Side mirror drag & effect on fuel economy - quantified

[orbywan]

I should have my camera back by Wednesday or so, I'll take more photos of the interior layout and provide some more info on the cameras and monitor.

I've gotten pretty comfortable with the side cameras, but driving at night in heavy traffic can be a problem. The problem with current generation small cameras suitable for this application, is at night headlights look like big fireballs coming at you. This can make it difficult to figure out how far away they are and how fast they're going. When they get closer, maybe 20 -25 feet away, then you can judge it pretty well, but by then they're so close it may be too close to change lanes or whatever.

I installed convex side mirrors on the inside of each window (will post photos of those as soon as I can) and those do help, but in heavy traffic at night, it is occasionally hard to sort out all the headlight pairs. Coming home from Phoenix last night I think I figured out a good solution for this. I think replacing my inside rear view mirror with a wide angle version will solve this problem. I just have to find one and try it.

Why is that any different that the side convex mirrors? Only trying it will tell, but I think the larger size of the center rear view mirror will reduce the fish-eye effect and make it easier to sort the images out.

I'd say in current form, this system is more effective than mirrors in most conditions, and not as effective as mirrors in about 2 or 3% of conditions, the worst being at night in heavy traffic, well see if a better center rear view will make the difference there.

If you're brave, and it is possible to see far enough back on either side of your vehicle in a pinch, removing the mirrors and adding the convex mirrors on the inside (without cameras) might be an option. There's a simple way to find out. Find the best location for mounting the convex mirrors, and then, here's the brave part: tape your current side mirrors off completely. Now, U]carefully[/U], drive around a little in non-insane driving conditions and see what you see.

If you're young (and your neck still has max rotation so you can look back once in a while) and you have great vision (so you can instantly go from looking forward in the distance to trying to see very small images in the convex mirror 18 inches from your face, in a heartbeat), then this might work for you.

For the average person, probably not. So anyway, the testing continues...

[Big Dave]

Thanks.

You told me what I need to know.

[steffen707]

Has anybody tried making their mirrors more aerodynamic by molding more of a teardrop shape in front of the mirror, and then kinda leaving the actual mirror part as the truncated kamaback?

This probably would add more frontal area to the car.

I know this was discussed in the thread, but i don't know if it was ever done, and reported.

[California98Civic]

Originally Posted by steffen707

Has anybody tried making their mirrors more aerodynamic by molding more of a teardrop shape in front of the mirror, and then kinda leaving the actual mirror part as the truncated kamaback?

This probably would add more frontal area to the car.

Aerohead once observed that his 1980s Civic saw no change of top speed with or without the mirrors... and he was at a track with top grade sensitive equipment for measurements of speed... Nonetheless. Mine is not a 1980s Civic, so I went ahead and deleted the passenger mirror on the hunch.

For your idea I don't think you'd have to increase frontal area to create more of the "tear drop" "template" shape. But I do wonder if it will work well. My understanding is that the air around the mirrors is quite turbulent already, due to interaction with the "A" pillars. I would wonder then how much benefit you'd really see from improving the design of the mirrors in this way. It might look cool and be a conversation piece about aero mods on your car, but so would removing a mirror, which is simpler. Still... you have to love what you drive and the projects you attempt are part of that... I don't mean to discourage.

You would need something clear enough to allow light and sight, yes? What?

[steffen707]

Originally Posted by Christ

Even at $200, that's 50g fuel, so if I get 3% better fuel economy than my current 53mpg, that's brings me up to 54.5mpg.

53mpg * 50 = 2650
54.5 *50 = 2725, an extra 75 miles per tank.

75/50=1.5 gallons saved per tank based on previous mpg
50*1.5=33.3e tanks before I start saving from the mod's benefits.

This is with fuel at $4/gal. It's $4.25 or higher for me, so payback time is less.


Realistically, most p people only use 75% tank capacity between fills. Scale the figures accordingly.

