Managing AC/heating system at start-up

8475 Views 30 Replies 4 Participants Last post by hasarad, Dec 29, 2020

Moviemike

Discussion Starter · Nov 23, 2018

Some cold weather tips for better mpg.
Get the engine warmed up as soon as possible. Best mpg is at normal (or perhaps higher) operating temperature. With my old gen 2 and currently with my Civic, I'll often put the CVT in "S" to increase low speed rpm,. I'll often leave it there until the cold light goes out. I've noticed doing so gets me to higher mpg operation earlier in my morning drive. How to get more rpm's on a cold gen 3 I can only guess at. The benefit of doing this seems greater on the coldest mornings.

I've not found much that works for maintaining summer mpg while using the heater. It appears though that the heater fan, over time, puts an energy drain on the battery. So what I've been doing is manually, frequently turning the heat on and off. I'll turn the heat off when I have high driving need for battery power, and turn heat on when low driving need, or downhill battery charging situations. My comfort is worth paying a small mpg decrease.

Another idea which doesn't seem to do much, has been to turn the heater temperature knob to its lowest setting when engine is cold. This will cut/reduce the amount of radiator fluid diverted from the cooling system to run over the engine toward the heater fan. The idea here is to prevent the cold/cool radiator fluid from slowing the engines' warming-up process. When doing this I'll turn the heater temperature knob to its highest setting once the engine cold light goes out

All this has given small but measurable mpg improvements. But by far the biggest mpg improvement comes from extra air in the tires. Four to five pounds over the recommended pressure I've seen suggested. Two summers ago I spent an afternoon experimenting with different air pressures. I checked vehicle steering response at different speeds, and the vehicles' willingness to travel in a straight line at highway speeds. I found a sweet spot between too much air and my desire to get more air for highest mpg. I try to check and adjust tire pressures to my sweet spot once a month. I also avoid or drive slowly over bumps in the road, they get much harder with the extra air.

Together with uphill, downhill battery management, and traffic concerns, this turns driving into something more like piloting an airplane, or playing a video game, as my daughter puts it.

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KlumzyDriver

· #2 · Dec 23, 2018

Moviemike said:
Some cold weather tips for better mpg.

I've not found much that works for maintaining summer mpg while using the heater. It appears though that the heater fan, over time, puts an energy drain on the battery. So what I've been doing is manually, frequently turning the heat on and off. I'll turn the heat off when I have high driving need for battery power, and turn heat on when low driving need, or downhill battery charging situations. My comfort is worth paying a small mpg decrease.

Another idea which doesn't seem to do much, has been to turn the heater temperature knob to its lowest setting when engine is cold. This will cut/reduce the amount of radiator fluid diverted from the cooling system to run over the engine toward the heater fan. The idea here is to prevent the cold/cool radiator fluid from slowing the engines' warming-up process. When doing this I'll turn the heater temperature knob to its highest setting once the engine cold light goes out

Moviemike, I appreciate your many tips and follow many of them on getting best mileage. Your stats show you are doing something right! Since your post on managing the heater settings I have been experimenting and offer the following gen 3 specific observations-

I don't think cabin heat is generated through electrical resistance, so it's not the heater fan itself that impacts negatively gen 3 mileage, especially at lower fan RPM settings where a fan draws minimal power- instead it is the demand for heat itself that negatively affects mileage in certain situations. I have noticed, for example, that even if the engine is warmed up, but the cabin is not (following your advice to warm the engine first) the very act of then switching on the heat or turning up the cabin temperature will cause the engine to start running continuously (until cabin heater temperature set demand is satisfied). By turning on the heat in this situation this also means EV mode becomes not available, even when coasting, simply because the engine can now be running solely based on the temperature DEMAND to warm the cabin.

I think this different than gen 2 where the warmed engine was always engaged and therefore had hot water circulating 100% of the time and always available for the cabin heater demands, except when both the car and engine was stopped. Gen 3 does not have the engine running continuously. I try to maximize mileage by running in EV mode (engine not running) when practical and running the engine no more than necessary (again, following your tip). I think this indicates a different approach than what we did with gen 2 with respect to cabin heater management when we want maximum mileage.

