Serious testing takes time and energy.

[95metro]

A-B-A testing is the ONLY method of properly quantifying the possible gains or losses of a "fuel-saving" (or power producing) device.

The absolute best method is usually not available to us. This would consist of a dyno, a rolling road, and a test lab with absolute controlled environment. This would remove most of the variables that on-road tests are generally prone to.

On-road tests with some form of data collection (ie - ScanGauge, SuperMID, data acquisition computer/software) are always at the mercy of the elements. Temperature, humidity, wind, and (most of all) the driver are variables that cannot be determined as to their affects on a given test.

However, a calm, warm day and a relatively flat road (or predetermined "track") will provide some data to at least make educated assumptions on. At the very least it puts theories in the "plausible" category.

For sake of reference I will refer to the chosen roadway as a "track".

"A" will refer to the test vehicle in "stock" or "current" (if already modified) condition.

"B" will refer to the test vehicle with the "device" or "additive" installed.

Weather and track conditions must be recorded before each run. For optimum results the test vehicle should be warmed to operating temperture and then driven on the track numerous times in its "A" condition to establish a baseline and/or margin of error between runs. I personally feel that multiple runs are necessary since environment and driving style could cause fluctuations in fuel economy during each run.

Example: Test vehicle in "A" condition
Run1: 42.5 mpg
Run2: 43.3 mpg
Run3: 42.1 mpg
Run4: 42.9 mpg

This establishes some form of baseline for what the test vehicle is capable of on this particular day at this particular time. The margin of error is 1.2 mpg between the best and worst runs. Now, let's attach the device/additive in question and do more runs (it may even be best to drive the test vehicle normally for a set amount of time before performing each set of runs).

Example: Test vehicle in "B" condition
Run1: 43.5 mpg
Run2: 42.8 mpg
Run3: 43.1 mpg
Run4: 42.5 mpg

In this particular example I would personally consider this "device" as busted. All of the numbers easily fall within the previously established margin of error and I would feel no particular need to continue testing. However, what if the results had been like this:

Example: Test vehicle in "B" condition
Run1: 45.5 mpg
Run2: 45.7 mpg
Run3: 44.9 mpg
Run4: 46.1 mpg

In this case every run is higher than the car in "A" condition. As a plus, it is even higher than our 1.2 mpg difference we previously calculated. At this point, the test cannot be considered conclusive at all. First, the test vehicle must be returned to its "A" condition and the runs must be repeated to make certain it returns to figures close to the original baseline. If it does not, then something changed the test conditions and the results must be scrapped.

If it does return to its baseline, the vehicle must now be placed back in "B" condition and the runs repeated once more. This is called "repeatability". If the numbers once again improve we know that the device is "working".

However, this still is not an absolute test. For one, only one vehicle is being tested. For another, the test should be performed again on a different day. Different vehicles and testing on different days would ensure that the device is indeed causing an improvement in mileage. If it really does work we should see slight to obvious results every time the device is added regardless of vehicle or environment.

[Jack]

Jeez I almost want to cut and paste that as a term paper.

Well done!

[95metro]

Thanks, Jack.

SVOBoy asked me to post this under Experiments to see if Matt would Sticky it. I think it's too short for a term paper...unless you add a legit experiment to it. Plus I don't know how it would look in a bibliography, "Testing method from some FE geek on the internet."

[Matt Timion]

proper testing is difficult, but consider the alternative: People reporting that devices work based on nothing more than "it seems to improve my gas mileage," or when people say ridiculous things like, "It improves fuel economy 8-20%." If they conducted an actual experiment why wouldn't they have an actual number?

I think real testing is what will seperate the men from the boys.

[95metro]

Hear, hear!

[cheapybob]

Your ABA method is correct, but short test runs can introduce error, too, IMO. Unless the temps, wind and road conditions are the same, they can skew the results, too.

I'm beginning to wonder if its really worthwhile. So few mods seem to make any significant repeatable difference. I seem stuck at about 53 mpg on my 60 mph test loop, and around 39 or 40 mpg for normal suburban driving. Both numbers are significantly better than what I started with, but additional improvements have all turned into mirages.

