Aerocivic - how to drop your Cd from 0.34 to 0.17

[aerohead]

Originally Posted by basjoos

It fits in a standard parking space. I didn't experiment with different boattail lengths. I used the tailcone of a Questair Venture kitplane (a 350mph airplane nicknamed "the flying egg" for its short fuselage) as a pattern in designing my boattail and just sized a pattern for the Venture's tailcone to fit the back of my car. I have a small air inlet slit at the top of the nosepiece that feeds air to the radiator. The only time I have ever had any overheating problems was when driving 75+mph on a 95F day. No problems in normal driving, even when climbing up US25 into the NC mountains. One of the things on my list is to install a manually operated radiator door in the front of the nosepiece.

View of the front and the air inlet slot (at the front of the hood on the passenger's side).

Hi Mike,there's a rumor that big oil is beginning to turn their drilling rigs upside-down and drill upwards.They've discovered that there's more oil to drill from the sky than there is left underground.And they showed a picture of an aerial oil "pool",and it looked suspiciously like your HONDA.Maybe they're finally catching on.So keep that"gusher" under a close eye,so she don't go a missing!

[basjoos]

Hopefully that means that eventually we'll be able to buy new ultra-low cd cars rather than having to improve an existing vehicle's sub-par aerodynamics. I have high hopes that the Aptera might be that vehicle. Then again, from its photos, I can see a few areas that could be improved on the Aptera.

[aerohead]

Yeah,know what you mean,but if a car like that got out in big numbers,it would really be a coup! Think of aero-modding something that got a couple hundred mpg to begin with! I have family on the West Coast and hope to "run across" an Aptera next time I'm out there visiting.Your CIVIC,I think may be one of those watershed vehicles,which really connects the dots for people who can't quite fathom the relationship between shape and performance.Everyone I show it to is really amazed! I think the impact of what you've accomplished will continue to resonate for years to come.Thanks for all you do,and keep an eye on ol' "Spindletop",your "gusher" car.

[basjoos]

Originally Posted by Energy Recruitment

) I'll let basjoos comment on the exhaust routing.

2) The lever for the hand throttle is to provide very fine throttle control when cruising. It's a mod that enables a more efficient driving technique.

When you get fuel consumption instrumentation in your car, one of the very first things you notice is the relatively BIG jumps in fuel consumption from incremental changes to the accelerator position. Changes that are literally imperceptible to the butt-o-meter will show up on an instant fuel consumption display.

The hand control permits much finer adjustment of the throttle once up to cruising speed. It may also be more comfortable to use than feathering the throttle by foot for long periods.

I don't understand your question about the exhaust routing.

The hand throttle has proved very useful for hypermiling (especially when DWL) and for giving my leg muscles a rest when on long trips.

[basjoos]

I had to take my car to the garage for a major service and had to remove the 4 wheel well skirts, outer side skirts, and the underbody panelling beneath the engine bay before I drove it to the garage. Overall I saw a 3-4mpg drop, with a noticeable reduction in coasting ability and an increase in the power level needed to maintain speed. At highway speeds it felt like I was driving in the winter at freezing temps in terms of its power and coasting characteristics. My car looks naked sitting there with its wheels exposed.

[MetroMPG]

Originally Posted by basjoos

I don't understand your question about the exhaust routing.

Sorry basjoos - that was just a link spammer who slipped through our defenses. He had just copied random text from further up the thread to post along with his link.

Hope you've got the car back together now!

[LarryClapp]

Some people I know do not like the way it looks. I do! Just different. Did you do boat tail at one shot, or in stages? My car is DD, and can't keep it garaged for more than 12 hours, and trying to figure out assembly schedule?

[basjoos]

My car is also my DD, so I usually don't have more time than over a weekend to install mods on my car. I built my original aluminum bar and clear vinyl boattail in one day. It took 5 days of vacation to build the permanent version of the boattail.

If I had to build the permanent version on the fly, I would have taken one day to strip off the tailgate and construct the aluminum bar frame. If I had to drive it the next day, I would have covered the frame with clear vinyl, hung the licence plate and lights on the back of the covered frame. Then on subsequent days off would have installed the aluminum sheet, lexan glazing, permanent electrical wiring, and the interior.

[wyatt]

Hey basjoos, I just came by 3 sheets of coroplast (ie. campaign signs). Full 4' by 8' sheets, and I am thinking the first thing I will do is the smooth under body. When you did yours, how did you work that with the exhaust? Is coroplast rugged enough to take that kind of heat? Also, any special considerations around the wheel/suspension area? I think the under body should take about two sheets, with enough left over for some frontal blocking. I guess the third sheet can be used for something else... perhaps making wheel deflectors/boat tails and a set of rear wheel skirts. Any thoughts?

