I was playing around with my Torque and discovered the engine idles at 1,000 rpm at speed above 38mph. At speeds lower than that the engine shuts down just like I would expect, once warmed up. I also checked putting the car in idle at freeway speed. The rpm stayed at 1,000 rpm. It would be nice to have a mod that shutdown the engine so you could coast in neutral with no gas consumption but you would have to start up the engine before you went back into Drive. Ideally you would also have flaps on the radiator intake to keep the engine compartment warm. (now an expensive mod.)
There is no gas consumption when you're coasting even thought the engine is rotating. Because of the gearing in the Gen 2 transaxle, stopping the internal combustion engine (ICE) at higher speeds would spin motor generator 1 too fast for safety. So, if the ICE isn't needed for propulsion at higher speeds (ie: coasting down a big hill, etc.) it shuts off the fuel and spark and opens the valves and uses MG1 to spin the ICE almost freely at 1,000 rpm up to about 65 mph. At higher coasting speeds, it has to spin the ICE faster. Not as efficient as stopping it all together, but not burning fuel either. Heres a nice explanation of the various driving modes. The section on coasting is the one that deals with your situation. Whats Going On As I Drive?
This is all you really need to know, but you need to actually believe it. The other thing you need to know is: Coasting in neutral is also a BAD thing, for several reasons. One is safety, two is there is no charging of the HV battery and 3 is no regen braking either. The question is a pretty good example of " A LITTLE knowledge can be a bad thing."
I first tried idle when by inverter coolant pump went out on my 01. The inverter was overheating on my regular commutes and by coasting down one side of a pass it did not. This bought me time to fix the inverter coolant pump. I disagree with coasting in Neutral is a bad thing. Safely, If you know the transmission controls well enough that you can use them without thinking there is no problem. Yes I admit one time I tried to accelerate when in neutral but handled that fast. Really it is just a matter of handling the control while parked till you are comfortable with them and can use them without thinking about it. Not charging of the HV battery. That is exactly what I am trying to avoid. Why charge when you do not need to. Yes if you are running the A/C or on a very long downhill that might be an issue. No regen braking. You take the car out of neutral before you brake. in fact I usually take the car out of neutral way before I break. If you are in heavy traffic with someone of front of you do not use neutral. Say you are on a downhill grade and want to accelerate. I put the Prius in neutral and let gravity do it.
otoh, you have to be careful not to overheat your brakes when not using engine braking on long steep downhills.
So at 72 miles per hour when mine switches from orange and yellow to just yellow from the battery, to the electric motor generator, to the wheels, my car is not running on purely electricity to maintain speed? Posted via the PriusChat mobile app.
You are entitled to believe anything that you want.......no matter how wrong it is. And your other statements show that you don't really understand how the hybrid system works. What you are doing defeats the best design features. You charge the battery going down hill because that is, in effect, FREE energy to be used later. I quit. Probably pointless. Mind already made up.
So the engine does shut down fuel & spark, it just maintains its RPM's? Posted via the PriusChat mobile app.
I'm thinking it must be using a small amount of gas any time it's running, but maybe very little. Each generation has a ceiling for keeping the engine off, by design: with our 3rd gen it's around 73~75 km/hr (45 mph). 4th gen it's higher again.
Deceleration fuel cut-off has been a feature of electronic fuel injection systems since the late 1960s. Spin the mill all you want, no fuel goes through.
You're half right. No fuel or spark. MG1 maintains the ICE's rpms. This keeps MG1 from spinning too fast and flying apart. It's hyper hard to wrap your brain around even watching the videos of how it works.
I wonder what the neutral selection is actually telling the computer to do, since the hybrid power split device does not allow for any kind of physical disconnect between its three connections (MG1, MG2 & ICE) Technically there is no neutral, at least no full-time neutral. So selecting neutral is really more of an "ignore accelerator pedal" mode. EDIT: Maybe it's useful as a way to take regenerative braking offline and force friction brakes to be the only braking used?
You nailed it with your edit. When you take your foot off the gas, the ICE shuts off, but it will still spin if your speed is more than about about 38 mph or so. But the car is regenerating electricity. When you put it in neutral, it stops regenerating and so the MGs are not providing any resistance. They and the engine never physically disconnect from the wheels, as you said, but in neutral there is no power flow in any direction. Sort of a synthesized neutral. More magic!
Synthetic neutral... yes that's probably the right way to look at it. Although you could potentially overspeed the MG1- but this could be mitigated by upping the field voltage at MG1 and then sinking the resultant current in MG2. An electrically-moderated neutral. There would be power flow, but only MG to MG, and it wouldn't be full time. Battery not involved at all. No proper way to illustrate that on the "video game" screen. (aside: I'm really glad I got rid of that when I switched to an aftermarket stereo) So the N position on the shifter is truly an "ignore skinny pedal and disable regen brakes" switch.
It's not electrical damage they are concerned about. It's simply the physical force of spinning too fast and parts flying off of it. That's a good way to put it. For those who haven't seen it, here's a popular video that shows how the Gen 2 transaxle works.
Weber Auto is so very informative. Just had my friend Matt watch this exact video while he was riding in my Prius because I didn't know how to explain that their is no direct connection between my ICE and my axles... Thanks for sharing. Posted via the PriusChat mobile app.
