Civic hatchback aerodynamics
 

So far, I have installed underbody panels, grill blocks, read wheelwell skirts, smooth hubcaps, and caulked all of the seams on the front and sides of the cars. After the caulk dried I used a razor to cut a line on those seams (doors, hoods, gas cap cover) that I need to open.

https://www.fuelly.com/attachments/fo...aa7b8ba6ad.jpg

https://www.fuelly.com/attachments/fo...c3ce8dfffb.jpg

https://www.fuelly.com/attachments/fo...85c69670cf.jpg

https://www.fuelly.com/attachments/fo...dc189a9c5c.jpg

Dood. you are my hero! Me
 

Dood. you are my hero! Me next! Well maybe not the caulk.

ballsy what motor you got
 

ballsy
what motor you got and whats the mileage gains like

JDM D15B and CX tranny. He's
 

JDM D15B and CX tranny.

He's not had it on for a full tank yet either!

is there a reason you didn't
 

is there a reason you didn't cover the whole rear well...?
i guess you probably couldn't get the tire off if you needed to...
hmm

i'm been trying to devise a way...maybe a clip system...
where you would have to lay down and reach way up to install/remove them...

Re: Dood. you are my hero! Me
 

Maybe if you used clear caulk, and used a piece of ice to smooth it into the cracks, the outcome would be a little cleaner looking.

All these caulk threads are reminding me of the "Caulk" skit that SNL did a little while back. I'm sure you can imagine the premise.

nice, basjoos.
 

nice, basjoos.

my car is going backward, aerodynamically.

my cardboard grille block that's been on since november is delaminated, the duct tape is in tatters and it's literally about to fall off on the road.

my aborted attempt at "scientifically" evaluating the belly pan hasn't been reproduced yet. and i don't want to put on the permanent version and miss the chance to know exactly what it contributes.

and my wheel skirts are off - though i did borrow the heat gun i'm planning to use to form the 90 degree lip in the plastic to mate to the wheel arch lip.

so why am i futzing around in the forum instead of making stuff...

ps - if ever there was a
 

ps - if ever there was a candidate for a boat tail (i.e. someone unafraid of altering the looks of his car), it's you. you're going to go far!

(on less fuel, of course)

Re: is there a reason you didn't
 

The other day while waking up (you know those half dream / half awake moments?) I actually figured out how to do this.

I'm currently finishing my basement and I picked up a "pocket hole" kit for making strong, simple joints with wood. I used it to build a bookcase, and I'm also going to use it for a few other things.

Essentially the plan is to make a wood positive, or maybe a wood and bondo positive. I'll then make a mold with plaster of paris and THEN i'll make another positive with fiberglass. I'll smooth it out (with some primer and maybe a little bondo too. In 3 or 5 locations on the back of the fiberglass wheel skirt I'm going to put a giant gob of plastic epoxy. When it dries I will use the pocket hole system and drill a few holes that will be angled.

At this point we can drill a few holes in the car using the small half inch "lip" in the wheel well and maybe put those little plastic female screw receivers (usually used for mudflaps) into these holes.

Anyway, it's a lot process, but it should be hella fun when it's done.

I've used Dzus fasteners in
 

I've used Dzus fasteners in the past for hoods, bumpers, front ends, etc... should be great for what you need.

https://www.kenlowe.com.au/body_hardware.htm

Some of the pictures there will give you an idea of what I'm talking about, I'll see if I can find some better ones.

800 ? 800: true);"
 

https://www.zealautowerks.com/images/dzusanim.gif

They have self sprung versions that are perfect for fibgerglass too, use these and you'll be getting much props from the racer crowd. =)

Re: 800 ? 800: true);"
 

I'm trying to understand exactly how this works and my mind can't grasp it. What does the spring do, and how is it held in place? Will it require me to weld the plate to the body?

Re: 800 ? 800: true);"
 

You don't have to weld the plate to the body, but most do. You could bolt it on if you wanted to remove it later.

Basically, the button gets riveted to the fiberglass (or whatever) wheel cover. then you attach the backing plate to the car where needed. When you tighten the button, it becomes flush with the car. Very clean and simple. Depending on the strength of your wheel cover, I think 3-4 fasteners would do per side.

excellent
 

excellent

pictures
 

I can't see the pics...

