Use flow though ventilation to limit air conditioning use?

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#1
We will be selling our TDI diesel back to VW soon and hopefully taking delivery of the currently shipping Model 3 by the end of Sept.. Our TDI Sportwagen with aftermarket window tint uses between 8 to 10% more fuel when running the air conditioner. When traveling by myself, I lay the windshield sun shade light grey side up on top of the fairly large black dashboard. Doing this dramatically reduces the interior reflected heat and reduces the temperature of the air coming from the vents while venting outside air though the open sun roof. I use the pop up mode of the sun roof which does not seem to increase drag or the sound level much. While driving in a areas with low humidity with outside temps below 80F, I am very comfortable using this method. In very cold weather the TDI fuel mileage is not effected after the engine reaches operating temperature. From what I have read, there are some things one can do to slightly improve cold weather model 3 efficiency (which can take quite a hit!) but would a flow though ventilation method work on a model 3 at temps below 80F? Since the model 3 doesn't have an opening sun roof, is there enough air flow while using the vent fan to keep the interior temp comfortable with outside temps below 80F?

Regards. Ron
 
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Rich M

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#2
When the climate is switched off, I haven't noticed any air flowing through. When it's comfortable enough to leave climate off I open both passenger windows about 2". This gives a nice whirlwind flow in the cabin.
 
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#3
When the climate is switched off, I haven't noticed any air flowing through. When it's comfortable enough to leave climate off I open both passenger windows about 2". This gives a nice whirlwind flow in the cabin.
Rich

Thanks for the reply! Never thought to ask if the Model 3 even had any kind of flow though ventilation (every ICE vehicle I have ever owned had a outside air vent mode). I have read that rolling down the windows on a very aerodynamic car traveling above 40mph would use as much or more fuel (electrons) than using the AC.
 

DXF

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#4
I have read that rolling down the windows on a very aerodynamic car traveling above 40mph would use as much or more fuel (electrons) than using the AC.
Yes, that's why I don't bother roll down windows unless I'm cruising low & slow. :p

I do NOT have a Tesla yet but I've found that, having installed high quality ceramic on sides & back of our Bolt has made a lot of difference here in the TX heat. We'll see come July-August but so far I've found that I don't need AC at all until high-80s, and then only sporadically. You can simulate it by manual setting recirculation to the face and bumping the fan a bit. Once it nears 90F I'll occasionally run the AC to take the edge off and then return to fan-only.

Although Tesla's controls do change with patches, I've seen via video reviews that it does have these manual mode options at some point and it's unlikely that Tesla would take such options away. The dash vent, which I've heard nothing but raves about, should ensure this is a very viable option (unless you're of that percentage of the population that has difficulty with higher temps or you live on the surface of the sun, AKA Arizona or such). I'll love to hear confirmation (or correction) from firsthand info but that's the assumption I've been running with.

In any event, the drain on range from A/C use is a lot less than running the heater (electric resistor heating in notorious for energy usage), so it not something to worry about much an unless you are really stretching the range or are trying to "supermile". It'll cost you maybe 10%-15% range to use it a lot, lower with a quality heat blocking tint job.
 

Rich M

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#5
I doubt opening two of the windows 2 inches is going to create any noticeable drag under 65 at least.
 

garsh

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I doubt opening two of the windows 2 inches is going to create any noticeable drag under 65 at least.
Yeah, all of those studies about how AC is more efficient than opening the windows are usually opening all of the windows the maximum amount. If you just open a couple windows part-way, you'll be pretty efficient.

If you open just a single window, you'll end up with an annoying buffeting resonance in any of today's aerodynamic cars. So you usually want to crack at least two of them open to prevent that.
 

DXF

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#7
I've tried the "crack" thing a few times. The thing is without substantial wind coming in the window you're potentially only just heating up the air in the car, and you're not getting airflow where it'll help your body do it's natural thing for you to feel cooler.
 

garsh

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I've tried the "crack" thing a few times. The thing is without substantial wind coming in the window you're potentially only just heating up the air in the car, and you're not getting airflow where it'll help your body do it's natural thing for you to feel cooler.
I usually open the driver's window about half-way, along with the rear passenger-side window less than halfway. That usually gets enough air hitting me to help. But of course, I haven't tried that with a Model 3 yet.
 

DXF

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I just noticed rrolsbe is in NM (I assume it's that Albuquerque). Pittsburgh PA is an entirely different world from this.
 

DXF

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Oh goodness. Yes, just use AC in New Mexico. The power draw is minimal - it's not worth worrying about in a Model 3.
It's similar to local here.

