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Chin Spolier - fast/easy/cheap/effective

Chin Spoiler - fast/easy/cheap/effective

Extra deep garden edging 6" deep x 20 foot long coil purchased at ACE Hardware for approx. $12.00.
Secured straight up though the lip with a dozen Stainless Steel #8 Phillips screws 32 tread count, 1 inch long, lock nuts (nylon insert type) 9mm.

I'll post the fuel savings later in the week. For the first 50 miles driven today I've gone though less than 1/8 of a tank, normal is a hair over 1/8 tank. At 70 mph the engine is turning at 2,050 rpm, I think that is about 200 rpm less than before. So it's like I'm driving 5 mph slower than actual speed on the highway, and that is bound to add up. Only a couple of hours to install.

Photo Gallery
http://s184.photobucket.com/albums/x295/kach22i/S10%204x4%20Pick%20Up/

I have enough material left over for two more trucks.

Automotive plus fill the binding holes, first securing point is centered.


Curb clearance is reduced from about 13 inches down to 7 or 8 inches, still double of my old Porsche 911 which has more of an overhang. I'm used to not pulling all the way up to a curb, don't do this modification if you are a curb knocker, or at least use a standard 4 inch PVC lawn edging in lieu of the deeper 6 inch one shown.


Some air gets in through the tow hooks, I'm not going to block these off until I can test engine temp's in summer while towing.



Compare it to my neighbor's stock S-10 4x4, from mid bumper down all that air gets compressed then sucked up under the vehicle by the vacuum/neg air pressure under the floor and tumbles around in drag causing vortexes.
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Old 03-29-2009, 09:26 AM
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Old 03-29-2009, 09:28 AM
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Nice! I like it.

It reminds me of the flex dams that were popular for 914's long ago.











Tim
Old 03-29-2009, 09:42 AM
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You know, that doesn't look too bad, George.

I don't know how effective it is with the truck lifted but it might help a bit.
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Old 03-29-2009, 09:45 AM
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Quote:
Originally Posted by Oh Haha View Post
You know, that doesn't look too bad, George.

I don't know how effective it is with the truck lifted but it might help a bit.

Yep, 7-1/2 inches of ground clearance is about double of most cars even ones which go though a Michigan winter.

It's designed for some snow and those ruts which form in the snow from tires.

The plastic lip of the original valance is a weak point, I could used metal straps and go up an extra 6 inches or so to secure to metal. However the new chin spoiler is flexible with a top loop which can compress with vertical loads. If impact loads occur they will be evenly distributed.

It's an experiment, time will tell if it works out.
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Old 03-29-2009, 09:55 AM
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Interesting.

From an aero point of view (ignoring cooling and curbs), is there such a thing as too much air dam? Suppose I used your trick and extended the 911's air dam to 1/2" from the road? Would I get instability?
Old 03-29-2009, 10:14 AM
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Neat idea! I've been tempted to do the same with the F-150.

Not sure why you are thinking you are getting a reduction in RPMs at speed since that would happen only if your torque converter (automatic tranny, right?) had been slipping or you were running larger tires.

Any mpg increases whould come from reduced throttle openings due to lower horsepower requirements at lower drag levels.

Keep up the good work!

Les
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Old 03-29-2009, 10:16 AM
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You know what? It looks a lot better than I expected when I began reading this thread. Keep us posted.
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Old 03-29-2009, 10:18 AM
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Quote:
Interesting.



From an aero point of view (ignoring cooling and curbs), is there such a thing as too much air dam? Suppose I used your trick and extended the 911's air dam to 1/2" from the road? Would I get instability?
Remember the warning from Porsche that adding a whale tail without the front spoiler would make the front end lose grip? I imagine that increasing downforce on the front and not the rear could lead to the opposite.

I'll give you credit George, that's not half bad looking.
Old 03-29-2009, 10:18 AM
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Quote:
Originally Posted by jyl View Post
1/2" from the road? Would I get instability?
My 1976 Ford van spoiler I made back in 1983 was about 3-1/2" from the ground. It was still like moving a brick through the air, but was not being knocked around the road on windy days. The steering was really lose on it, so this was an important improvement.

EDIT:
I have a fabric cover for the bed which I have not put on. I also have some metal straps and smoked acrylic. If all goes as planned, one day I will install a Gurney flap spolier which I can see through. This will be after the top half gets zebra stripes of course.

http://www.ten-tenths.com/forum/showthread.php?t=111608
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Last edited by kach22i; 03-29-2009 at 10:24 AM..
Old 03-29-2009, 10:19 AM
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Looks really great.

Actually that exact same stuff is used by miata folks to make airdamns. Yours looks better than most that I've seen.
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Old 03-29-2009, 10:26 AM
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Quote:
Originally Posted by oldE View Post

Not sure why you are thinking you are getting a reduction in RPMs at speed since that would happen only if your torque converter (automatic tranny, right?) had been slipping or you were running larger tires.
My thoughts exactly.
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Old 03-29-2009, 12:17 PM
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Quote:
Originally Posted by oldE View Post
Neat idea! I've been tempted to do the same with the F-150.

Not sure why you are thinking you are getting a reduction in RPMs at speed since that would happen only if your torque converter (automatic tranny, right?) had been slipping or you were running larger tires.

