2010 Prius Warm-up Stages With Notes on Their Significance and Detection Selected 2004-2009 (Gen2) Differences Noted 2010 (Gen3) Prius continues the Gen2 preference for emissions control over maximum fuel economy, evidenced by limitations imposed prior to completing warm-up. Owners can mitigate these limits by understanding the warm-up stages and the associated limits on Prius operations. Mere understanding of Prius behavior is also of value to the owner. All references to temperature refer to engine coolant unless otherwise noted. Unlike prior versions, if Gen3 enters Ready Mode at or above 60C/140F, the warm-up process is avoided and Prius is in Stage 4 (S4). Stage 0 (S0): An opportunity to enter EV mode* without the warm-up cycle if conditions are met. S0 begins upon entering Ready Mode (below 60C/140F), and ends when the engine starts (approximately 12 seconds later unless EV mode activated). Stage 1a (S1a): Initial warm-up with late ignition timing and diminished engine power. Engine-off at stops: No Engine-off gliding: No EV Mode: No Unless warm-up is avoided, S1a begins at the conclusion of S0. S1a terminates as follows, based on temperature when S1a begins: - At or below 40C/104F: approximately 50 seconds after the engine automatically starts [more testing at extreme cold temperatures needed?] - Between 40C/104F and 60C/140F: approximately 50 seconds after the engine starts (engine start delayed until accelerator pedal is depressed), or earlier if temperature reaches 65C/149F. With a ScanGauge II (SGII), S1a is denoted with IGN=-10. Without SGII, listen for an audible change in running. S1a is the worst stage because not only is Prius operation limited, but the engine does not even produce significant power unless power demand exceeds the HSI ECO area, and high demand on a cold engine wastes fuel and may shorten engine life. One should drive slowly or sit and charge the battery during S1a for optimal fuel economy. Tip: If stopped at or above 60C/140F, power off then re-enter Ready Mode to reach S4. Stage 1b (S1b): Continued warm-up with normal ignition timing and power (still no EV mode in Gen3 whereas the Gen2 allowed EV mode in S1b). Engine-off at stops: No Engine-off gliding: No EV Mode: No S1b is much better than S1a because the engine will power the car and the generators normally, but it still cannot engine-off glide. This stage is avoided if temperature exceeds 60C/140F when S1a ends. Otherwise, S1b begins when S1a ends and lasts until the following points depending on engine coolant temperature at the start of S1b: - Below 40C/104F: until 40C/104F. (I got engine off at stop with 103F, but msantos reporting 46C/115F for this transition on his Canadian model. Need more data...) - Between 40C/104F and 50C/122F: until 50C/122F. - Between 50C/122F and 60C/140F: until 65C/149F. With SGII, note the engine coolant temperature when IGN=-10 changes to a positive value, and note the S1b termination point from the table above. Without SGII, limited gliding capability or EV mode availability would indicate S2 has begun. The Gen2 begins S2 at 40C/104F. So the Gen3 sometimes delays S2. Tip: If stopped at or above 60C/140F, power off then re-enter Ready Mode to reach S4. Stage 2 (S2): Engine off at stops: Yes EV mode: Yes* This stage starts when S1a ends at 60C/140F or more OR when S1b ends. It concludes when temperature reaches 70C/158F. S2 is much better than S1b because engine-off gliding is available, provided the glide begins between 25 and 45 mph. On the Gen2, engine-off gliding only occurred in S3 (limited) and S4. Pulse & glide technique is thus available within limits (25 to 45 start point) in S2. With SGII, watch engine coolant temperature for the start of S3, then watch for a good idle check glide opportunity. Without SGII, attempt the idle check glide; if it occurs, you were in S3 but are now in S4. Tip: If stopped at or above 60C/140F, power off then re-enter Ready Mode to reach S4. Stage 3 (S3): Idle check stage. Engine-off gliding available if glide begins between 25 and 45 mph. EV mode: Yes* S3 raises the EV mode speed limit from 10 mph to 25 mph. More importantly, it allows the idle check (rough shut down) to occur, which is the normal entry to S4 and full operation. In the Gen2, the idle check required a stop (or nearly so) of a few seconds, but the Gen3 just needs a glide without the accelerator pedal depressed for a few seconds. Once the engine shuts off, S4 is attained. Query: must the idle check occur below 45 mph? If you can glide engine-off starting below 25 mph, you have completed the idle check and are in S4. No advantage to power off/Ready Mode tip in S3, since idle check ends warm-up anyway. From what is included here, one could argue that S3 is merely an ending to S2, but I have retained S3 because there are probably differences not mentioned, and for consistency with Gen2 nomenclature. Stage 4 (S4): Full operation. Engine-off at stops: Yes Engine-off gliding: Yes EV mode: Yes* Engine will run if engine coolant falls below ?C/?F (40C/104F(?) if in ECO mode) until that temperature reaches ?C/?F (?C/?F if in ECO mode). [I saw these temps reported here, but cannot find now.] Gen2 defended at 63C/145F until 73C/163F was reached. Full glide availability is a major advantage of S4. The availability of other driving techniques such as warp-stealth, warp-neutral, and super highway mode (SHM) is not yet addressed here. It seems unlikely they could be employed prior to S2, with some as late as S4 for unrestricted use? *Notes on EV Mode Recommended uses: Moving around the driveway or parking area Drawing power in expectation of major regenerative opportunity (e.g., about to crest a mountain) EV mode conditions: Engine coolant at or above 0C/32F (20C/68F on US models?) Windshield defogger not in use Hybrid system (HV battery) in the range 0C/32F to 46C/115F (no x-gauge yet?) HV battery state of charge (SoC) at or above 4 bars Speed below the applicable limit (10 or 25 mph) Not in S1a or S1b EV mode terminating conditions Failure to meet initial conditions (do limits differ?) Excessive power demand EV maximum speed by stage: S0 and S2: 10 mph S3 and S4: 25 mph (10 mph if engine coolant below 70C/158F) Note: Engine-off at stops and Engine-off gliding will not work while the window defogger is on, even if in a stage where they otherwise would work. I take most of this from Ken@Japan’s fine work, and from reading the Gen2 Five Stages ‘literature.’ Without a doubt, further refinement of our understanding is needed. Please share your knowledge and experience, especially where the preceding explanation seems incomplete, incorrect, or misleading. I have a Gen3 and a SGII, but have not really tested the guidelines above. So this is more an attempt to start a refining process within this community than a presentation of results. You are welcome to PM revisions to me or just post them up and I will incorporate by editing my post. __________________ Mods: ScanGuage II 3.15 w/ X-Guage OEM all-weather cargo mat WeatherTech front mats SunScreen Sunshade -front & front sides PSI 44/42 100% lower grill block (seasonal) -------------------------------------------------------------------------------- Last edited by ksstathead; 03-01-2010 at 10:22 AM.