Inertia vs aero drag vs rolling resistance in urban and highway driving

[Logic]

Originally Posted by Ecky

How I meant it was, the typical new vehicle weighs near 2 tons. 20% from that is 800lbs, or ~400 kilos. That's a lot of weight to remove, and, having seen some cars go on extreme weight loss diets, I'm of the opinion it is wildly out of reach. A percent of weight loss may be more useful in most driving scenarios than a percent of aero, but a percent of aero is a lot easier to achieve.

As an example, one forum member here did an extreme weight loss diet in a 2004 Saturn Ion. It started at ~26xx and ended (if I recall correctly) at 23xx. To get there, he removed the interior, removed all seats but the driver seat, lightweight battery, cut the support webbing out of the hood and trunk, cut the crash beams out of the doors, and took a hole saw to and made swiss cheese of every bit of sheet metal that didn't face the outside. He cut the floorpan out of the car behind the rear seats and replaced it with coroplast. Door latches deleted. Window hardware deleted. Speakers and "unnecessary" lights deleted. Exhaust deleted. Power steering, engine balance shafts, A/C deleted. You name it, he cut it out. I believe he didn't quite reach 15% weight savings.

I'm not advocating everyone build boat tails, but MetroMPG found a boat tail (alone) on his Insight (an already very slippery car) to improve ABA fuel economy by 10% on the highway. That suggests a near 20% improvement in Cd from that piece alone. I guess you can get at least half that from a small rear kamm or well placed spoiler, front grille block, smooth underbody, smooth wheel covers and rear spats - most of which I could put together in an afternoon with $50 in materials, and which would not alter the function of the car in any way.

Simply put, weight savings are great (I do them too), but they're much harder and more expensive.

Ah ok. thx

Yes the discussed Saturn is just crazy! (a great experiment though!)
But if you are looking for something to do on a Sunday, removing the odd bolt and cutting off the excess length is an easy DIY mod that can done bit by bit.
(I have a lathe so can cut neatly and even drill out the bolt's center)

But here's the challenge:
If around 98% of all driving is urban.
So the question becomes; what did MetroMPG get in city, stop-go driving?
(Besides the inconvenience of parking etc)

Car manufacturer's could easily put boat tails etc on cars, but don't because 98% of the time they would be increasing fuel consumption on average by doing so?

So the question becomes:
What aero mods can be done light so they are worthwhile on your/my car if it spends most (98%??) of it's time driving around town, with only occasional highway trips?

Wing mirror deletes obviously.
But at some point the weight of a replacement camera system may outweigh the aero and weight advantage around town..?

I think Moon disks are one, if they replace std hubcaps of a similar weight and because the top of the wheel is moving forward at 2X the car speed.

Faired in rear wheels? They seem popular with car makes, but not the general public.

Front spoilers also seem to be a win as they are on most cars to some degree already.
But that may be a 'stability/safety at speed' thing..?

Fairings (of a sort) or lips in front of the wheels too. (What are they called again?)

Flat bottoms to some extent..?

This depends greatly on the materials and design etc too.
A carbon or glass fiber flat bottom with fillets in all the right places may be a win overall, whereas a steel plate with angle iron stiffeners and mounting means is not.

(EV's are 'all in' as the batteries are in the floor already to keep the center of weight down.
A 'Kill 3 birds with 1 stone' thing...)

ie: Let's list aero mods that don't add weight, or if they do; can be made light and still be a win for the world average driving cycle.


I think Dielectric Barrier Discharge (DBD) may be an easy DIY one that's overlooked.
It's basically some strips of aluminum foil and Kapton Tape in the right places, and a cheap and light High Voltage but Low Amperage (= low Power) PSU.
Science studies say yes..?
https://ecomodder.com/forum/showthre...tml#post696530
Thing is; on a practical DIY level, no one really knows..!