[nd4z]

I am on a extended vacation in the Noth East for the last few months.
I am new to Insight driving for max MPG. I am on a constant learning curve. I did not take me long to figure out that to achive great milage per gallon, it requires lots of monitoring the inst. bar graph on the bottom of the display, and try and keep it as high as possible at all times. I am finding out that this is not as easy as it may seem. Since the weeather in the North East has been hotter than the last 50 years, it is very hard to drive with no Air Cond. running. I find that the little 1 liter engine has to give up a lot of its H. P. to run the A.C. compresser. This was cutting my gas milage to 57 MPG on interstate long trips. I tried running with Ecno mode fan only, with fan on max with windows closed. I was under the impression that with both windows wide open, the wind drag coming into the cabin of the car would ruin the drag coef. and there fore kill the gas milage. I tred the spray bottle of ice water and spritzing my fore head as some due on this site to keep cool. That, does not go over too well with the wife and her little Poodle dog. So on my last trip on the interstate from Syracuse, NY to Wilkes Barre, Pa. I opened both windows wide open.
Made the 140 mile trip with avg milage of 73 MPG. This was with my 2000 Insight,5 speed, overloaded. My wife,dog and myself our over the 360 lb limit. Not to mention all of our suitecases. I set the tire pressure to 50 PSI on all tires. At times on hills I was all the way down to 38 MPH. Ran my battery pack down to nothing several times on long hills, but it alaways managed to charge back up to full state. My point is that: It seems to me that gas milage is better by far, riding with open windows, than closed windows with AC on. I would like to get comments pro or con from this forum. I seem to get a lot of angry drivers, who have a problem with me going too slow for them. Some I would consider almost road rage. Blowing there horns, blinking lights, yelling, and in one case the single digit hand signal. This really upsets my wife. But all I do is give them a stupid smile as I wave at them. I think this upsets the Road Raged drivers even more. My experience so far tells me this: The Insight does not like A.C. ,up and down steep hills and high speed driving to get high MPG.
Seems like some drivers of big SUV's have a problem with small cars and saving gas. All the ones who blew the horn had no reson to, since I was way over to the right and they had pleanty of room to pass. They seem to just like to make noise against people saving gas.
I will keep you all posted, as I keep on truckin.
Thanks for a great Forum, that I totallyy enjoy reading.
Rick & :lol: Phyllis

 

[ethicalpaul]

Great post and great test, Rick-

Those mythbuster guys went up against that old tale about how using AC should result in higher mileage than having the windows open due to drag, and they busted it pretty good.

They ran cars around a track, one of them with AC and one with the windows open. The one with windows open was able to drive significantly further on the same amount of fuel.

they did use SUVs I think which probably wasn't the best choice for the test, but I think your test shows us that windows open is the more fuel efficient way to go for the insight too.

 

[iibbmm]

as much as I hate when people yell at me for going slow, I know it's my fault. If the traffic is moving at 60mph, and I'm going 45mpg just for the sake of economy, I'm the one being a jerk, and I will speed up if there is someone behind me.

Sure, they may be expressing their irritation in the wrong way, but if you are holding back traffic MERELY for the sake of higher mpg, you are doing something wrong.

 

[jbrasure]

Great post and great test, Rick-
Those mythbuster guys went up against that old tale about how using AC should result in higher mileage than having the windows open due to drag, and they busted it pretty good.

I sure love Mythbusters. It's one of my favorite shows on TV. However, I wonder if their test applies to the Insight. It's such a different beast compared to the SUV used in the Mythbusters test.

In my own tests, I seem to be getting better mileage with the AC off and the windows down. If I leave the AC on, then I get 52 MPG on the way home (in my CVT Insight). However, if I open the windows about 4 inches on each side, and turn off the AC, then I get about 57 MPG.

I've only tested this twice, so this could easily be due to wind conditions. I'll keep testing and post my results after a month or so.

 

[ethicalpaul]

as much as I hate when people yell at me for going slow, I know it's my fault. If the traffic is moving at 60mph, and I'm going 45mpg just for the sake of economy, I'm the one being a jerk, and I will speed up if there is someone behind me.

Sure, they may be expressing their irritation in the wrong way, but if you are holding back traffic MERELY for the sake of higher mpg, you are doing something wrong.

I would argue that they are the ones doing something wrong (driving fast for no good reason).

In my state of Michigan, I can go from 45 to 70 on the interstate. Where I choose in that range is up to me and me alone.

My boss told me once that his philosophy was to try to never inconvenience another driver. If that means going 75-80 so that fewer people have to pass me (one might call it 'driving with the flow of traffic'), I'm not playing.

