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Hi all.

When starting a trip in this terrible cold we've been having, I'm wondering whether it's better to:

a. FAS and glide as usual (pro: "free" miles, con: prolonged warm-up)

b. leave the ICE on until operating temp has been reached and then hypermile as usual (pro: operating temp reached sooner, con: "lost" miles at start)

Is there any way to know for sure w/out real time numbers, i.e., SG or similar trip computer?

Coaster,

Have you covered your radiator with cardboard yet?

CarChip tells me my Insight takes as long as eight minutes for the engine coolant to peak at 195F when the outdoor temperature is around 25-30F.

Also, set the heater temp to it's coldest setting, even if the fan is off.

Thanks for the suggestions, DF! Although it'll be tough setting the heater to cold! :eek:

Any thoughts on a) vs. b)?

My experience so far is that a warm-up P&G, ICE off is worth a couple of MPG (both near the end of warm-up and overall) over P&G NICE-on, at least in my car.

We haven't had such severe conditions as those in the North, but sometimes I drive in the teens at night.
All ICE's are relatively consumption pigs when cold.

On warm conditions on a given stretch I'll shut her down as often as possible but in the cold I'll keep it on as it struggles to warm up with the lowest amount of load possible. (Super careful in timing of lights etc)

Instead of rolling ice-off (Which I do in warmer weather) I'll keep ICE on and roll in neutral instead.
By the time I enter the freeway 2 miles after start-up the coolant has reached normal temps.
(If I were to key-off instead of N-roll it would still be stone cold entering the freeway)
But that doesn't mean it's warmed up yet.
Since the heater core acts as a mini-radiator and always has coolant flowing I keep cabin heat set to cold and fan off. After about 10 miles I move it about 1/2 way to hot, and after 15-20 miles switch the fan on if needed.

-Steve

Thanks, guys! Lots of helpful feedback...

Every vehicle is different, as well as the weather conditions, speed limits, stoplights and so on. For me, I have to look at each of the conditions to make the call when I go KEY-OFF FAS during warm-up. In general, I would have to say KEY-OFF FAS during warm-up in my FEH works best. By the time I get to a comparison point in distance, my average MPG has been better almost every time than letting it warm-up without KEY-OFF FAS.

From what I've read in the FEH PCM/ED manual, the PCM retains warm-up information in the Keep Alive Memory (KAM) during short key off stops. This would prevent a start all over again warm-up mode in the PCM each time you KEY-OFF FAS. Not sure about other vehicles, but it would make sense that they also work this way.

A warm-up for me in the FEH starts with the ICE at a idle (very little load) while the electric motors propel the vehicle to 40mph. Within a few blocks, the ICE starts to take over a heavy load pushing the vehicle and charging the battery with the small generator. If it's warm outside, I can begin a few fake shifts for regen to load up the battery, which warms the battery even more. My first road has a 35mph limit, but most people try to drive at 40-45mph. Depending on stoplight timing, I increase my speed accordingly for a KEY-OFF FAS, and Pulse with a KEY-ON restart as needed. Timing the last KEY-ON restart so the ICE is at the right temp and the battery has enough SoC for EV is important, because after a KEY-ON restart, it takes a minute or so to go EV. The average MPG at this point has been better than regular warm-up, and I can begin a repeated battery charge, discharge with EV driving the rest of the day.

GaryG

Hello everyone,

I don't own a hybrid, and being in Chicago's wintry hell (oxymoron intended) this February got me to thinking about you hybrid drivers. I know in my tdi's that if they sit shut off after reaching NOT for just a few minutes (<5) , I can see an approximate 50-75 degree drop. It then takes another 5-10 minutes to reach NOT.

Are your engine temps dropping while running in EV? What about heat in the car? If I have the blower fan set at med-high, would I notice a drop in engine temp and/or heat output in the passenger compartment?

I have been wondering about this for some time, and everytime I have seen a hybrid this winter I tell myself to remember to post the question on cleanmpg.

Regards,

Andy

Hi Andy:

___Temps do not normally drop anything near 50 – 75 degrees F but I have seen a drop of 10 after a ½ mile long FAS at higher speeds when first bringing her up. I am not driving a hybrid now but during the warm up, I did not and would not have a fan running. Until NOT, it was a lesson in futility imho. In terms of ICE operating efficiency that is, not ability to warm up the cabin.

___I have a question for you as well. Normally, a TDI will idle at .3L/hour steady state. During warm up idle w/ the higher revs in colder temps and all, are you seeing upwards of 1.0 + L/hour for those first few minutes?

___Good Luck

___Wayne

In cold weather... Warm up is about me. The heck with the car and mpg. I want heat and I want it NOW. I want my windshield clear inside and out.

With that being said. Im a sinner of biblical levels concerning this. The WAI helps some with warm up. My EX doesn't warm up well at all in temps below 32f. If the SG says theres 125 degree water in that block. Im getting my share of it.

psy

Hi Wayne,

I was going to quote from your text to open this response, but for some reason I can't type in the dialog box.

Unfortunately I don't have one of those fancy scan gauge units, so I couldn't tell you what fuel flow is.

The one disadvantage to the TDI is the LONG warm up times in the cold. If I use any heat at all, I won't reach NOT on my 9 mile commute to work. Hence the reason I installed engine heaters on both TDI's. Both cars start like a summer day, and I get instant heat :)

Sorry I couldn't lend more insight into Fuel Flow.

Andy

Are your engine temps dropping while running in EV? What about heat in the car? If I have the blower fan set at med-high, would I notice a drop in engine temp and/or heat output in the passenger compartment?
I don't see too much drop during EV-mode or ICE-off glides, and I can easily recover those drops during subsequent ICE-on segments. I'm sure it helps that I have my front grill blocked.

This assumes I'm not running the cabin heat. It's been an eye-opener for me to see from the ScanGauge how much the cabin heat speeds ICE heat loss and slows its gain. Coolant temp can drop by 10F or more sitting at a stoplight and by 20 or more during long ICE-off glides. Typical ICE-on pulses at speeds <40 aren't typically enough to recover that much loss.

Two morning commutes this week, both with outside air temps in the teens, demonstrate the slowed ICE heat gain. On one, I had to run the defroster for windshield fogging. The coolant temp was ~100F at the two-mile mark. The next day required no defroster (and I didn't run the heat), and at the two-mile mark the coolant temp was ~140F.

So unless I (or the occasional passenger) cannot tolerate it comfort-wise, I don't run the heat until the ICE is fully warmed. Afer that I shut if off during ICE-off idle or glides when the coolant temp drops below 170. I generally let the temp get back into the 180s before turning it back on.