I think your math is off. Consider this
10,000miles / 53mpg=188.6 gallons to travel 10,000 miles
10,000miles / 54.5mpg=183.48 gallons to travel 10,000 miles

saving you 5.12 gallons per 10,000 miles or $20.48 saved per 10,000 miles
$200 could have bought 50 gallons of gas / 5.12 = 9.76 multiplier

so in 97,600 miles this mod will pay for itself. From a strictly financial standpoint for most people a break-even point of 97,600 miles from now is a horrible return on investment. Imagine all the scenarios that could happen that make you sell the car, job, kids, car accident, ect. That's a long way into the future for most.

Although that's just a financial standpoint, there's external benefits from earth friendly, personal happiness, braggin, being a tinkerer, ect.

[steffen707]

Originally Posted by California98Civic

Aerohead once observed that his 1980s Civic saw no change of top speed with or without the mirrors... and he was at a track with top grade sensitive equipment for measurements of speed... Nonetheless. Mine is not a 1980s Civic, so I went ahead and deleted the passenger mirror on the hunch.

For your idea I don't think you'd have to increase frontal area to create more of the "tear drop" "template" shape. But I do wonder if it will work well. My understanding is that the air around the mirrors is quite turbulent already, due to interaction with the "A" pillars. I would wonder then how much benefit you'd really see from improving the design of the mirrors in this way. It might look cool and be a conversation piece about aero mods on your car, but so would removing a mirror, which is simpler. Still... you have to love what you drive and the projects you attempt are part of that... I don't mean to discourage.

You would need something clear enough to allow light and sight, yes? What?

Your words are not discouraging at all. I think i might just try my own testing with my particular car. As its been discussed every car would have a different outcome. The civic mirrors are relatively easy to remove if I recall. I'll try and provide some solid a-B-A testing.

[3dplane]

I don't know how much it helps or hurts but I made these mirrors out of styrofoam for my 94 protege:

(I have a piece of clear tape over the broken edge of the homemade plexi rain guard transitioning from the top of the mirror. Not on the picuture)











For size comparison to what came off:


It took about a week to get used to them but after that I was able to use them in traffic like a normal mirror.

I also don't drive with my arm over the door/ elbow stuck out the window anymore because as soon as the tip of my elbow makes it past the window channel, it's in "high speed" airflow which is an instant reminder to roll the window at least half way up. (no a/c in Florida weather ).

(..you know you're an ecomodder when you run the window up with the heater on in Florida so you can keep the grill block and take advantage of the aero mirrors... )

I actually have a thread on them:http://ecomodder.com/forum/showthrea...ors-19748.html

Cheers!
Barna

[radioranger]

anybody tried to relocate the mirrors to a better spot on the car say lower on the door or a bit further back from the windshield a pillar, I'm thinking as the air goes around the windshield there is a shadow there that might be ideal for mirror placement even if it was stuck to the side window somehow or offset from the stock location with a plate more towards the rear of the car, etc.

[aerohead]

Originally Posted by radioranger

anybody tried to relocate the mirrors to a better spot on the car say lower on the door or a bit further back from the windshield a pillar, I'm thinking as the air goes around the windshield there is a shadow there that might be ideal for mirror placement even if it was stuck to the side window somehow or offset from the stock location with a plate more towards the rear of the car, etc.

Some of the auto makers who published findings on their wind tunnel work with mirrors found it effective to simply move the mirrors further away from the body,into slower air.
AeroVironment did this for the Impact,and Subaru for their XT,both of 1987.

[Vekke]

I am making my own aeromirrors with covers. There are 3 pictures from the mirrors.

https://www.facebook.com/photo.php?f...type=3&theater

Frontal area is about 75mmx105mm=0,00788m2 vs regular Lupo 3L mirror (this is smaller than most mirrors already) 120mmx190mm=0,0228m2. That is 2,8 times smaller.

This design will lower your fuel consumption about 2-6% depending on the car. This version will go on sale if the tufts stays attached in the testing process. I will propably position this on the upper part of the side window. So window will still open but also there is less air there than in the A-pillar corner...

Tomorrow I will need better vacuum cleaner for vacuum forming because that is little bit out of shape. Thats fourth prototype made so far.