[Yoshi]

Just FYI...
Following is my collected data driving highway with CC set at 91km/h(actual was 85 km/h).

section km  mileage  alt change
    28km    24.5km/L      127m
    15km    18.7km/L      248m
    62km    40.8km/L     -663m

Saw such various mileage results even on constant speed.
The reason was the altitude change on each sections.
If we use 0.106L/100m fuel to cover the potential energy, the table becomes as follows;

section km  fuel used  fuel pot  fuel adj  mileage
    28km      1.14L     -0.13L    1.01L    27.8km/L
    15km      0.80L     -0.26L    0.54L    27.8km/L
    62km      1.52L      0.70L    2.22L    27.9km/L

Now, we can see constant about 27.8km/L mileage number for a virtual flat road.
Then, this number can be used for comparing the vehicle efficiency, such as tire change, Cd value change and so on.
And, the 0.106L/100m data can be used for comparing the engine efficiency, such as fuel change, acetone and so on.
Also, it shows calculated engine efficiency is 36% on my Prius.

Enjoy,
Yoshi

[Matt Timion]

Originally Posted by cheapybob

Your ABA method is correct, but short test runs can introduce error, too, IMO. Unless the temps, wind and road conditions are the same, they can skew the results, too.

I'm beginning to wonder if its really worthwhile. So few mods seem to make any significant repeatable difference. I seem stuck at about 53 mpg on my 60 mph test loop, and around 39 or 40 mpg for normal suburban driving. Both numbers are significantly better than what I started with, but additional improvements have all turned into mirages.

It can be a bit much to do testing. This is why I save testing for items I'm pretty sure are going to work. I'd rather be able to tell people "adding rear wheel skirts improved my fuel economy by 8%, and HERE is how I know."

Of course if an additive or gadget maker wants us to test for free I'd be more than happy to apply the same methodology to their product.

[95metro]

Originally Posted by cheapybob

Your ABA method is correct, but short test runs can introduce error, too, IMO. Unless the temps, wind and road conditions are the same, they can skew the results, too.

You're absolutely right, which is why establishing baseline and margin-of-error is so important, plus checking weather conditions for every run. You have to account for every possible condition and even then on-road testing is prone to error.

Long test tracks would be great, but unless you have a real race track to use weather conditions can change so drastically between points miles apart.

One thing I keep thinking as well is that every vehicle must have a plateau that can't be surmounted without extreme modifications (i.e. chopping your vehicle in half).

[Matt Timion]

Originally Posted by 95metro

One thing I keep thinking as well is that every vehicle must have a plateau that can't be surmounted without extreme modifications (i.e. chopping your vehicle in half).

I think you're right. And I think the plan is to find that plateau

[zpiloto]

Originally Posted by Matt Timion

I think you're right. And I think the plan is to find that plateau

That's the addicting part. Just when you think you maxed out you read something or think of some thing else to try. But the gains do get smaller and smaller the closer you get to the max. It looks like the max might be some where around 83% over epa

[maxc]

My goal is 100% over epa. I have take-no-prisoners approach to FE.

[ZugyNA]

Originally Posted by cheapybob

Your ABA method is correct, but short test runs can introduce error, too, IMO. Unless the temps, wind and road conditions are the same, they can skew the results, too.

I'm beginning to wonder if its really worthwhile. So few mods seem to make any significant repeatable difference. I seem stuck at about 53 mpg on my 60 mph test loop, and around 39 or 40 mpg for normal suburban driving. Both numbers are significantly better than what I started with, but additional improvements have all turned into mirages.

I see rear fender skirts...full moon wheel covers...rooftop vortex generators...tabs in front of the front wheels...maybe another 5-6% gain?

If your 60 mph baseline was 38 mpg...53 mpg = a 28% increase.

It can be frustrating...but it's supposed to be FUN. With fender skirts and vortex generators...you could buy and wear an "alien" mask...and fool them all.

I know I'm thinking of a nice 5 speed Saturn wagon sometime in the future.

[Mighty Mira]

Originally Posted by ZugyNA

I see rear fender skirts...full moon wheel covers...rooftop vortex generators...tabs in front of the front wheels...maybe another 5-6% gain?

As far as I am aware from reading his posts, he hasn't even done the undertray thing yet; the only thing he's done has been to block off part of the grille. Which I think is probably a fairly small grille anyway, compared to most cars, so blocking off part of it wouldn't yield much in the way of results.

Combining all realistic/cheap aero mods for the car:
-undertray
-front, rear wheel deflectors
-smooth wheel covers
-rear fender skirts

I would expect close to a 20% gain at around 60mph, at the very least 10%. I'd do the vortex generators last if at all.

Would you list everything you've tried out so far again?

[ZugyNA]

Originally Posted by Mighty Mira

I'd do the vortex generators last if at all.

Easiest and cheapest to do and probably good for a 1.5% gain?

