Phximiev
Posts: 1168
Joined: Thu Jan 15, 2015 7:25 pm
Location: Phoenix

Re: Aerodynamic Mods to Reduce Drag

Wed Apr 29, 2015 8:08 pm

Anyone from Finland interested in making contact with Petri re: a possible wind tunnel test? See the following email thread with Petri, who has a wind tunnel in Finland and Petri's email address.

Dear John,

Thanks you for contact.

I have not data for car aerodynamic data. We have wind tunnel and it is possible measurement also car twheel.
Is possible use speed 40-80 km/h.

Do you have a different Hubcaps? Have I understood correctly?

This is very interestin project.

I waiting more info.

Best regards

Petri
Wheel.energy@netti.com

John MacMullin kirjoitti 28.4.2015 18:16:
Petri:
I own an iMIEV and belong to the iMIEV forum. There is a
debate/question about whether wheel skirts actually make a car more
efficient.
I originally contacted Frank and he has referred me to you.
So, to my original question posed below: Do you have a wind tunnel
that can test whether wheel skirts make a car more aerodynamic?
And then, have you done such a test and if so can you share the
results?
2012 iMIEV ES
2014 Chevy Volt

pbui19
Posts: 139
Joined: Tue Jan 07, 2014 12:17 pm

Re: Aerodynamic Mods to Reduce Drag

Sat Jul 11, 2015 10:48 am

hi all, I am finally at the point when I can start tinkering with the iMi. I am going to start with aero mod since most of my driving is highway speed. The easiest was to remove both wipers, but kept the driver wiper in the back with a 14mm wrench in case it rains. That's a fat chance in drought Cali. There is less noise on the freeway so it must be helping some.

Does CaniOn display the coolant temperature any where ?

I am thinking of doing partial or adjustable full grill block to minimize air flow but would like to have a way to monitor the coolant T.

-Paul

NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Thu Jul 16, 2015 9:58 am

Removing the wipers will only make a tiny improvement, if any. The biggest improvements will come from a properly designed Kamm back, and a belly pan, and smooth wheel covers. A grill block is good, and side view video mirrors help two ways: reduced frontal area and lower Cd.
Sincerely, Neil

http://neilblanchard.blogspot.com/

JoeS
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Location: Los Altos Hills, California

Re: Aerodynamic Mods to Reduce Drag

Fri Jul 24, 2015 11:45 am

NeilBlanchard wrote:Removing the wipers will only make a tiny improvement, if any. The biggest improvements will come from a properly designed Kamm back, and a belly pan, and smooth wheel covers. A grill block is good, and side view video mirrors help two ways: reduced frontal area and lower Cd.
Neil, I understand about the windshield wipers - it's simply that their protrusion intrudes into my field of view and also partially blocks my dashcam.

In looking at the battery pack's belly pan, it appears to me that Mitsubishi did not bother filling in the gap between the pack and the car body when they widened the car for the US market. Any ideas on how to cover that huge gap at the aft end of the car?

I'm game to install side-view cameras - anyone know what the latest and greatest out there are, together with nice dashboard-mounting displays?

Regarding wheel covers, I had Moon discs on my Insight but their slight movement chewed up the wheels' finish. I might try again with a set for the i-MiEV but need to research how to prevent the galling. I'm presently making another set of fibreglass/foam sandwich rear fender skirts - I screwed up the first set as I did not add enough curvature to keep them from touching the tires.

Anyone do a grill block (best for winter, methinks)?

Sheesh, all this work, the results of which will probably be comparable to simply slowing down just a few mph! :geek:
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

JoeS
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Re: Aerodynamic Mods to Reduce Drag

Fri Nov 20, 2015 2:10 pm

We have at least three threads pertaining to aerodynamics on this Forum:

Aerodynamic Mods to Reduce Drag (this one):

http://myimiev.com/forum/viewtopic.php?f=14&t=1745

DIY Boat Tail for Better Aerodynamics:

http://myimiev.com/forum/viewtopic.php?f=14&t=326

iMiEV CdA:

http://myimiev.com/forum/viewtopic.php?f=22&t=264


I am still considering adding Airtabs as shown on the i-MiEV here:

http://myimiev.com/forum/viewtopic.php?p=2725#p2725

I had noticed that the Leaf has these protrusions on its underside:

Image

Surely there was a purpose to adding these, other than structurlly stiffening that panel?

Just thought I'd raise this topic again as I am still wondering if anyone has any real-world experience?

BTW, came across a website which gives a nice overview of the history of vehicle aerodynamics in the last century:

http://www.curbsideclassic.com/automotive-histories/automotive-history-an-illustrated-history-of-automotive-aerodynamics-part-1-1899-1939/

http://www.curbsideclassic.com/automotive-histories/an-illustrated-history-of-automotive-aerodynamics-part-2-1940-1959/

http://www.curbsideclassic.com/automotive-histories/an-illustrated-history-of-automotive-aerodynamics-part-3-1960-present/

And a discussion regarding cross-section area in addition to Cd -

http://www.curbsideclassic.com/automotive-histories/automotive-aerodynamics-drag-area-size-matters/


EDIT:

Here's a report they did on a Honda Civic, where they festooned the sides with the Airtab vortex generators, resulting in a 4% reduction in horsepower required at 55mph. They extrapolated the data to say that a further reduction of 2% could be had if they had put the Airtabs across the roof, yielding a total horsepower reduction of 6%.

http://www.airtab.com/Site/documents/HondaWTReportV6.pdf

All other things being equal, a 6% power reduction translates into a roughly 3.6mile range increase. Why didn't Mitsubishi install these, or did the marketeers say that would look too dorky?

