Video: discussion of several GM Volt aero features

[basjoos]

Why do they always have to plaster a fake grill on the front of the car even when it doesn't need a front opening for cooling? If it doesn't need that front opening, they should have a smooth rounded surface on the front, not those recessed grill blocks. Although they got the generalized aero right, it looks like they compromised on a few of the details to follow "automotive tradition". I guess the Volt's styling isn't quite as revolutionary and aerodynamically functional as they claim it is.

Tacking fake grills on a car is almost as bad as tacking fake shutters onto a house, another one of my pet peeves.

[donee]

Hi Basjoos,

Yea, I agree. The Prius got away from that front grill, with the little smile gril.

They still have the wheel house bulges on the Volt, too. Not good. This is the socalled "muscular look". Originally, those were mimics of add on fender flares. The flares were a aftermarket thing to allow safe use of bigger tires (and avoid throwing stones into other cars, or have the fender cut the tire). Over time, it became design lanquage for a car with extra HP. So, its just "leaned behavior" hogwash that they would put those into a new design, rather than something that truely improves performance.

One good thing on the wheel houses, is they have a very small gap to the tires. You cannot see that on this video so much, but go over to Charlie Rose web sight, and search on Lutz. BTW, Lutz said the production volt has a Cd of .28.

I think I will be adding the 5 mm Gurnee flap on my Prius though. I have some "FOAMIES" 6 mm thick sheet stock which I wll do this with.

[aerohead]

Originally Posted by Tango Charlie

What are 'counts of aero' ? Is this a GM buzz word, or is it an aerodynamics's term?

Doax is correct.I have only two sources which use the term.One a 1982 article by Road & Track,the other Mechanical Engineering Magazine.

---------------------------- The term is considered valid when associated with a particular development vehicle ( like the Volt ),in a particular wind tunnel ( like GM's).

------------------------------- Also,Road and Track "rounds" counts within Cds published by carmakers.

-------------------------- Example: A Firebird,which scored Cd 0.316 would be rounded up to 0.32. A GMC S-15,with Cd 0.495 would remain 0.495,and a car with Cd 0.294 would receive 0.29.

-------------------------------- So like the discussion about the CRX HF,and CRX Si,they may have only been separated by a few "points",however when "rounded",look more dramatic in efficiency differences.

------------------------------ I suspect other magazines also "round." Very frustrating when attempting to distinguish individual features,adding or detracting from aero efficiency.

--------------------------------------- To cloud matters even further,the EPA does not recognize"protuberances" when factoring sectional area.If a vehicle is tested with antenna and sideview mirrors,their area is not factored into drag measured,leading to an arbitrarily high Cd.

-------------------------- Drat!!!!!!!!!!! A can of worms!

[Bror Jace]

”Why do they always have to plaster a fake grill on the front of the car even when it doesn't need a front opening for cooling? Although they got the generalized aero right, it looks like they compromised on a few of the details to follow "automotive tradition".

Guys, GM is trying to sell the notion that enviro-friendly, high-tech vehicles can be practical, cool and even a little sexy. That’s why they styled the volt to look muscular ... as if it was the forthcoming Camaro’s lil’ brother.

I’d prefer a straight-up form-follows-function design … but I’m weird. I know why GM is doing what they’re doing … they’re trying to sell green tech to the unwashed masses that won't buy something that looks like an egg ... or your Honda. So, I cut GM a lot of slack in this area.

[donee]

Hi Bror,,

In other words, Homer Simson's brother works in the design deparment of GM, and they invited Homer (otherwise known as marketing group studies) into design the car. Maybe you have seen that Simpson's episode? It did not turn out good for anybody.

[Bror Jace]

Yep Donee, until a few years ago, I've seen every episode of The Simpsons.

But I don't think it's a good analogy ... at least a far-less-than-perfect one. Homer, a perfect idiot, ended up with an over-sized monstrosity packed full of every feature one could dream up.

The volt is a fairly attractive car ... if you like the modern muscle car look.

[aerohead]

I think Chrysler is still stinging from the 1934 Airflow.The Volt won't help us if it doesn't sell,and so the "moderate" within me will allow for some styling concessions.Commuting 40 miles a day on solar electricity is worth a concession or two.Perhaps down the road,consumers will be more comfortable with eggs.If Volt owners start asking GM dealers about basjoos aero "styling",in a positive light,it may open the flood gates to real wind tunnel winners in the nearer future.Hope so.

[Bicycle Bob]

After what GM did with the Impact, I worry about the Volt. The team at Aerovironment had to butt heads with the GM design guys to save that design from mediocrity, and then GM management eventually trashed it anyway.
Many years ago, GM and Firestone were fined for conspiracy to eliminate the competition of municipal transit systems. They had bought them up, and not shut them down in any obvious way, they just transferred their incompetent executives there to eventually fire themselves.

[Bicycle Bob]

Originally Posted by lunarhighway

maybe they mean Cd?

there's an interesting bit about the rear spoiler, where the first version is straight and the second seems to have something which reminds me of a gurney flap.

i've seen certain BMW's wich also have a small gurney flap like spoiler added. and quite a number of cars with a slight upward sweep to the rear spoiler lip.

given it's shown in this video i wonder what it's use is and how it works to aid FE. it would be a relative simple and good looking addition to my car, but i'd like to understand better what it's supposed to do.

A big feature like a trunk-mounted spoiler may build up pressure ahead of itself to prevent separation on a back window. However, the small lips that sharpen trailing edges are intended to gather the existing boundary layer and trip it into the trailing vortex in an organized fashion, so that there are fewer sub-eddies. It is better to have one or two large, stable circulation patterns in a "trapped vortex" than just chaotic flow.

[lunarhighway]

A big feature like a trunk-mounted spoiler may build up pressure ahead of itself to prevent separation on a back window. However, the small lips that sharpen trailing edges are intended to gather the existing boundary layer and trip it into the trailing vortex in an organized fashion, so that there are fewer sub-eddies. It is better to have one or two large, stable circulation patterns in a "trapped vortex" than just chaotic flow.

so adding a small ridge just ahead of the trailing edge could be beneficial for FE...


what i don't get is why GM seems to be strugling wich the mucle car look and it's aerodynamics.

in europe trough opel GM has produced some examplary aerodynamic vehicles with cd's between 0.29 and 0.26, from the 80's untill now and with the upcomming opel insignia with a Cd of 0.27 they show they still got it.
and lets not forget the eco speedster... not suitable for the road but certainly a door aero exercice and that car's nose did look like the volt a bit.

there's people working at GM that can totally put together a working practical car with good even sporty looks and top of the line aerodynamics.
just let them do their job and put in an electric engine and slap on whatever badge they want... now remind me again but didn't GM already had some sort of electric engine somewhere they could put in....