Best method for street driving

search 'pulse and glide'. if you're doing short trips with a cold engine, you need a pip.

 

Once the engine is warm, it can if you do it right. But the details depend strongly on your particular situation, which doesn't match the CAFE / EPA test profiles.

Keep in mind that since the mid-1980s, the EPA label has been discounted from the actual lab dyno tests, and the highway number is discounted more strongly than the city number. So the EPA city number being higher than highway number isn't as meaningful as it appears.

On your GenIII Prius, Pulse & Glide works better below 46 mph than on the open highway. If you can adapt it to the local city traffic and stoplights, it can work wonders after the engine is warmed. But not everyone has the right conditions available.

A good DWB style (driving without brakes) should be a higher priority than P&G. But for short trips and errands starting with a cold engine, don't expect great results with any method (except an engine block heater).

 

I have no problem getting high mpg on short runs after the engine is warmed up. However, if your short runs involved a lot of stop and go due to lights and stop signs, then your mpg will suffer. There's not much you could do about it except drive really slow but that may piss the people behind you off. Getting 59 mpg on highway is really good. You should be happy.

 

Right here from the PriusChat Shop. While a necessity for a competitive hypermiler, it may well be more hassle than it is worth for others. And it will need a timer to keep the block heater energy consumption from exceeding the gas energy savings.

 

The problem is Prius warm-up is a pretty significant hit, ~1-1.5 miles, ~3-5 minutes, 30 MPG if you are careful. But once the engine is at operating temperature 65-70C, your mileage significantly improves and after 20 minutes when the transmission is warmed up, again, much better mileage.

As the others have pointed out, the technical solution is a PiP or some sort of plug-in. But let me share some technical details about Prius warm-up:

• 45-55 seconds - catalytic converter warm-up. During this time, the engine runs in a mixture rich, "Open Loop" which means it uses a stored mixture table (i.e., fuel trim is the technical term.) If you are gentle with the accelerator to stay in speeds under 35 mph and use "N" to coast, you can get some early distance, a 1/4-1/2 mile, without a steep mileage hit. The battery will drain a bit but that can be made up once the catalytic converters come online.
  • ALTERNATIVE: start the car and let the engine run until it shuts off before moving out. I learned this trick from Ken@Japan
• 1-5 minutes - this is when the engine is warming the coolant up. My data suggests as low as 65C, the car becomes much more efficient. After 70C, you are essentially in Prius 'briar patch' and just drive the car normally. It may sound counter productive but I have no problem with doing 50 MPG in this period as the traction battery recharge becomes a fraction of the engine load.

If you can order your trips, do the longer one first and then the shorter ones. This lets the car warm-up as much as possible so on the subsequent errands it uses the left-over warm as much as possible.

Most of all, experiment! You're going to have this car for awhile so try different techniques and tricks and make a record. For example, you might have the option of using a 'downgrade' or avoiding an 'upgrade' during warm-up. Try both routes and measure the effect.

Bob Wilson

 

Great post !!..

 

Drive like you have a load of eggs on your back seat - ie very gently.

 

I do a lot of city driving too. Check out Wayne Gerdes videos on YouTube. Here's one that's especially good for city driving: www.youtube.com/watch?v=49Zyyhqwh30. Wayne suggests when you are stopped at a traffic light, accelerate in EV mode until you reach 15 or 16 MPH and then light the ICE. When conditions allow and nobody is behind me, I do this and found it helps to increase MPG. Also, check out Hobbit's articles. Do a Google search on "Hobbit Prius" and it will guide you to his articles. Consider installing Scan Gauge II. It helps keep me in the "sweet spot" that Hobbit recommends. There's lots more information such as tire pressure, top tier gas, etc. So I suggest reading as much as possible. I read and re-read Hobbit's articles.

 

not sure why you would need cruise control to maintain 27-28 mph on side roads, i do it routinely. the battery will not deplete, if you go too far in ev, the ice will come on to recharge it. this won't be as fruitful as pulse and glide, but if your in traffic, it is sometimes unavoidable.

 

Or use what John1701a recommends, "JUST DRIVE IT." When I did my marathon drive, I had no illusions that it was going to reveal a secret to Prius mileage. As soon as it was over, I returned to my regular driving style and mileage.

The marathon refined but did not teach anything I didn't already know . . . 25 mph in warm weather gives 99.9 MPG. The marathon applied the Japanese practice of breaking it into smaller chunks. Each drive was artificially extended to an hour, to dilute the warm-up costs, instead of the usual 15-20 minute trips. The marathon took two weeks to burn 10.9 gallons over 1,000 miles for a tank would usually take three weeks and 600 miles.

My regular driving uses cruise control but I will follow slower traffic. Once I reach cruise control set speed, the only time the speed increases is when in "N" coasting a shallow downgrade. But going no faster than the posted speed limit or local traffic. Also, I tested alternate commuting routes to tradeoff between duration and MPG. I'm careful about my warm-up protocol, the first 1-1.5 miles, but not a fetish. My foot is seldom on the accelerator as the cruise control does a better job of steady speed.

MPG is a function of speed and nothing else comes even close. So "JUST DRIVE IT" but choose routes and traffic practices that allow steady, slower speeds. Higher MPG is simple physics and applied engineering.

Bob Wilson

 

We've got the block heater, and use it pretty religiously. I also hooked up a ScanGauge, and must say, on occasions I've started up stone-cold, the coolant temperature gets into +50 deg (C) range pretty quick, with the exhaust gasses being used to raise coolant temperature.

Main way I can see to improve short trip mileage is to avoid short trips, LOL. There's only so much you can do, but, try to avoid impulse trips, consolidate trips, consider walking if it's practical, and so on.