Serious testing takes time and energy.

[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

[GasSavers_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.