I will double check later today and tomorrow.

Excellent chart!
I will study as will others and post here with any tweaks or new discoveries.
Thanks for sharing.

Bob, the main difference between 3 and 4 is the ability to start a glide below 25 mph (in addition to between 25 and 45 mph). Stage 4 is the goal, but life is pretty good once you reach stage 2.

There are probably other advantages to s4 and/or s3, such as the car's propensity to allow super highway mode or to induce warp stealth, but I have not seen them documented.

I think it allows lower than 60C before defending temp, and that it does not take you all the way back to 70C when it does defend. But that is more an impression I hold than fact.

I think it is more like it can drop to 40C and it will then warm to 60C.

I have noticed on about five occasions now that the car does not go directly to stage 4 if the temp is greater that 60C at Ready. The engine doesn't start unless it needs significant power. But it doesn't stop quickly like it does in stage 4 either. Instead, it continues to idle in the 1000 to 1100 rpm range (when your foot is off the gas pedal) until you come to a complete stop, and then cuts off about 5 seconds later (similar to Gen II idle check). It will continue to do this multiple times (if you are in stop-and-go traffic) until it is good and ready to enter stage 4. It seems like the engine wants to run about 50 seconds before its satisfied.

This behavior is consistant with my Gen II. Although the Gen II engine will start 10 seconds after Ready even if the engine temp is greater than 65C and even with no gas pedal, and run for about 55 sec.

I've tried to capture this in rev 2 of the diagram by adding a fourth condition for the duration of stage 1b: "if CWT > 60C, ICE on for approximately 50 sec."

Of course, I would like the community to check this out and help us get this right.

After a few more "cold starts" (temps now range from 50s to 70s F) I'm positive that the ICE provides power to wheels and generation during warmup in the stage 1a as per the energy use display if one moves forward, even at low speed. My previous impression of no ICE power was when I backed up only.

If so, why is it different from what is described in this thread? The energy display lies? Difference between US and Japan models?

The energy display lies. No doubt if you push it hard enough there is some power from the ICE in 1a, but not efficiently.

The ICE will generate -some- some torque during warmup, 72% of which will go to the wheels, and 28% off to MG1, so the energy display is not "lying", however the amount of power transferred is very minimal

This helps. I saw no logic in the fact that energy display would be programmed to lie.

I was also surprised to read that with the ICE running in S1a, that it would run "doing nothing" - it is mechanically impossible. (I mean, the ICE cannot rotate with no load at all - it will still move MG1, at least, right? or can you have MG2 and ICE rotate with MG1 completely stuck (and that would require current on it...)?)
I mean, during the first 50secs it is clear that the car moves electrically only and that the ICE does not contribute to the torque to move it, but at the same time the ICE is moving MG1 which will make some current that MG2 can use.

So for me in S1a, the ICE contributes, minimally, to the electricity necessary for MG2 to push the car, via MG1. And this because the accelerator will not allow (for small gas pedal requests) the ICE to actively participate in the delivery of torque/power to the wheels, and have MG2 do all the work.

Moreover - you are not allowed to leave a car idle for any time if parked (even in a private garage/parking lot). So I cannot leave my car sitting there for 50 full seconds (and that is a lot!) to wait for S1a to finish. The only thing I can do then is drive *very* slowly - which I can since I live on a side street with 30km/h max speed limit, and all sorts of stuff happening - and use as least as possible all accessories (A/C off, radio off, lights off if possible).

I have to time which stretch of road I need to cover to make the 50 secs. I can likely shave 10-15 secs when pulling out of the parking spot. But I cannot simply stay there. It would be hard to explain the police or the passer-by (germans like to play the police) that I am actually polluting less because my car needs 50secs to warm up "ecologically"....

I will also need to test, with same morning temp, and assuming I manage to drive the same distance in the same way/speed, the differences in fuel consumption over my "benchmark" distance of 3km. I use this distance to see if the warmup was a "good" one or not....If I am at <7L/100km I am very happy - else it is a crappy day... And believe me - over the length of my commute (14-17km depending on route), the 3km FE make quite a difference on the overall FE of the leg....

This must be another difference between the Japan and US models. My US model gen 2 does not enter S4 while entering READY mode at high ICE temp either. The engine would come on for tens of seconds. Maybe the reason is that CA's pollution standard is higher than Japan's?

During Stage 0/1a warmup, the North American Prius ICE runs at exactly 1280 RPMs.

While parked, at first it draws slightly on the battery, but after a few seconds it does generate power through MG1 for a handful of horsepower. Amps go into the battery to charge it and SOC goes up by a few percent (1-4%) by the end of Stage 0/1a warmup.

Observation from EU model 2011. S1a takes always 50 seconds. No matter if it is > 0 deg Celsius or less (tested in -6 deg Celsius).

If car is exposed for few hours in temperatures under 0 degress Celsius ICE starts in less than a second from READY. No way to even try to enter EV mode.

It is possible to enter EV mode from S0 if temperature is slightly over 0 deg Celsius if conditions permit (min 4 battery bars, no heating, no defroster).

If I start engine with 2 bars after S1a (change in engine sound after 50 seconds) it often puts one more bar into battery if stand still.