Questions for Hypermilers - GreenHybrid

VaBeachPrius · #1 (**permalink**) 10-19-2006, 06:03 AM

Background info:

2006 Prius, 2160 total miles. Current tank: 440 miles @ 72.0 mpg on the MFD, Average Temp: 65F, Light wind, dry roads, concrete/ashphalt, suburban driving (30-45 mph speed limits), Driver only (225 lbs), 44/42 PSI, conventional oil - full mark.

Background for questions:

I have been focusing on keeping the SOC as high as possible by pulsing with the ICE (showing orange arrows) and one yellow arrow charging the battery. I have found/read that pulsing with a lower SOC seems to result in a lower instantaneous MPG when pulsing. When I pulse as described above, from 30 to 40 mph, I usually see from 30-35 instantaneous MPG. I have measured the distances of my pulses with a handheld gps and can figure out how far I need to glide (no arrows) to acheive a certain target MPG before pulsing again. Obviously, pulsing with a higher instantaneous MPG over the same distance will result in a shorter glide distance needed to acheive high FE.

Questions:

How do I verify that my acceleration rate is optimal? Can view? Tach?

After the car and tires break-in shall I see a higher MPG? 5k miles? 10k?

What % increase will a 25F ambient temperature rise (next summer) do for me?

Is it better to P&G from 40 to 30 or 35 to 25? Teddy_Girl used 37 to 21 MPH?

What speeds were used by the August marathon milers?

Will synthetic Mobil1 0w-20 improve matters?

Does 1/4" below full on the oil stick matter?

Comments:

I realize it is not practical to get 100 mpg or more in city traffic unless I am a real a hole to others. It is a topic which has struck a nerve with my engineering mind. I think I have actually answered my own quesitons. Of course, all the things mentioned above play a role. I just need a good stretch of road with two lanes in each direction, summer, a well broken in car, synthetic oil, etc.

Thanks for listening.

FireEngineer · #2 (**permalink**) 10-19-2006, 07:05 AM

1. Keep doing what you are with your GPS measurements and plot them. You should see very little gain/loss from where your at. The pulse is also going to change depending on ambient temperature and battery temp so you may be plotting till June to get a good idea. And when your done share it with us.

2. Yes. Yes.

3. From where you are at now at least 5%, possible 10% if you limit your AC use and keep your battery cool.

4. Longer the glide the better, top speed does not matter as long as your under 40 MPH.

5. If I remember top speed was generally 35-37 MPH but some kept down 30 MPH tops with a glide down to 15 MPH.

6. Yes, more so when the temps go below 20 if your comparing to Mobil1 5w30.

7. Although no definitive answer, the general opinion is yes. Also the oil must be filled slowly when changing.

Considering your conditions and current MPG you could well hit 80MPG by June. Go Mobil1 as soon as you can, pump up your tires another 6 psi (good for a 1-2 MPG, the Marathon was at 60 psi), get an alignment with just slight positive toe (+.05), practice, practice, practice. You should be a hypermiler in no time.

Wayne

PS. Don't get frustrated when temps dip below 30 and you can't P&G like you do now. And get a engine block heater and use it below 50 degrees to shorten the initial warm-up hit.

VaBeachPrius · #3 (**permalink**) 10-19-2006, 07:49 AM

Thank you for your reply. I will go out again with a table that I just made with Instaneaous MPG (IMPG), Pulse Distance, and Glide Distance for a 100 MPG goal so that I can roughly see what my performance is as I drive rather than holding a GPS, trying to operate a calculator, switch screens on the MFD, keep my eyes on the road, and look for traffic behind me.

I believe a 10 mile stretch of 25 mph roads with two lanes in each direction would be ideal.

As hard as it is for me to imagine at such slow speeds (P&G range as opposed to speeds of commercial airlines), that the air resistance is really that big of a factor. I know that doubling the speed quadruples the resistance (1/2 rho v squared?). I can't imagine it being a big deal at 40 mph, but it seems that I slow much more quickly from 40 to 32ish, than from 30 to 20ish. Internal friction and rolling resistance might be playing more of a role at 40 than at 20. When I accelerate from 20 to 30 my IMPG is in the lower 20's regardless of SOC. I do see a change in IMPG when I pulse from 30 to 40 depending upon SOC.

Any tips on increasing my IMPG at lower speeds?

I think I need to install a traffic light controller on my car like the fire trucks and ambulances use so that I don't have to go through the painfull process of starting and stopping repetively (SP?).

Thank you again.

FireEngineer · #4 (**permalink**) 10-20-2006, 07:06 AM

For your table be sure to keep outside air temperature and battery SOC as other conditions.

For low speed pulse you just have to learn to feather back some when you don't like the IMPG. You may find yourself accelerating slower with higher IMPG so again experiment. And remember that the MFD display has a delay to any action you do, anywhere from 1 to 4 seconds. When you change something hold it for a while to make sure the MFD catches up with you.

Wayne

VaBeachPrius · #5 (**permalink**) 10-20-2006, 08:43 AM

I was out yesterday afternoon and ran thirty minutes with 3 of the consumption bars at 100 mpg and 2 at about 95 mpg. I think I covered around 15 miles or so on a couse of 1.5 miles with no real convienent (sp?)ways of turning around.

Observations:

1. I only regen'ed 1/2 a little car over the 30 minutes (consumption screen).
2. I coasted like I have never coasted before.
3. P&G between 35 and 30 mph. Goal was 30 impg for a 0.1 tenth of a mile. Was able to glide for the 0.233 miles and sometimes more to get me to 100 mpg overall.
4. The complete starting and stopping at one locaiton on my loop was a killer for overall FE.

Next:

1. I need a loop of 5 miles with a 30 mph speed limit, few traffic lights, and light traffic.