SoopahMan,

I generally P&G between 20 to 35 mph if nobody is around and between 35 to 40 mph if I am in traffic with people behind me. The pulse and glide technique will generally work for any combinaiton of distance pulsed for a given instantaneous mpg value (impg). You have to be the judge to fit a pulse and glide "event" into your traffic situation to maximize your mpg's.

In a wide open environment, if you pulse at 25 impg for 0.1 miles, you have to glide for 0.3 miles to acheive 100 mpg for that event. The total distance traveled is 0.1 + 0.3 miles = 0.4 miles. The amount of gas used = 0.1 mi / 25 impg = 0.04 gal. The resulting mpg is 0.4 mi / .04 gallons = 100 mpg.

From my rationale in other posts. Keep your SOC high; don't use electric mode if you don't have to. With a high SOC, you will be able to accelerate faster (covering a shorter distance) while maintaining a given (and often higher) impg value. Example, with a high SOC you might go from 20 to 40 mph in .17 miles with a 25 impg value. With a low SOC (2 bars) you might go from 20 to 40 mph in .21 miles with a 25 impg value. You have traveled further during your pulse and must glide further to achieve the same mpg.

Another example. What if you slowed your acceleration to a 35 impg value. It would take you much longer to reach your goal speed (i.e. greater distance), but your glide distance would be reduced.

You could accelerate like a bat out of hell at 9 impg for .03 miles, but you will have have to glide for 0.5055 miles to acheive 100 mpg; traffic conditions might not allow you to glide for that long.

See my glide distances table below. Print it and go out and experiment. Try and accelerate at a constant impg (like 20 impg). Estimate the distance traveled (just try and pulse for 0.1 miles) and use the chart to figure your glide distance (0.4 miles). Then try to glide that far. This chart is set up for 100 mpg, you can easily fix it or develop your own for whatever goal mileage you have.

You should see some level of consistency between your bars. Do you see 70 mpg and 30 mpg for your bars? Are they that far apart? There is a very simple equation that lets you know how far to glide after a pulse.

I hope this helps.

 

Interesting. My pulses and glides are much longer - I tend to pulse up to 40 or 41 then glide as low as 25. I assumed kicking the gas engine into gear on and off more frequently would be less fuel efficient; I also wasn't sure if frequent pulsing would cause the Glide to have the engine idle needlessly. I'll try pulsing more frequently, thanks for the Excel table.

Pulsing at 20mph gets me impg of ~20, pulsing at 35mph would likely get me impg of 35-40... .

One thing I do contend with here is gradual hills - so at times Gliding works for a half mile without losing any speed, at other times I wonder if Gliding is saving me any gas at all (slight but continuous incline).

 

The hills might explain your consumption screen being tall, short, tall, short, etc. It is flat here along the coast. Do your hills and inclines correspond with your consumption screen?

By the way, another excellent segment on the way home, 85ish mpg (according to the MFD) over 20.4 miles. I cannot wait until there are more warmer days. I am considering a scangauge as I might be exceeding the 99.9 mpg on the consumption screen for a few minutes here and there. However, at $170, it seems like an expensive toy for a car which has the consumption screen.

I paid for my block heater today. It should be here in a couple of days. I will bet my mileage will be much better with the ability to remove at least one cold start per day.

 

The issue I am running into is that I am finding it virtually impossible to maintain highway speed (60-70 mph) using just the ICE without some form of asssit from the EM. Everytime I eliminate the yellow arrow from the battery to the EM the car decelerates. It could certainly be my inability to "fine tune" my foot to pedal feel, but so far I can't get the car to maintain its speed without a periodic assist from the EM (and thus the battery).

At slower speeds (25-40 mph) I seem to have more success in maintaining the speed without any help from the EM. Is my experience typical or are there other tricks I need to learn?

 

UTpiper,

The last threads between SoopahMan and myself are dealing with acceleration rates and techniques at speeds less than 42 mph. Steady state cruising on the freeway at 60-70 mph is an entirely different story as the engine spins when the car is traveling above 42 mph.

At freeway speeds you are going to see several different arrow combinations. You may see orange arrows from the engine to the wheels, yellow arrows from the electric motor to the wheels and to the battery, yellow arrows from the electric motor to the wheels and from the battery, just green arrows (brief, but possible, requires feathing with the peadal typically on a downhill segment), just yellow arrows from the electric motor to the wheels only (brief, but possible, requires feathing with the peadal typically on a downhill segment), or no arrows at all (coasting).

 

Thanks for the clarification. OK, one more question related to speeds under 42 mph. If I understood the gist of the thread you and Soopahman were engaged in, my optimal situation for FE is when there is not a yellow arrow coming from the battery to assist the ICE? Is that the basic concept or at least a semi-accurate interpretation?

If so, here is my question. Does that mean at slower speeds when I could be utilizing just the EM and not the ICE (thereby obtaining off the chart impg) I am still better off engaging the ICE as the amount of fuel used by the ICE to recharge the battery is greater than the amount of fuel used to propel the vehicle? It seems counterintuitive, but given the possible energy transfer inefficiencies, I guess I could follow that logic.

I'm interested in your thoughts as I am continually trying to increase my overall mpg but finding it difficult given 50% of my driving is freeway based.

UTpiper

 

Highway driving is a different story - there are a lot of threads here about highway efficiency, you could search for one and ask a question in it to keep the discussion organized.

As for times when you're moving at lower speeds, that's more or less what I'm seeing from Ken and Bob's numbers - although inevitably the Prius uses electric-only below 10mph (sometimes all the way up to 30mph if you have a full battery). I let the Prius do so, both because the Toyota engineers knew what they were doing, and RPM efficiency graphs show that the Prius ICE is less efficient below 25mph than in any other range. So even if the gas efficiency of using that electric motor might come to 50%, the gas engine trying to accellerate you at 5mph might be 30%, so the Prius uses electric until it's worth kicking in gas.

What I'm a little torn about now is whether it's better to push the engine at ~20mph so that there's a yellow arrow coming from the electric motor (but no yellow arrow from the battery) - the gas engine feeding the electric to expand its torque. I wonder whether pushing it then is more efficient (higher RPM means more efficiency) or if accellerating with a green arrow to the battery is better at 20mph. If it's the latter, that rate of accelleration is amazingly slow - impossible in traffic, and even outside of traffic I don't know if I could tolerate accellerating at a rate that I suspect I could beat by getting out and pushing.

 

I have tried to attain that status of yellow from the EM only (assuming an orange arrow from the ICE) and find it is extremely difficult to acheive in normal driving. Invariably I get either the yellow arrow to the battery and none to the drivetrain from the EM or just orange arrows from the ICE to the drivetrain. It appears from my attempts the balance point to acheive yellow from EM while ICE engaged is very narrow. Is that everyone else's experience or am I simply not well trained yet?

UTpiper

 

I can get that to kick in relatively consistently. If you keep trying you'll get to a point where you know how far to push your foot down without even looking at the display. However, how far to push varies at different speeds - you have to push harder at 40 than at 20 to get it.

 

Lately I've been accellerating gradually - basically red arrow to wheels, green arrow to battery - to try to get the best MPG. I just started a new tank tonight and decided to experiment with accellerating with red and yellow arrow to wheels, no arrow to or from the battery, and to my surprise my mileage seems to have benefited. I'm going to guess that I accellerate in such short bursts that I'm gliding for a higher percentage of the trip that leads the MFD to read out this way - I'll keep at this for the rest of this tank and see how my numbers vary.