I drive 65 in my diesel beetle because:

- it seems to get the same mileage anywhere in the range of 60-70 anyway
- I like 65 because I almost never have to pass anyone
- There is no instantaneous MPG display so I can't tell my mileage at any given time

But if and when I get my tax-break 2006 Insight (if they are going to make them), I will be working hard to maximize my mpg, rest of traffic be damned. My belief is that I will be doing things "right" and the rest of them are "wrong" so why should I do it their way??

 

[james]

"I wonder if their test applies to the Insight. It's such a different beast..."

If anything, the Insight should show a bigger difference, since the AC requires a much larger fraction of available power.

I've tried a similar test. There's a fairly steep 10 mile downgrade that I drive frequently. With windows up and AC off, I maintain about 60 mph in fuel cutoff mode. With windows down, I don't see any difference. Switch the AC on, and there's a 5-10 mph drop.

 

[Resist]

I seem to get a lot of angry drivers, who have a problem with me going too slow for them. Some I would consider almost road rage. Blowing there horns, blinking lights, yelling, and in one case the single digit hand signal.

Please don't go so slow as to jeopardize the safety of others by slowing the flow of traffic. And don't give anti-hybrid drivers a reason to say Hybrid cars are to slow for the road.

I think the myth of open windows with no A/C vers closed windows with A/C on was true back in the day of poorly designed vehicle aerodynamics. But since vehicle designs have improved over the years an open window doesn't drag a car down as much as the power and mpg loss from A/C. But when all A/C units go electric, you will see this change.

 

[Dougie]

"Switch the AC on, and there's a 5-10 mph drop."

But think about how the A/C system works. There's a compressor and a pressure valve, so when you first turn on the system the compressor runs continuously to build up pressure. Then, after the system has stabilized, the compressor only runs when the pressure gets below some point.

So it's a complicated balance between a bunch of factors. To do a comprehensive test you'd have to compare the effective (wind chill) temperature with the windows open with the effective temperature with the A/C, and the test would have to be over a long enough time for everything to stabilize.

I'm not saying whether one or the other is better, just that it's very hard to do a good test of something like this...

 

[Calpod]

James wrote:

I maintain about 60 mph in fuel cutoff mode.

If you want to be more efficient don't use "Fuel cut mode". all you are doing is using the engine as a brake, you will be more efficient keeping your foot on the gas where is closest to 150 and then use the AC.

These last 2 weeks we have had temperatures of about 100 here in the LA area, and I was able to still be in the high 80's or 90's.

If you want to use AC you have to give up something, it will be mileage, charging or speed, it's your choice.

But most important, keep your foot on the gas, (Just don't get in an accident) if ever so slightly, you'll see the difference.

 

[Resist]

It's better to use the A/C going down hills and on level roads. Then turning it off for going up hills or when you accelerate.

But the worst thing to do is have your tires over inflated to a cold psi of 50, while your vehicle is over its weight limit on a hot day.

 

[The Citrus Smoothie]

I once saw an article that quoted a 4% reduction in MPG for driving along in a saloon with all four windows open. Therefore, as a very rough rule of thumb, you would expect to see a 1% reduction driving along with one window open - may be less with reduced buffeting and Insight design, so call it 0.5%. Definitely more efficient than the 5 MPG drop seen on 60 MPG Insights with A/C on - what's that? 8%?

 

[Aaron Cake]

In the Insight, having the A/C on can mean that lean burn isn't available at speed. Obviously, this means a drastic reduction in mileage. I have not experienced this myself, since my A/C has never even been switched on. I drive with my windows open, and have noticed no mileage change vs. when the windows are closed.

As far as driving 40MPH on the freeway, that's just rude and unsafe. If you want to drive that slowly (hell, I drive 40 MPH in town) please take secondary highways and don't risk the lives of others to save some gas.

 

[Insightful Trekker]

<snip>

So it's a complicated balance between a bunch of factors.
<snip>

Your correct Dougie. To get an accurate number as far as a loss for A/C on vs. windows open you'd have to be able to isloate many secondary factors. However the loss is so great that the MPG meter says it all :!:

FYI:

In a Honda A/C system the compressor merely cycles in response to evap temp which is used to prevent evap freexe-up. Yes, several other manufacturers use the pressure cycling system since evap temp will precisely correlate to refrigerant pressure in a closed system.

Trying to cycle the compressor at a higher evap temp will be more MPG efficent but cause insufficent dehumidification of the air and except in desert climates a rather cold sticky environment.

HTH!

