Thanks very much.

So, since these rpm's are well below those in the table by SPL, this situation would technically meet the SPL criterion for Heretical mode.

Does everyone agree?

 

heretical mode = open loop mode = fuel cut mode = warp stealth mode

i.e., above 42 miles per hour, the consequence is a maximum fuel economy as the action of zero fuel being consumed while moving at a forward rate of speed which may or may not be constant without regard for the amount of time spent in this mode.

 

Thanks to nyceshirtz for the quick and clear reply.

I was supposing that an rpm lower than the SPL table might be necessary but not sufficient for Heretical mode. The way I read some of the explanations of Heretical mode, I would suppose that this mode requires also that the ICE would be producing power.

Anyone agree?

 

i do not agree. using the energy screen display, it appears the same as when one is in ev mode; i.e., the energy goes from the wheels to the battery as it is; for example, while regenerative braking. zero ICE power. once pedal pressure is applied; however so slight; the energy screen shifts depending on one's speed from either the battery to the wheels(when in ev mode) or from the ICE to the wheels, battery or both(when not in ev mode). if the ecu determines that more power/speed is needed; i.e., using cruise control; it is dependant upon how much power/speed is needed and the ecu decides which power source(ICE, Battery, or gravity) can be utilized to fulfill the power/speed requirement.

 

Thanks again for the quick and clear reply.

I think this means that you have a much broader view of what it is that could/should be called Heretical mode than do some of the other contributors to this and the heretical mode post.

I'm still trying to sort out my understanding; so I hope that others will "chime in" to this part of the discussion.

 

not really....im still trying to find out how to max my fe and how to force/cajole the tch to enter whatever-name-u-want-to-call-it mode when i deem it possible; i.e., approaching a long downhill run... lol tch stated that he could go into this mode at will. i am awaiting his reply as to what specific operations/steps he performs that permits him to overide the ecu.

 

As the editor of the FAQ and with the thought in mind of adding in this topic to the FAQ (which, if I'm not mistaken, was the original point of this thread), I have to report that I've stopped following this conversation.
If, and when, there is a general concensus as to the points that you guys want to add to the FAQ, can someone please prepare a simple set of Q's and A's that you want to be appended to the FAQ and send me a PM.
I would like to add in one request....that is, to keep it simple.
The FAQ was designed to be a quick and easy reference for the new owner (or forum visitor) to see the important and oft discussed topics and learn.
I am very interested in the TCH and love to learn, but this topic, with it's long and complex discussions/arguements only serve to confuse me (and probably others).

 

Suggestion...
Instead of appending this and possibly other, advanced, topics to the FAQ...why not create a second FAQ, called Advanced Topics FAQ.
The original FAQ is titled New Owner's FAQ (2.2), and as the name suggests, it is written for TCH newbies.
A discussion such as the one in this thread, really doesn't fit with a "new owner's" FAQ, rather it would be best displayed in a parallel FAQ.
A secondary advantage would be that the FAQ could be edited by someone who better understands this, and possbily other, topics.
I asked admins to lock my FAQ to keep extraneous comments out of the thread. The downside of locking it is that I lose the ability to freely edit the thread. Instead, I have to ask permission from admin to unlock it.
In any event, I'd really appreciate a second FAQ.
Good idea?

 

Haraldo,

I think that is an excellent idea. Having a newbie FAQ and and Advanced FAQ (or something) make a lot of sense. Most folks won't really care about forcing Heretical mode, but I for one would love a consistant way to get into that mode. I have seen it many times and its really amazing. >60 MPG at highway speeds (nice!). Sometimes the car just seems to slip into this mode, while other it doesn't. I don't have a good feel for the difference...

John

 

After reading the recent posts I have come to the conclusion that most of you are confusing heretical mode with fuel-cut mode. I believe that this comment also applies to LOL TCH's posts. No-one ever said that heretical mode was easy or simple to understand. Its very name arose because of the perceived "heresy" when the early researchers, trying to figure out what Toyota was actually doing in the Prius, came to the conclusion that there was a reverse-direction of energy flow occurring during this mode of operation. The reverse energy flow is the origin of Toyota's name for it (energy recirculation mode), but at the time Toyota was staying mum on the details of the internal operating modes of the Prius.

Can such a counter-intuitive mode of operation ever be explained in a simple and easy-to-understand way? Maybe not, but I am trying! Bear in mind Einstein's dictum that a theory should be as simple as possible, but no simpler. I'll make a further attempt at producing a better Q&A, but I'm not sure that it will ever be easy or simple.

