Aerocivic - how to drop your Cd from 0.31 to 0.17

[freebeard]

This thread -- 580 (now 581) posts
Anal Probe in Central -- 845 posts

But I think that some of that is due to the 'marketing' (thread title) and forum.

Does anyone know how to scrape the whole 58 pages into a single text file? I'd throw that at OSX's Summarize tool.

[godscountry]

Originally Posted by basjoos

New... Aerocivic has a web site: www.aerocivic.com

I started this project after the Katrina-insired gas price runup since I have a long commute. I first learned to drive during the 1970's oil embargo and have been perfecting my hypermiling tenchniques ever since. My car is a 92 Civic CX, which I bought new, and was giving me low 60's to low 50's before I started aero modding it.
Side view

Side view with open hatch

Rear view of boattail

Cargo area inside boatail, extending the interior of the car into the boattail added 20cu ft to the interior space. Also there is a hidden compartment under the new load floor in the boattail.

Radiator inlet slot (coroplast has since been replaced with aluminum sheet)




The end result is a car with such low drag that the results of coastdown testing is linear out to 90mph (it coasts almost as well at 80mph as it does at 50mph). I have to get it over 90mph before I start to feel the wind load from high-speed driving. OEM max speed was 95mph. I have had it up to 100mph with plenty of power remaining at that speed (estimated top speed of about 140mph). Wind noise is much reduced from stock. Approximate mileage on a flat road at 85F, 95mpg at 30 to 65mph, 85mpg at 70mph, 65mpg at 80mph, 50mpg at 90mph.

Additional mods planned, include replacing the current one-size-fits-all radiator inlet slot with a driver-adjustible radiator door. Eventually I plan to automate the door by using a Basic Stamp or similar process controller to monitor the coolant temps and adjust the opening to the actual cooling needs.

Most of my driving is at night, especially in the winter, and night driving is costing me 2 to 3 mpg in additional electrical load from the lights. About half of this loss is from the parking lights, the remainder is from the headlights. I want to replace the parking and dome lights with LED's. Since retrofit LED headlight kits are still several years off, I want to investigate installing a switch to kill one of my headlights and/or a dimmer control to reduce the headlight's intensity and power drain for situations where I don't need the full intensity of the headlights for visibility.

Love what you done.How about having a bodyman smooth it out,pull some molds,sell them for others.using 3m's new tape to install them.Add on aero panels.With a expert redoing some of the rear and lighting, it would be better looking then the new VWXL1 limited production car.I often think of new ways to build efficient vehicles,the one I like, is to section a car length wise,remove just enough for one seat and room to move,then apply aero mods or leave it as it is.Either way the cd is a lot better.You could add a tilting front and rear suspension,but if you look at the Nissan Delta race car[not their design,just engine used]it is very narrow in the front and wider in the rear.It has about half the power and looks like it would never handle on a racetrack,but it handles very well and goes just as fast.Thanks for sharing your cool car

[CFECO]

LED headlights are here now, both Aircraft Landing lights, and Automotive. They are not cheap though. $500.00 and up...

[gil]

Originally Posted by CFECO

LED headlights are here now, both Aircraft Landing lights, and Automotive. They are not cheap though. $500.00 and up...

I bought a pair for my corolla. $400.00 on eBay, Truk lite LED lights.

Gil

[Oceanic815]

Having just read this entire thread over several hours, I am amazed. Great work!

[j12piprius]

Originally Posted by basjoos

I don't have any photos as it is nothing special. The air coming off the radiator enters the engine compartment and then, since the underside is paneled and it can't exhaust there, uses the existing openings that are there to allow for suspension movement of the FWD drive shafts to exit into the front wheel wells. A smaller amount of air passes down the paneled central exhaust tunnel to cool the exhaust pipes and cat to empty into the right rear wheel well.

I'd like to try your method through the wheel wells, but it seems to me that simply closing off the underside would reduce radiator cooling and not increase it. Am I missing something in your explanation?