You'd think all the BEV manufacturers would be implementing something like this, if it really worked...
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
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Re: Aerodynamic Mods to Reduce Drag

Sat Nov 21, 2015 3:39 pm

JoeS wrote:Here's a report they did on a Honda Civic, where they festooned the sides with the Airtab vortex generators, resulting in a 4% reduction in horsepower required at 55mph. They extrapolated the data to say that a further reduction of 2% could be had if they had put the Airtabs across the roof, yielding a total horsepower reduction of 6%.
I'm a *little* suspicious - This test was run by the makers of the AirTabs as a way to advertise how well they work and thereby generate sales. They rented the wind tunnel, likely had boxes of the tabs which don't take 5 minutes to install, yet they have to 'extrapolate' how well they might work if added to the roof?

I understand it's hard to generate real world data, so using a wind tunnel is easier, but I also wonder about the changes you would see if the wheels were actually turning 55 mph as opposed to being stationary in a wind tunnel, and the car was moving over real pavement as opposed to the slick smooth bottom of the wind tunnel? In short, I'd be quite suspicious that the 6% figure would be accurate for any given body shape in real world conditions
All other things being equal, a 6% power reduction translates into a roughly 3.6mile range increase. Why didn't Mitsubishi install these, or did the marketeers say that would look too dorky?
No doubt they don't make the vehicle look better and that alone would probably turn off a few buyers. I do not doubt for a second that there is some benefit to using Vortex Generators as the lions share of vehicle drag is that pocket of turbulent air you're dragging around behind you - Boats have the same problem and you can design to minimize that drag if that's something you truly want to do. The extended Kamback (which looks a lot like the aft end of many sailboat hulls) would go a long way toward lessening that drag, but oh boy, what a price you'd pay - A.) Who wants that fugly tail hanging back there and B.) What a pain in the neck when it comes to parking, or loading/unloading cargo for an urban commuter car. If the negatives didn't outweigh the positives, I think you'd see lots more of this sort of technology out there in the real world
You'd think all the BEV manufacturers would be implementing something like this, if it really worked...
I think it's the minimal gain vs the change to the look of the car - You quoted a 3.6 mile range extension (2 to 2.5 might be more realistic for our body shape in real world conditions) but that assumes running 55 mph for the total duration of a full battery charge. How often does that happen in the real world? Mitsu thought they were designing an urban commuter car, not a (very short) freeway runner. I've never come close to running 55 for even a third of a charge, so the actual gain for me would be much less - Probably less than one mile. Not worth the 'dorky look' alone, even if the tabs were free, IMO

While it doesn't make much sense for the factory to do it, if an individual thinks there's a real benefit there, I guess it makes sense for them to add something like this - I've seen much less beneficial things sell to 'believers' over the years. 30 years ago if you bought every gizmo from the JC Whitney catalog which guaranteed you a 5 or 10% improvement in mileage, you'd be getting 200 mpg or better!! :lol:

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon, 14,000 miles
1979 Honda CBX six into six

databeestje
Posts: 80
Joined: Tue Nov 24, 2015 2:47 am
Location: Netherlands

Re: Aerodynamic Mods to Reduce Drag

Sat Nov 28, 2015 6:32 am

I was considering closing the gap in the front of the airdam where the radiator sits. I can't imagine the electric motor generates enough heat to warrant a gaping hole in the front of the bumper.

I would be inclined to think that there is enough of a gap behind the front bumper for the fan to do it's thing and provide cooling to the radiator. I have not looked at what sort of engine temperatures most people see, and what's left of that number by the time it reaches the front radiator. Is the radiator in the i a leftover from the ICE model, because that would imply something of 30-40kW thermal envelope sizing.

So basically a sort of styrofoam plug to seal it off, tape that against the bumper for testing and see how it does. It might be needed to a lip (splitter) to the bottom of the bumper that protrudes about an 3-5cm out to get it to working.

PV1
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Re: Aerodynamic Mods to Reduce Drag

Sat Nov 28, 2015 6:56 am

I've seen the motor as warm as 80 F in sub 20 F weather while driving down the highway. The highest temperature I've seen was 130 F while crawling around the city. These temperatures were seen with OVMS, which read the temperature sensors the car uses.

There may not be that much heat, but if the motor is 90% efficient, it's producing 5 kW of heat at full throttle.

You could do double duty. Redirect the motor coolant to the heater core and plug the radiator opening. You'd get a reduction in aero drag, plus free heat.

I would definitely leave it open during the warmer months, though. Electronics are more efficient the cooler they are.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

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Driving electric since 2-21-2013.

NeilBlanchard
Posts: 353
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Location: Maynard, MA Eaarth
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Re: Aerodynamic Mods to Reduce Drag

Tue Dec 01, 2015 11:04 am

I think a full belly pan is going to have a more substantial benefit, than vortex generators. The air flow under the i MiEV is not clean, and so vortex generators will have haphazard, if any benefit.
Sincerely, Neil

http://neilblanchard.blogspot.com/

genec
Posts: 59
Joined: Sun May 03, 2015 2:38 pm

Re: Aerodynamic Mods to Reduce Drag

Tue Dec 01, 2015 1:10 pm

I'm surprised Mitsubishi didn't see that possibility (longer rear end) during their design phase and then built it that way. Imagine tons more space AND better MPGe!!!!!

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