where to start

[laack]

it took a while for the parking lot to get completely cleaned up where i didnt mind crawling around. I started with just a basic air dam, but have some questions about maximizing its effectiveness.

I currently have it set up with 3 inches of ground clearance and just paralleling/contouring the lower end of the bumper. my first observation/appreciation for it was how quite the it is now at highway speed. There are few hills here so i can only do modified coasting measurements. I have shifted my coasting points to turnoffs on my usual route to/from work by about .2 miles

i haven't done any tufting tests so i don't know if i am creating too much wake to get the most out of the air dam. How far should it extend laterally to minimize wake and drag?

Pictures to come later.

[saddlsor]

Front tire deflectors. Find some mud flaps or something similar, and screw them into the wheel well lining. Place them to cover from the inner half of the tires to 3-5 inches inward of the tires, as viewed from the front. You will see that the car companies do it this way, and it is for a good reason, aerodynamically speaking. You can play around with how low to make them, but I would start with them extending 5-6 inches from the ground.
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when you did this did you try different angles or just at a flat angle in front of the tires? I'm wondering if it's best to angle them in a little or send the air to the outside of the car. thanks

[saddlsor]

Originally Posted by laack

it took a while for the parking lot to get completely cleaned up where i didnt mind crawling around. I started with just a basic air dam, but have some questions about maximizing its effectiveness.

I currently have it set up with 3 inches of ground clearance and just paralleling/contouring the lower end of the bumper. my first observation/appreciation for it was how quite the it is now at highway speed. There are few hills here so i can only do modified coasting measurements. I have shifted my coasting points to turnoffs on my usual route to/from work by about .2 miles

i haven't done any tufting tests so i don't know if i am creating too much wake to get the most out of the air dam. How far should it extend laterally to minimize wake and drag?

Pictures to come later.

I can't help you with the tuft testing but I also installed an air dam on my 95 civic. I used an old conveyor belt and set the clearance to 2.5 inches. it did scrape some but didn't matter with the belt. I gained 3 mpg with it but have to take it off in the winter. was thinking about doing an undertray just so I wouldn't have to remove it. the only thing is I don't know if it would work as good as a airdam and it's a lot of work to install an undertray. maybe I'll let you do it first.

[laack]

a couple pics. where would you make changes to it if any? Grille block pending still, i want to wire in an led to the radiator fan first. any diy's on how to wire it?

[stockrex]

Originally Posted by saddlsor

I can't help you with the tuft testing but I also installed an air dam on my 95 civic. I used an old conveyor belt and set the clearance to 2.5 inches. it did scrape some but didn't matter with the belt. I gained 3 mpg with it but have to take it off in the winter. was thinking about doing an undertray just so I wouldn't have to remove it. the only thing is I don't know if it would work as good as a airdam and it's a lot of work to install an undertray. maybe I'll let you do it first.

why take it off in winter?

laack any gains with your mod?

[gone-ot]

Originally Posted by stockrex

why take it off in winter?

...from my college years in Flagstaff during the winter: the idea is to drive over the snow not "snow-plow" your way through it...that's why it's removed.

[laack]

Originally Posted by stockrex

why take it off in winter?

laack any gains with your mod?

I'm still on the same tank, but I'll post the first tank numbers. I'm going to take a 3 tank average since weather has warmed up a bit since the start of this tank plus I just started using a different fuel injector cleaner, which netted an extra 1.8 mpg on the last tank.. I got too antsy with the air dam so i didn't get to do a multiple tank average to see improvements from injector cleaner (lube control fp plus). It has however smoothed out my idle and resulted in starting up quicker so even if it doesn't improve fuel efficiency my engine is running better.

I am pretty excited to see some numbers though, i'm at 260miles at the 1/2 mark on the tank. I'm usually at 180-210 at a half tank.

[Istas]

Congratulations on your first mod. Those are some encouraging numbers (though to tell for sure how much is the mod and how much is you attempting to get the best fuel economy possible, you'll need to do some A-B-A coast testing and/or cruise control testing).

As for how far back to go with the air dam, I'd say go back as far as the bumper/fender does. You want to direct the air as smoothly as possible down the side of the car, which means trying to not throw air out to the side of the car. You might be okay simply following the lower curve of your bumper, as seen here.



Even a partial undertray can help, a lot of the aero mess under my car had to do with the wide-open underside of the engine bay, and it practically ducted air up into the front wheel wells. Having even a short undertray like this helped the air to go past that more smoothly. Though of course with coroplast you'll need to make sure it doesn't melt.

If you're going to use an undertray I think it's best if the bottom edge of the airdam is level with the tray, and that both are no lower than the lowest points on the underbody of the car. Having less air passing under the car is good, but if you lower the airdam too much you're increasing the frontal area of the car, which means the car's pushing more air than it needs to. From what I understand, an airdam lower than it needs to be helps compensate for not having a smooth underbody. (I forget who, but someone on here had a GIANT coroplast airdam on the front of their pickup and it helped a lot because of how aerodynamically 'dirty' the underside of your average pickup is)

[laack]

first tank mpg was satisfying, but i was hoping for a little more. MPG with a mix of 70/30 hwy/city was 45 mpg. driving style: neutral coasting when ever possible, slow accelerations, 60 on hwy traffic permitting, otherwise 65 following semi's.

I was averaging 40-42 all winter so warmer weather alone would account for at least 1 mpg gain. I use the same pump a the same gas station (shell on my way to work) every time so given my unsophisticated calculations its about as accurate as i can get. I still plan to do an average before i make any other changes to configuration. It will be trimmed up first since i'm scraping a bit still.

What kind of gains would i expect from rear wheel deflector/strakes? any tips to reduce separation at the rear of the car? I thought about trying to figure out how to attach the extra coroplast that i have (smaller sheets) but i can just picture wind catching the leading edge of what ever i connect it to and ripping it off. I'm adding additional weather stripping as previously recommended to the hood. If it doesn't add any mpg, hopefully it will at least quiet the ride a bit.

[gone-ot]

Originally Posted by laack

...so warmer weather alone would account for at least 1 mpg gain.

...although this data derives from an '09 Pontiac Vibe 1.8L (DISI) with 4-speed automatic, it might provide a "closer" estimation of fuel economy versus temperature.

1) 28 data pairs [ one in morning (am) and one in afternoon (pm) each day ]
2) temp range: lowest am temp = 37°F; highest pm temp = 84°F
3) roadway: 4-lane freeway driving 95% of the time (time: 05:00 am, ~05:30 pm) 5% urban street & stoplights
4) distance each way: 26.2 miles
5) slight 0.2% road grade (altitude: 2330' home, 2550' work)
6) two rainy days, two windy days

...the linear regression equation (so far) from the data pairs:

MPG = (°F)/5 + 25

...with correlation coefficient of about: RR = 0.8-0.85

...obviously only 100% relevant to my vehicle, but might be useful as a "rough approximation" guess-ta-mation.