Hues10

So I have seen videos of the Toyota Hybrid system with its two motors and electronic transmission and such. But, I was driving yesterday watching the little engine/hybrid arrows graphic we have, and I got to thinking about what really happens to the engine when running on battery power only? Because when I am going between 40 and 50 mph, the engine is starting and shutting off multiple times depending how hard I feather the gas peddle. It is somewhat seem less, so I can't believe the engine totally shuts off, then fully restarts every time. I can see the fuel being shut off, but I would think that the pistons are still moving all the time so as to not be a jarring experience when the enginge "comes back to life". It would also be less friction and wear and tear on the engine internals as well if the pistons and cams remain moving with the oil pumping and keeping everything lubed even if not firing with the fuel injectors. So what do my fellow hybrid owner's think? I know, get a life and think about real problems and things. But c'mon, I am driving and enjoying music and such, so the mind wanders. Thanks all.

ChronoR

It stops the engine. The magic of the hybrid system is the hybrid electric motors being able to spin the engine up to speed to start it without a huge jolt although it's still significant in our GS450h because of the big engine. It's nearly imperceptible in some of Toyota's other hybrids. It also isn't helpful to spin the "dry" engine since that's just engine braking but in a hybrid it'd be better to recapture energy using regenerative braking instead.

This is a really good demo you can play with to see how it works (needs flash):
http://eahart.com/prius/psd/

You can easily see why our top electric speed is about 42MPH by playing around with it.

Hues10

Well there goes my theory of a continual "on" ICE without the fuel injectors working. There is a slight jolt I feel, especially when first starting up. Seems to be more noticeable when it is colder here in Florida (which never gets real cold). At least I know what the Planetary gear set is all about, instead of just hearing those buzz words. Thanks ChronoR, as always.

ChronoR

Diesel cars actually do that when coasting. Probably some gasoline cars too (there's also cylinder deactivation where individual cylinders aren't fueled even while the engine is running).

But there's little point in that for a hybrid.

Lwerewolf

Your theory is partially correct - above a certain speed, the engine always spins - in fuel cut mode (when not on the gas) or otherwise. The other time it does that (fuel cut) is when you initiate engine braking - B-mode or S-mode (whichever you have) on the transmission. Otherwise, the switchover between engine vs battery propulsion seems to be based on power draw and battery charge/discharge rate limits (temperature/etc), to my knowledge.

If you want a useful dashboard display, get this:
http://hybridassistant.blogspot.com/
Kind-of costly for an OBD2 dongle, but the app is very good. The toyota one is overly simplified - if you keep your instant fuel consumption meter on, you can guess when the engine is running without the display telling you, but only if it's using fuel - usually MAF calibration (idle speed control learning, etc) or producing heat for the cabin... and the S-mode of the transmission, which won't automatically turn it, but won't let it stop if it is - great for throttle response. If the engine is running in fuel cut mode, you have no visual way of knowing.

ChronoR

Yes, the engine does start spinning above 42MPH, hence my comment about top electric speed. I misread your meaning.

There's no B mode in the GS450h though. It'll automatically use the engine as bleed off for energy if the traction battery is full otherwise it's just friction brakes and regenerative braking.

Not sure how the Prius does it, but the EV light on the GS450h is an absolute indicator of whether the engine is on regardless of fuel cut (if the light is on then the engine is off) as well as the tachometer of course. Combined with the instantaneous MPG display, you can easily tell if it's in fuel cut mode or just running idle.

Lwerewolf

No B-mode, but the S-mode serves mostly the same purpose - the car goes in full CVT mode when you floor it regardless

Haven't noticed the engine ever running to bleed off energy... then again - 3rd gen in my case, this may have changed. Thought it's just friction brakes when the battery can't take it. On that note, 3rd gen doesn't have a tacho either, don't mind me

ChronoR

I guess they may have made changes in the 4GS. We don't have an S-mode that works they way you describe, Sports mode adjusts the throttle response and how fast the engine kicks in (if it's off) from what I can tell (it's supposed to increase the electric motor power too but that's hard to quantify).

As for spinning the engine, I've only ever noticed the engine drag when going down a long enough slope to fill the battery. It's quite noticeable because even if you're below 42MPH, the engine will suddenly kick in and the EV light turns off.

The whole hybrid system is incredible ingenious anyway.

ChronoR

So I played around with Shifter mode and turns out it does add engine drag like you said... mostly in S1 and S2 with a small but perceptible amount in S3. I guess I noted that it wasn't anything like gear shifting when I test drove my GS450h and then never used the mode again.

