Added Cruise Control to New Prius!

Tom Cole wrote:


I'm not sure what you're claiming is not correct. Here's a description of the operation of the Prius.
http://www.cleangreencar.co.nz/page/prius-technical-info
MG2 has to be rotating or the front wheels are not rotating. However, the front wheels CAN still be rotating if the gasoline engine is stopped. That's why I said the Prius is more of an electric drive with a gas-engine assist. The gasoline engine can still provide power to the front wheels through the pinion gears, but only if MG2 is operating. If MG2 is not rotating, the gasoline engine will turn MG1 but the front road wheels will not turn. There's no similarity to a diesel-electric locomotive. The simulation on this page will help you to understand the relationship between MG1, MG2, and the gasoline engine.
http://homepage.mac.com/inachan/prius/planet_e.html
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On Mon, 04 May 2009 17:11:19 -0700, "David T. Johnson"

I am aware of these two sites.
The problem may be one of over-simplification. Yes, MG2 is directly connected to the wheels and must rotate when they do. However the wheels are also directly connected to the Power Split Device (PSD). Therefore when the wheels are rotating the MG1 and/or the ICE must also rotate. Your explanation implied that it was only the MG2 that drove the wheels. Not so. MG2 may be driving the wheels, or being driven by the wheels (as a generator) or may be free-wheeling. Independently, under the control of the computer, power may be supplied from the MG1/ICE combination via the PSD.
The only time the MG2 is solely in control is when reversing, although, even then I have experienced the ICE starting when extreme reversing power is needed (e.g. to get a stopped front wheel over an obstruction such as the kerb).
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Tom Cole wrote:

No, it didn't. Electric drive with a gas-engine assist. (I have no idea why that is upsetting to people here.) The gasoline engine could not 'assist' if it wasn't also able to supply power to the wheels. When you push the 'accelerator' pedal down, the computer first puts current through the MG2 windings and then uses MG1 to start the ICE turning if more power to the wheels is needed as the speed increases and/or if the battery needs charging. The throttle for the Prius gasoline engine (ICE) is always controlled by the computer which also monitors the road speed so the cruise control elements are already included on every Prius.

No, the ICE is completely unable to supply power to the wheels when reversing because the ICE, like all gasoline engines and unlike MG2, only rotates in one direction...and there is no 'reverse' gearbox on a Prius. The ICE is only charging the battery if it is running while you are reversing so in reverse, the Prius is electric drive only.
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Because it's not true? Is that a good enough reason?
Because people just ignore reality and make up their own "facts" as it suits them, and then spew those "facts" to the world?
You WANT it to be "an electric car", but it's not. Suck it up and deal with it.
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On Mon, 04 May 2009 23:46:58 -0800, "David T. Johnson"

I agree that it seems illogical that the ICE should be needed when reversing under full power, yet the ICE *does* start under these conditions on my 05 Prius and also on my wife's 03 Prius, even when they are in EV mode. We reverse into our garages and if the approach is misjudged such that the front wheels are stopped at the kerb, applying full accelerator to get over the steep bump will cause the car to come out of EV mode and the ICE to start.
I have also experienced this when reversing up steep driveways in EV mode.
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wrote:

What I have read says that the Prius reverses on electric power alone (and, with no transmission other than the power split device, that seems logical). The engine may turn on for many unconnected reasons, such as recharging the traction battery, maintaining engine temperature, and the like, but there is no reverse _gear_.
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wrote:

Is there a forward gear?
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Tom Cole wrote:

The MG2 electric motor is the only device that powers the wheels when reversing. If the ICE starts, it is doing so to charge the battery but it cannot directly supply to the wheels in reverse but it CAN do that in the forward direction, as long as MG2 is also turning. If your reversing requires more power than is available in the battery, the ICE will start to charge the battery which then supplies battery current to MG2 to maintain the reversing. The ICE can't directly power the wheels in reverse because the ICE (like every ICE) only rotates in one direction. It would take a 'reverse' gear box to translate the ICE 'forward' rotational direction into the reverse direction...and such a gearbox does not exist on the Prius...which also does not have a 'transmission' to power the vehicle forward with different 'gears' since the MG2 can supply the necessary torque for slower speeds without the need for gears.
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The ICE can't directly power the wheels

The Prius ICE only rotates in one direction however this behavior is not universal. Some internal combustion engines will run in whatever direction they are started. A good example of this is found in model airplane engines.
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I believe that, in general, two-stroke ICEs can in either direction while four-stroke ICEs can run in only one.
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But it can't reverse direction without shutting it down and starting it up again. And as, Mike said, it's only two-cycle engines that can do this.
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Actually, I know from experience that model airplane engines do sometimes kick into reverse while running. My brother and I had model cars with model airplane engines, and we learned that the right impact can make it happen.
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wrote:

I don't know how you do it, but I come to a complete stop before shifting from forward to reverse and visa versa. I'll bet a four cycle engine could be designed to run either way.
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That has nothing to do with reversing the direction that the ICE turns.

Then why hasn't anyone done so yet?
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wrote:

I didn't say it would be practical, only possible. Why don't they sell passenger cars with 12 wheels? Oh hell, you win Michelle.
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I didn't realize that this was a contest.
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Either 2 or 4 stroke engines will have the axis of the crankshaft displaced to accommodate more efficient coupling during the power stroke. Can only run in one direction ...
On Thu, 07 May 2009 15:35:49 -0700, "David T. Johnson"

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On Fri, 08 May 2009 15:39:38 -0400, Steve Giannoni

Actually, I have seen large marine Diesel engines which could run in either direction. They were brought to a complete stop, the intake and exhaust were switched, then the engines were restarted going the other direction. You design engines correctly, that's possible.
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Your exception doesn't really break the rule. There are several design features of normal engines optimized for rotation in only one direction. eg - intake vs. exhaust : valves, ports, open/close positions, etc. ..., connecting rod bearings, ...
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My mistake - NOT the connecting rod bearings.
On Sun, 17 May 2009 11:54:51 -0400, Steve Giannoni

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