1st Gen RX-7?

[Stan]

I was sitting around thinking about what production cars are inherently the lowest drag and wondered how the first-gen RX-7 measures up.



I see it has a pretty good nose even bone stock. And the rear isn't too bad, either.



Of course, that 12A rotary isn't exactly designed for maximum FE, is it?

Still, drop in a first gen Miata 1.6L engine w/5-sp, tall rear gear, and the usual aero mods and I'll be it would make decent hypermiler.

Just a thought...

[DifferentPointofView]

I don't know if this info is totally correct... but...

The relatively tiny stature of the rotary engine allowed for a much lower hood line, as well as a low sitting front fascia, which nearly comes to a point. The windshield and roof line were also tested heavily in the wind tunnel to yield the lowest possible coefficient of drag without making the interior head room seem ridiculously cramped. The headlights are a hideaway flip up style which helps to bolster the already excellent aerodynamic effect of the front end. All of these features put together help the first generation RX-7 to yield a minute 0.36 coefficient of drag, which was as good as the Porsche 924 of that era, and even with the headlamps open, the coefficient of drag only increases to 0.38, which is equivalent to the drag of one of its nearest competitors, the Datsun 280Z.

original link http://www.mazdaforum.com/mazda/rx-7.asp

[SVOboy]

Damn, not the best! I'd just start with a CRX if I was looking for a small, stock car. .30!

[MetroMPG]

Ben's got a point there. The RX-7 is one of those "looks aerodynamic, but really isn't" kinds of vehicles. The CRX would be a much better starting point.

[DifferentPointofView]

The audi A2 had a Drag Coefficient of .25 and if you compare the RX-7 to this most people would say that the RX-7 is more aerodynamic.

[Stan]

Oh, I know the RX-7 is not a particularly good starting point for a hypermiler...the engine alone disqualifies it. What attracted my eye was the aero nose. Compared to what basjoos had to do to his civic to give it that kind of nose, the RX-7 is light years ahead.

The RX-7 has some easy cleanup items that would really help...exposed wipers, huge mirrors sharp cornered front fenders. And that drip rail is probably half his drag right there!

I'm really just musing about shapes. As basjoos has shown, a long sloping nose coming to a smooth point gets the air going in the right direction, and the RX-7 has that feature without having to go to the extremes basjoos had to go to.

It's all good.

[MetroMPG]

Let's not forget though that Cd is just one side of the story. Cd x A is the big picture, and if the RX-7's A is sufficiently smaller than the A2's (which I'm guessing it may be), the total drag of both vehicles may not be that far apart.

But your point stands, DPV, when strictly evaluating shape.

[AndrewJ]

Wikipedia puts the second gen RX-7 at a respectable 0.31

There are a few surprises on their list.
95 Mazda Millenia 0.29
85 Subaru XT 0.29
95 Mitsubishi Diamante 0.28

Might be a good basis for a FE project for someone.

[Stan]

Wow, what a great resource...thanks!

[AndrewJ]

As far as I'm concerned
Wikipedia = God


They even have the little table where they give total drag numbers (Cd x A)
pretty sweet.
No big surprises there though.
Insight 5.10
CRX 5.17
Hummer H2 26.5