It feels like "Shifting" is more like "power requesting". S1 and S2 also lets the RPM spin up high without the CVT lowering them back to 1200RPM. As I go up all the way to S6, it feels like slowly going towards ECO mode in terms of how (un)eagerly the engine goes up in RPM as well as how fast the engine shuts off into EV mode (when possible). It also seems to entirely override the Sports/Normal/ECO mode. Definitely more interesting than I thought the mode was.

Hues10

Ok, I will have to reread through this thread again as you both are very thorough, which is great. Most people probably do not care, but I find it interesting. So let me add another question in the mix, I find myself in my daily commute to work (18 miles round trip), in stop and go, from one light to another light traffic, and I end up using the paddle downshift button to slow the car down even more before I brake to a stop. It seems that upshifting does nothing when accelerating, but downshifting definitely simulates a downshift in a regular transmission, and slows the car down quicker. I do this as well when approaching a turn, so I do not have to touch the brake when entering the turn. Call it my little Gran Prix racing circuit fun on my commute. The question is, am I hurting the car by doing this? It is not like I am downshifting from going 75 mph to 1st gear or anything like that. I am probably going at most 45, I downshift twice to get to 20. It goes from D4 on the first downshift, and then D3. Sometimes I get to D2. I figure we have paddle shifters, why not use them. It is like when I had a manual transmission and I was using the engine to slow the car down. Opinions?

ChronoR

You're not hurting anything. Have as much fun as you want. From what I can tell, it's just engine braking (plus max regen) and it's not going to wear out our transmission (super tough planetary gears) nor our engines (bullet proof Lexus engine).

With that said, you get the maximum fuel economy by coasting as long as possible then applying the least brakes possible to max out the regen. Both the friction brakes and engine braking are pure energy losses.

Hues10

Believe it or not, I thought downshifting was actually helping the Regen process quicker. I thought I noticed the power needle go "further South" when I downshift, which I took as recharging the battery just a tad quicker. It is not like I am riding the downshift around town (like riding the brakes). I literally downshift for at most 10 seconds and either turn or stop behind the other car. Once I accelerate, I will upshift (which doesn't do anything), and then the transmission usually goes back into 'D' on its own. I figure, we have paddle shifters and as well as the manual shifting on the gear selector (do not use that one), use it every once in a while. At least I am not looking at my phone while driving

Lwerewolf

The transmission still has an aux. electric oil pump that can go bad... well, the bearings that cost about $5 can... eventually...

The engine is a lot less robust, but still one of the most robust ICEs overall. Not a UZ, though

Read up on the "pulse and glide" prius driving technique - not saying that you should be using it, but understanding why it works will make you understand Toyota hybrids very well. The efficiency gains are primarily from the atkinson engines (where present - rx400h, ls600h and 3rd gen GS 450h don't have them >_<), the eCVT and the ability of the car to function without engine power (real coasting, not much waste in traffic jams, etc). The small EV propulsion ability + the torque fill + all that are just slight bonuses. The primary idea is to get a very efficient engine running primarily in its sweetspot (around the best BSFC) and to avoid running it when unnecessary - idling, crawling in traffic jams, etc, etc. The regen braking is, well... read up on Ni-MH batteries' charging efficiency, couple that with the waste of converting the energy twice, and you'll get the picture - it's nice, but coasting is always better. I wouldn't annoy traffic, though - the gains of pulse and glide (if they are at all present in a 450h) are not worth the hassle

Bottom line is - don't be afraid to accelerate, but coast longer instead of braking hard.

Paddle shifters = that annoying thing that you have to use to keep the engine at near max RPM before attempting a tight overtake (and engine braking, of course)

ChronoR

To be fair, charging NiMH's in the SoC "sweetspot" (which Toyota definitely keeps our traction batteries in) is nearly 100% and likewise with Lithium Ion batteries. You'd lose more from the conversion electronics that step down from our 500-650V motors to the 288V battery pack.

But it's still not 100% and it's definitely more efficient to coast.

Im2bz2p345

You'll get a similar affect if you switch from Sport/Sport+ mode to Eco, which reduces the battery power to the engine + changes the throttle response and uses more regenerative braking. Try to switch modes before you're approaching a turn (give yourself ample time to slow down) and you'll experience what I mean. You can also do the same thing as you approach a red light.

The 4GSh doesn't have a "engine braking" mode like the Toyota Prius "B mode," which keeps the engine running while going down a hill and simulates "down shifting" in a normal car:
I'm an oddball driver and constantly playing with the drive select (it keeps me occupied since when I last had a sporty car, it was manual transmission).

I only use the paddle shifters if I'm trying to show off it's torque to friends

All the best,

~ Im2bz2p35