ANY point to aero mods at 45mph and below? - Fuelly Forums

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Old 03-07-2008, 09:59 PM   #1
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ANY point to aero mods at 45mph and below?

I'd like to know if any of you have any experience with any benefits of aero mods on a car at town speeds, . 90 percent of my driving is in town, and it's held me back from trying any aero stuff, since I don't know if I'll see any benefit for my efforts.

I suppose at speeds approaching 45mph a lowered drag number couldn't hurt, but my money's on weight reduction for increasing city FE. I'm contemplating removing my back seat to see if it will help, and I already run 50psi tire pressures. My car's an auto pig though, and from what I hear they resist FE improvements pretty hard. I know all my efforts to apply hypermiling techniques haven't done much for me.
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Old 03-07-2008, 11:30 PM   #2
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The little driving that I do is in town at 45 MPH. I have a full belly pan ( from bumper to bumper, as well as wheel spoilers.
I have probably saved .005 percent of a gallon of gas in the last six months.
It was fun though.( adding the aero mods )

I too air my tires up to 50 psi since I assume this is what will benefit me the most. My max. pressure is rated at 44psi.
I would hate to think that you are driving your car with your kids though.
I drive alone - so if I have a blow out, its just me wrecking - unless I careen into that soccer mom in the oncoming lane - damn )
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Old 03-08-2008, 08:52 AM   #3
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I'd argue that you can see aerodynamic improvements down to as low as 20 mph, but the cost to benefit ratio makes it the last area to focus on particularly if the majority of your speeds are actually less than 45 mph.

To put it into perspective, 90% of my driving is at 40 mph or less, and I am currently on track to better the rated city economy by 30% in my Escort. I don't really have what I consider significant aerodynamic mods with only a grill block. I do however have LRR tires and do allot of P&G'ing and some EOC'ing. Also, any time I'm going faster than 25 mph, it's in top gear.

I doubt any aero mod could match or add much to that. The bulk of my inefficiency right now is likely in idle time and warmup fuel enrichment, but there's not allot more I can do about that except to install a block heater.
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Old 03-08-2008, 09:36 AM   #4
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In front of my house there is a slight grade, which transitions to level, then uphill a bit, then back to level. Coasting, my Honda would max out at 40 mph on the first level area. I added the pictured air dam, and now it will max out at 42 mph. (a 5% improvement) When it reaches the second level portion of the road, you can really see the mph improvement here also. Well worth the effort of install...
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Old 03-08-2008, 10:04 AM   #5
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Arent those wood blocks located at little dangerously?
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Old 03-18-2008, 09:40 AM   #6
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Any improvement in coefficient of drag helps at speeds as low as 15-20 mph.
Don't think so roll down the window and stick your arm out at 20 mph and place your hand palm flat against the wind. Tell me how much of a pressure difference you feel between palm forward and palm down. At the lower speeds < 40 mph vehicle weight becomes more of a factor than aerodynamics. If I was spending most of my time driving at the speeds you describe I would be driving the lightest car I could justify with smallest engine available in that model with a Cd under .32.
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Old 03-18-2008, 09:53 AM   #7
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Heck, cycling on bikes (the pedal type) aero mods and position make a difference...I am sure they do on a vehicle also.
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Old 03-18-2008, 10:08 AM   #8
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The thing with cycling though is that you can change your Cd by 40% between sitting up arms wide and crouching and tucking, so difference is a little more drastic, then going to a reclining bike typically drops it a bunch too. So as a comparison to cars, one is kinda talking the difference between driving an 8ft square cube, vs say a honda element, vs an insight, all with the same weight and motor. Which one would see a noticable difference with. However, I wouldn't expect to see measurable differences at city speeds until you had shifted the Cd by 15% or so, which is quite an achievement.

If you drove fairly constant speeds in the city, light traffic, only the limit keeping you slow, you'd probably see 20% of the efficiency improvement, whereas at highway speeds you see 80% of it, so if an aero mod picks up 2mpg on the highway, expect it to pick up 0.5mpg in the city if it doesn't get lost in the noise of heavy traffic and lots of lights. If you do a bumper to bumper crawl for 30 mins every day, you'll probably never notice.
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Old 03-18-2008, 12:42 PM   #9
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tweakmenow -

Quote:
Originally Posted by tweakmenow View Post
In front of my house there is a slight grade, which transitions to level, then uphill a bit, then back to level. Coasting, my Honda would max out at 40 mph on the first level area. I added the pictured air dam, and now it will max out at 42 mph. (a 5% improvement) When it reaches the second level portion of the road, you can really see the mph improvement here also. Well worth the effort of install... ...
That airdam is really nice. I can't tell if it is home-made or something you buight that is *for* the Civic. Can you tell me how you did it?

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Old 03-19-2008, 07:26 AM   #10
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tweakmenow -
That airdam is really nice. I can't tell if it is home-made or something you buight that is *for* the Civic. Can you tell me how you did it?
I'm guessing it is plastic lawn edging. It is a popular item for making air dams & side skirts from as it is cheap, durable, easily bendable and able to survive the occasional curb or steep driveway.
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