Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
#11
08-21-2008, 04:14 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
Q: What is "Heretical Mode" (also called "Energy Recirculation Mode" by Toyota)?
A: This is an observed mode of operation of Toyota’s hybrids that initially fooled the engineers at the DOE. Because the correct explanation for what was actually happening in this mode was deemed to be so counter-intuitive, it was dubbed "heretical mode" by the community of Prius researchers. Toyota’s name, "energy recirculation mode" gives a clue as to what is going on. Usually, power flows from the ICE to the wheels via two pathways in parallel: (i) the mechanical path through the gears in the Power Split Device (PSD, the planetary gear set); and (ii) the electrical path from Motor-Generator 1 (MG1, which is connected to the PSD) to Motor-Generator 2 (MG2, which is coupled to the wheels). However, if the vehicle is fully warmed up, the high-voltage battery’s state of charge is good, and one is cruising at approximately constant speed on relatively flat ground, Toyota’s engineers realized that they could achieve even greater overall fuel efficiency by operating in an electrically-induced "super overdrive" mode. They do this by using MG1 (powered by MG2, which bleeds off some power that would otherwise go to the wheels) to force down the ICE’s rpm while maintaining approximately the same power output from the ICE (this is known as "lugging" the engine). This drop in the ICE’s rpm moves the engine’s operating point into one of significantly greater efficiency, while at the same time reducing engine noise significantly. The reverse direction of electrical power flow from MG2 to MG1 in this mode is the reason for both the names by which it has become known.
Q: How can you tell when the vehicle switches into heretical mode?
A: One indication can be that the ICE’s rpm suddenly drops substantially (one needs a ScanGauge, or equivalent tool to be able to read the ICE’s rpm), and at the same time the ICE’s instantaneous fuel consumption (in L/100 km as displayed by the FC gauge in metric vehicles) drops dramatically. In US vehicles, the instantaneous fuel economy (in mpg as displayed by the FE gauge) rises dramatically. Engine noise drops at the same time. [It should be noted that similar changes in ICE rpm and FC/FE can also indicate the use of battery assist. In this case an assist arrow will show power flowing from the battery to the wheels. In heretical mode no such arrow appears.] Make sure that the arrow from the ICE to the wheels does appear, as heretical mode only occurs when the ICE is providing power to the car. This said, one should understand the vehicle is often moving in and out of heretical mode quite smoothly and imperceptibly as one drives, as MG1’s direction of rotation changes from positive, through stationary, to negative, or back again. The amount of reverse power flow (i.e., the "extent" of heretical mode, and so the efficiency boost) varies smoothly most of the time, and so the absence of a clear "shift" into super overdrive does not mean that one isn’t in heretical mode.
Q: How can one trigger heretical mode?
A: LOL TCH has made some suggestions, copied in post #1 above. But, the car will automatically take the opportunity to use heretical mode whenever it deems conditions to be suitable. The key is cruising steadily on relatively flat ground. This is all the user has to do. (See the second part of the previous answer.) <HOW ABOUT THIS
Q: How can one confirm that one is in heretical mode?
A: The table given in my post #66 in the thread "Heretical Mode":
https://www.greenhybrid.com/discuss/f49/heretical-mode-14215/index2.html#post147039
will enable those with both a TCH and a ScanGauge to determine approximately when they are in heretical mode. At a given road speed RS, if the ICE’s rpm Ne is below the number given in the table, the car is in heretical mode. I copy the table below for convenience:
skip to below
A: This is an observed mode of operation of Toyota’s hybrids that initially fooled the engineers at the DOE. Because the correct explanation for what was actually happening in this mode was deemed to be so counter-intuitive, it was dubbed "heretical mode" by the community of Prius researchers. Toyota’s name, "energy recirculation mode" gives a clue as to what is going on. Usually, power flows from the ICE to the wheels via two pathways in parallel: (i) the mechanical path through the gears in the Power Split Device (PSD, the planetary gear set); and (ii) the electrical path from Motor-Generator 1 (MG1, which is connected to the PSD) to Motor-Generator 2 (MG2, which is coupled to the wheels). However, if the vehicle is fully warmed up, the high-voltage battery’s state of charge is good, and one is cruising at approximately constant speed on relatively flat ground, Toyota’s engineers realized that they could achieve even greater overall fuel efficiency by operating in an electrically-induced "super overdrive" mode. They do this by using MG1 (powered by MG2, which bleeds off some power that would otherwise go to the wheels) to force down the ICE’s rpm while maintaining approximately the same power output from the ICE (this is known as "lugging" the engine). This drop in the ICE’s rpm moves the engine’s operating point into one of significantly greater efficiency, while at the same time reducing engine noise significantly. The reverse direction of electrical power flow from MG2 to MG1 in this mode is the reason for both the names by which it has become known.
Q: How can you tell when the vehicle switches into heretical mode?
