Aerocivic - how to drop your Cd from 0.31 to 0.17

[basjoos]

Originally Posted by martae

Great job Basjoos, but why didn't you start with a civic VX instead of a CX ? It was the high mileage model. Feather light aluminum wheels. Wider ratio transmission with a higher final drive ratio (2000 rpm at 60 mph). Variable valve timing with a twist. In this engine only one intake valve opens below 2500 rpm. Since there is only one intake valve open more of the pressure drop between the atmosphere and the cylinder is across the valve rather than the throttle plate. This gives a more turbulent fuel air mixture which allows a leaner fuel/air charge, greater torque at low engine speed, and no predetonation . The use of a very sensitive oxygen sensor (unique to the VX) allows more precise control of the FA mixture making a very low idle possible. On a warm day mine idles at about 500 rpm. The practical effect of these engine tweaks is high torque at low RPM sort of like a diesel. As I'm sure you guys know, the great weakness of the Otto cycle (the spark igniton gasoline engine is an Otto cycle engine) are the large pumping losses at part load caused by sucking the FA charge past the throttle plate. The ability of this engine to deliver good torque at low RPM (and thus lower pumping losses) is the secret to the high fuel economy this car delivers. The CX and the VX share the same body, but the CX is listed at EPA 42/46 and the VX at 47/56. The VX also offers higher power since the engine has the same displacement, but four valves per cylinder (92 vs 70). I bought mine new in 1992, have put 208 thousand miles on it and still average 45 mpg to work and around town. When the car was new 52 or 53 mpg was not unusual on a long road trip. The fact Honda could do this with the technology of 15 years ago shows what a bunch of liars the auto companies are when they squeal about a 35 mpg average fuel economy rule.

I started with a CX (which I had bought new in 92) rather than a VX because that was the car I was driving at the time I decided to start aero modding my car. The CX and VX share the same transmission. The main differences being the in engine,, lighter wheels, some additional interior features in the VX (the CX is the bare bones Civic model) and some underbody aero to slightly reduce the Cd of the VX. The VX and CX have the same weight. When new, my CX typically gave me 51mpg on the highway in the summer (44mpg highway in the winter) and 38mpg was the worst I ever got with it (in snow driving and winter tires). Interestingly, when I installed a DX engine at 245,000 miles (but kept the same transmission), the mileage remained the same, but my 0 to 60 times dropped to 10 sec.

[dennishay]

You were talking about changing the intake for the coolant to vary with need of cooling, have you thought of a heat exchanger for the intake air for combustion or for that matter from you exhaust, routing the cool air through the rad, then to an exhaust heat exchanger then to the engine, in effect reclaiming the heat that would have been waisted... there is an interesting article in Popular Science about using the heat to produce steam in the engine...

http://www.popsci.com/popsci/technol...cbccdrcrd.html

[basjoos]

I figure my intake air gets warm enough just from the tightly cowled engine compartment (its completely underpanelled, with a mostly blocked grill and the hot radiator air exhausted out through the front wheel wells). They've had some discussions of warm air intake temps at Gassavers and concluded that although warm intake air improves mileage (at the expense of power, you are in effect driving a less powerful engine with a more open throttle plate with reduced pumping losses), but if the intake air gets too hot, it has detrimental effects on mileage (perhaps because the engine ECU isn't programmed to handle intake temps that are way above what its programmers thought it might ever experience).

[MetroMPG]

FYI - for those interested in the subject of radical aero mods, you might want to check the thread about Harry Stevinson, my friend's dad. He was bitten by the same bug that got basjoos ... 70 years ago:

DIY aeromodding in the 1930's: Model T - 38 mpg, 70 mph

[basjoos]

All of this recent activity used up all of this month's bandwidth on my free Photobucket account. Next month's bandwidth allotment will become available on Jan 2.

[SVOboy]

If you want to send me the pictures I can host them on the ecomodder server for you.

[voxelman]

The images can also be seen at this site: http://www.cleanmpg.com/photos/showg...=500&ppuser=18

[MetroMPG]

Originally Posted by basjoos

All of this recent activity used up all of this month's bandwidth on my free Photobucket account. Next month's bandwidth allotment will become available on Jan 2.

I've posted the images on the Ecomodder server - they're all visible now. No more Photobucket bandwidth problems.

[voxelman]

If we get the aftermarket body mod industry to start thinking ecomodding, changes like the ones Basjoos has made might be accomplished in a weekend. See: http://www.bodykits.com/store/home.php?cat=1281 as an example.

[SVOboy]

I do believe newton has had that thought (of making aero body kits for ecomodders), and I definately think it's worth a go. If I knew anything about molding and all that jazz I might play with it myself...

If someone made a boattail for a prius I'm sure that would get the business going.