 

[Dgate]

I would have thought the more aerodynamic the shape,the more drag an open window would have.The air flow adheres to the body surface and is interupted by the hole upsetting the flow from that point on.
Something like an SUV with the cleaness of a barn door makes very little difference in having a window open or a door for that matter :lol:.

I have driven vehicles that when the window is down there is no buffeting of the driver at all which usually indicates a bluff front such as a truck etc which puts the drivers window in a low pressure area as the air flow is diverted wide of the opening.
Try the same with any aerodynamic design and your hair-do will get rearranged :wink:
Also no one has mentioned battery pack heating which the A/C prevents,sometime we have to forego economy.

Dgate

 

[boogetyboogety]

Our CVT has earned a 55.2 LMPG over ~25,000 miles, divided by intelligent Insight driving (me, ~20,000 mi.), and My Beloved, who drives it like it was a Civic, with NO regard for mileage, ~5,000 mi.).

And we have never... NEVER... turned the A/C ECON switch off since we bought the car new. It's always set at 72. :shock:

That's not to say we haven't driven with the windows down from time to time, for very short distances, for various reasons, but I'm willing to bet less than 25-30 miles during the car's lifetime (and no, the A/C stayed on even when exposed to the outside air, this is Texas, folks, and My Beloved does not suffer lightly). The aero design of the Insight seems to me to be so clever that papers and light objects -- even in the storage area -- suffer little or no buffeting with windows down. :lol:

I would love for my Mythbusters heroes to do an Insight test to answer this question once and for all, but what are the odds... I'd rather see JATO-powered cars [not] fly into cliffs and crash-test dummies survive airplane drops by riding inflatable rafts down to the ground a la Indiana Jones... :roll:

 

[Lawson Huntley]

We have high summer temperatures and very high humidity in the Carolinas. In the city (Charlotte) we have very heavy traffic, lots of bumper to bumper stuff, and I just use the A/C, usually in the ECON mode but sometimes in AUTO.

However, when I drive in the country or interstate (no steep hills) I open my windows about 1/2" and use the A/C in ECON mode only on downhill stretches where I can still achieve lean burn. Having the windows slightly open does not seem to lower my mileage. In fact, the first time I achieved over 100 mpg for a relatively short trip was with the windows just slightly open.

Even with the windows all the way down I get much better mileage than when using the A/C. It seems that the horsepower required to run the A/C compressor is enough to keep the engine out of lean burn except for when I'm going downhill.

 

[james]

"...don't use "Fuel cut mode". all you are doing is using the engine as a brake..."

Well, I WANT to use the engine as a brake (and charging). Didn't I say that this is a steep downgrade? With, if I didn't mention it, curves. And a rather steep drop on one side The 60 mph or so that it maintains without my foot on the gas is just about the right speed.

"...you will be more efficient keeping your foot on the gas..."

Why do you think so? If I press the gas pedal even slightly, it lessens the amount of regen I get. Press a bit more and it's entirely off, further yet and the display shows less than its 150 mpg max.
Well,

 

[Calpod]

Sorry James,

I was referring to when you are NOT going downhill, I also go down a 7% grade, and you have to use regen or you will pick up speed really quick, what I was referring to is when you are going on flat, or just a small downhill.

MIMA will allow you to go down and still charge without taking your foot completely off the gas.

 

[james]

"MIMA will allow you to go down and still charge..."

Sure, as soon as Mike gets the prototype boards in & tested, I can get one of the next batch. Though in fact I wouldn't need MIMA going down this hill, as it's about perfect for charging. Going up is where I think it'll really help, though. It should let me keep revs up without draining the battery in the first half of the climb, then watching as charging robs engine power on the second half.

 

[nemystic]

After about 3 months of commuting with the MIMA modification in hilly terrain, I believe that foregoing the benefits of fuel-cut to use the regen with some throttle enables better ultimate fuel effeciency by maintaining a high SoC and thereby enabling electric priority assist on the uphill segments.
I wouldn't be able to confirm that this is valid for terrain with smaller hills, such as < 3.5% grades.

In the mountains, there's probably some benefit to being able to disable the forced charge until reaching the summit, after which it should be possible to regen to 100% indicated SoC while regulating the speed without the brakes. This will of course depend upon the terrain.

With the existing state of the art, the MIMA modification isn't a panacea. However, with energy storage capacity that could be increased in proportion to the altitude of the driving terrain, this is still, in my opinion, the "holy grail" of Insight modifications.

Returning to topic; since I don't have air conditioning, it's not possible to do to a controlled experiment to compare fuel economy of open windows vs. A/C. However, there's a lot of good information in another thread on this forum.

http://www.insightcentral.net/forum/vie ... 8&start=15