[basjoos]

Since the underpanel covering the bottom of the engine compartment keeps radiator exhaust air from exiting out the bottom of the engine compartment, I exit most of this air out through the front wheel wells where the low pressure created by the spinning wheels helps to pull the air through. A smaller amount of radiator exhaust air also exits through the covered central tunnel where it cools the exhaust pipe and cat, eventually exiting at the right rear wheel well.

I'm not trying to increase radiator cooling, as the whole point of an adjustable grill block is to tailor the cooling air flow (and its inherent air drag) to match the cooling needs of the engine. Since the openings from the engine compartment to the front wheel wells are much smaller than the original cooling opening out of the bottom of the engine compartment (now blocked by the underpanel), I use the slight suction created by the spinning front wheels to help move air through the engine compartment. This allows me to have plenty of cooling air flow when the adjustable grill block is open, but limited air flow when the grill block is closed and acting as a flow restrictor against the pull created by the spinning wheels. Most of the time my grill block is closed or barely open.

[j12piprius]

Thank you for the detailed explanation.

Originally Posted by basjoos

I use the slight suction created by the spinning front wheels to help move air through the engine compartment.

Did you do anything to create that suction, or is it already there on my car as well?

limited air flow when the grill block is closed and acting as a flow restrictor against the pull created by the spinning wheels. Most of the time my grill block is closed or barely open.

The steep hills are where I'm having some issue in my civic (with grill open and full outlet venting). I did pull the a/c fan fuse, but don't know if it affects engine heating. How do you get cooling with the grill block closed, and limited outlet venting, especially when climbing steep hills in the heat?

[3-Wheeler]

Originally Posted by johnlvs2run

......Did you do anything to create that suction, or is it already there on my car as well?...

Basjoos already answered that question here....

Originally Posted by basjoos

Since the underpanel covering the bottom of the engine compartment keeps radiator exhaust air from exiting out the bottom of the engine compartment, I exit most of this air out through the front wheel wells where the low pressure created by the spinning wheels helps to pull the air through.

Originally Posted by johnlvs2run

...The steep hills are where I'm having some issue in my civic (with grill open and full outlet venting). I did pull the a/c fan fuse, but don't know if it affects engine heating. How do you get cooling with the grill block closed, and limited outlet venting, especially when climbing steep hills in the heat?

I also have a small area for air flow due to a grill block, and recently drove on an 80F day up some 1/2 mile long hills by LaCross WI.

The grill block was on the car at the time, and I did the following to keep engine coolant temps down:

1) Slowly decrease speed from 55 to about 30 mph on a road with two lanes going up hill.
2) Kept engine rpm close to 3000 rpm on the Insight. I rarely spin the engine this fast in normal conditions.
3) The higher engine speed also means higher coolant speed through the engine block, which keeps it cooler than lugging the engine up a long hill.
4) Keep engine load on the lighter side. I gear the car according to load.
5) Engine temp at the top of several hills was about 210F, which is really good since more than 1/2 the radiator is blocked off.

Jim.

[basjoos]

Originally Posted by johnlvs2run

Did you do anything to create that suction, or is it already there on my car as well?

The steep hills are where I'm having some issue in my civic (with grill open and full outlet venting). I did pull the a/c fan fuse, but don't know if it affects engine heating. How do you get cooling with the grill block closed, and limited outlet venting, especially when climbing steep hills in the heat?

That suction is developed by a wheel spinning within the close confines of a wheel housing. Having a skirt over the wheel well opening does help to increase that suction just as the housing around a squirrel cage blower helps to strengthen and direct its flow.

I get a small amount of cooling airflow through my radiator even with the grill block closed as some air leaks around the edges of the closed grill block. When climbing a long steep hill in the heat, I'll open the grill block and let the front wheel suction do its thing. Then when going down the other side I'll gradually close the block as the engine's heat production drops.