[SentraSE-R]

I found the positive part of the Hot Rod Magazine article to be more useful than the negative part.

Top 5 Easy Aero Mods That Almost Always Work
We pressed Eaker to give us clues about simple aero tricks for typical musclecars-stuff that will work nearly every time even without tunnel testing. The delta between Cd numbers is often referred to as "counts," or thousandths of a point, so the difference between a Cd of 0.250 and 0.200 is 50 counts. Eaker gave us some rough estimates on how many counts of Cd you might improve when these mods are applied to a typical older musclecar. Try these next time you're at the track.

Lower the ride height: "Dropping the car-front or rear-will always reduce drag." On our Camaro, raising the tail 1.5 inches changed the Cd from 0.201 to 0.227.Improvement: At least 20 counts per inch

As an example of trying things that are not necessarily legal, we flipped over our original spoiler and taped it to the middle of the decklid to find where the air was most sensitive. This was a loser. Instead, we found that the spoiler was best in the conventional location but that the shape and position of the outer side edges and trailing edge were very critical.

We did lots of hoodscoop testing with Harwood's scoop part numbers (left to right) 3161, 3164, and 3182 borrowed from Barnett Performance. We also tried our old 6-inch cowl hood and a bone-stock flat hood we borrowed from Camaro Specialty and taped all the scoops in place on that hood. All the scoops were swoopiest when extended back to the windshield. Believe it or not, the cowl and the PN 3182 aero scoop had the very same Cd as the flat hood, and the other two scoops were just 10 counts worse. Better yet, the ram-air of the aero scoop was estimated to give us 24 hp at 250 mph.

Block the grille: Eaker's tip is "Always get air around the car rather than through it." Stopping air from entering the grille has shown dragstrip e.t. reductions of a tenth or two even on 120-mph cars. This will also reduce front-end lift, and when the front end raises due to lift, drag increases even more. (Bonus tip: Stiff front springs can also help prevent front-end lift). Grille blockage is more effective on older cars than on newer ones with sealed radiator areas, and obviously, it can only be used for short-duration events due to reduced engine cooling.
Improvement: 15 to 30 counts of reduction in Cd and 50 to 100 counts in reduction of Cl

Add a front air dam: "You can usually get 90 percent there just by adding a dam straight down from the front bumper, just like the one on your Camaro." Even Bonneville guys ask us why we have that big barn door on the front of the car, but keeping air out from under the car both reduces drag and neutralizes lift for solid aero gains.
Improvement: 20 counts less drag, 50 less lift. The taller the car sits, the more important the air dam is.

Seal the back of the hood to the cowl: This is another area that's less critical on newer cars that are already well sealed. Cowl-induction hoods have a high-pressure area at the base of the hood. Air does not travel out the back of the hood; it is forced down into the engine compartment. That air must escape through the car, causing flow disruptions and drag.
Improvement: 10-20 counts less drag, 50 to 75 in lift

Remove the outside rearview mirrors: Factory mirrors hanging off the doors are almost always obstacles to airflow. The '94-up Chevy Impalas and Caprices are notable exceptions; on those cars, the Cd actually gets worse when you remove the mirrors.
Improvement: 10 to 20 counts of drag