Civic hatchback aerodynamics

[basjoos]

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.

[krousdb]

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

[molecule]

ballsy
what motor you got and whats the mileage gains like

[SVOboy]

JDM D15B and CX tranny.

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

[molecule]

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...

[Bunger]

Originally Posted by krousdb

Well maybe not the caulk.

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.

[MetroMPG]

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...

[MetroMPG]

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)

[Matt Timion]

Originally Posted by molecule

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...

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.

[Bunger]

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

http://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.

[Bunger]

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

[Matt Timion]

Originally Posted by Bunger

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

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?

[Bunger]

Originally Posted by Matt Timion

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?

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.

[molecule]

excellent

[tomauto]

I can't see the pics...

[basjoos]

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.

[SVOboy]

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

[Matt Timion]

Originally Posted by SVOboy

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

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

[thisisntjared]

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

[SVOboy]

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

[molecule]

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

[Compaq888]

Originally Posted by SVOboy

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

DAMN!! :JAWDROP:

[The Toecutter]

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...

[Matt Timion]

Originally Posted by The Toecutter

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...

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

[basjoos]

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

[MetroMPG]

Originally Posted by basjoos

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

there's a technique described in the last post in this thread:
http://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...

Originally Posted by metrompg

a simple scangauge trial i did yesterday - MPG at increasing speed intervals, flat road, no wind, warm (60 ish), cruise control, top gear:

69 mpg (US) @ 65 km/h (40.4 mph)
62 mpg (US) @ 75 km/h (46.6 mph)
55 mpg (US) @ 85 km/h (52.8 mph)

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!

[tomauto]

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)

[SVOboy]

I just dont see how more heat could help mpg.

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

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

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

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)

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.

[MetroMPG]

Originally Posted by tomauto

I just dont see how more heat could help 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.

[basjoos]

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.