Best way to accelerate

Evan said it. From a dead stop to the speed limit I use it all the time, for an increase of 5 or 10 miles and hour, where the speed goes say from 40 to 50 I watch amp draw most often and use as light a pedal pressure as traffic behind will allow. Once at speed again I take my foot completely off the gas and then slow back on to maintain speed. Just my own quirky way of doing it, but I think my mileage show there is some merrit in my madness. I just check my last tank and it was 41.6mpg USG

 

This is an interesting question, and while I think you would have to take some measurements to really determine the answer, I do think there are a few principles to think about:
1) If it weren't for friction, air resistance and engine inefficiency it would take exactly the same amount of energy get to a certain speed, whether you got there quickly or slowly, so it all comes down to a question of inefficiencies and losses.
2) The IC engine is less efficient at lower RPM's so in terms of the engine it is better to have it revving high.
3) Air resistance and friction forces will go up at higher speeds so in terms of these losses it is better to be driving slow. Slower acceleration would mean less time spent at the higher speed and less energy lost.

I don't know where the "break point" is but I think based on the above, the rule of thumb would be accelerate quickly until the engine is running at an efficient RPM and then hold steady until you reach your speed.

My personal preference is to accelerate quickly (as long as it is safe) up to my cruising speed for these reasons:
1) It's fun, and everybody deserves a little fun.
2) I know my car has low drag and can shut off the engine if I need to ease up and coast.
3) When it's cold in Calgary I think that working the engine harder sooner will warm it up sooner and pay dividends in efficiency.

 

<div class='quotetop'>QUOTE(jkash\";p=\"58593)</div>

But aren't you measuring mileage over time instead of mileage over distance? In other words, you may be getting higher mileage bars but it may require more of them to get where you're going.[/b][/quote]

Bingo!! The 5 min bars are worthless for determining actual mpg, esp. the short mpg gain or loss of a brisk or slow acceleration.[/b][/quote]

I have a case in point. I was stuck at a left turn the other day for over five minutes. The five minute bar went to 100 mpg but I had only traveled about 50 feet. The mileage on the display was unchanged.
[/b][/quote]

Your example doesn't really relate to my experience. I was stating my observation from the first 5 minutes of starting the car from my house with generally the same distance each time.

 

I think the biggest variable for the first 5 minute block is OAT. and how long the ICE has cold soaked. If you let the car sit overnight in, as an example, 20C about 68F the time to get the car to go into S4 might only be 5 minutes but if the temp drops to 10C about 50F it'll probably take about 8 minutes and at 0C 32F it will take almost 10 minutes maybe longer depending on terrain. The S4 start temp is 70C, below that you can't get the ICE to go into S4.

 

For Evan the screen's I use are as follows
screen #1
current draw
bsoc
rpm
engine temp

screen #2
battery voltage
current draw
O2 sensor#1 output
O2 sensor#2 output

screen #3
MG1 temp
MG2 temp
bsoc
battery voltage

other screens show air intake temp and rate of air flow into engine, throttle position, MG2 torque and several others. The first screen is the one I consider the most useful for daily usage.

 

Frank, are you using the Prius MiniScanner to obtain your information?

 

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I totally understand where you are coming from, but I'm just stating my own observation from what I considered the same distance using the same starting position. And even though you can say that I'd be traveling a farther distance using fast acceleration, I don't think its that significant considering its about 30-35 mph on average with a couple stop signs.

 

that'd be the one, can't wait for the model for the 04-05 Prius.

 

Absolutely! The Prius would do a better job of "training" us drivers about fuel consumption, if it displayed mileage versus distance instead of time. You have hit the nail on the head deh2k.

 

The energy consumption screen has been a topic of discussion since the 2001 came out. Doesn't really give me any useful information.

 

NiMH: While I agree with your conclusion that efficiencies and resistences are the factors involved, you left out, or ignored, two important points:

1. At city speeds air resistence is negligible.

2. The PSD almost totally decouples engine rpm from vehicle speed. The Prius can run the engine at a high rpm even at a standstill, sending power to MG1, which sends current to MG2, which provides torque to the wheels more efficiently at low vehicle speeds than the engine can.

A theoretical analysis would have to take into account the characteristics of the PSD and the program instructions of the ECU, as well as the efficiency curves of the engine and MG1 and MG2. This is probably a hopeless task for an amateur.

Observation of actual mpg is the only useful approach. That would require driving a controlled route for a significant distance using different tecniques on different runs. And the distance must be long enough to eliminate the effects of having different battery SOC at the beginning and the end.

 

for me, brisk is watching the speedometer and counting by ones as it goes up. brisk is counting rapidly.

moderate would be about 2-2½mps (120-150 miles per minute)

to gauge this. counting would be at just about normal conversation speed. realize that some can talk faster than others and if you consider yourself a fast talker than these guidelines dont apply to you.

also, moderate to me may not be moderate to you. another guide would be to engage cruise control at 25 mph and then hold speed increase. the acceleration you get would be just under moderate.

since cruise control is something that we all have, maybe referring to moderate increases can be compared to that rate since it should be similiar in all our cars.

 

I have gotten better mileage by accelerating slowly. My overall strategy for high mileage is to minimize use of the battery. For maximum tank to wheels efficiency, use the engine as much as possible and you will minimize the inherent losses involved in the electrical generation and consumption process. The purpose of the electric motor is to overcome the slow acceleration characteristics of an otherwise very efficient engine. The exception to this strategy is that the engine is indeed quite inefficient at startup speeds up to around 6 mph. Above some speed, the innefficiency of low rpm is surpassed by the inefficiency of the conversion process. My results have been excellent.

 

Ray, I like your logic here. What mileage are you seeing?

 

Duhh, now I see your license...56? WOW! Really?

 

I have been doing some experimenting. I can get better milage up to about 18 mph ( weird number but there it is) on electric then ICE cuts in. Between there and 23-25 the best I can do is in the low teens for mpg. After that if I need to accelerate I can get 20 to 32 mpg but at the high end I am accelerating very slowly and in danger of really making people behind me angry. I am not seeing a great improvement in over all mpg if I am a bit more aggressive with mpg in the high teens and very low 20's to 35-40 mph and then back off a bit and accelerate to speed. That is how I am seeing it. I wish I had a mini scanner for the 04. Any word on the mini scanner for the 04-05.

 

I don't think I quite agree with this statement, since the whole idea behind this car is to make maximum use of the battery so that when starting from a standstill point you can make use of the high torque at low rmp from the electric motor and use the inertia and force of gravity to ideally re-gain that energy. If you don't make use of the battery you are just driving a conventional car.

 

My findings show the cruise control tries to maintain aprox. 20MPG for its acceleration +/-2MPG. Of course, this only works above 25MPH.

As for the statement SynergyGuy makes, you forget that more power can be generated by MG1 and directly used by MG2 than can be delivered by the battery to MG2, and doesn't need to be replenished. This recycles power not given to the wheels from the ICE through the PSD back to the wheels through MG1 to MG2, and still using MG2 to provide more efficient torque at low speeds. That is the beauty of Synergy drive.

Also, whatever is taken from the battery needs to be replenished utimately by ICE, diminishing overall MPG after acceleration from what you initially obtained during acceleration. It all depends if efficiency of using battery power for more power at low speeds exceeds deficiency of recharging it when done.