(please keep this simple, so I can understand it)
I thought I understood this, but not really.

1. If the car is below 40 MPH and needle is 'in the blue', the battery is either powering the wheels, or the wheels are recharging the battery, but in either case the engine isn't being spinning, right?
2. Okay, now you speed up to 45 MPH and the needle pops up to 60 MPG. Assuming you are coasting (foot not on gas), what just happened? I believe (from reading hundreds of posts) that the engine must spin (without any gas being used) once the car tops 40 MPH. Is this state any less fuel efficient than when it is in the blue? I believe some of the energy is now being used to spin the engine rather than recharging the battery, so there is some net energy loss (right?), but in terms of mileage is there any loss of efficiency when the needle is at 60MPG versus being in the blue?

Thanks!

 

Haroldo,

There are two states that the ICE can be in at this stage. If going down hill and/or coasting, the engine will be spun by the M/G in a "fuel cutoff" state. This will spin the ICE but no fuel is being burned.

Case 2 would be similar but the ICE is very lightly loaded and barely using fuel but IS running and consuming fuel at the rate of 60 mpg (or better).

The ICE engine spin up is to prevent an over rev condition of the M/G. So the answer about mileage is "it depends". Don't you just love an answer like your mother used to give? Remember when you asked "why?" and she said "Because"

 

You need to look at it from different perspective.
The bottom of the MPG meter says E, it does not say 100MPG or infinite MPG, it simply says E-lectric mode with ICE not spinning.
Now, for all practical purpose, the minimum MPG on that particular meter is 60MPG, so if it shows 60 MPG, it means 2 things: the ICE is spinning and your instant MPG is 60 MPG or better. There is nothing in between 60 MPG marking and E-mode on the bottom and the space in between is there just for visual reference so one can easily tell status of ICE. I hope this makes sense.

 

Coasting above 41 miles per hour, the ICE is just spinning and no fuel used.
However, we need a certain amount of energy to spin it.
Wayne Brown's simulator shows it.
PriusChat post

Ken@Japan

 

I think I understand it, (and wanting to keep it extra simple) to answer the basic question... whether ICE is spinning or not spinning, it uses no fuel, although it might sap some energy.
The main confusion is the oft mentioned stage 4 (please keep any replies simple) where some will come to a complete stop and wait for up to ten seconds for the ICE to kick off, thus forcing the car into stage 4 (and give the car the ability to automatically move in and out of EV).
The confusion lies in the understanding whether this really does anything to benefit fuel efficiency, or not. Yes, I understand it takes energy to spin the engine (below 40 miles per hour when coasting), but if the ICE uses the same fuel (none) when coasting with the needle at 60 MPG as it does in EV, what is the reason why people try to manually get in to stage 4 as soon as possible?
Energy spent spinning the engine might better be used to recharge the battery, but assuming the battery were fully charged, the energy couldn't be utilized anyway, so in effect it's lost, anyway, right?
So...to conclude my confusion...what does stage 4 get you in terms of fuel efficiency?

 

unfortunately, the tch instrumentation does not give you the complete picture. under 39 miles per hour, in ev mode, when the ICE does not spin, zero fuel is being used. above 39miles per hour, there is another variable which one can only observe with a scangauge. it is the open loop/closed loop status indicator. This indicates when the oxygen sensor is being used to control the mixture (closed-loop) and when it is not (open-loop). It is usually closed except when the engine is cold or under full throttle acceleration. this indicator, along with the RPM indicator and GPH (gallons per hour) fuel rate will tell you when you are in fuel-cut mode or not. fuel-cut mode is when zero fuel is being used and RPM is greater than zero while in open loop status. I have observed that the open loop/closed loop indicator is the key to maximizing fuel economy over 39 miles per hour. when in open loop status, over 39 miles per hour, RPM greater than 0 and GPH is 0, (fuel cut mode) MPG is displayed as 9999(infinite). when in open loop status, over 39 miles per hour and RPM greater than 0, GPH greater than 0, MPG is less than 9999. obviously, fuel is being used. the key to maximizing FE over 39 miles per hour is the open loop/closed loop mode. what triggers the TCH in deciding what mode to be in is unknown to me. see my previous post https://www.greenhybrid.com/discuss/...uestion-17734/. i am sure this will further compound the complexities in understanding the MPG meter.

 

Thanks for that explanation (not sure if I understand all of it), but the one question I have is that your scan guage shows some fuel being used "...when in open loop status, over 39 miles per hour and RPM greater than 0, GPH greater than 0, MPG is less than 9999. obviously, fuel is being used...", how much is being used? Is the gauge actually measuring fuel going from the tank into the cylinders? Or is it a statistical or technical glitch in the gauge that picks up the appearance of fuel being used, when none is (since the ICE really isn't running, is it?).
I'm simple, but to me, either the engine is on or it's off. If it's on, I understand the fuel usage, but if it's off, and only spinning (either with the loop open or closed...what ever that means) I don't understand what the fuel is doing?

 

the scangauge measures the fuel being used via the OBDII interface. at times, minimal fuel is being reported as being used (0.04 gph - .25 gph) when over 39, rpm >0. under 39 miles per hour, there is an acknowledged bug that the scangauge displays 0.03-0.04 gph while rpm = 0. it should report 0 gph but it doesnt. rick of scangauge says that he will fix the problem when he next updates his product (im not sure if it is a toyota reporting problem or scangauge interpretation problem). im still trying to find out the triggers for open loop/closed loop status. once someone identifies what these variables are, it would help to explain why the TCH goes into and out of EV mode under 39 miles per hour as asked in my post regarding the open loop/closed loop thread. regarding your question about the fuel being used, the answer is it depends. the ICE can idle at about 900 rpm with minimal fuel used, or it can spin at 800 rpm without any fuel being reported as being used. it appears to me that it all depends on the open loop/closed loop status. im not sure if the open loop/closed loop status is a result of the ICE consuming fuel or the reason the ICE consumes fuel. hope this sheds some light.

 

08' HCH2
This is probably in a post somewhere ... but finding it ...

I'm driving along about 30 mph, come to a slight down grade and take my foot off the gas. The instant mpg sitting at ?50? (taking about 3 or 4 seconds to do so) drops to zero. Charging is blank, no assist, no charge. The car just continues to roll along same speed. When the slight down grade changes - up or down, let's say more down hill, I get 1 or 2 bars green charge and impg jumps up to 100. If I touch the gas peddle the impg jumps up, but I've gone 1/3 mile that way, figure I could go 10 miles if the road never changed.

WT?? - explanation???

Tks