[SVOboy]

But also ugliest and least return,

[cheapybob]

One thing I noticed today when my Daughter came home with the 99 was that my 97 is missing the front air dam. The reason I haven't tried a belly pan is because the friend that works at the place that makes thin aluminum sheet stuff hasn't gotten me any, yet. No, I haven't tried rear wheel skirts, yet, either, again due to lack of materials. But given that the aero mods up front "should" have given me at least 1 mpg, I don't have much faith that rear wheel skirts will give me much either. To be honest, from what I've seen thus far, I found no measurable gain at all from smoothing the whole front end airflow wise by eliminating most of the holes and protrusions, including windshield wiper removal. The impression I've gotten from it is that it must not be making much improvement in the drag coefficient, or I'd see it on the scangage.

I'm not going to mess with those vortex generators. That might help for a box shaped truck trailer, but I don't think it will buy any measurable MPGs for a car thats already fairly efficient.

BTW, 53 mpg vs 40 mpg is a 32.5% increase.

Not trying to be a "naysayer", just haven't found any measurable improvement from areo changes, and I think some of you are dramatically overestimating potential percentage increases in fuel economy from the mods you are suggesting. Then again, if the percentages you are giving are for drag reduction, they might be correct, but its just that reduction in areo drag won't increase fuel economy by the same amount.

[zpiloto]

Just need to keep chipping away at it. Nothing alone is going to give you a huge jump in % but you just keep adding and modifying stuff and with all of it working together it does give you a big increase. There is also a ceiling. At some point the increases will stop. Then you get a new car and start over again

[ZugyNA]

Well...the difference of an avg 33-34 mph vs 47 mpg with a tailwind tells me aero mods work....IF you could reduce aero drag by 50%....there was about a 25 mph tailwind...driving at 55 mph.

[cheapybob]

Originally Posted by ZugyNA

Well...the difference of an avg 33-34 mph vs 47 mpg with a tailwind tells me aero mods work....IF you could reduce aero drag by 50%....there was about a 25 mph tailwind...driving at 55 mph.

A few thoughts...

What production car has the lowest drag coeff? Figure no matter what you do, you won't get there. Take your car's drag coeff, and figure you can improve it some percentage of the difference. Honda Insight .25 vs Civic Hatchback .36 takes 32% more power to move through the air

http://www.insightcentral.net/encyclopedia/enaero.html

My SC1 stock should be .33. It looks like the newer 2001/2002 SC1 didn't have a spoiler, and as a result the drag coeff dropped to .31 for them. EPA ratings were the same from 98 to 02, so I'd say it might have helped a little, but not enough to add 1 mpg. I went out and looked at the spoiler, and its integral to the trunk, not just attached, so I can't just remove it.

http://www.autoworld.com/SC1and2.htm

On the other hand, I agree that a substancial reduction will help, and your example of MPG into a headwind or with a tailwind is valid.

Any thoughts on whether air dams work to improve MPG? If so, how much? On the race track they allow for a higher speed on the long straights, so there must be SOME aero advantage, and its just a question of how much it is at our lower highway speeds.

[zpiloto]

Start with the belly pan for the biggest gains. Look at Keeps on Rollin' - basjoos. There's a thread around here somewhere showing his transformation. Search the archives. He went from high 50 to high 60 and 70 with aero mods. With a good belly pan an airdam is not much help. I know on my car, CD .33, a full airdam decreased FE by .9 MPG. Only after cutting out all but the area around the tires did it come back to a no loss situation.

[cheapybob]

Well, I need to get the materials for the bellypan real cheap for it to make economical sense as I see it. Hopefully I'll be able to get enough material to make a front grill cover (currently its about 6 sq ft of race tape), rear wheel skirts, wheel covers, and side skirts. If I ever get the material, I'll remove my front end cover after making a pattern, and make a test run for MPG before adding the aero stuff, and than make another MPG test run after its all installed, hopefully under similar weather conditions.

As a separate issue, I'll probably check into whether the newer, more aerodynamic trunklid would fit my car and what one would cost. Thats likely not a paying proposition, though.

[ZugyNA]

Wellllllll..........

I do my own mechanical work and the last thing I'd want would be to have to remove shields to get to things that need to be checked or repaired.

My fender skirts are a pain as far as checking tire pressures if chance doesn't put the air thingamabob where I can get to it.

Also...cars are designed for a lot of airflow around the trans...exhaust...and diff (if rear drive)....for cooling.

So a compromise might be an air dam at around the same ground clearance as the rest of the stuff under the car...can't say how it affects mpg though.

Another thing (might have mentioned this before ;-)).....covering extra holes in the front and covering the gas tank area at back likely could be just upping operating and fuel temps...which will improve mpg.

