I'm confused about S4 mode ????????

[uart]

In these forums I often see people talking about getting the Prius in "full hybrid" or "S4" mode for maximum efficiency, but when I looked it up I found it a little confusing.

From what I've read the only way to get into S4 mode is to be in S3 mode and stop with the ICE running and then wait 5 to 10 seconds until it shuts off. Then apparently you're in S4 mode.

My question : Is there really no other way to get into S4 mode other than stopping like that? For example, if I drive non stop for 100 miles on a warm day do I really never get into "full hybrid" S4 mode.

I've seached the forums and googles but so far I haven't found any other description of how to gt into S4 mode other then the following :

S3:
When the system temperature reaches 73 C. (163.4 F.) the computer goes into Stage 3a. In S3a the ICE will not shut off unless you come to a full stop for 5 or 10 seconds. Paradoxically, it is more reluctant to shut off than it was in S2, and in S3a it shuts off very roughly. You will feel the car shudder. But once it does shut off at a full stop in S3a, it will then be in Stage 4 operation.

[TheForce]

If your driving non stop you don't really need to be in S4. S4 is only really useful if your in city driving or your trying to pulse and glide.

And yes the only way to get into S4 is to come to a stop and let the engine run for 10 seconds.

[spinkao]

Originally Posted by uart

In these forums I often see people talking about getting the Prius in "full hybrid" or "S4" mode for maximum efficiency, but when I looked it up I found it a little confusing.

From what I've read the only way to get into S4 mode is to be in S3 mode and stop with the ICE running and then wait 5 to 10 seconds until it shuts off. Then apparently you're in S4 mode.

My question : Is there really no other way to get into S4 mode other than stopping like that? For example, if I drive non stop for 100 miles on a warm day do I really never get into "full hybrid" S4 mode.

I've seached the forums and googles but so far I haven't found any other description of how to gt into S4 mode other then the following :

It seems there isn't. I tried many times. You can drive 100 or more miles and warm up your engine to the edge of explosion, but you won't get into the S4 ops unless you stop with the engine running and wait until it stops. I don't know why it is implemented this way, and I asked here at the PC and the techs in the Toyota dealership - nobody was able to give me a valid answer.

Apparently, the gen III Prius behaves differently, if I can judge from a test drive I had - I didn't notice that behavior. Perhaps the gen III owners could tell us how their cars behave?

I would be really grateful if anybody could ever explain me why is the S3-S4 transition working the way it is, as it really annoys and puzzles me all the time I have to drive wastefully in the 3a mode, unable to stop because of the traffic...

[bestmapman]

You should note that S1-S4 is not Toyota terminology, it is our terminology. So Toyota people won't know what you are talking about if you say S4 to them. Toyota won't say why and no one here is figured it out why the S3-S4 transition is the way it is.

So there is no why, it just works that way in the Gen II.

If you would install an EV switch, you can force the ICE to go out below 34 MPH just like you are in S4 anyway.

[spinkao]

Originally Posted by TheForce

If your driving non stop you don't really need to be in S4.

Well, I would dare to respectfully disagree. I often find myself diving wastefully in the city in the 3a mode, unable to stop for a relatively long time because of the traffic. It is really annoying. Especially when I finally come to a stop at lights and the green shows *before* the engine stops - that really makes me mad, as I have to go because of the cars behind me before getting into the precious S4 stage...

If I feel the transition is just about to occur, I even wait for that additional second or two when the green shows up, making the drivers behind me mad, not knowing what am I waiting for .

[spinkao]

Originally Posted by bestmapman

You should note that S1-S4 is not Toyota terminology, it is our terminology. So Toyota people won't know what you are talking about if you say S4 to them. Toyota won't say why and no one here is figured it out why the S3-S4 transition is the way it is.

So there is no why, it just works that way in the Gen II.

If you would install an EV switch, you can force the ICE to go out below 34 MPH just like you are in S4 anyway.

I didn't tell them about the "S4", I just explained them what I meant and they knew what I am talking about, but also didn't know the reason.

There *is* why. This simply puzzles the engineer in me - I *have* to know . This car is an engineering marvel, there *has* to be a reason, however bizarre .

I have the EV switch (it is a standard feature here in the Europe), but it is not helpful when I want to P&G...

[ken1784]

Originally Posted by uart

My question : Is there really no other way to get into S4 mode other than stopping like that? For example, if I drive non stop for 100 miles on a warm day do I really never get into "full hybrid" S4 mode.

If you're driving below 34mph during the 100 miles trip, you're always at S3a and the ICE continues to run.
If you're driving above 34mph, you're at S3b and it's identical to S4.

If your coolant temperature is above 66C(150F), following sequence will reach you S4 instantly;

• power off
• wait for 5 seconds
• power on

However, it's hard to accomplish the sequence during non stop driving.

Ken@Japan

[hill]

Originally Posted by bestmapman

You should note that S1-S4 is not Toyota terminology, it is our terminology. So Toyota people won't know what you are talking about if you say S4 to them. Toyota won't say why and no one here is figured it out why the S3-S4 transition is the way it is.
. . . . . . . . . . snip

Yes . . . remember in Detroit? Otsuka-san, the chief engineer looked like we were from mars when the S3-S4 transition topic came up ... and the 'why' question was asked. I thought that would be the defining moment in understanding what that is all about ... to no avail.

[spinkao]

Originally Posted by ken1784

If you're driving below 34mph during the 100 miles trip, you're always at S3a and the ICE continues to run.
If you're driving above 34mph, you're at S3b and it's identical to S4.

Well, my own experience is a little different. If I was driving faster than 34mph and I slowed down, my car would maintain the S3b until the ICE has to run. So, for example, if I am in the s3a, accelerate and get into the S3b and then slow down again, I can run on electricity under 34mph as long as: a) I don't stomp on the accelerator, forcing the ICE to kick in, b) the SOC doesn't drop below a certain level. Only when the ICE kicks in for whatever reason, the car engages the S3a again - that is how my Prius behaves.

Originally Posted by ken1784

If your coolant temperature is above 66C(150F), following sequence will reach you S4 instantly;

• power off
• wait for 5 seconds
• power on

However, it's hard to accomplish the sequence during non stop driving.

Ken@Japan

Well, as you said, this procedure does not help much, does it ?

Ken, you know the Prius forward and back and have a lot of insider info. Do you possibly know what are the technical reasons behind this? It is torturing my curiosity since the day I drove the Prius for the first time .

[spinkao]

Originally Posted by hill

Yes . . . remember in Detroit? Otsuka-san, the chief engineer looked like we were from mars when the S3-S4 transition topic came up ... and the 'why' question was asked. I thought that would be the defining moment in understanding what that is all about ... to no avail.

Oh, looks like we'll never learn the truth then... This is one of the PRINCIPAL questions that have been torturing the humans from the very beginning! "What is the Purpose of Life?" "Is there a God?" "Who *really* killed Kennedy?" "Why is the S3-S4 transition in the Prius implemented the way it is?"