Hopefully my commute will push it back up from the weekend. My batting average is really starting to suffer!!

I haven't even had the car broken-in in good weather yet!

 

Yeah, this weather is discouraging. Through the first or second week of January, I was still managing to get tanks near 50 mpg and I thought we might have a nice mild winter without a huge FE hit, courtesy of global warming (it's terribly ironic, actually). There was a lousy tank back in late November, I think, but nothing really awful.

Then the cold started to hit us- ice, snow, wind. Lately I am really having to work hard to keep it above 45 for this tank, and for a little while at the beginning it was barely pushing 40. I'm sure that I've had a couple of days with an average under 40- it's painful. But sometimes you just have to have the heat on high, you know? Not to mention headlights, wipers and defrost all going at once--- and the time it takes that engine to heat up? yuck. I feel positively guilty turning on the radio.

Oh, how I long for spring. But the snowflakes are skidding by my window as I type this- drifting and dancing, and promising another slick night and disappointing mpg.

 

When stopped, will your HCH run the ICE to maintain some minimum coolant temperature?

We found the Prius Classic won't auto-stop until 70C and will run the ICE when the coolant reaches 60C. The mechanical thermostat is set to 82C to deal with high temperatures. So I'm curious if the HCH cars have a similar maintenance of a minimum coolant temperature?

Thanks,
Bob Wilson

 

It's a very rare-occurance for my autostop to engage this winter. I am not sure what the requirements are.

 

My Dad's HCHI won't autostop when the ambient temperature is less than freezing. I believe that they lowered this requirement for the HCHII. They may have even gotten rid of it? I havn't driven my car too much yet to know. I just used up my first tank this weekend! I've owned the car for a month now, so its obvious I don't drive much. The HCH does require the engine to warm up before it will allow autostopping, but the exact temps I am not familiar with.

 

Noflash - the coolant temp has to be warm enough (about 9 blocks on our display) AND the IMA battery temp has to be warm enough. I've had the Block Heater working before I leave each day (well, almost each day) and can have the Auto-Stop kick in within about 1.5 miles and that is starting at morning temps of 15-25 F. This Block Heater REALLY makes a difference for those in colder climates (Leahbeatle - it would really benefit you btw).

I've had days where I either forgot to plug it in or something like that and had to start the morning in a dead-cold car with no assistance. Brrr is there a big difference with no Block Heater. There were some days where I kept running the same morning drive -- 7.2 miles mostly downhill and mostly Interstate with 6 blocks of city driving. From there is it the same 15.9-mile trip to the office mainly Interstate but getting to the Interstate can be between 2 and 10 minutes of city stopping and waiting for the green lights.

Here are the results noting when I had and when I did not have the Block Heater warming the car prior to leaving.

01/19 = 7.2 mi @ 43.8 mpg and 32 F w/o Block Heater (23.1 mi @ 44.8 mpg)
01/22 = 7.2 mi @ 52.6 mpg and 36 F w/o Block Heater (23.1 mi @ 47.3 mpg)
01/23 = 7.2 mi @ 55.3 mpg and 33 F w/ Block Heater (23.1 mi @ 47.3 mpg)
01/24 = 7.5 mi @ 53.4 mpg and 32 F w/ Block Heater (did not go to office at this point)
01/25 = 9.0 mi @ 50.2 mpg and 28 F w/ Block Heater (24.9 mi @ 46.9 mpg)
01/26 = 7.2 mi @ 49.0 mpg and 28 F w/ Block Heater (23.1 mi @ 42.2 mpg) <-- severe headwind
01/29 = 7.2 mi @ 48.1 mpg and 18 F w/ Block Heater (did not go to office at this point)

The average MPG and Temp of the two trips without the Block Heater were 48.2 mpg @ 34 F and with the Block Heater were 51.2 mpg @ 28 F. So when the temps are an average of 6 F lower the average mpg was HIGHER by 3.0 mpg. Just imagine if the temps were 34 F like before instead of 28 F. I also showed the resulting reading once I got to the office. Many times it is around 47 mpg with or without the Block Heater to start the day but you can see that as the temp drops the MPG still remains about the same (46.9-47.3 mpg for days of 28 F and 33 F compared to 44.8-47.3 MPG on days of 32 F and 36 F. Even today when it was 18 F outside I arrived at 7 miles with 48 mpg. That is half the temperature of 36 F when I got 52.6 mpg (without the Block Heater).

