VW's 1L is back ("XL1" latest version of concept, side-by-side seating this time)

[ai_vin]

Originally Posted by Piwoslaw

Putting the radiator(s) in the back would require a long length of plumbing (weight) and lots of coolant to fill it (more weight). The gains in simplicity and weight savings outweigh (pun intended) the extra aero drag.

If that were true then the ecomodders here who added weight in the form of aeromods would have seen little benefit. I'm thinking aero trumps weight and besides, an extra 20[?] feet of water-filled coolant hose can't weigh THAT much more than a DIY boattail.

[NeilBlanchard]

I think that aero drag definitely trumps weight -- see the aero motorcycle fairing on EM's home page.

That being said, the flow through the radiator can be ducted / improved in the front of the car. There are several threads here that reference the Hucho tome on this -- the best setup is an intake down low on the front (slightly below the stagnant point, I think?) and the exhaust up through a louver in the hood; which is located at a low pressure zone. And the whole thing is ducted, too.

The same principle can help with the air flow through the passenger compartment -- intake in a high pressure zone, and the exhaust out the back into the low pressure zone, behind the car. This both improves air flow through the car (with less drag) and it can pressurize the trailing pocket of air behind the car; which can actually lower overall drag.

See the original Insight and the Aptera for examples of this.

[Piwoslaw]

Originally Posted by ai_vin

If that were true then the ecomodders here who added weight in the form of aeromods would have seen little benefit. I'm thinking aero trumps weight and besides, an extra 20[?] feet of water-filled coolant hose can't weigh THAT much more than a DIY boattail.

But 20 ft of water-filled coolant hose probably won't give you a 15% increase in FE.

In many cases a lightweight coroplast grille block will counter the fact that the radiator is in the front.

[Piwoslaw]

Originally Posted by NeilBlanchard

That being said, the flow through the radiator can be ducted / improved in the front of the car. There are several threads here that reference the Hucho tome on this -- the best setup is an intake down low on the front (slightly below the stagnant point, I think?) and the exhaust up through a louver in the hood; which is located at a low pressure zone. And the whole thing is ducted, too.

Like in Vekke's Cordoba?

[some_other_dave]

Originally Posted by ai_vin

The radiator and air conditioning compressor were located at the rear in order to eliminate a high drag radiator opening in the front (or nose).

Why isn't that done more often?

Probably a combination of several things. One being public acceptance. After all, cars are "supposed" to have radiators in the front, aren't they? Another big one is packaging. The necessary ducting would take up cargo or passenger space, and those latter two can easily be sold. Not so a special enclosed rear-mounted ducted cooling system.

Not to mention it would be more expensive to make, and therefore would be more expensive in the showroom.

-soD

[Frank Lee]

The main reason I wouldn't want a rear radiator on my car is that is where the trunk is and a radiator back there would reduce it's utility. Also, the long piping could have reliability or cost or some sort of drawbacks... although if there were extruded aluminum heat exchangers running here and there under the car, perhaps the radiator itself could be eliminated??? Then there is my pickup- for sure I don't want a radiator anywhere near the tailgate; it'll get smooshed, or the load will obstruct the airflow, or something. On Moon Unit, the wagon, there aren't any good places for a rear radiator either.

Now, were I to modernize my Corvair with a liquid cooling-medium engine I would probably pursue a rear radiator location as there is no trunk in the back for a radiator to interfere with. I find it odd that the Corvair is popular for mid and rear engine, liquid cooling-medium conversions and yet 100% of them go with a front radiator.

I should point out that even though I love my rear-engined vehicles, they are saddled with a built-in reduction in utility as stuff-movers, in that anything put into their front trunks really, really needs to fit properly and the lid be fully latched down, whereas in contrast, you can let a rear trunk lid or hatch stay open for oversized cargo to stick out of with little bad consequence. Even better yet is the ability on some cars to fold down the rear seat for more cargo room- not an option with a front trunk. Additionally, weight variations on the rear end of a front wheel steering vehicle (from empty to fully loaded to even substantially overloaded) have a relatively minor impact on handling whereas having the trunk on the same end as the end that steers makes the vehicle's handling exceedingly load-sensitive. Furthermore, having the trunk on the same end as the steering wheels forces the trunk to be smaller within the same size exterior envelope because the wheelwells intrude further into the trunk space because the wheels have to turn (not rotate) for steering. So, I reluctantly have to say, front engine front drive is where it's at for max utility, safety, and efficiency.

I do believe the VW 1L could be front engine fwd with no performance penalties, and then they'd have a rear window and hatch or trunk as well.

Interestingly enough, this latest 1L, in spite of having the engine towards the rear, has the radiator up front!

[ai_vin]

I think "some other dave" and "Frank Lee" have given us the real reasons, or at least reasons that are better than 'weight over aero.'

After taking another look at the picture of the Probe V's rear I'm now thinking most issues with the necessary ducting taking up cargo or passenger space can be overcome; the vents in this case occupy only a narrow strip at the bottom of the rear panel.

[botsapper]

An example of rear radiator placement for cleaner front aerodynamics and some benefits of the recent discussions, Meredith effect radiator. Cooling drag - some thrust = less net drag.
Dramatic drag reduction compared to conventional front radiators.

http://i101.photobucket.com/albums/m...aham227/51.gif
http://www.ipmsstockholm.org/magazin..._002_small.jpg

Example rear rads, (don't know if I like);
http://img156.imageshack.us/img156/9428/00338ej.jpg
http://sphotos.ak.fbcdn.net/hphotos-..._1417679_n.jpg
http://www.bespokeventures.com/blog/...0/tsblog05.jpg

[basjoos]

Originally Posted by JasonG

It looks like the cd should be a lot better than 0.18

Basjoos did better than that with rippled sheet metal (no aerocivic disrespect but its like the time and $ money difference between weatherspotter and the zombieinsight )

.

The main reason the Cd isn't lower is that they are producing a car that has to meet existing EU government automotive regulations and that they hope to sell to the typical automotive consumer, so they can't go out as far on the aerodynamics branch as I can. If they added a complete boattail, front wheel well skirts, low rounded nose, no exterior side mirrors/video, and more aggressive wind deflection around the wheels, then they could have lowered the Cd further. But some of these mods may not allowed under EU automotive regulations, would require more maintenance or have cold weather constraints, or be more susceptible to road debris damage than the aero mods they included.

[NeilBlanchard]

This is good news!



http://www.plugincars.com/volkswagen...id-109650.html