A: One indication can be that the ICE’s rpm suddenly drops substantially (one needs a ScanGauge, or equivalent tool to be able to read the ICE’s rpm), and at the same time the ICE’s instantaneous fuel consumption (in L/100 km as displayed by the FC gauge in metric vehicles) drops dramatically. In US vehicles, the instantaneous fuel economy (in mpg as displayed by the FE gauge) rises dramatically. Engine noise drops at the same time. [It should be noted that similar changes in ICE rpm and FC/FE can also indicate the use of battery assist. In this case an assist arrow will show power flowing from the battery to the wheels. In heretical mode no such arrow appears.] Make sure that the arrow from the ICE to the wheels does appear, as heretical mode only occurs when the ICE is providing power to the car. This said, one should understand the vehicle is often moving in and out of heretical mode quite smoothly and imperceptibly as one drives, as MG1’s direction of rotation changes from positive, through stationary, to negative, or back again. The amount of reverse power flow (i.e., the "extent" of heretical mode, and so the efficiency boost) varies smoothly most of the time, and so the absence of a clear "shift" into super overdrive does not mean that one isn’t in heretical mode.
Q: How can one trigger heretical mode?
A: LOL TCH has made some suggestions, copied in post #1 above. But, the car will automatically take the opportunity to use heretical mode whenever it deems conditions to be suitable. The key is cruising steadily on relatively flat ground. This is all the user has to do. (See the second part of the previous answer.) <HOW ABOUT THIS
Q: How can one confirm that one is in heretical mode?
A: The table given in my post #66 in the thread "Heretical Mode":
https://www.greenhybrid.com/discuss/f49/heretical-mode-14215/index2.html#post147039
will enable those with both a TCH and a ScanGauge to determine approximately when they are in heretical mode. At a given road speed RS, if the ICE’s rpm Ne is below the number given in the table, the car is in heretical mode. I copy the table below for convenience:
skip to below
...
RS ; Ne
[km/h] ; [rpm]
50 ; 1088
60 ; 1306
70 ; 1524
80 ; 1742
90 ; 1959
100 ; 2177
110 ; 2395
120 ; 2612
130 ; 2830
140 ; 3048
150 ; 3265
160 ; 3483
170 ; 3701
180 ; 3919
190 ; 4136
200 ; 4354
RS ; Ne
[m p h] ; [rpm]
30 ; 1051
40 ; 1401
50 ; 1752
60 ; 2102
70 ; 2452
80 ; 2803
90 ; 3153
100 ; 3504
110 ; 3854
120 ; 4204
By the way, the formula relating Ne to RS for the transition between normal and heretical mode is:
3.60 Ne = 78.37 RS [for RS in km/h] = 126.13 RS [for RS in m p h]
and it might be worthwhile including it as well for people who might want to calculate values other than those given in the tables....
RS ; Ne
[km/h] ; [rpm]
50 ; 1088
60 ; 1306
70 ; 1524
80 ; 1742
90 ; 1959
100 ; 2177
110 ; 2395
120 ; 2612
130 ; 2830
140 ; 3048
150 ; 3265
160 ; 3483
170 ; 3701
180 ; 3919
190 ; 4136
200 ; 4354
RS ; Ne
[m p h] ; [rpm]
30 ; 1051
40 ; 1401
50 ; 1752
60 ; 2102
70 ; 2452
80 ; 2803
90 ; 3153
100 ; 3504
110 ; 3854
120 ; 4204
By the way, the formula relating Ne to RS for the transition between normal and heretical mode is:
3.60 Ne = 78.37 RS [for RS in km/h] = 126.13 RS [for RS in m p h]
and it might be worthwhile including it as well for people who might want to calculate values other than those given in the tables....
Good?
#12
08-22-2008, 08:38 AM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
haroldo — I suggest removing the words "and it might be worthwhile including it as well" from the very last sentence. Feel free to delete the parenthetical statement "(See the second part of the previous answer.)" in the third Q&A if you prefer. It's referring back to points made at the end of the second Q&A. In this third Q&A I leave it up to you as to how you reference LOL TCH's suggestions copied into post #1. It might be best to just link to the original post by LOL TCH.
Stan
Stan
#13
08-22-2008, 07:57 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
I regret ever using the term "heretical mode" in my original postings way back when. When I tried to find an explanation for phenomenon I was observing, I scoured the posts on cleanmpg.com, priuschat.com, and priusonline.com for answers. As many of you know, the Prius has many more tricks up its sleeve if your trying to exploit Toyota's HSD (just check out those sites). The only ones I've been able to replicate are the obvious EV mode, warp stealth, and what I thought was Graham Davies' original description of the "heretical mode". This was the best explanation I could come up with. I'm not doubting SPL's calculations as I've never taken the time to prove or disprove them. But I can say one thing for sure and that his rpm numbers given in the above post and and in his previous posts do not match what I'm seeing. Again, perhaps I was incorrect when using the term "heretical mode". But one thing is for sure, I can cruise for miles getting 70-110 mpg without relying on the EV mode and without pissing other drivers off because I'm driving too slow. What I describe in the first post works 100% of the time and is worth the time if your so inclined. I think I need to come up with a new name for this one.
