[ aero-mods Installment#10-( Interference-Drag) ]

[aerohead]

Note from Darin (admin): this installment is part of a series posted by Phil (aerohead) about the effectiveness of various aero mods - usually with quotations and citations to source data.

See the Aero mods data index here.

End note.

---

More debris! This is a follow-on to stuff Darin and others have already posted. I'm only going to touch on things I have numbers for. I'm guilty of minimizing the importance of interference-drag earlier, and since re-visiting my articles and numbers-crunching on CRX data, I'm gonna be a camp-follower for those who are ferreting out the significance of "excrescenses" ( sp?).

All the modern Btu-stretchers are mirror-free designs for instance and if the big-boys are sweating after details like this, then it's okay for me to look there too. I've included my Bonneville numbers but don't take it as a jab at mirror deletion. So lets get to it.

Interference-Drag

1963, Kelley & Holcombe, GM, "....very efficient body shapes can be greatly increased in drag by the application of small projections."

1975, Car and Driver Project Aerovan: side-mirror deletion reduces drag 6-percent. Roof spoilers (as mentioned in installment on aftbodies/spoilers) increase drag 15-52 percent with 2-6 mpg loss.

1981, CAR and Driver, April: Ford Escort mods: at 60-mph, 12-cubic foot rooftop cargo carrier costs 6-mpg (19%), hood open and locked at 12-inches (300mm) costs 2-mpg (7.1%), open side windows cost 1.0-mpg (2.7%).

1982, Volkswagen AG, wind tunnel, 1982 VW Scirocco (all at 55-mph):
empty luggage rack = 13-percent increase
lowered side windows = 4.6-percent
mud-flaps = 7-percent
auxiliary fog-lamps = 2-percent
radio antenna = 1-percent.

1986, Subaru XT, wind tunnel development: side mirrors moved out 80mm from body, side glass made flush, door handle made flush, all mods together = 3-percent drag reduction.

1988,Texas Tech University Aero Lab: pickup truck roof "eruption" responsible for 20-percent of truck's drag (note: the motor industry refers to pickup trucks as a two-door sedan sans trunklid ).

July 1991, Bonneville International Speedway, Wendover, Utah, U.S.A., the Phil Knox, 1984 CRX 1.3 streamliner: windshield-wiper and driver side mirror deletion demonstrate no improvement in top speed. A cardboard and duct-tape cowl fillet over the wiper area demonstrates a 0.28-mph improvement to top speed. A cardboard and duct-tape 30-degree rear spoiler at boattail causes a 2-mph speed penalty.

August, 2003, the Phil Knox Dodge D-100, without hood, doors, and truck bed overheats in a matter of a few miles at 60-mph, and cannot operate long enough for mpg testing. With the bed removed mileage drops 2-mpg at 60-mph (a drag increase from Cd0.50 to Cd 0.62 is estimated).

1999,VW 1-Liter Car (Cd 0.15 and 257mpg) has no side mirrors.

1999, GM Program For New Generation Vehicle (PNGV) car, with Cd 0.163 has no side mirrors. Interference drag of body cut lines, wheel covers, styling features raise drag by only 0.007.

General note about side-view mirrors: the air velocity at the cowl area can be accelerated to 25-30 percent higher velocitiy do to airstream deformation, and consequently, the actual drag of a mirror in that location will register higher due to the local velocity. My '64 Ghia had fender-mount mirror, out ahead of the windshield to keep it in slower air. Looks like mirror deletion and camera/view-screen is way of the future.

[NeilBlanchard]

Hello,

I was just in WalMart (I hate that store!) because they sell a small wireless backup camera, similar to this one:

Older version, I think?

The one in the store had a much smaller bezel around the screen and it had four buttons. The camera is virtually the same as this:


The clarity of the screen is okay -- I could pick out my son standing 50' or so away from the camera. I don't know how it would work at night. The cost was ~$98.

I think it uses Bluetooth between the camera and the screen, and you need 12v connections for both. I don't know if you could use two in the same vehicle, without interference between them.

I could easily see how one could cut off the lecense plate bracket, and mount the cameras on the stub of the mirror (where it pivots) on my xA. And I was thinking of getting a small plastic/rubber ball and cutting it to form a small shroud around the camera after it had been positioned to give a proper view.

Who's going to do it first?

[Edit: Of course, the Aptera (Cd 0.11) has no side mirrors -- no mirrors at all, actually.]

