pulse & glide... accelerate fast or slow?

Then iMPG = .5 MPH wouldn't be linear either, right? I kind of expect that.

 

This is why track bicycles have no dérailleur, brakes, or freewheel device. They use a fixed gear ratio, optimized for the speed of the race. It's hard to get up to speed, even harder to stop, but it makes for the most efficient drivetrain possible. As others have pointed out, the whole reason for transmissions and big engines is to make real-world driving practical. The Prius HSD is inefficient, but not as inefficient as a normal transmission and engine.

Tom

 

When I P&G, it's generally with the terrain in order to keep my speed more or less constant for the sake of anyone behind me. (My concept of good hypermiling is that nobody really notices that I'm doing anything odd.) So my acceleration rates are generally chosen so that I hit the crest of the hill at whatever speed experience tells me will keep my down-hill speeds within my comfort zone. I do impose a 2400RPM cap but I get good results as long as I keep the ICE below that mark during the pulse.

 

You also need to note that the graph for instant L/100km only has a range of 1 to 10L/100km which is a highest consumption of 23.52MPG meaning it is only going to be usable over about 47MPH. You could use the numerical reading on the power screen but it is harder to visually process while driving.

If your ideal rate of acceleration is to maintain a ration of 1MPG = 2MPH then this will be a straight line graph.

I'm confused, I just tried to work it out and it's too hard for my tiny brain

 

Hmmm... good point. Anyway, rather than refine my P&G technique I really just need a block heater.

 

Do both.

 

Okay, for the Nth time, FORGET about this "deadbanding" theory.
If the SoC is below 60%, the system will send charge to the
battery, over a wide range of engine RPM and foot demand, and
there's not a lot you can do about it. If you're above 60% then
you'll get assist. Once you *stabilize* at 60% SoC will you
commonly see the "engine only to wheels" state, but there are
always little currents going back and forth to/from the battery
just about all the time, especially on transients where your
foot position is changing. But overall the system seeks 60%
and it's no use worrying about what the arrows are doing when
it hasn't gotten there yet.
.
We also know that the no-arrows "glide" state can pull up to
5 amps or so from the battery before the "electric drive" arrow
appears on the MFD. That's helping push the car, whether it
shows or not. If you want a true no-traction-power situation
you have to knock it into Neutral, and you'll probably find
that your glide speed drops just a wee bit faster.
.
_H*

 

So, when I combine that with Hobbit's last post, and simplify, I get the following:

Adapt the pulse rate to exploit the terrain and traffic conditions.


How about coining a new phrase like "Terrain And Traffic Adaptation" (TATA) or "Terrain And Traffic Exploitation" (TATE)?
As in "Unless you are driving on flat empty road, you should P&G with TATE."

 

Oh you can't use TATA as it is a car maker in India, India's largest car maker and I think the owner of Jaguar either now or soon to be.

 

That reminds me of my old RC electric car. The slight drag of the motor and transmission friction during coasting was amplified by the gear ratio by a factor of about 4 or 5. I found that if I set the throttle trim to always supply a minimal amount of power, the large reduction in drag more than compensated for the slight increase in power consumption. From your description, it sounds almost as if the Prius is also programmed to secretly add a little anti-drag power during no-arrows gliding. Does it always add a little extra power during no-arrows gliding?

 

I have tried putting my car into neutral on a stretch of road when I'm coming home from work. It is a slight down hill and a long flat with a sweeping right hand bend then a tight left hand turn into another street. (Remember I'm Australian so reverse this to picture it if you drive sitting on the wrong side of the car.)
If I use a no arrows state from the top of the hill using the throttle I accelerate down the hill from 50km/h up to about 55km/h then gradually slow down on the flat and right sweeper to just a little fast to take the left hand turn so I lift my foot half way through the sweeping right hand bend to take the bend at a nice speed.

If I travel the same stretch of road but put the car in neutral at the top of the hill I can't get all the way to the left hand turn at the same speed without putting the car in drive and applying a little power half way through the right hand bend.