In fuel-cut mode the ICE is not producing any power — it is actually dissipating (i.e., wasting) power since it is actually being spun without fuel in order to protect MG1 from over-revving. In fuel-cut mode the ICE icon plus arrow to the wheels does not appear in the Multi-Functional Display (MFD). Fuel-cut mode is sometimes called "warp stealth mode" because one can, on flat or slightly downhill roads, apply a little accelerator to maintain the car's speed without starting fuel-burning in the ICE. This can only be done for a limited time, as NiMH battery power is being consumed in the process — the battery-to-wheel arrow will show in the MFD. The FC gauge will read precisely 0 L/100 km, while the FE gauge will read 60 mpg. The updated ScanGauge should also show 0 L/100 km or 9999 mpg.

In heretical mode, on the other hand, the ICE is sending power to the wheels and the ICE icon plus arrow to the wheels must be present in the MFD. If they aren't there, it cannot be heretical mode. Fuel is being consumed. How does this differ from "normal mode" (or as haroldo has cleverly, but naughtily, suggested be called "orthodox mode")? In normal mode, power is flowing forwards from the ICE to the wheels (i) mechanically via the Power Split Device (PSD, the planetary-gear set), and (ii) electrically via MG1 and MG2. Electrical power flows from MG1 (acting as a generator) to MG2 (acting as a motor). In heretical mode power is still flowing from the ICE to the wheels mechanically via the PSD, but now power is actually flowing backwards from MG2 (acting as a generator) to MG1 (acting as a motor). This reversed electrical power flow direction is the origin of Toyota's name "energy recirculation." Why would they do this? Because by doing so they put the vehicle into an electrically derived "super-overdrive" mode, in which the speed of the ICE is forced down into a region in which its thermodynamic efficiency is significantly increased, while producing the same power. The rate of fuel consumption goes down (but not to zero!), as indicated by the FC gauge. Correspondingly, the FE reading in mpg goes up (but not to 60 mpg!). No battery power is consumed in this mode, and it can be continued indefinitely.

What determines whether the electrical power flow is in the forwards or in the reverse direction, for this is the only sure way to distinguish normal from heretical mode provided that the ICE is indeed sending power to the wheels (i.e., the ICE icon plus arrow are present in the MFD)? It's the direction of rotation of MG1 that distinguishes these two situations. If MG1 is rotating forwards, the car is in normal mode, and if MG1 is rotating backwards, the car is in heretical mode. The borderline between these modes is when MG1 is not rotating at all. At a given road speed, the faster MG1 rotates backwards the "stronger" is the heretical mode, or equivalently, the greater is the amount of "overdrive" being simulated. How can one tell the direction of rotation of MG1? One needs to know both the road speed RS (in km/h or m p h from the speedometer) and the ICE's speed Ne (in rpm from say ScanGauge). So, a ScanGauge or equivalent is needed. The formula relating MG1's speed Ns (in rpm) to RS and Ne is:

Ns = 3.60 Ne - 78.37 RS [for RS in km/h] = 3.60 Ne - 126.13 RS [for RS in m p h].

The table I gave before is computed by setting Ns=0 in these formulas. Notice that, because of the '-' signs in the formulas, when the engine's speed Ne falls below the values given in the table (at a given road speed), MG1 spins backwards, and the car is in heretical mode. The further the engine's speed is below the table value, the more heretical the mode becomes. There is a continuum of degrees of heretical mode possible. Assuming that one drives at a constant speed on a relatively flat road, the extent of heretical mode will vary continually as the slope of the road changes slightly moment by moment. The car is frequently changing smoothly from heretical mode (Ns<0), through the borderline case (Ns=0), to normal mode (Ns>0), and back again as one drives along. You don't have to do anything to get heretical mode operation, other than to drive a warmed-up Toyota hybrid, with an adequately-charged NiMH battery, at a steady speed on a relatively flat road. Indeed, I'm not sure that one can actually do much beyond this to "trigger" or "control" heretical mode operation.

To conclude: heretical mode and warp stealth mode (= fuel-cut mode) are quite different creatures. Have a look at my post #61 in the previously cited thread "Heretical Mode" for a numerical illustration of four of the fundamentally different modes of operation of the Toyota hybrids. The fifth fundamental mode is, of course, what I prefer to call pure-EV mode, when the ICE is stationary, the car is moving either forwards or backwards, and electrical energy is being shuttled between the NiMH battery and MG2. Once warmed up, the TCH spends a large fraction of its cruising time in heretical mode — probably far more than you realize! It's one reason that it's so quiet (the engine speed is so low). Finally, the best cruising FE on mainly flat roads is obtained by using cruise control. With the cruise control "on," the TCH's computers are given free rein to control all aspects of energy management, and one will often notice an immediate improvement in the instantaneous FE reading caused by the TCH computers' use of stronger heretical mode than was being allowed under manual accelerator control.

Stan

P.S. I have added a number of additional sentences at the end of this post clarifying and elaborating upon my earlier comments.