The internal circulation method can get him out of most A/C usage until at least the end Summer towards the end June when OMGOMGWTFDidIMoveHere season starts. :p Even then, manually keeping the fan up is going to noticeably drop the A/C demand. ((And opening a window will only make it worse, as he'll basically be in a convection oven that'll sap away his energy.))

P.S. It also kinda depends on what he keeps his A/C set on at home/work, what he's used to.
 

PNWmisty

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The great thing about electric cars is the firewall doesn't become heat soaked like it does in ICE cars. That hot firewall is responsible for much of the A/C cooling load. ICE engines radiate a lot of heat!

I don't understand some Model 3 owners reluctance to use the A/C to get a little cool air to the cabin. All existing Model 3's are rated over 300 miles. As long as you don't overdo it, it doesn't take much electricity. The A/C compressor is run by a high-efficiency variable speed electric motor and the system works a lot more efficiently than the one in an ICE vehicle due to always running at optimal compressor speed and the fact that the refrigeration lines are not running through a hot engine bay. And that it takes a lot less cool air to keep the cabin comfortable due to the lack of radiated and conducted engine heat.

I hate being uncomfortable, sticky and hot which is one reason I'm loving the Model 3 so much. Pre-cool for 3 minutes before I drive, get in a cool, comfy car and drive off with the fan keeping a nice cool breeze going.
 

DXF

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#13
I don't understand some Model 3 owners reluctance to use the A/C to get a little cool air to the cabin.
10%-15% of range is still 10%-15%. :p

It depends on how into the "it's a game to see how far we can/how low we can get the Wh/m number" the driver is. *shrug*

The thing about having such amazingly efficient engines and aerodynamic body shapes along with accurate, immediate energy usage stats is relatively small amounts of energy that were difficult to notice much less quantify become much more notable amounts. So now you've got a choice on what you want to do with that, if you want to act on it or disregard it and "not enough to matter".

Same thing with driving speed. And how much of that range you have need for, too, in your given circumstances.
 

DXF

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BigBri

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#16
Not had any 35C days yet but the AC is the 3 is excellent. My Leaf on Auto will run at top fan speed for 5 minutes and then the cabin tends to be comfortable. The 3 its damn near instantly comfortable even when the cabin is very hot. The fan hits 4 or 5 for a minute and drops down to be barely audible.
 

garsh

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#17
When, in April in PA? LOL
We get these things called "seasons" in Western PA. We get strong swings in temperature from one part of the year to another. Temps go up to the 90s and 100s in the summer.

One of the posters in that thread you linked said that the Model S AC uses 2kW. Wow! The AC on my Leaf will start off at about 400W when first turned on in hot weather, but once the car has cooled down, steady-state usage is around 100W.

Hopefully the Model 3 AC is more efficient than the version in the Model S.
 

DXF

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#18
We get these things called "seasons" in Western PA. We get strong swings in temperature from one part of the year to another. Temps go up to the 90s and 100s in the summer.

One of the posters in that thread you linked said that the Model S AC uses 2kW. Wow! The AC on my Leaf will start off at about 400W when first turned on in hot weather, but once the car has cooled down, steady-state usage is around 100W.

Hopefully the Model 3 AC is more efficient than the version in the Model S.
The 2kW rating is maximum output, it doesn't really speak about efficiency at all. BigBrl mentions the Leaf is much slower to cool the cabin.. Although the M3's better venting likely helps immensely on perception (thus the basis for my suggestions), that's an obvious reflection of having a lower top-end output.

Even when ambient air temps are comparable, PA is at a higher latitude. You simple have to fight more solar radiation, coming through the windows at the least but also beat down on the vehicle in general, further South. Expectation of %1 on range in the summer is not going to be realistic. As I said, not sure what's going on with what you're reporting on the Leaf. *shrug*
 

DXF

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Well, that depends on where in "TX" you are. Albuquerque is probably much like Fort Davis, not so much like Houston. Relative humidity makes a big difference which, being relative, varies a lot from place to place and from day to day.
I'm inland a ways from the Gulf (not Houston proper) and regularly travel further, though usually not as far as any definition of 'West Texas' that I'm aware of? True though that Albuquerque sees far, far less humid days than me (and you, I expect, in DFW). That can certainly lower his A/C demands in the evening, and to some extent during the day for the same temps, as he'll get cooling at night over there that I don't see even in relatively dry times. The sun radiance factor though matters a good deal, and he'll be very similar to us (why tinting is so important).