[MetroMPG]

Depending on the vehicles, when you're dealing with small potential savings by deleting conventional outside mirrors and replacing them with cameras/screens, I'd want to know the power consumption of the electronic replacements before coughing up the dough.

Phil: if that info is "debris", let me say thanks again for the flotsam & jetsam!

[NeilBlanchard]

Hello,

I'm going to try a coasting test with the mirrors in standard position vs with them folded in. If a difference is noticeable, then I may try one. I am not really confident that someone at WalMart can tell me if two of these cameras can be used together at the same time.

The screen is a 2.5" LCD and together with the Bluetooth and the the camera, I can't think it is more than 15-20watts consumption?

[Blue07CivicEX]

Unfortunately this camera system doesn't look feasible, I didn't look at the manuals to wire it but I did read more about the specs and how it works. It seems to tap into the backup lamps for a trigger sense to turn on and wake up the lcd and camera (I'm sure this could be fixed) the manufacturer says it shouldn't be run full time as it will cause early failure.

Also, the one review I read says if you're around a 2.4ghz wifi it will cause the LCD to go haywire.

Last but not least there is only one channel of RF causing only one camera to work in an application two active camera's within 30ft will cause interference and again display going haywire.

On another note, this sparked my interest and I am doing some research on placing an old dell PC I have in my console and having 2 USB webcams looking out my back side windows with small (4" diag) lcd displays mounted on the inside of where the sideviews used to be. I speculate (yeah yeah i know not good to do) the extra demand on the battery/alternator will be negligible compared to the reduction in cd.

I welcome corrections to my possibly flawed plan.

[i_am_socket]

I like the plan, can't wait to hear the results. I'd also like to see differences in the visible area of the rear sides vs std side mirror locations. If the rear sides is better, I'm all about deleting 'em ;-) 'Course testing would show if Cd reduction is offset by power consumption.

[aerohead]

Originally Posted by MetroMPG

Depending on the vehicles, when you're dealing with small potential savings by deleting conventional outside mirrors and replacing them with cameras/screens, I'd want to know the power consumption of the electronic replacements before coughing up the dough.

Phil: if that info is "debris", let me say thanks again for the flotsam & jetsam!

Darin,this stuff was all over the place.The up-shot is that doing the installments has forced me to better organize ,as I need to back up whatever I post,per Randy-The-Hacker recommendation.It's been an interesting experience! More on the way, once I hear back from Michigan on some stuff.

[cfg83]

NeilBlanchard -

Originally Posted by NeilBlanchard

Hello,

I'm going to try a coasting test with the mirrors in standard position vs with them folded in. If a difference is noticeable, then I may try one. I am not really confident that someone at WalMart can tell me if two of these cameras can be used together at the same time.

The screen is a 2.5" LCD and together with the Bluetooth and the the camera, I can't think it is more than 15-20watts consumption?

Why not stick one of those special curved mirrors on the end of the mirrors that you have folded in? Not the circular mirrors, there are many other shapes. That way, when they are folded in, they will still be "useful". This will increase your frontal area when your mirrors are not folded (unless the new mirrors are very flush), but who cares at sub-35 MPH speeds?

I wouldn't get the powered cameras because of the 15-20 watt consumption. I think that's on a par with headlight power consumption. Maybe an AC delete would balance that out.

CarloSW2

[NeilBlanchard]

Hello,

Standard headlight bulbs are 50-55watts IIANM. The cameras could consume 15-20watts -- do you have any links?

[Blue07CivicEX]

http://sewelldirect.com/CarElectronics

Under safety is where there are two backup cameras one with a 2.5" and one with a 3.5" lcd, they don't give the power specs for the setup but I checked a 7"tft lcd and it was <8w so I would speculate that it would be approximately that for 1/2 the lcd and a camera added (plus wireless coms).

Adding a "mini" PC and webcams would be significantly more power but whether the extra power consumption would be enough drag on the engine to hurt mileage more then sideviews would? I have no idea. another option would be to power the camera's or a PC from something along the lines of a motorcycle battery, reasonably light and would run a pc for a couple hours or the camera's for basically ever... but then you're adding what 10lbs/battery? 20AH motorcycle battery weighs 11lbs (just a quick google search for a motorcycle battery for a large honda bike).

Anyway! just my two cents I can see the options but I have no idea what would be the most mpg efficient I don't have the eco-modder background to support that.