Saturn Sports Coupe Aerodynamics

[Peakster]

Originally Posted by BluEyes

Yeah, 0.31 to 0.33 only changes drag by about 0.6hp at 65mph.

Does the site that you got that info from list other cars or only Saturns?

The site that I found lists only Saturn models. I thought that a 0.02 Cd change would be quite substantial (or at least noticeable in a car's physical appearance).

[kickflipjr]

The only difference I see is the fog light area of the bumper. .02cd if pretty small.

Late sc1 are my favorite saturn model. It should be good for 40 to 50 mpg (or more if you are hardcore).

[cfg83]

Peakster -

Originally Posted by Peakster

The site that I found lists only Saturn models. I thought that a 0.02 Cd change would be quite substantial (or at least noticeable in a car's physical appearance).

I thought those pictures looked familiar! That seems to be a "web capture" of a 200X Saturn website. I like that website for the specs I can pull off of it.

I went to the trusty Miata tire calculator website :

http://www.miata.net/garage/tirecalcold.html

And compared these 2 tire sizes :
P185/65R14 85S (Stock with Saturn SC1)
P195/60R15 87H (Stock with Saturn SC2)

Here are the tire size comparisons :

SC1 tire diameter : 23.5"
SC2 tire diameter : 24.2"

So the SC2 has slightly larger tires, leading to increased frontal area. If you want to go really hardcore, go to tirerack and get the specs on the original stock tire for these models.

Question : Is the wheel size taken into account for Cd calculations?

Also I agree with what other people said about the spoiler, I think it is just for show. Even though my 1997 SC2 had a spoiler, I think the aesthetics of the car are great without one.

Question : Would the addition of the 3rd door (which I love) increase the curb weight of the car? I would think yes. I have an original 1997 sales brochure. If I find it, I will post the relevant specs.

I don't like the plastic redesign of the S-Series (in year 2000?). My favorite is the 1997 to 1999. Very clean lines. I wish they had introduced the 3-door right off the bat (I love the idea of intelligent assymetry in a car, and a suicide door too!!!!!). That original coupe design is why I have a Saturn right now. You could get a sporty looking coupe with 28/40 MPG!?!?!?!?!? And it's American made?!?!?!?!?!? Whoda-thunk?

CarloSW2

[Peakster]

Originally Posted by cfg83

And compared these 2 tire sizes :
P185/65R14 85S (Stock with Saturn SC1)
P195/60R15 87H (Stock with Saturn SC2)

Here are the tire size comparisons :

SC1 tire diameter : 23.5"
SC2 tire diameter : 24.2"

So the SC2 has slightly larger tires, leading to increased frontal area. If you want to go really hardcore, go to tirerack and get the specs on the original stock tire for these models.

But remember, the SC2 has a lower cd than the SC1, according to that site.

I wish they had introduced the 3-door right off the bat (I love the idea of intelligent assymetry in a car, and a suicide door too!!!!!). That original coupe design is why I have a Saturn right now. You could get a sporty looking coupe with 28/40 MPG!?!?!?!?!? And it's American made?!?!?!?!?!? Whoda-thunk?

Yeah, I think it's the closest thing to a 'modern Fiero' I can find these days (without wasting mucho dinero on a Solstice). Sporty looks with great FE and body panels that don't rust! I've always wondered why the resale of these cars are so much lower than similar Japanese models, since almost every Saturn I find at the junk yard has well over 300,000kms on the odometer. They must be real reliable.

[cfg83]

Peakster -

Originally Posted by Peakster

But remember, the SC2 has a lower cd than the SC1, according to that site.

Oops !!! I'll have to go back and look at that some more. Maybe the SC1 tires are skinnier?

Yeah, I think it's the closest thing to a 'modern Fiero' I can find these days (without wasting mucho dinero on a Solstice). Sporty looks with great FE and body panels that don't rust! I've always wondered why the resale of these cars are so much lower than similar Japanese models, since almost every Saturn I find at the junk yard has well over 300,000kms on the odometer. They must be real reliable.

