MMD Front Chin, GTC200 spoiler, APR splitter?? Downforce equation.

[exxit]

Hey track stang S550 friends...


To preface this, this is my first venture into a "track build" on a mustang platform... I've been doing my best to absorb info on how to keep the car balanced and maximize its viability on stock tune/stock power.

I recently added an MMD chin spoiler on a rear spoiler delete car and am trying to figure out if I need to pair my APR GTC200 and carbon trunk (the weight delta is maybe 5lbs, i got a screaming deal and don't want to drill my stock trunk) with an APR splitter under the MMD chin. The stock chin is hardly about 2 inches at its longes, and the MMD's sides extend out a good 6 inches.

Does it seem like I have enough in the front already to support a low rise wing, or will I need a splitter that extends even further than the MMD chin to accomplish this without upsetting the car.

I plan to play around with how this feels at the track (spoiler delete and MMD chin), but am theorizing that the delta between the stock chin spoiler and this one will cause oversteer at speed, making the wing already necessary.


Happy to be schooled here in case I'm going about it the wrong way.

 

[SMGDHG]

Hey track stang S550 friends...


To preface this, this is my first venture into a "track build" on a mustang platform... I've been doing my best to absorb info on how to keep the car balanced and maximize its viability on stock tune/stock power.

I recently added an MMD chin spoiler on a rear spoiler delete car and am trying to figure out if I need to pair my APR GTC200 and carbon trunk (the weight delta is maybe 5lbs, i got a screaming deal and don't want to drill my stock trunk) with an APR splitter under the MMD chin. The stock chin is hardly about 2 inches at its longes, and the MMD's sides extend out a good 6 inches.

Does it seem like I have enough in the front already to support a low rise wing, or will I need a splitter that extends even further than the MMD chin to accomplish this without upsetting the car.

I plan to play around with how this feels at the track (spoiler delete and MMD chin), but am theorizing that the delta between the stock chin spoiler and this one will cause oversteer at speed, making the wing already necessary.


Happy to be schooled here in case I'm going about it the wrong way.

Sadly without an actual wind tunnel to give factual numbers, the best answer (which you've already got) is testing out on track. If you have a handling imbalance at high speed which is not present at low speed, then you know you have an aero imbalance. IE if your car oversteers in low speed corners, but plows like a pig at high speed corners, you know the df being generated at the rear of the car is much more than the df being generated at the front.

Do you have hood vents? Hood vents reduce drag, reduce lift and if paired with a splitter in some applications (check out racelouvers) allow existing splitters to work better, therefore adding downforce. Oh and they also help with cooling.

GTC-200's don't make a ton of downforce, I think around 80lbf at 100mph. They have a nice chart on their website.

Also consider adding canards to increase front downforce. I have a set of @AJ Hartman canards on my car and they have been great. After destroying my splitter, I ran without s splitter for about 6 track days. All I had up front were the canards + massive hood vents and in the rear old gen GTC-200 out back. The car had a minor aero imbalance at high speeds, but it was by no means undriveable. I have since added a Laguna seca boss spec splitter to the front and the balance is fantastic, slightly biased towards front downforce.

AJ's canards (for a set of 4) are anywhere from 30-50lb-f. A splitter is so variable in how much df it creates, that it is hard to say. The GTC-200 has flow charts on APR's website, but keep in mind I think they test the wing in ideal conditions. So for our application (ie mounted on a car body), the wing will likely produce less.

Good luck and let us know how it goes!

This setup has had a good balance, it is slightly front biased in high speed corners

 

[AJ Hartman]

I'd think you'd have a rear bias with only a lip up front. The wing you have is... pretty terrible in performance terms, but still producing more Df than just the lip you have on the front. Df happens when you get low pressure across a surface. The lip you have has no real underside surface for low pressure to act upon, so its hardly doing much of anything in Df. I'd suggest adding a splitter, but thats also a loaded questions cause a "splitter" can be made to add a little Df, or you can make a "splitter" that would greatly overpower the wing you have and the car would be extremely loose and practically undriveable.