Love letter about Windows - Kia Niro Forum
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post #1 of 26 (permalink) Old 06-09-2019, 10:52 PM Thread Starter
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Cool Love letter about Windows

So delighted that I can open the front an/or back windows at road speeds with no buffeting! I realized that I was driving 50 with the windows still down an inch or two from parking and started to grin. I played with them at various speeds and could only get a small amount of discomfort with only back passenger barely open while running AC and fan at max. Yes, most of the time I will still use just AC, but I love knowing I have a choice of putting my windows down!
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post #2 of 26 (permalink) Old 06-10-2019, 09:13 AM
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There are certain combinations of window openings that can cause those unpleasant standing waves but this car is not as extreme as many cars.

It takes really hot weather for me to use AC so I have my windows open a lot. The thing for me is to optimize the ventilation and keeping the noise level as low as possible. Even after a year of ownership, this still takes some experimentation with how much to crack each windo - I'm assuming because of outside wind direction and magnitude.

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post #3 of 26 (permalink) Old 06-10-2019, 11:55 AM
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I have a different take on this.



Having a window open will affect the aerodynamics of the car. If you have air circulating into the car while driving then you will be changing the drag coefficient as air is now taking a different path. This will affect the efficiency that the car will drive at.


In a gasoline-only car, the A/C unit pulls power away from the engine to drive a compressor. This reduction in HP results in the engine requiring to rev higher to produce additional power and in turn uses up more fuel. However, the NIRO does not have the A/C running on a pully off the engine. it is pure electric. An electric motor is 100% efficient compared to the average engine that is more around the 30-35%. So although we in an HEV do use the ICE to supplement drive and recharge the battery, as a whole the A/C is far more efficient in the system as a whole. Compound that with by keeping the windows up, I am also not losing drive efficiency through reduced aerodynamics. I will have windows down when driving in a subdivision at 40-50kph (25-30mph) as the impact of aerodynamics on the car is not as great at these speeds as when you are driving at highway.
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post #4 of 26 (permalink) Old 06-10-2019, 02:49 PM
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If you have a small child, as do I, you know that opening ONE rear window does indeed cause buffeting and it is VERY annoying. Thank goodness for the window lock button!!

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post #5 of 26 (permalink) Old 06-10-2019, 04:53 PM
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Quote:
Originally Posted by Roadkill401 View Post
So although we in an HEV do use the ICE to supplement drive and recharge the battery, as a whole the A/C is far more efficient in the system as a whole. Compound that with by keeping the windows up, I am also not losing drive efficiency through reduced aerodynamics.
As far as I know, this is a complete old wive's tale. I get the logic which no doubt drives this narrative, but it appears to be wrong. In my ICE car, the difference between windows open driving, and windows closed driving was about a 3 mpg hit to efficiency (over 10%). That's my anecdote and certainly the Niro AC is more efficient than that, but here is a test in a Tesla (which also has an electrically driven standard AC (not a heat pump)) by someone who believed the same thing. Bjørn Nyland is a Norway based YouTube star who is all about EV cars. Tends to have very long videos but this one is pretty short. Listen to the first few minutes and the last few if you need to save ten minutes.

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post #6 of 26 (permalink) Old 06-10-2019, 05:05 PM
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From the information I've received over the years, the break-point between windows down and running the A/C is 40-50 MPH. Below that, the aerodynamic change isn't enough to overweigh the MPG hit. Over that speed, then it's more economical with the windows up and the A/C on. Of course, this is all based on a gas-only car.

But for me, it's far more a comfort issue. I hate the noise and buffeting that I get even at speeds of 30 MPH. I have always accepted the slight loss of MPG for a higher level of comfort. As I approach my golden years (actually already residing there!) I place an even higher value on comfort over a slight increase in cost per mile. Driving under EV power, I greatly enjoy the quiet.

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post #7 of 26 (permalink) Old 06-10-2019, 08:22 PM
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Yup, that is how old wive's tales work, repeated over many years. Repetition doesn't make it true. Certainly drive your car in a manner suiting yourself for comfort. Comfort is your rationale, not efficiency.

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post #8 of 26 (permalink) Old 06-10-2019, 09:51 PM
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Yup, that is how old wive's tales work, repeated over many years. Repetition doesn't make it true. Certainly drive your car in a manner suiting yourself for comfort. Comfort is your rationale, not efficiency.

Where the test in the video was a part let down was that that the internal temperature inside the car was totally different. So he had the A/C turned on and got the temperature down to 23c where during the other two the temperature is at 28 and 27c. The second the third test was purely rather than having the car cooler, has a higher amount of air moving around inside the car. Now I would like to see if instead of setting the A/C to 20 and it running full time on the compressor and never actually getting down to that desired temp, if he would have done the same run with the A/C set to 26 (as that was the temp he said was comfortable with the fan set to 7 so you get the cooling effect of just air moving past your body. This way the A/C is only maintaining a comfortable temp and not running full time un-needed.




Also.. Please re-read what I posted. Your video linked I believe did show that there was a loss of efficiency between driving with the windows up and the fan blasting away, and driving with the windows rolled down 10cm. So YES you do loose aerodynamic efficiency. As well, I stated that in an ICE ONLY car the A/C is pulling the power off the engine. In the NIRO HEV it is electric so the A/C is more efficient compared to ... the ICE ONLY CAR. So how does what someone testing in a BEV have to do with anything? There is no ICE motor inside that vehicle at all. I bought my Niro Hybrid to replace a Gas Guzzling Crossover car. I didn't buy a Niro PHEV and clearly, I did not buy a Tesla or a Leaf or an E-Pace or any other type of BEV. I got a NIRO HEV.


The video went and tested the temp inside the car and it was a good 4-5deg difference. And he also stated that it was nice and quiet inside the car. Then you get to compare this with a car with windows wound down that is not only hotter (actual temp) but also much noisier. Yes with the setting chosen the A/C did use more power to run but how much more is it inside the Niro HEV?, and compare that to a similar size ICE only vehicle and what impact does that have on the fuel consumption?


I don't have the numbers, but if running the A/C in the Niro reduces my fuel efficiency by <5% I am not going to bat an eyelash at it, as I would rather have actual cool and none of the noise. (Heck, I have about 25-40% fuel efficiency loss running the heater and defogger in winter time for my comfort.) But all this is nothing compared to the on average 20% loss you get running an A/C inside an ICE car that is also multiple times more compounded with the fuel efficiency difference between my Niro Hybrid vs most every other comparable gas engines ICE car.



In your video test, you have a choice of getting 3.4% worse electric economy to get a cooler car with much less noise. I think I will take that any day at highway speeds. But everyones priorities will very depending on their wants.
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Last edited by Roadkill401; 06-10-2019 at 09:59 PM.
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post #9 of 26 (permalink) Old 06-11-2019, 09:21 AM
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Not sure of your point here. Yes, Bjørn preferred the AC for comfort as do you. Fine, as I said. No, it is not as efficient as windows open. I also said the Niro has a more efficient AC than most ICE cars, including mine. As far as I can tell, you agree with me, and him.

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post #10 of 26 (permalink) Old 06-11-2019, 10:10 AM
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I had to take some smelly stuff to the garbage transfer station yesterday, so had a window down. I found the buffeting/roaring with a rear window down to be as bad as any other car I've owned, and with a front window down it just wasn't a comfortable drive. And this was never exceeding 45 MPH, and in most cases less than 40. Windows up for me as much as possible.

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