Black & Green modding thread (1998 Civic DX Coupe base)

[California98Civic]

A while back MetroMPG wondered aloud on my transmission swap thread if I had a general build thread for "Black and Green." I didn't. I do now. I'll use this thread to discuss and document future mods. My one "ecomod" planned for the near future is a group of aerodynamic mods to the tail end of the car: (1) rear wheel skirts; (2) rear box void that includes a flat trunk lid spoiler and a diffuser; and (3) a bellypan for rear section and maybe middle but not front.

For the sake of documenting the car's current state, here is a list of the current mods, cut-n-past from my garage page:

HYPERMILING (the best mod is the human ECU)
I always use EOC and P&G on surface roads, and a mix of these and "GLEN" on the freeways. I also use MPG-optimized routes, trip combinations, and driving times as much as my commuter schedule allows.

AERODYNAMIC
2.5" lawnedging airdam
Side skirts v2.0 (cut rain gutter, flat black paint)
Full upper grill block (v1.0) & 80% lower block (v1.2).
175mm wide tires on rear only (185s still on front).
Passenger mirror replaced with internal convex.
Half-moon style wheel skirts (removed).
Mudflap delete.
Passenger-side wiper delete (and RainX application).
Radio antenna moved to dashboard.
Thrush Turbo muffler (smaller than OEM, better for planned belly plan's rear diffuser).

MECHANICAL/ELECTRICAL
1993 Civic CX transmission with 93,000 miles on it (installed when odo read 203,000 miles). The CX gear ratios: 3.250 (1), 1.761 (2), 1.066 (3), 0.853 (4), 0.702 (5), 3.153 (r), and 3.250 (final reduction). The DX gear ratios were: 3.250 (1), 1.782 (2), 1.172 (3), 0.909 (4), 0.702 (5), 3.153 (r), and 4.058 (final reduction).

An injector kill switch

Tires overinflated (60psi).

An "Externally Powered Electrical System" (I plug the car in when I'm home). The set-up combines an alternator on/off switch, 7 LED brake & running lights and a H4/HB2/9003 HID kit for the headlights, a deep-cycle Odyssey PC1200 battery with metal jacket & XSP-586 SAE post adapters (installed @192K miles), and a 25-amp on-board battery charger. I've also pulled one of two 5w license plate bulbs. For notes on why the 25 amp charger is important see this post.

A Warm Air Intake (WAI). And CAI/WAI manual switching ability for hottest days.

13" wheels and 175/70s on rear (replaced 14" 185/65s).
NGK single-platinum spark plugs.
Radiator/grill ducting (v.1.2).
6K oil change schedule.
Fully synthetic Mobil 1 "Fuel Economy" 0W-30 (5w-30 for warmer seasons).
Royal Purple 5w30 oil in the manual transmission.

WEIGHT REDUCTION
251lbs removed (to approx 2011lbs* curb weight):
9.7lbs VX wheels on rear only (replacing 18lbs alloys), 9lb thrush muffler (replacing 18lb OEM), AC, rear seats, power steering, and numerous other things small and large.

[Jakins]

What all did you delete for the weight reduction? I think all I took out was te spare tire and I weighed my car at the metal scrap yard and it was 2200 pounds with a half tank of gas. That's with the hx chassis that is supposed to be 2400 pounds

[California98Civic]

Originally Posted by Jakins

What all did you delete for the weight reduction? I think all I took out was te spare tire and I weighed my car at the metal scrap yard and it was 2200 pounds with a half tank of gas. That's with the hx chassis that is supposed to be 2400 pounds

200 pounds sounds too high for just the tire and associated parts. 2400 sounds too heavy for a 1997 curb weight too. Here is a list of what I deleted. I didn't have scales or anything so I just used the official 2262 curb weight for my baseline. Each item would get weighed after removal by putting it and myself on a scale and subtracting my weight.

On the tail-end aero mods first on my list, I am looking for advice. I'm using Hussain Ali's paper on drag reduction as inspiration for designing the box cavity. Here an image capture of the a table of core findings:



I will focus on the box cavity, wheel skirts, undertray, and diffuser, since I already have the other mods. Any thoughts on this study, my possible designs, or testing? I know my car is a coupe and not a hatch like the Audi A2 Ali tested, but I plan my own ABA coasting tests with versions of the "black and green" box cavity.

Here is the final version Ali tested. The diffuser is 2* instead of six because of interaction with the box cavity.

[California98Civic]

I have a nice pile of cardboard now--including some big sections--and black duct tape for building and testing designs.