I suggest if one is going to manage the cabin heat with trying to maximize mileage, the time to turn on cabin heat in a gen 3 would be 1) after the engine is warmed up from a cold start 2) turning on the heat when the engine is already running to power the car anyway; i.e; when the car has power needs that exceed what's available in EV mode one would be benefiting from getting "free" heat, since an already running warmed engine has to shed surplus heat anyway. This might mean, for example, turning on the cabin heat when ASCENDING a hill, NOT on when descending, at least until the cabin is warmed to the set temperature.

I'm far from an expert, but maybe this post will make others consider this approach or comment otherwise if offering a different theory.

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Moviemike

Discussion Starter · #3 · Dec 23, 2018

KlumzyDriver said:
I suggest if one is going to manage the cabin heat with trying to maximize mileage, the time to turn on cabin heat in a gen 3 would be 1) after the engine is warmed up from a cold start 2) turning on the heat when the engine is already running to power the car anyway; i.e; when the car has power needs that exceed what's available in EV mode one would be benefiting from getting "free" heat, since an already running warmed engine has to shed surplus heat anyway. This might mean, for example, turning on the cabin heat when ASCENDING a hill, NOT on when descending, at least until the cabin is warmed to the set temperature.

I really like your theory! Particularly point #2 above. :wink:

Moviemike

Discussion Starter · #4 · Dec 26, 2018

A Final Cold Weather mpg tip

Sunshine!!

When possible park the car in the sun. The sun will not only warm the interior, leading to less heater use. It will also reduce the cold under the hood, leading to faster engine warm-up and top mpg performance sooner.

This idea came up awhile back at InsightCentral.net. I initially thought the impact would be too small to notice an effect, but I was wrong, it does. My driveway runs East-West. To catch the sunrise I parked the car near the East edge. Cloudiness, overcast, showers is normal weather in Oregon. On those rare sunny mornings when my car is parked out of the shadow of nearby houses, the cold light will go out sooner, and full electric operation is sooner as well. I haven't looked at the mpg impact, but it could be 0.25 - 0.5 mpg improvement on the day's mpg, ....perhaps more.

CommonSenseAl

· #5 · Mar 28, 2019

I don't like turning on the car and then the gas engine starts right up because the AC/heating system is on.

Is there any option to leave the AC/heating system OFF when you start the car instead of returning to the last setting?

insightfully

· #6 · Mar 28, 2019

CommonSenseAl said:
I don't like turning on the car and then the gas engine starts right up because the AC/heating system is on.

Is there any option to leave the AC/heating system OFF when you start the car instead of returning to the last setting?

To leave the AC/heating/radio off before starting the car, I think you'll need to turn those off when you shut the car down. @andrew28 mentions no music or heater on at start in this post, so it's possible to manage with some pre-planning.

I kind of view it differently, coming from an older car. While it's not optimal for mpg, I prefer to have the engine come on to give it some warm-up time while not under a driving load. (This is usually ~30 sec while I wait for garage door to close and I check surrounding mirrors.) The high voltage battery also charges up a little before my drive, while the engine runs.

elvin

· #7 · Apr 1, 2019

It would seem from my experience so far, to best start with climate control off (needing to remember to turn it off before you power off) since it seems more than often (at least in the early spring/late winter) that leaving it on almost immediately kicks the ICE on.

I think the tips I've gathered so far, is to delay turning on the climate control until you hear the ICE kick on for other reasons. And still at that point, you could keep demand on the system low, by setting AC to off, and temperature closest to ambient as comfortable (58 deg when it's cold outside, since LO would ramp up the fan). Otherwise, there's no temp gauge to tell you when the ICE is warmed up to minimize electric heating demand.