Last edited by LOL TCH; 08-22-2008 at 07:59 PM.
#14
08-23-2008, 04:26 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
I have been trying to find out what parameters cause the tch to go into open loop mode(visable with a scangauge only) as i have observed that instantaneous mpg (also visable with a scangauge) is reported as 9999(infinite) with 0.00gph fuel flow(fuel-cut mode) while going over 41 mph.
LOL TCH: I have read your posts numerous times, but i am unable to recreate the "sweet spot" at will... what is your secret? maybe i am missing something.
thanks in advance for your answer!
Last edited by nyceshirtz; 08-23-2008 at 04:28 PM.
#15
08-23-2008, 04:45 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
I do not think we're quite there yet.
I'm a mechanical engineer with 3 degrees and a background in design. If this doesn't quite do it for me, I suppose there are others who would be left cold.
How exactly can we tell if we're in Heretical mode without a scan gauge?
What exactly is the difference between heretical mode and the formerly called heretical mode of LOL, and why did he need to give up on identifying it as heretical?
LOL supposed that he needed a new name. If so, how about Warp Heretical Mode or False Heretical Mode or Pseudo Heretical Mode or - for contrast - Orthodox Mode?
Does anyone confirm the identification of this mode?
If it is really as good as claimed, it is probably worth it's own FAQ's ?
I'm a mechanical engineer with 3 degrees and a background in design. If this doesn't quite do it for me, I suppose there are others who would be left cold.
How exactly can we tell if we're in Heretical mode without a scan gauge?
What exactly is the difference between heretical mode and the formerly called heretical mode of LOL, and why did he need to give up on identifying it as heretical?
LOL supposed that he needed a new name. If so, how about Warp Heretical Mode or False Heretical Mode or Pseudo Heretical Mode or - for contrast - Orthodox Mode?
Does anyone confirm the identification of this mode?
If it is really as good as claimed, it is probably worth it's own FAQ's ?
Last edited by Smilin' Jack; 08-23-2008 at 04:46 PM. Reason: typos
#16
08-23-2008, 08:02 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
Can someone please set up an idiot's guide to this phenomenon...this stuff is too complex for many (well, at least one...me!)
Thanks!
Thanks!
#17
08-24-2008, 09:52 AM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
The so-called "heretical" mode is sustainable for quite a while on flat ground. From the pieces I've put together of everyone's descriptions and my own observations (without SG), the ICE is operating, one electric motor is connected to the wheels and is actually generating electricity, while the other electric motor serves as the gearing to make the car go faster than the actual ICE turning by itself would drive it.
The ICE is able to operate at a lower (more efficient) RPM, but still able to produce enough electricity to allow the other electric motor to act as the "overdrive" [since there are no actual transmission gears]. This results in outstanding fuel efficiency on flat terrain (my car can do 60MPH and still show well over 50MPG) that is sustainable for a long time.
There's just not enough power to do it going uphill, and on downhils there's no need for the engine to provide power at all.
#18
08-24-2008, 02:49 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
I think what you're describing, over 41MPG and NO fuel being used, is referred to as "warp stealth". I don't think it's sustainable over the long haul since I believe it requires a downhill grade (no free lunch).
The so-called "heretical" mode is sustainable for quite a while on flat ground
The so-called "heretical" mode is sustainable for quite a while on flat ground
I have noticed that whenever 0.0gph fuel is indicated on the SG, the open-loop indicator(on the SG) displays open. obviously, when the downhill terrain flattens out or when the terrain starts to incline, it is the end of the event; no matter what it is called. i have travelled the same downhill slope numerous occasions, at different times of the day, week, month, different speeds. sometimes the car goes into open-loop mode(0.0 gph used); sometimes it does not. i have found no correlation with any of the SG variables that i monitor(rpm, gph, mpg, coolant temp, air intake temp, throttle position, miles per hour). the only correlation i found is that when the open/closed indicator shows open, gph reads 0.0 and the mpg displays 9999mpg. miles per hour has varied from 42mph up to 65mph. in this mode, the rpm increase is directly proportional to the speed. the higher the miles per hour, the higher the rpm, while the fuel consumed stays constant at 0.0gph(fuel-cut mode - my terminology). when the event is over, the open-closed indicator displays closed, gph increases greater than 0.0gph and rpm may increase or decrease depending on the miles per hour at the time.
#19
08-24-2008, 03:28 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
........... the only correlation i found is that when the open/closed indicator shows open, gph reads 0.0 and the mpg displays 9999mpg. miles per hour has varied from 42mph up to 65mph. in this mode, the rpm increase is directly proportional to the speed. the higher the miles per hour, the higher the rpm, while the fuel consumed stays constant at 0.0gph(fuel-cut mode - my terminology). .............
Thanks.
#20
08-24-2008, 03:44 PM
Re: Heretical mode (moved from Proposed tweaks to the FAQ (setting up for 2.3) )
55mph, 980<rpm<1000
60mph 1260<rpm<1289
