New member with a tech question

[9G-man]

Hello all,
I'm new and thought I'd introduce myself. I haven't been able to stay away from this site for weeks now since I found you folks. I like the enthusiasm here and the wealth of knowledge to be gained about the Prius.
I intend on being a happy owner shortly, as soon as my current ride sales. I've had the opportunity to test drive one last week and I was impressed.

I have a technical question though...During those times when the car is in motion and the ICE is "shutdown", Is the engine still recipricating mechanically inside and simply being deprived of fuel and/or ignition OR Literally disconneted from the drivetrain and at rest internally?

[efusco]

Depends. It can remain completely shut down--no fuel, no motion, etc. at speeds below 42mph. At 42mph plus it will engage and spin but does not, necessarily, need fuel--it is passively being spun by MG1. That is due to rpm limits.

[9G-man]

Interesting, Thanks. Ive searched and found much info on basic hybrid engine operation, but if anyone can direct me to info specific to this subject I'd enjoy reading up on it.

[mehrenst]

The ICE runs when the ECM decides it needs to run and when it isn't needed it doesn't rotate. There is no magic "speed" except once you get to about about 43~44 mph. At this speed the ICE is needed to maintain speed or accelerate. If you are going downhill (regardless of the speed) the ICE will shutdown and the Motor/Generator will start to recharge the battery. If you step on the brake the MG increases its output to provide dynamic braking. If you want to use the ICE for braking purposes, e.g., its a long downhill slope, is relatively steep, and the battery is near full charge you can force the ICE to rotate by putting the selector in "B". Under these circumstances no fuel is fed to the ICE, the valve timing is adjusted (I think), and the ICE is operated similar to a "Jake Brake" on a truck.

About the only time you can expect the ICE to not run is when you are backing up. Backup is totally electric. However, if the ECM decides the ICE is needed for a variety of reasons it will start the ICE even when you are backing up.

One of the strange things that often happens is the ICE will start shortly after doing a Power On. It's my understanding that this is part of the power up cycle and is used to ready the ICE for operation by moving hot water from the thermos flask into the ICE. (done to reduce emissions) When you Power Off you will hear what sounds like a pump. It is a pump and it moves hot water from the ICE into the thermos so the ICE can be preheated during the next startup cycle.

[kirbinster]

http://home.earthlink.net/~graham1/MyToyot...PriusFrames.htm

Check out the above link it is chocked full of info on the Prius and hybrid technology.

[9G-man]

The above should keep me intertained for a while. I understand the planetary gear that links the drivetrain components together, and thus, the way each component's rotational speed would differ, but I don't understand how any one component (the ICE) could be internally at rest sometimes since they are all mechanically linked together. ICE, MG1, MG2, Differential, Axel, Wheels, when the car is in rolling motion.

[longjohn931]

Many thanks to our esteemed moderator Evan, who has posted multitudes of knowledge based articles and links, this excellent article should satisfy your questions.

http://priuschat.com/forums/files/oakridge...elabsreport.pdf

I was trying to remember another link that shows numerous pictures of the ICE and Hybrid components broken down, without success, maybe someone else can direct you.

[mehrenst]

longjohn... Thanks for the URL. The ORNL report positively 8) RADIATED 8) information.

[DanMan32]

http://home.earthlink.net/~graham1/MyToyot...ions/EvMode.gif

Which can be found in http://home.earthlink.net/~graham1/MyToyot...gOnAsIDrive.htm
(Website frame bypassed)

Notice the planetary gear carrier is stationary, which is what ICE is connected to.
In the classic, because of the max RPM of MG1, ICE had to turn at 42MPH or more. For the newer Prius, MG1 has a higher max RPM, but it has been thought by casual observation that the HV ECU still limits MG1 RPM during EV where ICE will still turn after 42MPH.

But I believe your question is, what prevents ICE from turning on its own due to torque forces? Have you ever tried to turn an engine? Ain't easy.

[Russ Yost]

Here's another URL I like:
http://www.toyota.co.jp/en/tech/environmen.../hsd/index.html