If it is terribly cold (and it'd have to get pretty bad), it seems like turning on the seat warmers a bit seems to provide enough heat for comfort without a big drain kicking on the ICE. I find that even on the lowest setting for a little while (then turning it off) goes a long way to making things comfortable even if climate control remains off.

It seems from what I've read in the forum so far is that AC in the summer will not kick on ICE as aggressively (I haven't experienced a hot season yet with my Insight) but the strategy might be, operate with the windows open to cool the car down first, and similarly close things up and turn on the climate control once you hear the ICE kick in.

I know there's probably little MPG savings gained by gaming the HVAC this way, but it seems to help keep the car quiet at least during the start of a drive. Any other tips to add?

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andrew28

· #8 · Apr 1, 2019 (Edited)

elvin said:
It would seem from my experience so far, to best start with climate control off (needing to remember to turn it off before you power off) since it seems more than often (at least in the early spring/late winter) that leaving it on almost immediately kicks the ICE on.

I think the tips I've gathered so far, is to delay turning on the climate control until you hear the ICE kick on for other reasons. And still at that point, you could keep demand on the system low, by setting AC to off, and temperature closest to ambient as comfortable (58 deg when it's cold outside, since LO would ramp up the fan). Otherwise, there's no temp gauge to tell you when the ICE is warmed up to minimize electric heating demand.

If it is terribly cold (and it'd have to get pretty bad), it seems like turning on the seat warmers a bit seems to provide enough heat for comfort without a big drain kicking on the ICE. I find that even on the lowest setting for a little while (then turning it off) goes a long way to making things comfortable even if climate control remains off.

It seems from what I've read in the forum so far is that AC in the summer will not kick on ICE as aggressively (I haven't experienced a hot season yet with my Insight) but the strategy might be, operate with the windows open to cool the car down first, and similarly close things up and turn on the climate control once you hear the ICE kick in.

I know there's probably little MPG savings gained by gaming the HVAC this way, but it seems to help keep the car quiet at least during the start of a drive. Any other tips to add?

I make sure my hvac is off before turning off the car. When I start it up the next time, it will be in EV mode, and I get to drive it down my street quietly before it kicks on the gas generator as I'm entering the main street. I agree it would be nice to have an engine temperature gauge.

I have an EX so no seat warmers but my old ford fusion did. The seats always heated up quicker and it was comfortable enough that I left the air vent heat off. For the Insight I do the following depending on how cold it is...

If it is just cold, I can drive without the heat.
If it is really cold, I will drive 2-3 miles before turning on the heat. Once it gets comfortable I will turn it off.
If it is unbearably cold, I would had remote started the car, and left it on for the whole trip.

Based on my brief experience in warmer weather with the AC on. (60F-70F outside temp) It didn't seem to impact my fuel economy as much as having the heater on. I would most likely do the same and let the car air out before starting the AC in the summer. This is my first summer with the car so looking forward to see how different it is compared to the winter. :smile:

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andrew28

· #9 · Aug 22, 2019

mgldan said:
At the time I bought it I told myself that I’d use it in the summer to cool down the car. But even with my black leather interior, I find that a few seconds of AC is (personally) enough, so I don’t remote start over the summer either. I don’t need the entire car to be cool to find it driveworthy.

It probably helps that I’m in the driver's seat. Backseat passengers don’t have vents.

The winter is a totally different story.

The AC works so well and quick that I don't need to remote start the Insight during the summer except when I have passengers in the back.

pasei

· #10 · Oct 28, 2020

Took out my car and my OBD reader for a ride with 50°F and I found something quite interesting... When the engine is on solely for the purpose of heating, for instance at a red light, it does NOT charge the battery at the same time (a.k.a. the battery amps are 0). That is true most of the time, although in the initial start up of the car, it charges the battery for a few minutes but even there, it actually stopped the charge (but kept spinning) even before reaching 130°F coolant.

However: when it spins for heat only, the fuel rate at idle is less than the fuel rate at idle when it actually charges. Something like 75% less. Which makes sense since the generator is disconnected.

