First few minutes mpg

OK, I see.
So, you were driving in "D" at 20 mph vs in "N" at 30 mph.
That's why you saw 20 mpg vs 40 mpg.
We know the warming up fuel becomes very thin in "N", then it causes to delay finishing (postponement) the warming up process.

It is not important to see better instantaneous mpg at a moment, but it is important to see better average mpg at a goal point.

Do you see any difference on the average mpg when you finish driving?

Ken@Japan

 

Ken you seemed to have studied this as much or more than anyone else. I have a number of short trips that bring my milage down. They are 1-3 miles with cold engine, and I'm wondering if you have speed/wait suggestions. The trips have numerous steep hills, often with stop signs or lights at the bottom of hills. Speed limit is 35mph, but I can go slow. I noticed my bad milage when I fill up on the weekend and do these trips (and linking trips doesn't really work). I tried slowly accelerating to 25mph and get about 30mpg, I think i was getting slightly better milage accellerating fast to the speed limit and braking. Given all the down hills and braking if I have a warm engine, I go to ev mode and it definitely helps. So is it go slow for s1a till the first stop sign, then accelerate briskly?

I'm happy with my milage on the highway and longer trips.

Thanks.

 

1-3 miles short trips, that's a worst scenario.　
I think there will be not so much difference by changing your driving style.

The special magic to improve your short trip mpg will be...
A ) use an engine block heater
B ) use a thermistor hack

Or, ride a bike, an electric bike or a NEV (Neighborhood Electric Vehicle)

Ken@Japan

 

That's what I thought. There are 8, two mile trips a week (4 round trips) to go on runs, now that its warming up I can ride a bike to those, the others will just keep pulling down my average. One reason for the prius is that I was getting about 16mpg in the city in the previous vehicle (much worse than epa). So this is much improved. It gets very hot here in the summer, so I expect that even these bad trips will improve soon.

The thermistor hack looks promising, but maybe I'll try it next winter after we get some feedback on whether it causes any problems. I have a neighbor that rides a motorcycle in nice weather to save fuel, but he gets worse fuel economy than I do. We may try building a hybrid motorcycle as a experimental project.

Thanks for all the technical information on the stages.

 

Thx. Ok, I see that the ignition timing is normal after S1a. But is S2 better to start driving? What is the approximate time between S1a and S2 (where the 'Prius acts normal")?

Even if fuel efficiency improves when driving after S1a, what about the conventional wisdom to warm-up cars in extremely cold temps just so the parts/components are lubed up decently before one starts driving? I am sure this is still valid?

 

conventional wisdom == military intelligence (no offense soldiers, it is just a cliche).

0W-20 and S1a warmup is the most you need to get modern cars lubed, unless you are in a racing or other high-performance situation.

With thinner oil, absent the anomaly of S1a retarded timing, modern cars just need a second to develop oil pressure and off you go. I love watching the 0W20 going in my filler hole, because it is the slickest looking substance I think I ever saw.

In extreme cold, you need to avoid hard driving because even if you warm up for an hour, only the ICE is warmed, not the steering linkages, etc.

 

cool. thx.

 

I had a block heater on my G II and it allowed me to go to stage 3 only 400 meters sooner on my commute, (6.4 km versus 7.0 km without plugging it in), all conditions equal.
They cost a lot to have installed, and I didn't take the option on my new Gen III Prius, because I thought it was a waste of time, money and electricity.

 

Re: First few minutes mpg with picture now.

I wrote as follows;

Your data is...

(1) 1280 rpm first 2 mins under 25 mpg -> 4.5 miles 52.1 mpg
(2) 1280 rpm -> 4.5 miles 41.0 mpg
(3) 1600 rpm first 2 mins over 25 mpg -> 4.5 miles 50.5 mpg
(4) 1600rpm -> 26.3 miles 54.5 mpg (can't count this because different goal point)

I think it is hard to judge which method is more efficient from your data now.
We need more data to judge them.

Ken@Japan

 

Of course, a thermistor hack user has to be very careful in mind to know what's going on the ICE.
My recommendation is...

• let the ICE run during the first 1 minutes (S1a) warming up
• after the 1 minutes, use the hack as needed
• when you pulse, the hack is not needed
• when you glide or engage the EV switch, the hack helps a lot

I introduced it since 2007 for the Gen2, and no one found any problems since then.

I installed the hack for following person's Gen2 on January 21st, 2007.
Since then (95,000 km odometer), his mpg number is increasing and the Prius odometer is now over 185,000 km (115k miles).
CNN Video - hybrid hackers

Ken@Japan

 

with trips that short, its tough to get any real conclusion unless you measure data over several trips. for short ones like that, i would have to take at least 10 measurements. i tracked my commute to work, going and coming (7 miles) which is also relatively short trip. i had variances of 10 mpg on some trips with no real explanation. temps, weather, etc about the same until i started tracking my SOC with it. then i noticed that just starting with a few less bars than the normal 6 would cost me 3-4 mpg.

if i were you, track 10 trips on each, toss out the high and low and average the remaining 8 and see what happens

 

Re: First few minutes mpg with picture now.

Your 4th min MPG suffers if you go up to 1600 RPM. First 2 mins looks better but you pay it back on the 4th min.