[basjoos]

Coroplast is made of polypropylene, which has a melting temp of 340F (173C). I have it within 2" of exhaust components from the exhaust manifold to the catalytic converter and within 1" of the muffler where the exhaust temps have cooled off a bit. I used aluminum sheet (roof flashing) for portions of the underbody that are closer to the exhaust system. The main consideration around the wheel/suspension area is to allow space for the full range of movement of the suspension and the lock to lock pivoting of the front wheels.

[Tercelerat0r]

@basjoos major major props on really going all out with aeromodding your CX...is it actually a Civic CX or a CRX? I have a friend who has a Red CRX that looks alot like your CX, and even stock he gets like 40mpg.

[basjoos]

Originally Posted by Tercelerat0r

@basjoos major major props on really going all out with aeromodding your CX...is it actually a Civic CX or a CRX? I have a friend who has a Red CRX that looks alot like your CX, and even stock he gets like 40mpg.

Its a 92 Honda Civic CX. When stock, it gave me upper 40's mpg in the summer and lower 40's in the winter.

[basjoos]

As requested, here are pics of my car as it currently looks.

[basjoos]

Wayne Gerdes got a chance to drive my car while at the mpg meeting at Columbia. According to the SuperMID he got 93.8mpg while driving my car on about a 8 mile stretch of interstate at a range of speeds between 65mph and 45mph. He said it coasted better than any car he has ever driven and would beat anything except an Insight in highway driving at the speeds he was driving at (and that it would beat an Insight at higher speeds where it couldn't remain in lean burn).

I averaged 65mpg driving both to and from the meeting at the speed limit and averaged 62mpg on the stretch heading home on I-26 at 70mph in heavy traffic where I couldn't do much DWL.

[Cd]

93.8 MPG ! That's great !
Now the questions that I think all of us are wondering :

1 ) How much of this was coasting with the engine off / in neutral
2 ) Was any of this going downhill ?
3 ) Did you reset the SuperMID mid trip, or at the beginning of the trip ?
4 ) Was the engine aready warmed up, or did you have a cold start ?
5 ) The 93.8 MPG was his average MPG ?

(93.8 MPG is fantastic, and I was just wondering how much of this amount could be attributed to the lower Cd of the car versus driving style )

Major props on having the balls to really go overboard and create something that YOU like, and not worry about what others think of it !

[basjoos]

About a third of it was coasting with the engine off. It was a very gently rolling terrain with the downhills so gradual that no other car would have been able to maintain speed on them (Wayne mentioned that even a HCH or Prius wouldn't have been able to maintain speed on them without having to use the engine). From a topo map, there was a net 20 foot drop from start to finish on that 8 mile segment. There was a light front quartering headwind. I reset the MID at the start of the return leg after Wayne had a chance to get a feel for what my car could do. The engine was warm as I had recently gotten back from giving someone a ride. That 93.8mpg was the average over that segment, which included accelerating the on-ramp onto the interstate, cruising on the interstate, exiting the interstate and catching 2 red lights on the way to the dealership. Wayne mentioned the total lack of wind noise in my car and the sturdiness (lack of popping, grinding, and other noises from the mods) of the mods. He also mentioned that he could probably have gotten 120mpg if my car had a lean burn engine and that it could probably remain in lean burn to over 80mph. One of the reasons that Wayne ridge rides is to catch the attention of overtaking traffic that something is different (driving slowly) about his car. He found that with my car he was catching the attention of overtaking traffic without having the ridge ride.

The good mileage was a combination of low Cd and driving technique. The low Cd enabled Wayne to FAS on very gentle downhills that would have been impossible to FAS at highway speeds with any other car, so he could spend more coasting with the engine off than he could if he had been driving the HCH.

[Christ]

I'm not sure, and I'm too lazy to look back... but is the new boat tail smoother than the old one?

It looks better somehow than the old one did.

[basjoos]

It has a smoother transition where it attaches to the OEM hatch hinge on top, but otherwise is very similar to the old boattail except for the additional taillighting.

[MetroMPG]

Thanks for the update & pics, Mike.

The additional lights are a wise addition, and will be part of my car's evolution when the time comes add tapered bodywork that will require the obscured OEM tail lights to be supplemented with extra lighting.

[Christ]

Something seems different, I guess.

Nice job fixing/replacing it though.