Question about FP Rear Spoiler W/ Gurney Flap

[jaylarold]

I've always liked the looks of the GT350/GT500 Rear spoiler with gurney flap, and have been considering swapping it out with the stock performance pack spoiler. My question is whether it would actually provide some beneficial downforce on the track or if it would upset the aero balance without any additional front or underbody aero additions that the GT350/500 and Mach 1's have. I have considered adding the additional lower front spoiler that used to come on the PP2 cars, as I prefer a mostly stock look to my cars, but was worried about smashing it on curbs and speedbumps all the time since my car will be slightly lowered. I have also looked in to the the GT500/Mach 1 rear valance kit that adds some rear underbody aero as well.

Link to the spoiler in question

 

[yotah1]

That "swing" as we called it internally (spoiler / wing hybrid), along with the GT350R and GT500 CFTP wings are the only ones that actually provide downforce on the Mustang production cars. Everything else only reduces lift, but still doesn't actually produce real downforce.
I would pair it with a PP2 chin spoiler in the front to keep the car balanced, otherwise you'll start getting some understeer.

"Diffusers" on Mustang are pretty much useless unless you run a flat underbody. GT350, GT500, Mach1, even GT4, are just dust and rocks catchers more than diffusers. There is so much turbulent airflow under our cars, from the floor not being flat, to the rear subframe & control arms being all but aerodynamic, diffusers are pointless and create more drag than anything else.

 

[jaylarold]

Thanks, yotah. I have read some stories on the forums about the rear diffuser being quite the rock collector, so if it's more or less useless then I'm happy to avoid spending time and money on one more thing.

 

[blacksheep-1]

Generally speaking, the rules structures of the misc organizations provides a great way to use aero since most of us don't have wind tunnels. Back in the Grand Am, and PWC days, they spelled out the aero requirements. Currently the Gt4 spec cars spell out the aero requirements for the S550 platform. To venture away from.those specifications is always sketchy.

 

[Tonymustang302]

That "swing" as we called it internally (spoiler / wing hybrid), along with the GT350R and GT500 CFTP wings are the only ones that actually provide downforce on the Mustang production cars. Everything else only reduces lift, but still doesn't actually produce real downforce.
I would pair it with a PP2 chin spoiler in the front to keep the car balanced, otherwise you'll start getting some understeer.

"Diffusers" on Mustang are pretty much useless unless you run a flat underbody. GT350, GT500, Mach1, even GT4, are just dust and rocks catchers more than diffusers. There is so much turbulent airflow under our cars, from the floor not being flat, to the rear subframe & control arms being all but aerodynamic, diffusers are pointless and create more drag than anything else.

I feel attacked

 

[yotah1]

Rule of thumb for the diffuser to work :
ground clearance around 55-70mm
ramp angle max 11 degrees
full flat bottom leading to the diffuser to avoid turbulent air
ideally flat bottomed control arms too

Anything other than that is just marketing BS from either the manufacturer or the aftermarket company.

It always makes me giggle when I see companies showing some CFD images with colorful airflow lines and say they tested it. When we run CFD for our programs, we run the entire vehicle (inside and outside, because airflow within the car impacts airflow around the car), and we take into account panel gaps, fit and finish, nuts and bolts... and we run this on a computer farm that costs millions and takes 3-4 days to run the whole thing. And even that, we use those numbers very carefully because your CFD is only as good as whatever the dude that coded the original software did ...

But yeah, rule of thumb is above, and as Blacksheep rightfully said, deviating from what official racecars do is always sketchy unless you have the budget and manpower to do the same job as an OEM aero team.