Under Body and Fuel Eco
Under Body and Fuel Eco
(OP)
I had a friend send this to me today and I thought it an interesting topic. Any of you guys have thoughts on this? Admittedly the 33% number sounds high and at the very least opens the door for any self respecting engineer to say….”ok so how did they arrive at that number”, but that aside; here it is.
***************I have read that around 33% of a vehicle's drag comes from air traveling under the car. Why don't auto manufacturers work on the underneath of production cars? I'm thinking a flat bottom would do wonders for drag and aero stability by reducing lift. I know you may not be able to get a true flat bottom but I'm thinking you could do allot better than they do now. I think the closer to zero lift you get the safer these cars become especially on the highways.*********
***************I have read that around 33% of a vehicle's drag comes from air traveling under the car. Why don't auto manufacturers work on the underneath of production cars? I'm thinking a flat bottom would do wonders for drag and aero stability by reducing lift. I know you may not be able to get a true flat bottom but I'm thinking you could do allot better than they do now. I think the closer to zero lift you get the safer these cars become especially on the highways.*********





RE: Under Body and Fuel Eco
Rod
RE: Under Body and Fuel Eco
Most engine bays have an underskirt now, and most front bumpers are designed to reduce the air going under the car to some extent.
A fill underskirt would:-
Cost a lot.
Not be visible to the buyer.
Be VERY prone to damage.
Significantly reduce ground clearance.
Cause overheating problems of exhaust system and adjacent components.
Increase risk of some mechanical noise transmitting into the cabin, but may reduce some other noise, like wind noise.
Regards
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RE: Under Body and Fuel Eco
That's the killer
Plus to be honest at 0.3 the Cd is not a big contributor to fuel consumption, all things considered.
And the lift arguments are spurious.
Cheers
Greg Locock
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RE: Under Body and Fuel Eco
Rod
RE: Under Body and Fuel Eco
RE: Under Body and Fuel Eco
That's 26 feet farther per gallon of fuel.
Sanity ultimately prevailed, and the idea was dropped.
RE: Under Body and Fuel Eco
True this is a supercar company, but other lower companies, like Toyota, Mitsubishi, Subaru, and Honda also do the same thing.
Under many lower sports cars, the under-body is covered by plastic covers, to give the under-body a flatter surface.
My car for example (Mitsubishi 3000GT), has these plastic covers. I removed them one day to see just how big an effect it would have on the cars handling and it was quite significant! From as low as 60 mph the car's "nose" got very susceptible to cross winds, and at speeds over 100, the car was very unstable, steering wheel shaking etc, and the car kept 'wandering'.
Put the covers back on and the car would climb to 135mph and remain as straight as an arrow. Also the time to get to those speeds was significantly less than without the covers.
Also note in NASA Time attack classes, you are penalized 7 points for running a skid plate or flat bottom floor, because it makes such a big difference to the cars aerodynamics.
I am currently working on a project to fabricate an aluminum skid plate to replace the plastic covers, and make the under-body of my car as flat as possible, I also want to make an under-body shield for the gas tank that would incorporate a diffuser, to add even more downforce.
RE: Under Body and Fuel Eco
Been around a while. Right off the top of my head, the GM Corvair, the VW beetle, the Austin Mini...I'll bet several more. I doubt the designers of these cars were thinking much about aero, obviously...they were FLATBOTTOMED, though.
Rod
RE: Under Body and Fuel Eco
Regards
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