They have their share of manageable problems, but I think there were some good design concepts built into them that made them cheaper to maintain. I remember reading that the engine bay was designed for easy access so that an average Jane or Joe could change the fluids.

But they have always been poo-pooed in the press. Cheap interiors, not much pizzaz, and such. There is almost NO performance aftermarket for Saturns, so you don't see many of them tricked out. They were designed to compete on their own terms with the Japanese economy cars, and they came up short in the eyes of buyers.

Th one thing that really depressed me about the Saturns is that the Kit Car Culture didn't jump on them like they did the Fiero. I think the specific "space frame" shape of the Saturns may not have been conducive to what Kit Car junkies want, but the body panels were just *waiting* to be swapped out with aftermarket body panels, but no one ever did it.

CarloSW2

[The Toecutter]

Yeah, 0.31 to 0.33 only changes drag by about 0.6hp at 65mph.

.6 hp saved is still good for an extra 1 mpg or so at that speed, assuming nothing else was changed.

[GasSavers_BluEyes]

Wow, you're right. I didn't think that 0.6hp out of 20hp or so that it takes to keep the car moving would make that much of a difference.

Just running some quick numbers, a BSFC (lb of fuel per hour per hp for the uninitiated) of 0.63 gives a 1mpg gain, but my modeling of the V6 in my car predicts a BSFC in that area, so I suspect the Saturns 4 would do better. If the engine is really slick and the BSFC is down around 0.32, that 0.6hp savings would be worth a 2mpg gain at 65mph.
Of course, this is all assuming the same BSFC for both engines, which is not true. Even if it was the same engine in both cars, the BSFC would rise slightly as you throttle back to reduce the output by that 0.6hp, so there are alot more variables, but the potential is certainly there.

[The Toecutter]

Now try that same math for a .20 drag coefficient, which is well within the realm of possibility on a car that size while retaining the basic overall style.

[omgwtfbyobbq]

Originally Posted by The Toecutter

.6 hp saved is still good for an extra 1 mpg or so at that speed, assuming nothing else was changed.

Generally, BSFC increases. Sometimes as much as the gain in glider efficiency. Depends on the vehicle/engine, but it is something to consider. It's also why Erie Rogers can see a ~35% increase in fuel efficiency from tires, synthetic oil, and a odd looking wing, while MetroMPG only saw a ~30% increase from a grille block, wheel skirts, alternator/mirror delete, transmission swap, synthetic oil, tires at ~45psi, and an underbody panel. Given the same vehicle, I bet MetroMPG's mods could blow Ernie's out of the water, but MetroMPG has to deal with a much greater drop in BSFC compared to load than Ernie does.

edited for clarity

[The Toecutter]

Yeah. But finding engine maps for specific cars hasn't been very easy, making it a lot harder to predict the effects of these modifications. I'd really love to see someone build a 40 mpg V8 land yacht priced like an Aveo. In theory, it is perfectly possible. THAT is what American consumers want, but there just isn't much profit margins in low maintenance, efficient vehicles, and you compromise all sorts of markets you can otherwise create by offering every tiny incremental step between present day and hypercar. To maximize profits, car companies ration out advancements as slowly as they can, so much so that it took 80 years for two companies to make and market an Insight and Prius to beat the 1921 Rumpler in drag coefficient.


Like the Ford Tempo, the Saturn SC2 could have been such a great platform for a practical, efficient car. But the manufacturers never make them the best that they can. Instead, we get a product that shows only marginal FE improvements over the norm.

Even a car with a relatively low .25 drag coefficient has a lot of room for improvement. Isn't the lower practical limit something around .11 for a road car?(eg. solar powered cars, ect.)


Even fullsize luxury cars, minivans, and SUVs with large engines could be consuming about half the horsepower at speed that they do today. This corresponds almost to a doubling of fuel efficiency at speed, but not quite a doubling since the lower engine load means lower thermal efficiency.