Mid-engine, Rear- engines superior for aero?
I was thinking the other day, since the grille on cars is a aerodynamic nightmare, wouldn't cars with rear engines be better, since a front grille is not needed?
Discuss... |
i think a better way to look at it is the location of the radiator which is what allows the engine coolant to release heat.
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The grille is only one part of the whole picture but yes superior aero is more easily achievable with the engine mid or rear mounted. Then again you could say the same for 2 doors versus4 doors versus wagons.
Citroen managed very respectable Cd numbers from their cars which were mainly 4 doors and front engined and front drive as well. Check the CX , GS models for the 4 doors and the SM model for the 2 door. Pete. |
I think Tourigjm hit the nail on the head. You could theoretically design a front-engine car with the same Cd as a low drag rear engine setup, by using active cooling inlets/radiators on the side of the vehicle, and waste heat ejected into the low pressure wake. Of course the plumbing/ducting would be a nightmare for the front engine version.
Another advantage to rear engine placement is you can adopt a 100% smoth undertray since there is no hot exhaust pipe running down the center of the vehicle that needs to be left exposed. |
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Having had several rear-engine vehicles, I can say I like the handling dynamics of them- nice, feather-light and responsive steering, not to mention superior traction. From a strictly utilitarian standpoint, though, it is better to have the trunk in the back, both for super heavy and oversize loads. And they are more sensitive to crosswind gusts. |
[QUOTE=aerohead;52060]RiseAbove,in the phil knox aerodynamic photo albums,under Book Illustrations,second row from bottom of 1st page,is an illustration of Walter Korff's zero-drag,cooling system design.I
The label actually reads "ideal low drag cooling system." I used to be inspired by the North American Mustang aircraft, on which it was claimed that the radiator enclosure had negative drag - sort of like a hot-air jet engine. However, the Voyager team did their own testing, and could not get the cooling drag to be less than 20% of the total on their whole aircraft. One has to assume that they were competent researchers. The front end provides the most direct flow to the rad, and does not have to disturb the rest of the shape. There may be some existing cars that could be improved by relocating the rad and ducting to the rear in a combined effort to solve other problems - it is not that difficult - VW did it on the wasserboxer Vanagon, in the other direction. However, I agree with Mr. Lee - a front engine is good for stability, which becomes much more important on a light, streamlined car. |
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I've never seen a cross wind that will actually screech my tires sideways causing me to correct. The oversteer/understeer characteristics of a street vehicle are determined by the weight distribution and wheel alignment. 99% of new cars are front engine because all that weight at the front causes the front to break away first so the car ploughs when the driver panics and slams the breaks and cranks the wheel. It is easier to survive a front-on collision, that is why they do this.
I went for a few ride-alongs in a friends MR2 at autocross and he was always battling oversteer becaues the rear end has more sideways momentum in a turn making it more likely to break traction. As for the original topic, you could make one hell of a sleek frontal shape, top, bottom and sides if there were no ducts there for cooling or intake. A RR car definately has more aero friendly potential. I can't think of a high-speed supercar with the engine up front. |
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