What is "Brisk" acceleration?

I have tried it all ways, taking into account the mileage and affect on state of charge. I try to minimize draining the battery to accelerate, to a point, due to the affect on future mileage. I have looked at it tank by tank and day after day on sections of my commute. I have concluded that the best acceleration rate for fuel efficiency is fairly light. 0-30 is around 15 seconds and 0-60 is around 50 seconds. This lightly uses the battery but I think that loss is overcome by achieving greater efficiency from the engine at that loading. In Austin and central Texas that means that around 25% of the other drivers will pull ahead of me from a stop light and another 25% will overtake me before I reach 60 mph. Mostly, the rate I use is common among other drivers who don't punch it. Your Traffic May Vary.

Brisk is a poor descriptive term that could range in interpretation from what I describe here, up to a rate just under full throttle, while many would say that the Prius is barely capable of brisk acceleration. I hope this helps.

 

I also accelerate slowly and agree more or less with what Ray says.

But the concept behind "brisk" I think is based on the idea that max. engine efficiency is at some high hp output and this should be best. This is not quite correct, both because of the hybrid battery cycle issues Ray mentioned, but also because it fails to take into account the total fuel used over distance including your constant speed cruise.

There are really 5 kinds of acceleration you need to be aware of:

1 battery power ultra slow.
2 gas power ultra slow
3 gas power without battery
4 gas power at max linear point.
5 gas power at max engine efficiency.

Item 1 is simple, it is accelerating so slow you can stay on battery. This is pretty hard but can be very beneficially done in traffic jams esp if you have an ev button.

Item 2 is close to 3 but consider it separately for a minute. Assume a gas only engine power and you need say 14 hp to cruise on your level windless road at steady desired speed. So you set the engine from a stop at 14 hp you will eventually reach your desired speed and have used 0 extra fuel for accelerating. Now suppose you wish to accelerate faster: Any more power will use more fuel and you have a net loss of fuel economy even though the engine is getting more efficient.

Item 3 Ray covered well.

Item 5 is simply read off a graph of engine efficiency. I have not seen very good curves for this but it is somewhere near max output, so lets say it is 70-80% percent max, so you aren't flooring it but you are looking for 20-30% lesss than max acceleration.

This can work well for you if you accelerate and then coast, and alternate. This will
minimize fuel used.

Now item 4 is very useful but I am still hazy on the acceleration rate here. To get it you need good efficiency curves. From these you want to graph just efficiency vs hp. Then convert these to fuel flow rate vs hp.

Then figure the hp you need to cruise at your desired speed. And mark the peak efficiency point and the peak hp points.

Once you have this data you can plot your trip with fuel rate vs time.
Find your total fuel used over some distance and that is your fuel cost.

Do again for different acceleration rates ending up at the same cruise speed and distance. Then you can see what is really best.

So all we need are good curves for the engine.

But it should be apparent that the best "brisk" acceleration rate will not be some constant value but will vary with temperature conditions (which affect engine rpm) and with the final desired cruise speed.

My guess is that slower acceleration helps mostly when traveling at lower speeds where the engine efficiency will drop off faster. That is why we run on battery some at lower speeds but not higher too.