As most have read, the Prius is supposed allow electric-only travel at speeds between 0-42mph, with the ICE starting at speeds greater than 42 regardless of conditions. I happen to know this is incorrect. On a recent trip, I was coming out of the mountains and with a long downslope the battery charged completely (8 bars, all green). When the road leveled off I was going 53mph. Looking at the energy screen showed only the electric motor powering the car. In fact, while watching the energy screen, I was able to accelerate to 55mph and travel over a mile (all at 55) with just the electric motor powering the car (according to the energy screen). The ICE finally started up when the battery dropped back to 6 bars (blue). Anyone else achieve "high speed steath?" (Not coasting where the energy screen shows no energy transfer). Thanks, Shawn
There is a simple misunderstanding at play here. Faster than 42 MPH, the engine starts to SPIN, not consume fuel. It has to do that, based on the Planetary-CVT design. That motion is just a very low resistance rotating of the engine to keep the power-carrier for it active. No gas is injected until more power is needed than what the electric-motor can handle by itself.
The VVT-i come into play here also by lowering the compression to about 9to1 so as to lower the drag and in B mode it will go as high as 13-1 to provide more resistance.
my car will kick in the ICE at 41, not 42... Ill be stealthing fine at 40, but as soon as i hit 41, BAM, the ICE comes on
The ICE will always come on automatically at 41 (42) mph when accelerating in electric mode from a stand still.
I'm going to take a huge risk and disagree, slightly, with John. I believe that the ICE does, indeed, have fuel injected during these hyperstealth speeds over 41/42mph. It's a VERY small amount, but enough to power the ICE to spin rather than to act as a JAKE brake as it does in B mode. BTW, don't assume that what you see on the Energy display is really what's happening.
From what Ive read, but Im no authority, there is no fuel supplied but the valves are held open, thus removing the compression and reducing "friction" from the ICU. I would guess, that the motor is turned by the MG1 is at the same time.
What they should've done to better show this on the energy display is have the engine icon animated. You'll also notice that during your 5 minute startup period the engine will be running as your stopped - not providing energy to the battery, just going through it's normal startup. It's nothing serious, but it'd be an added bonus to have the engine animated, in my opinion. As an aside - I think Evan hit it on the head with the 'small amount' being injected. Sure I don't know much if at all anything about ICEs, but wrapping my brain around an engine that can run without fuel makes my head hurt. -m.
Without taking sides between John and Evan, the idea would be that the engine can spin without fuel, pushed by the electric motors and the gear geometry, but itself doing no work. What I'd like to see on the display is: 1. The amount of current going to/from the battery. 2. The engine temperature, so I'd know when it's warm enough to enter phase III. I guess I don't care whether the engine is spinning, if it's using no fuel.
Toyota quite intentionally played it conservative with what they decided to present on the Multi-Display. They did it for two very important reasons... One was that they didn't want to frighten people away. The fear of computers is very real still, even though many people own them now. They really don't feel comfortable taking advantage of all the features (yet). So keeping it simplistic was essential. You can also think of it as special-effects; too much can distract you from the intent of a movie, or in this case the drive. The other was to avoid liability. The "change is bad" attitude is an unfortunate reality. So starting with the basics was a good plan. It also sets them up for new opportunities later on. Once HSD becomes commonplace, Toyota will need other aspects of appeal to encourage new sales. By then, Multi-Displays will be common, rather than rare like they are now. At that point, lots of new features will be added. Just imagine some of the animations and on-going statistics that could be shown. Also keep in mind that increasing the size will be easier too. That in itself will allow for greater detail to be added without a concern about being able to see it while driving. The future holds great potential. I can't wait!
What I'd really like to see provided is a serial port to download the data to a laptop or pda and get infomation such as total fuel used per mile travelled BSOC information such as voltage average per 5 minute time, and amperage regenerated per 5 minutes and do this for each trip and log the start time and end time for the trip max engine rpm on the trip max MG1 and 2 speeds on the trip etc. there is a ton of info in the computer that could be downloaded and reviewed. Now a lot of people would have no use for this but us cult members would have something to do over Saturday morning coffee.
Evan is partly right with his theory that there is some fuel injected into the engine but almost all EFI equipped automobiles cut the fuel under high manifold vacume conditions, with the throttle positioner on the idle stop and the engine at normal operating temp an the speed sensor providing a signal and the gear selector in drive or overdrive. When the O2 sensor say's the cat is cooling off then the computers sends the signal to inject fuel to put hydrocarbons in to the cat to keep it lit and up to temp.
Hey John how about a banner ad at the bottom of the mfd with a running display of all information you could program into it. Battery temp and %charge and MG1 and 2 speeds and cat temp. it would be better than CNN
Frank, You are an excellent candidate for one of the miniscanners that is being developed!! Check the Files section at theMiniscanner Yahoo Group for information on how to make a deposit or donate to the cause. It's a good effort and should be a VERY handy tool for the geekiest of the Prius geeks.
umm i have experienced what was described and when coasting the engine does not come into play since besides vehicle speed, you must also have petal pressure. when coasting you only have one component which explains why the engine was not running. iow, the operation of the car is the same as when you are slowing down although because of the slope you arent slowing down. there is another thread in this forum that talks about the motor doing some high RPM revs when coasting down a hill which can occur if the battery is charged to full capacity in regen mode.
The ICE is controlled electronically in the prius, not the usual cable. Thus pedal pressure is NOT required. I definate does, always, kick in at speeds above 41mph. Whether fuel flows or not, I can not say with certainty, but from the feel when it kicks in I think it is flowing and the ICE is running, I've paid pretty close attention.
Just to clarify. I was NOT coasting. I was travelling on level road (or it appeared to be level; this can be deceiving, I know). The energy screen showed flow from the electric battery at all times, and no flow from the ICE to the wheels or the battery. Now it may be that the ICE was turning with the valves open. If so, I could not hear it (a real possiblity). Thanks, Shawn
Yes, that was clear, and was my understanding. The ICE is/was definately spinning but under no drag/strain so you would not hear it. If you coast/drive down a hill in stealth very slowly gaining speed right at the 41-42mph change over you'll feel and just barely hear a thunk and slight change in sound as the ICE fires up and begins to turn. I do this every day on my way home from work. You likely won't notice unless you have the radio quite low.
ok i thought the original post said you were coasting... ill be honest with ya, i have music on all the time and couldnt tell you when the engine starts running unless i happen to have the power screen on... but ill be honest with ya... now that im used to the screen i ignore it alot.