[Ted Hart]

Hi, all!
Now that you've jacked around with aero mods, tire pressures, "trim tabs", belly pans (what a pain!), and all this "Tornado" rubbish...let me just say: Have you thought about modifying that stuff in your gas tank? It used to be known as "gasoline"...but, lately it smells funny (like 3-in-1 oil?), if a bit is spilled while refueling / pouring onto a smooth concrete surface...it's still damp hours later! The gasoline of yesteryear would have evaporated in a few minutes! This is the stuff your engine is supposed to run on ??? Ah! the 21st century!
Can the gasoline be changed? Cheaply? Safely? Legally? You bet!
Just as soon as Matt Timeon sends me an SSAE with his address, I'll send him info you'll be able to see , once posted by Matt. -Ted Hart

[Ted Hart]

Originally Posted by 95metro

Hear, hear!

Hear, here? We used to have a sign over the wall-mounted telephone (in our machine shop) which said this! The sign is "disappeared" one clean-up day... so I put up a pencilled sign "Where, where?" !

[Ted Hart]

Originally Posted by zpiloto

Nothing alone is going to give you a huge jump in %. There is also a ceiling....

Hi, "zipiloto"!
Sorry about the "zip" typo...but I thought I'd leave it alone! LOL?
You say "Nothing alone will give you a huge jump in %." You were talking MPG, yes? If Matt ever posts my run sheets...I will show you how to achieve a minor miracle.
What you do is ... increase the torque output of your engine (at the same throttle setting). Then, watch your mileage soar! It's about the efficiency of conversion of the energy in gasoline to mechanical energy (torque).
Looking at the conversion picture from another direction... have you notice the MPG rise (on a MPG gauge of some sort) when you lift your throttle foot just a bit? Same thing! Lower the load, MPG goes up.
Today's gasolines are not going to make the power (torque) of yesteryear's gas ... so, you're not gonna get the torque to generate the potential mileage
in a gallon. If the gallon is not burned "properly", less MPG is delivered.
Thus sayeth the "magic bullet"... under the ceiling!

[rookie]

Originally Posted by cheapybob

One thing I noticed today when my Daughter came home with the 99 was that my 97 is missing the front air dam. The reason I haven't tried a belly pan is because the friend that works at the place that makes thin aluminum sheet stuff hasn't gotten me any, yet. No, I haven't tried rear wheel skirts, yet, either, again due to lack of materials. But given that the aero mods up front "should" have given me at least 1 mpg, I don't have much faith that rear wheel skirts will give me much either. To be honest, from what I've seen thus far, I found no measurable gain at all from smoothing the whole front end airflow wise by eliminating most of the holes and protrusions, including windshield wiper removal. The impression I've gotten from it is that it must not be making much improvement in the drag coefficient, or I'd see it on the scangage.

I'm not going to mess with those vortex generators. That might help for a box shaped truck trailer, but I don't think it will buy any measurable MPGs for a car thats already fairly efficient.

BTW, 53 mpg vs 40 mpg is a 32.5% increase.

Not trying to be a "naysayer", just haven't found any measurable improvement from areo changes, and I think some of you are dramatically overestimating potential percentage increases in fuel economy from the mods you are suggesting. Then again, if the percentages you are giving are for drag reduction, they might be correct, but its just that reduction in areo drag won't increase fuel economy by the same amount.

Hear is an article on aero mods done in a windtunnel ,hope its helpfulhttp://www.hotrod.com/techarticles/b...ips/index.html

[cfg83]

rookie -

Originally Posted by rookie

Hear is an article on aero mods done in a windtunnel ,hope its helpfulhttp://www.hotrod.com/techarticles/b...ips/index.html

Someone posted a thread on this, but I never saw the article/URL until now.

That side view of the red camaro reminds me of CO ZX2's air dam.

From a practical urban driving standpoint, it would be cool if the air dam was retractrible below 40 MPH. It would probably need to be in 3 parts, 2 sides and a front, where the front overlaps onto the sides to make sure no frontal air gets into the seams on each side.

CarloSW2

[Booster]

Hi there!
Do you know how much cost testing at authorized testing labs in Canada, any contact info?

[thecheese429]

I like the way that the Mythbusters did their tests with the golf ball car myth. Even though they didn't use ABA, they did use a small removable fuel tank and weighed it before and after each run, simply because they didn't have the time to run a whole tank of gas with each mod. That is just something I might try in the future, making it possible to determine the improvement (or not) of something in just one afternoon.