I need a little help re: mounting points for a diffuser/undertray. Has anyone done this on a 6th gen Civic that might share ideas for where and how to mount the undertray?

I have read brucepick's thread: http://ecomodder.com/forum/showthrea...tml#post225094. But his rear diffuser seems to be curved a bit, and I'd like it flat and adjustable in place, so I anticipate I need some way to suspend the aft edge below the bumper.

In this pic and in some of the other pics attached below, you can see parts of the chassis from which I might mount rails. Any advice?

[California98Civic]

The rear box cavity will need a diffuser and the diffuser will need at least a partial under tray (belly pan). So I am thinking of designs.

The first four pages of this diffuser build (and one later post with photos of the prototype) are useful: http://ecomodder.com/forum/showthrea...nel-15189.html. I want to imitate his use of togglebolts in the existing subframe, aluminum c-channels(?), and folded coroplast on the diffuser.

Here is an image of a recent Civic hybrid's undertray. I like the fact that they leave space for things to heat to escape and for service access. I'm also thinking of oil drip from my ancient engine:



And here is my first effort at "drawing" a prototype:



dark green = vertical line, curved inward toward the trunk lid
orange = vertical section follows tumblehome, curves to spoiler & trunklid
light green = flat spoiler

The goal is to allow flow to "skip" the dead air around the tail lights, create cleaner separation and a smaller wake, and therefore as I understand it produce less drag. I know any benefit will be smaller than a boat tail. I don't want a boattail because of the loss of window and trunk functionality and the increased fabrication difficulty.

[Jakins]

i have a pretty nice belly pan if you want to see some pics. i cut the piping off the end of my muffler and tucked it up real high so it was out of the way. it was real easy. oh and yah, i wasnt suggesting my spare tire was 200 pounds lol. that was just the only notible thing i could remmember removing. i guess i also have everything a/c removed and power steering. and my front bumper support from back when i had an inter cooler when my civic was turbocharged.

[California98Civic]

Originally Posted by Jakins

i have a pretty nice belly pan if you want to see some pics. i cut the piping off the end of my muffler and tucked it up real high so it was out of the way. it was real easy.

I'd love to see the pics. Post 'em up! I also adapted my exhaust piping with a Thrush muffler that is not a fart can but is a lot lighter and smaller in diameter than the OEM Bosal one. It was partly in prep for a diffuser.

[California98Civic]

I have begun building first version box cavity using good thick cardboard. I changed the design to a simpler box, like the one pictured in post #3. And I extended it to about 150mm instead of the 100mm size they tested. I'm skeptical this will produce results on its own that I'll be able to measure with my crude methods, but I'm willing to try it out. I'll finish it today and test it tomorrow using coasting on a hill nearby. I'll post results and photos sometime Sunday night or Monday.

[EDIT: AS OF TUESDAY (6/11) MORNING I HAVE BEEN UNABLE TO GET THE TIME DURING HOURS IN WHICH THE WEATHER CONDITIONS ON THE COURSE ARE APPROPRIATE. WEDNESDAY LOOKS GOOD. I'LL POST RESULTS AND PICS THEN.]

EDIT 2: WEATHER REPORT CHANGED (6/12) FROM LITTLE WIND TO 8-10MPH WIND ... MIGHT HAVE TO WAIT DAYS, JUDGING FROM WEATHER FORECASTING.

[Jakins]

id suggest not using a Robert Thomas sign because he loves dead racoons. for some reason in west texas he ate 18 animals. i had to stop and zip tie it back up and there was flesh hanging out of his mouth. freaky. then he got a live skunk. that thing stunk up my car for a few months. but his results are unarguable. just got to keep him fed.





i started the front but hooking it under the bottom and then tieing the other end to the front sway bar. leave a big hatch for the oil plug and oil filter.



the front is taped together because i didnt have any of the giant signs. just small ones. use the big 8 footers to make it all one piece.

[California98Civic]

Originally Posted by Jakins

id suggest not using a Robert Thomas sign because he loves dead racoons. for some reason in west texas he ate 18 animals. i had to stop and zip tie it back up and there was flesh hanging out of his mouth. freaky. then he got a live skunk. that thing stunk up my car for a few months. but his results are unarguable. just got to keep him fed.

Hahaha! Any trouble with Robert Thomas getting hot headed from that muffler attached to his forehead?

And thanks. It looks like lowering your ride made it quite a lot easier to get around suspension elements.

My testing is delayed again today... too much wind on the course (8-10mph), so I might move on to designing adjustable-angle rear diffuser prototype. The aero study I am using suggested the box cavity interacts heavily with under car flow, so diffuser is important anyway.

james