Just got back from a trip to
 

Just got back from a trip to Savannah, GA. This is the first long distance trip I have made in my Civic Hatchback since I installed the aero mods. Even while cruising at 75mph on the interstate, I was getting 62MPG. In the past, I would be getting around 44MPG while travelling at these speeds. Since I couldn't do a lot in the way of driving technique (other than a small amount of drafting) to improve mileage on a flat coastal plains interstate, this mileage improvement is purely the result of the aero mods I installed. Its interesting that although everybody is *****ing and moaning about the higher gas prices, this has yet to change their driving behavior and the traffic on I-95 was going just as fast as it always does.

Damn, 62 mpg at 75 mph,
 

Damn, 62 mpg at 75 mph, that's ridonkulous.

Re: Damn, 62 mpg at 75 mph,
 

Agreed. I'm going to start planning some aero mods as soon as the engine is swapped, which should be VERY soon now.

wow! that is crazy! i wish
 

wow! that is crazy! i wish the pics were still working....

Next time they're up I'll
 

Next time they're up I'll have to duplicate host them.

high priority thread... it
 

high priority thread...
it should almost be a sticky...
even without pics
i could see this rounding up over 50% of available mpg gains on my car
i found some good stuff in my garage too
ICING
and a sheet of thin/clear plexi

Re: Damn, 62 mpg at 75 mph,
 

DAMN!! :JAWDROP:

you should try to calculate
 

you should try to calculate your Cd using the coast down method, after figuring our your rolling resistance and such. I'd be interested in knowing.

I suspect you got your Cd down to around .21-.23 to get those MPG figures.

I'm also trying to figure out a way to mimic the effects of the caulking without a car looking like a rolling sicence project. I'm thinking of using bondo to do it, only smoothing it out. A razor could cut those seems just as well. Done right, you could no doubt paint over such a smooth surface and it would look real slick, as if it came like that from the factory...

Re: you should try to calculate
 

I've been wanting to do the same thing. Perhaps it's also possible to sand down the caulk once it has dried.

I'm not familiar with the
 

I'm not familiar with the coast down method for Cd calculation, how do you do it?

Re: I'm not familiar with the
 

there's a technique described in the last post in this thread:
https://www.gassavers.org/forum_topic/weight_reduction.html

i haven't tried it. can't say for sure how well it works.

basjoos - again i have to say i'm impressed with the numbers you've achieved. 62 @ 75 is astonishing.

to compare...from another thread...

i could only get 62 mpg when going nearly 30 mph slower!

sure, there's probably a temperature difference between your recent driving conditions and my observations, but wow! i think i'd be lucky to get 62 mpg in the low 50 mph range when it actually gets hot here!

heat = mpg ??
 

I just dont see how more heat could help mpg.

Also, I have a question about the thermostat modication (170 to 192 degree mod) Where does all the mpg improvement come from?

From what I can see, the only way you are gaining anything is from the electric fan not being used as much but crap, why wouldn't you just have the alternator turn on while your coasting?

I totally dont see a point to the warm air intake. Maybe it is because I live further south. Maybe I am wrong, but doesn't heat hinder any performance? (speed or economy for that matter)

Quote:I just dont see how
 

Hot air = less dense = less gas = more throttle opening = same gas but less friction = less gas overall.

Warmer engines are more efficient. Plus honda ecus pull 3% fuel when you hit 195 on ECTs compared to 180.

It hinders speed, but not economy. OBD2 might be different than obd0/obd1 hondas, but Rick (rh77) saw good increases with a WAI on his obd2 integra.

Re: heat = mpg ??
 

other warm ambient benefits:

- less time in open loop (less time spent warming up)
- less tire rolling resistance
- reduced aero drag (less dense air)
- reduced losses to lubricants which are more viscous when cold (bearings, engine oil, transaxle fluid, etc)
- higher tire pressure (if you last filled it when cooler)
- and more i can't rhyme off the top of my head at the moment.

That is the one nice thing
 

That is the one nice thing about southern summers. Although they may not be the most comfortable for the driver, those hot and humid conditions give the best FE. When I was getting that 62mpg@75mph, the ambient temp was around 85F with high RH, since a stalled warm front was sitting over the area.

perfect conditions. that's
 

perfect conditions. that's awesome.

i love reading these posts. they inspire me to continue chipping away at my car's aero issues.

i pulled a hubcap off the car tonight and brought it inside to mull over how best to streamline it (cover it fully or just cover the holes). and i worked on my permanent set of side skirts this afternoon as well.

what's up with photobucket? how come your pics disappeared?

maybe thats why we are
 

maybe thats why we are burning a hole in the ozone layer
warming up earth permanantly to save fuel
its all intentional...of course...