So I suppose the take away is really wait until the engine is warm if you wish to use the heater? If you want to hypermile of course... not sure I'm gonna sacrifice the little comfort left in 2020

(just kidding, I will).

Mobilcams

· #11 · Oct 28, 2020

pasei said:
Took out my car and my OBD reader for a ride with 50°F and I found something quite interesting... When the engine is on solely for the purpose of heating, for instance at a red light, it does NOT charge the battery at the same time (a.k.a. the battery amps are 0). That is true most of the time, although in the initial start up of the car, it charges the battery for a few minutes but even there, it actually stopped the charge (but kept spinning) even before reaching 130°F coolant.

However: when it spins for heat only, the fuel rate at idle is less than the fuel rate at idle when it actually charges. Something like 75% less. Which makes sense since the generator is disconnected.

So I suppose the take away is really wait until the engine is warm if you wish to use the heater? If you want to hypermile of course... not sure I'm gonna sacrifice the little comfort left in 2020 (just kidding, I will).

I've noticed even in warmer weather, when the system is first started in the morning - it seems to not charge the battery and actually seems to take more energy than usual from the batteries during acceleration (the engine doesn't seem to rev up to generate electricity readily). It's like the system is taking it easy on the engine during initial warm up. Another thing I have also noticed is my Insight likes to charge the battery up to 80 percent and hold it there for a few minutes even at an even speed before it goes to EV mode. It actually won't go into EV mode even when you try to force it at these times (even though the engine IS warmed up). It will simply say EV mode not available. The systems in these cars are very interesting. I wish we had a full whitepaper on all the different modes and scenarios that tell us what the system is doing and why.

pasei

· #12 · Oct 28, 2020

Mobilcams said:
I've noticed even in warmer weather, when the system is first started in the morning - it seems to not charge the battery and actually seems to take more energy than usual from the batteries during acceleration (the engine doesn't seem to rev up to generate electricity readily). It's like the system is taking it easy on the engine during initial warm up. Another thing I have also noticed is my Insight likes to charge the battery up to 80 percent and hold it there for a few minutes even at an even speed before it goes to EV mode. It actually won't go into EV mode even when you try to force it at these times (even though the engine IS warmed up). It will simply say EV mode not available. The systems in these cars are very interesting. I wish we had a full whitepaper on all the different modes and scenarios that tell us what the system is doing and why.

Exactly, for the warm up I had observed the same thing: Warm Up Engine for Better MPG?
It does prefer to tap into the battery rather than rev up during the warm up, probably to save the engine's life. Smart guys at Honda!

For the second behavior, I have not noticed exactly the same but I noticed the charge level is quite random at times. Maybe to keep all the cells cycling every so often?

insightfully

· #13 · Oct 29, 2020

Mobilcams said:
Another thing I have also noticed is my Insight likes to charge the battery up to 80 percent and hold it there for a few minutes even at an even speed before it goes to EV mode. It actually won't go into EV mode even when you try to force it at these times (even though the engine IS warmed up). It will simply say EV mode not available.

Speed <40 mph -or- maintaining a consistent speed at low throttle while >40 mph is what it seems to take for my car to switch to EV mode... even while going downhill.

The systems in these cars are very interesting. I wish we had a full whitepaper on all the different modes and scenarios that tell us what the system is doing and why.

Definitely would be awesome to have the algorithms for the Gen3 Insight documented in the way the Prius does! But even the detailed Prius version is based on empirical observation.

hasarad

· #14 · Dec 21, 2020

pasei said:
Sounds about right!. I am also still wondering if actually turning on the heater can be beneficial for long drive as it heats the battery through the cabin. I think this has been discussed somewhere in this forum.

