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This morning I was having some hideous glide entry issues, which is normal for a Monday morning if I didn't drive on Sunday. At one point I gave up and just went for a NICE-on, which ended while I was headed for a red light. This is where it gets interesting. I had not made the S4 transition, and I was moving at about 32mph. Normally this would mean the engine keeps running until I enter EV. Instead, the ICE shut down as soon as I entered D. Wierd, no?

The same thing happened on the other side of the light (this time at ~38mph) so I danced as follows:
-Shift to N
-Foot off accelerator
-Shift to D

And it worked! So there are two primary possibilities: either I performed the magic incantation just as the coolant temp crossed the threshold (and I'm selling snake oil), or there's something about this sequence that actually tricked the ICE into shutting down. Unfortunately I'm waiting for my SGII so I don't know.

Thoughts?

I am wondering if being in "N" while crossing the S4 theshold allowed the computer to make the transition with the idle check.

If this is true, it would allow for the S4 transition without the idle check.

Tim, please clarify: You never stopped to allow the S4 idle check, correct? If so, based on your first instance at 32 MPH, it wouldn't seem to matter whether your maneuver happened to coincide with crossing the S3/S4 temperature threshold. It simply doesn't shut down at that speed without stopping. Unless .... ;)

I can't wait to check this out on my way home today!

Correct, I didn't stop to allow S4 idle check until later in the drive. I'm pretty sure that this procedure did not complete the idle check (at least what we're used to) because the next time I stopped, I did tap the gas pedal and got the usual ~7 second idle followed by normal S4 behavior.

Hi Tim:

___Nothing and I mean nothing gets me more excited than someone seeing and documenting a better way to transition a vehicle into a more fuel efficient mode of operation. If you can find the S4 transition w/out an idle check using the D-N-D technique, hot damn!!!

___Good Luck

___Wayne

I've done such dances any number of times, and for the most part
the car just resolutely stays in 3a or 3b until the official
check can be done. But I too have had the occasional "mystery
S4" and never knew where it came from. Sometimes if the ICE
is still hot from recent running it'll jump into S4 after the
cat warmup, but not always.
.
I wonder if Toyota would ever field a CMPG "group query" to
eventually get to the bottom of why all this happens...
.
_H*

After playing with this a bit more I have a theory, but I'm afraid it's not that exciting.

I think what happened is I probably dropped it in neutral while above 34mph, and the ICE came up to temperature. (Or maybe it got done with its silly coolant pumping cycle that I still don't understand.) Anyway, I suspect that it was ready to shut down but couldn't because I was in N. When I flipped back to D to grab regen at ~32mph, the ICE just did what it wanted to do. Think of it as the opposite of Warp Neutral.

What I have backing this up is that I can do it over and over again from S3. Just dump it in N with the ICE spinning above 34mph and put it in drive with your foot off the gas when you drop below the magic number. This probably tricked me into thinking that something special happened. I tried a couple of times to N-D-N into a glide below 34mph from a fully-warmed S3 with no joy. But the few chances I had were only a couple of seconds, so I would like to do some controlled testing to see what happens if you let it idle for longer periods of time.

Rumor has it there will be a SGII on the doorstep next week, which should help.

Hi Tim,

How are you sure the engine went off? When I first got the MYCANSCAN/EEE PC, it became apparent that many of the warm-up glides I was doing, even some with MPG pegged at 99.9 on the Prius display were with the engine running.

I was very supprised by this, because the car was VERY quiet during these warm-up glides. Now, I do not even try to go into a glide until I am past the common engine temp milestones ( stage 2 - 70 C in the cooler weather - mostly mornings, 73 in the warmer). And get glide/engine-off like 90 percent of the time I try to go into them. Then there is the stage 3a at a temperature point is 80 C. I believe I have seen the car go into stage 4, without a stop, after a slow down then accelleration, when above 80 C. I do not think its CAT temperature, which is also displayed, but more likely simply going slow, accelleration, then throttle lift. I see the engine stay on after the throttle lift, then all of sudden just shut off, while I was not even expecting it too. It may be related to torque demand. It will do it slightly downhill. With the throttle lift the ECU thinks you want to maintain speed, and it can figure out how much torque is needed by the electronics. If that torgue goes below 0, it probably transitions to 4, then.

OK, I've played with it a few times, and I can't reproduce it except in S3 above 34 MPH, as you suggest.

How are you sure the engine went off?

Analog tach. I learned long ago that the MFD tells you nothing about the ICE during a glide.

Believe it or not, I had a something a bit similar occur to me last week. I was doing some EV-assisted P&G in town soon after startup. During a pulse, the jerk next to me decided to switch lanes and cut me off, so I had to lay off the gas and then lightly tap the brakes to stay safe. Due to the circumstances, I wasn't messing with my EV switch that moment, and I generally even choose not to in this sort of situation because of the 2-second lag of the Coastal EV mod.

Once I fell to a good following distance again, I was about to put my foot back on the accelerator, but at that moment I glanced at my CAN-View and saw the the following:

Engine RPM: 0
Engine Temp.: 130°F
Mode: Stealth

...so I wound up riding out the glide, very confused.

Somehow... magically... my engine shutdown at 130°F with me going somewhere around 25-30 MPH. I, however, wasn't messing with my gear selector like the OP was. It wouldn't happen again on a subsequent attempt. Computer error, maybe? ;-)