No time to work on my wheel
 

No time to work on my wheel skirts. Im swamped at work! WHo knows when I will get that done.

I don't know why the photos
 

I don't know why the photos stopped appearing, but I'll post then again below.

https://www.fuelly.com/attachments/fo...df3051d27c.jpg

https://www.fuelly.com/attachments/fo...814114937f.jpg

https://www.fuelly.com/attachments/fo...2fc3cec8b5.jpg

https://www.fuelly.com/attachments/fo...52be62628d.jpg

https://www.fuelly.com/attachments/fo...2872db55e9.jpg

https://www.fuelly.com/attachments/fo...c26a657a73.jpg

The aero mods resulted in no
 

The aero mods resulted in no noticable change at low speeds (below 35mph), but significant changes above 60mph. The increase in drag that I normally start to notice as I get above 65mph is greatly reduced and when I let out the clutch and coast, the speed takes much longer to come down than it used to. The decrease in drag has given me the effect of a horsepower boost at highway speeds and I can now pull hills in 5th at 65mph that I used to have to shift down to 4th to maintain speed on. Wind noise is greatly reduced and road noise is somewhat reduced. All in all, it was a great return on about $50 in parts and most of a day's worth of work on the car. It resulted in an mpg boost at interstate speeds from 44mpg to 62mpg and the mpg's for local driving went from the 54mpg typical for this time of year up into the upper 60's (hopefully into the 70's with some more tweaking and warmer weather). If the car companies were serious about improving mileage, you think they could do this treatment to the new cars they sell.

i can't wait
 

I just can't wait to start my own undertray. This seems like almost an obvious thing to do to vehicles. The general public just doesn't realize that it can hurt economy of a vehicle. Maybe it is because they can't see it normally.

How many mounting points did you have on the undertray?

On the Civic hatch, the
 

On the Civic hatch, the exhaust runs down the center tunnel and then cuts over to the right side of the car by the rear wheel. I ran Coroplast down the left side from under the front bumper to the rear of the car, spanning from the the plastic curb at the side of the vehicle (where the lift points are) to the frame at the edge of the center tunnel. On the right side, the Coroplast ran from under the front bumper to just ahead of where the exhaust pipe curves to the right side of the vehicle. Then I spanned the tunnel with roof flashing. I drilled and tapped for 8-32 screws (used screw and fender washer) about every 14" or wherever I could find a suitable attachment point if the frame wasn't available over the the entire span. I ran white duct tape over the seams and screw heads and ran metal foil tape over the seams by the roof flashing. The hardest part was bridging the area under the gas tank, since I obviously couldn't drill into any of the metal there and the exhaust ran through the linkages of the right rear wheel which limited where I could use Coroplast over there. In the engine compartment there is a fairly large opening on either side opening into the front wheel well where the drive shafts attach to the front wheels, so I used these for the radiator air exhausts. Since I took these pics, I've had to open up the grill block some more, so I now have a single center 4" x 4" opening and the smaller opening on the right side. The taped-over opening is for the AC radiator and I'll open it if I need it when it gets hot enough to require use of the AC. Once I determine how much radiator opening I need, I'll replace this grill block with one that I can manually adjust the openings of from inside the car. Look at Krousdb's undertray installation on the Del Sol Aerodynamics thread for additional pointers as I used his installation as a referance when installing my own underbody panels.

Parts list: (2) 4'x8' sheets
 

Parts list:
(2) 4'x8' sheets of 4mm thick corrugated plastic (Coroplast)
(1) 20"x 10' roll of aluminum roof flashing
(1) box of 8-32x 3/4" panhead screws
(1) box 3/4" fender washers
(1) roll of white duct tape
(1) roll of heat resistant foil tape
(4) 14' pizza pans (for flat hub caps)
(2) tubes of caulk

Tools required:
Enough jack stands or blocks to suspend your car high enough to work under with all 4 wheels removed (be careful!).
Cordless drill
Drill and tap for 8-32 threads
Box cutter for cutting Coroplast
Tin snips for cutting flashing
Screwdrivers, etc.

my dude was the first to
 

my dude was the first to ever say anything about plugging up the front of my car...
i passed it off...i should have listened...

my dude
 

?????