It does. There's a trick though. Wait a bit for the engine to warm normally before kicking in the heat. Start at a low temp so it doesn't force ICE to run, and gradually raise it a degree every few minutes. It's like a game to keep the ICE from forcing to kick in. It takes a while to get the feel, but it works. I can still pull 60s drives in the winter.

pasei

· #15 · Dec 21, 2020

hasarad said:
It does. There's a trick though. Wait a bit for the engine to warm normally before kicking in the heat. Start at a low temp so it doesn't force ICE to run, and gradually raise it a degree every few minutes. It's like a game to keep the ICE from forcing to kick in. It takes a while to get the feel, but it works. I can still pull 60s drives in the winter.

So what I do is I just keep it off until my OBD reader tells me the coolant is like at 150° or more!

But my real question was, once the engine is piping hot, let's say 180° on the highway, and you're OK with the seat warmers even though it's pretty cold in the cabin. SHOULD WE turn on the heat (0 impact on mpg at this point) to warm up the batteries to have a better mpg?

andrew28

· #16 · Dec 21, 2020

I turn on the heater immediately and set it to 65F auto. Not worth freezing to get above 50mpg when gas is cheap. 🥶 I'm still averaging 47mpg per tank. On trips farther than 10 miles I always get above 45mpg. Like tonight my trip from Saugus to Boston(12 miles) in the rain I got 50.3mpg with outside temps in the low 30s.

insightfully

· #17 · Dec 21, 2020

pasei said:
But my real question was, once the engine is piping hot, let's say 180° on the highway, and you're OK with the seat warmers even though it's pretty cold in the cabin. SHOULD WE turn on the heat (0 impact on mpg at this point) to warm up the batteries to have a better mpg?

The HV battery operates best >59F and is 'happiest' at <68F... so my vote is to turn on the heat (or at least crank up the passive heating) if the cabin temperature is cooler than 59F, to help get the most out of HV battery dis/charging cycles. This would have the most helpful mpg effect on longer drives though; on shorter drives, the heat spent on warming the cabin and the number of HV battery cycles you could get would be a lower return.

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pasei

· #18 · Dec 21, 2020

andrew28 said:
I turn on the heater immediately and set it to 65F auto. Not worth freezing to get above 50mpg when gas is cheap. 🥶 I'm still averaging 47mpg per tank. On trips farther than 10 miles I always get above 45mpg. Like tonight my trip from Saugus to Boston(12 miles) in the rain I got 50.3mpg with outside temps in the low 30s.

Nice! I'm blaming the Conti tires for the differences in mpg because I think I got the hypermiling techniques semi-mastered haha. I also like to let the engine get up to temp to reduce wear, but that's my OCD side.

insightfully said:
The HV battery operates best >59F and is 'happiest' at <68F... so my vote is to turn on the heat (or at least crank up the passive heating) if the cabin temperature is cooler than 59F, to help get the most out of HV battery dis/charging cycles. This would have the most helpful mpg effect on longer drives though; on shorter drives, the heat spent on warming the cabin and the number of HV battery cycles you could get would be a lower return.

Exactly what I was looking for thanks! If only the OBD could report battery temp

I also wonder if the HV battery heats up a lot after a few regen brakings or not much.

insightfully

· #19 · Dec 21, 2020

pasei said:
Exactly what I was looking for thanks! If only the OBD could report battery temp I also wonder if the HV battery heats up a lot after a few regen brakings or not much.

Thinking of the analogy to charging my Li-Ion cell phone battery, it does get warmer as it gets charged. Would make sense that the HV battery also picks up heat from being re-charged... but without a way to measure, hard to say how much the temperature increases. Maybe a distant/indirect way to measure would be a temperature probe stuck into the rear battery vent area (?).

Reactions: 1

hasarad

· #20 · Dec 21, 2020

pasei said:
So what I do is I just keep it off until my OBD reader tells me the coolant is like at 150° or more!

The ICE will continue to run regardless of engine temperature when there is a significant amount of difference between the set temp and current cabin temp. That's why I creep the setting up as the car warms. It would be nice to not have the ICE forced on automatically when cabin temp is set high. We all know the engine will get hot enough eventually to do the job without running constantly.

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