1968 Mustang aero upgrades suggestions

[jsulse]

My research has yielded two major easy aero upgrades for the 1968 Mustang, front chin spoiler and custom under tray. My questions are:
1) should a rear trunk lid spoiler be added also?
2) how to best shape the under tray?

Each car body style has it's own aero profile so what works on others may not work on the Mustang. For instance, on my 1975 280Z a rear spoiler needs to be installed to balance a front spoiler's effects so each end gets equal down force. Is it the same for the Mustang body? And for the under tray I have really nothing to go on in terms of it's shape and size, can't find any pics on web. Things that need to be considered are engine cooling, brake cooling and letting the air that gets into the engine bay a way to get out, preferably not under the car. I am thinking of extending the under tray back to the oil pan should be a good start.

J

[Handy Man]

Most mustangs experience a lot of front end lift at speed, which is why the chin spoiler is popular. An under tray will help as well, and in general is usually a good way to reduce lift without adding much drag. I've never seen an aero analysis done on a 68 mustang specifically, but I would be cautious about adding a bunch of front end aero without anything to balance it out on the rear. You could end up with a car that is prone to oversteer at high speeds, which wouldn't be much fun (I've made that mistake. Added a splitter and under tray to a race car and spun it at every single race until I installed a wing)

For the under tray, I would try extending it back to the crossmemeber that goes under the engine. That would be a good structural member to attach it to, and would still give plenty of vent area behind it. All my experience has been with SCCA's SM class rules, which only allow under trays to extend to the centerline of the front wheels. In my experience that still adds noticeable downforce without any significant side effects.

[HellPhish89]

Most mustangs experience a lot of front end lift at speed, which is why the chin spoiler is popular. An under tray will help as well, and in general is usually a good way to reduce lift without adding much drag. I've never seen an aero analysis done on a 68 mustang specifically, but I would be cautious about adding a bunch of front end aero without anything to balance it out on the rear. You could end up with a car that is prone to oversteer at high speeds, which wouldn't be much fun (I've made that mistake. Added a splitter and under tray to a race car and spun it at every single race until I installed a wing)

For the under tray, I would try extending it back to the crossmemeber that goes under the engine. That would be a good structural member to attach it to, and would still give plenty of vent area behind it. All my experience has been with SCCA's SM class rules, which only allow under trays to extend to the centerline of the front wheels. In my experience that still adds noticeable downforce without any significant side effects.

Instead of adding splitters, add things to release the air pressure that builds to cause that lift. The tray in conjunction with adequate venting will kill a ton of lift. If you need more, then look into splitters and such. Just be sure you keep everything balanced.

[Zspoiler]

Look at the Shelby and the Trans Am Ford Mustangs of that era,for suggestions.They did a lot of "Aero" work back then.

[Handy Man]

Instead of adding splitters, add things to release the air pressure that builds to cause that lift. The tray in conjunction with adequate venting will kill a ton of lift. If you need more, then look into splitters and such. Just be sure you keep everything balanced.

Good point. Well placed hood and fender vents go a long way. If you want to be scientific about it, buy a magnehelic pressure gauge and run plastic tubing to the top & bottom of the hood/fenders in various locations to measure the pressure differential at speed. Find the place with the largest pressure differential, that's where you want to cut your vent.