I never knew why this happened but now I do. It is the same every time, the road isn't affected by wind, it has houses and large bushy trees each side.

 

Watching CAN bus messages, the accelerator pedal value is shown between 0 and 200.
The HV battery ampare value is almost zero on the pedal value 3.

Ken@Japan

 

For the original question this may be considered a wee bit off-topic, but it relates to the ongoing discussion on gliding, so ...

I've noticed something recently on my semi-regular part time commute that demonstrates 1) this in part and 2) a certain "release" point at about 37-38 MPH.

To explain: This route includes a toll bridge with a fairly steep downhill approach. (Skwyre7 and other locals, if you're reading, it's the Boulevard Bridge.) My tactic on the side opposite the toll booth (traffic permitting) is to begin the downhill at about 20-25 MPH in neutral, transitioning to warp neutral at 45-50 MPH at the bottom. That's generally enough to allow me to neutral-glide to the toll booth and drift through the booth safely with Easy-Pass activation of the cross-arm.

Coming down the hill, there is a noticeable point at 37-38 MPH where I feel this release. It's similar in nature to a conventional transmission that is suddenly shifted into neutral but much more subtle. I never notice it on shallower inclines, presumably because gravity isn't tugging at the car as hard.

Recently I've watched CAN-View during the descent, and I notice a progressively increasing degree of current flow into the battery, up to about 12-13 amps at the release point. Post-release, it instantly reverses to a 1 amp (give or take) flow out of the battery.

So as I think about it now, it's like there is a small amount of regeneration up to the release speed even with the car in neutral. What would explain this?

 

Prius design intent was to minimize emissions. The Atkinson cycle engine does this but it has lousy low-speed torque. Toyota's solution is to supplement it with the electric motors (which does not require the battery), which allow the engine to operate most of the time in its optimal speed and power range, and also allow recapturing energy (using the battery) while the car slows down instead of only wasting it as heat with friction brakes.

The principles:

- Accelerate briskly so that the engine is optimized.
- Gliding (no arrows) is better than coasting.
- Coasting is better than braking.
- Braking is better than stopping completely.

Figuring out how to apply these principles is the trick. Ideally one would always accelerate to the speed which then allows you to glide to your destination, but of course this is almost always impossible in real situations. Also it's hard to know when the engine is being used optimally (maybe Toyota could add a dash indicator for "engine optimization"?).

 

Remember that in N, the Prius still has all of the transmission and drive components connected. There is no normal clutch mechanism to decouple the parts. If the ICE is off and the car is moving, MG1 and MG2 will both be spinning, resulting in a bit of drag and a voltage at both. Whether any current is sent to the battery is a good question, but I wouldn't expect anything more than a residual amount.

Tom

 

The owner's manual is clear about that: the battery is not recharged at all while in Neutral.

 

Great thread everybody. I haven't even received my Prius yet and thanks to this forum I think I am ready to drive it very efficiently from day one. One question though, what is CAN? I tried to search first.

Thanks

 

Controller Area Network. It is a method by which the car's various computers communicate with each other and the outside world. It sends vehicle operational data via the car's OBDII (On Board Diagnostics II) connection to devices enabled to capture them. In my case, I have a device called CAN-View (no longer sold for non-plug-in Prii) that displays data on the car's display for parameters such as current flow into and out of the battery, ICE RPM, brake and accelerator pedal position, electric motor and inverter temperatures, exact battery state of charge, etc., etc. It can also display diagnostic trouble codes (DTCs) when they occur.

A Google search with "CAN bus" will reveal lots.

 

True, but the previous posters were talking about very small amounts of current; not enough to consider charging by any useful measure of the word.

Tom

 

Sometimes during a no-arrow glide, the MFD still shows MPG ranging in irregular numbers like 49, 63, 87, etc., as opposed to 99.9.

This occurs before the car is fully warmed up, in the 1st 2-4 minutes of driving. I'd think that a glide is a glide, and if the MFD is showing "no arrows," i.e. no energy use -- then what's sucking up those various MPG's ?