The resulting end-of-day displays for the above days are:
01/19 = 66.9 mi @ 45.4 mpg and 32 F average temp w/o Block Heater on first trip
01/22 = 151.4 mi @ 47.7 mpg and 33 F average temp w/o Block Heater on first trip
01/23 = 82.0 mi @ 47.1 mpg and 32 F average temp w/ Block Heater on first trip
01/24 = 25.4 mi @ 38.8 mpg and 33 F average temp w/ Block Heater on first trip
01/25 = 173.2 mi @ 47.4 mpg and 25 F average temp w/ Block Heater on first trip
01/26 = 112.5 mi @ 44.3 mpg and 23 F average temp w/ Block Heater on first trip
01/29 = 155.9 mi @ 45.1 mpg and 20 F average temp w/ Block Heater on first trip

After the first trip the numbers sort of merge together as a 7-mile trip compared to 150 miles for the day total isn't a big percentage but even the last three days are impressive to me -- days in the 20-25 F temp region and I'm doing 150 miles a day and averaging 45 mpg. I was really expecting this to be in the mid-30s so I'm real pleased with the results so far.

This also doesn't take into account that I don't start the car and let it idle and warm up and don't have to sit and wait for hot air to come out of the vents and the fact that the Auto-Stop can occur anytime after about 1.5 miles which is when the coolant gauge is at 9 blocks on the readout. Also, I get to brag about having a "plug-in" hybrid as there is a cord hanging out the front of the car -- <snicker>.

 

The reason I asked is we found the operational modes of the Prius are determined by the engine ICE coolant temperature. The intake air temperature is only used for mixture calculations. So by adjusting the coolant temperature with bias resistor circuit on the coolant thermistor, we can 'fool' the car into thinking it is nice and warm. This has several benefits:

• earlier ICE auto-shutdown - I can take my summer, warm-up route and the ICE will stop at the light. Also, auto shutdown modes below 42 mph work.
• longer EV mode at the end - now when coming home, I can get very long 'stealth' mode, low-speed coasting to my home.

I'm not seeing 'summer' MPG but I am seeing Spring/Fall MPG.

A UK Prius owner, Clive, came up with this hack and two of us in the USA have been refining the technique:

http://hiwaay.net/~bzwilson/prius/pri_temp.html

We suspect it may have wider application so I thought to bring it here ask if you' all have investigated this technique.

Thanks,
Bob Wilson

 

I've gotta get a block heater.

 

I haven't been doing terribly, actually, even without the block heater, in terms of getting my car to AS. I do not warm it up before driving it- I key, then go, and it usually starts to AS somewhere midway through my 22 mile commute to/from work, less than 6-7 miles in, I think, because about half the time it'll AS by the time I hit my first turn on the way home, which is 4 miles along, and I always end up stuck at that left turn lane. Usually in warm weather I'll key off at that light if it doesn't AS, but in winter I often can't, b/c I need the defrost running or I have visibility problems. So except in the very stormiest weather, when I can't turn the defrost off all the way home, I'm getting an AS when I need it for pretty much 3/4 of my drive every day.

So what gets me in the winter can't necessarily be solved with a block heater- running the heat and especially the defrost seems to be what really drains my mpg, and I've gone without heat for so much of the time now that I'm starting to get frostbite trying to get better mileage. It's ridiculous, but I keep doing it. Sigh. I guess this is an obsession. But on the bright side, I filled up today after 497 miles at 46.5 mpg. Not bad considering the yick weather we've had these last few weeks, barely going above freezing once, with a fair bit of ice and snow.

 

Leah - You made 497 miles on that tank and have made 497 posts as well (play that number tonight on the lottery - you still have time). Kudos on maintaining the good numbers but remember that in the same conditions I get the AS to work in as little as 1.5 miles on my 22-mile commute, have heat instantly (no frostbite), and run the defroster quite often if needed (only turning it off before coming to a stop so AS can kick-in where I turn the Defroster back on and stay in AS - a great feature). You did know this, right? That you can wait until the car comes to AS and then turn the defroster back on and the car will remain in AS (until it feels it is too cold). So with the Block Heater the windows clear within the first mile so I can turn off the defroster and just stick with floor heat for the rest of the trip (and usually by the end of the first mile of the commute I've had to turn the heat down to 68 F as anything over 72 F is just too toasty when the car is warmed up).

I really wish there was another member in my area without a Block Heater (Civic or Prius or Escape or Mariner or Lexus ...) just so we can compare/contrast the two scenarios. Maybe try and find a candidate in Chicago with a Block Heater and go out to dinner (and spend a good 90 minutes at dinner to let the cars cool down) and then go out and get into the Block Heater car (obviously you should have tried to find a place with an outlet on the outside of the restaurant) and see how soon before it AS and gets HOT air (not lukewarm tepid air but HOT air). Then go back and take your car and see how much longer it takes to AS and get hot air and see what the resulting 5-mile trip results in for FE. =)