Nissan 240SX aerodynamic modification

[raylit20]

Hi guys, I have a 1990 Nissan 240SX hatch and I'm looking to lower my Cd. I'm considering a grille block, mirror delete, and a boat tail. Following in Basjoos's footsteps.

Can anybody help me determine the optimal angle/length for a boat tail on this particular car?

This is the body style I have.

[JRMichler]

I'd start with a tuft test on the rear to find if the flow is attached before designing a boat tail.

[cRiPpLe_rOoStEr]

That's already nice-looking in its stock form. I'd also not start immediately with a boat-tail...

[freebeard]

I'd start by measuring your parking spot. I have a 14' car and it fits under the carport, but if I add a 3' boat-tail, somethings going to be sticking out in the rain.

Beyond your question: move the rear view mirrors to the tops of the front fenders, Moon disks in front and fender skirts in back, add double-walled side skirts [like basjoos] and clean up the underside with a rear partial pan that sweeps up into a
diffuser that ends at your new boat-tail.

I'd say about 18". Do you have a picture with the trunk or hatch half open?

[mcrews]

that is a very clean 240!!!!
Certainly admire your desire to jump right in!
There is a guy on here who can overlay the 'perfect curve' on your picture.
He did it for me on my Q45.

I will look for the thread tonight.

[JRMichler]

Is that a pair of pop up headlights sticking up in front? If so, I'd start by streamlining those two parachutes. And a grille block.

[cRiPpLe_rOoStEr]

I'll second that. Pop-up headlights are a problem.

[raylit20]

There is a factory option available to convert over to flush mount, non popup headlights but the cost is considerably more than the vehicle itself is worth, thus it's not feasible to do so. The headlights remain down when not in use, and my night driving is solely in town where aero drag is limited to begin with.

Also, factory Cd is approximately .30 (Let's go for .20 with mods! )

Mcrews, that isn't my car - It was a nice side profile shot I found online.

Parking is not a concern as my garage has room to accomodate my 19' Lincoln with room to spare; Thus my 14 foot Nissan has some room to grow before I run into any space issues.

[Sven7]

Tuft test the rear window to see if it has attached flow.

Then read my Anal Probe thread- the 1G Probe has a very similar shape to the S13.

Those tires look really low profile. Make sure you get a set that is the same or larger rolling diameter compared to stock.

[freebeard]

Wielding the notorious Template, this is what most people would give you. Match the ground plane and peak of the roofline.


I would listen closely to what Sven7 has to say. The roofline probably has good attached flow. But the lower body has the air moving differently. Notice the overall length doesn't change much.


My understanding of The Template is that you treat the underbody separately. So here it is matched to the wheelbase.


Then I take those two results and combine them.

At this point It's down to picking a truncation. Again I would listen to Sven7 on how big a bustle you might care to drag around.