Any mpg increases whould come from reduced throttle openings due to lower horsepower requirements at lower drag levels.

Keep up the good work!

Les
My rpm's (as I recall them for earlier today) - automatic trans

2,050 at 70 mph
2,150 at 75 mph
2,300 at 80 mph

Before the front chin spoiler was put in I think rpm's were up another 200, I'm looking to go from 18.5 mpg to 20 mpg. I just noticed the rpm's today because the radio seemed some much clearer and more detailed without the extra engine noise.
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Old 03-29-2009, 12:31 PM
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Quote:
Originally Posted by oldE View Post
Neat idea! I've been tempted to do the same with the F-150.

Not sure why you are thinking you are getting a reduction in RPMs at speed since that would happen only if your torque converter (automatic tranny, right?) had been slipping or you were running larger tires.

Any mpg increases whould come from reduced throttle openings due to lower horsepower requirements at lower drag levels.

Keep up the good work!

Les
Won't a torque converter "slip" some (unless it's a lock-up model) based on load. As far as I know, a torque converter's lock up is not based on anything rigidly mechanical like gears. It's based on fluid and viscosity and load, so if you take a 3000 stall torque converter and hook it up to a car with 150 lbft of torque and 3000#s and then to another with 600 lbft of torque and weighing 4000#s, the stall speed will be higher on the heavier higher hp/tq vehicle.

I don't know if that lip is enough to make a big enough difference in drag to make a 200 rpm difference at speed, but theoretically, it is possible.
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Old 03-29-2009, 02:16 PM
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If you really want to boost the mpg's, remove the rear tailgate. Look at it like a giant parachute catching air and slowing you down as you drive.
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Old 03-29-2009, 02:25 PM
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Quote:
Originally Posted by Por_sha911 View Post
If you really want to boost the mpg's, remove the rear tailgate. Look at it like a giant parachute catching air and slowing you down as you drive.
That looks like it might work but I can attest (at least with my old Dodge) that it does nothing for fuel mileage. I just went through the Michigan interstate system (from extreme south to extreme north). I would say that was a good test. If you have ever driven those roads you will know aero has a great deal with fuel mileage.
That splitter looks remarkably good.
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Old 03-29-2009, 02:36 PM
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Quote:
If you really want to boost the mpg's, remove the rear tailgate. Look at it like a giant parachute catching air and slowing you down as you drive.
Urban Legend... MPG does not vary much whether the tailgate is up or down.

http://www.gminsidenews.com/forums/f22/leave-tailgate-up-better-gas-mileage-11678/

Quote:
"Putting the tailgate in the down position tends to increase turbulence and drag of the open box," explained Jack Williams, of Ford Aero Systems Engineering. "We've seen drag increase as much as .5 to 1 percent. Flow-through, web-like fabric replacement tailgates tend to increase drag even more; we've seen increases as much as 4 to 5 percent." In a nutshell, all of that extra drag translates into worse fuel economy for the vehicle.
http://www.roadandtrack.com/article.asp?section_id=18&article_id=1455&page_number=1
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Old 03-29-2009, 02:40 PM
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I will be shocked if it makes a measurable fuel consumption difference.

Change all your fluids to full synthetic. Tranny, engine, and rear-end.
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Old 03-29-2009, 04:59 PM
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Originally Posted by Por_sha911 View Post
If you really want to boost the mpg's, remove the rear tailgate. Look at it like a giant parachute catching air and slowing you down as you drive.
I thought that and lots of other folks have thought that. The mythbusters even tested it and asked Ford Truck design engineers if they could explain it. Yes, they did explain it. IIRC, the air that goes over the top of the vehicle creates a clockwise swirling vortex in the bed. That vortex has a similar effect to making the truck a fastback. The air that isn't part of the vortex flows right over the back of the vehicle. They said that opening the tailgate actually reduces the effect and hurts the drag of the truck.
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Old 03-29-2009, 06:34 PM
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I found a this

Quote:
Tailgate: Up or down?
Myth: Driving your pickup with the tailgate down gives you better fuel efficiency than with the tailgate up.

Test Setup
Adam and Jamie were each given identical, new model pickup trucks. They both had equal mileage, same tire pressure, and 30 gallons of gas. Jamie drove with the tailgate up and Adam the tailgate down.

The rules:

They have to maintain the speed limit
All acceleration must be done by cruise control
No drafting
Windows up, A/C must be exactly the same in both cars
The Test
After 300 miles there didn't appear to be much difference in the gas consumed, but after 500 miles Adam (tailgate down) ran out of gas. Jamie made it another 30 miles before he ran out of gas. This result was the exact opposite of the myth.

Water tunnel visualization
According to the experts, a circular pillow of air forms behidn the cab of the truck when the tailgate is up. This "separated bubble"/"locked vortex flow" keep the faster moving air from contacting the truck, and thus reduces drag. With the tailgate down, the bubble breaks down and is no longer able to keep the fast moving air out, increasing drag.

In their scale model with the water tunnel, they were able to see that the increased drag. With the tailgate down, the particles in the water were dropping down and hitting the tailgate.




mythbusted
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Old 03-29-2009, 06:37 PM
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