Do front, side, rear splitters/diffusers actually add any performance?

[Rev_Night]

Hey peeps,

I am looking to take my lightly modded 2019 Kia Stinger GT AWD to the track about 2x a year. I am researching what mods will apply to this end, rather than simply just buying everything, and I am reading the various performance claims about splitters/diffusers. Saying that they force air pressure down onto the car, prevent air from lifting the car, and thus will help on corners, high speed, etc..

Is there any truth to any of these claims? Is there any evidence to back it up? Right now I am looking at around $1000 for all 3 and I am wondering how much of a benefit I will actually get.

M&S Front Splitter
M&S Side Splitter
M&S Rear Diffuser

thanks yall.

 

[Kimberly Lazarski]

Diffusers work by controlling turbulence at the tail end to improve laminar flow. They can improve downforce and reduce drag. On street cars it's more about efficiency, as we're not likely to be regularly driving at speeds where downforce starts to matter (130mph+ it starts to matter).

A properly designed one can help a great deal with efficiency. Airflow under the Stinger and G70 are already well-controlled with the belly pans smoothing the bottom end, but the stock rear diffuser design seems to be mostly for styling. You could try a ghetto approach of taping tissue to the back end of the car and try different diffusers to see which designs give the smoothest flow, maybe mock them up with coroplast and when you find which works best buy the one in that style that works best. You could try the same with the other body add-ons. Any gains at street-legal speeds would likely be negated by the added weight.

The Physics of Diffusers: How to Make a Car Really Suck

Gettin' down with downforce.

www.caranddriver.com

 

[Rev_Night]

That article is great, but I am driving a sports sedan not an F1. Do these have any practical impact for this car?

 

[Kimberly Lazarski]

That article is great, but I am driving a sports sedan not an F1. Do these have any practical impact for this car?

About as much as a ram air intake - not effective or only barely effective at street-legal speeds for performance. You may get some fuel economy improvements with some aero mods but with many of them the weight may actually degrade performance. If you've got the time and access to a wind tunnel or willing to fudge it with streamers and cameras on the street, go for it and share your data!

 

[Rev_Night]

That's good to know and basically aligns with what I already thought. And even at the track I would be going at most 100-110, and thats just for a single straight away. All other speeds is 30-60mph with all those corners.

They are for looks and nothing else.

 

[MerlintheMad]

The OE design of the Stinger is evidently well carried out: at the "Green Hell", of all places (that was actually a selling point for me; I kept rereading that chapter in the promo book ). I've taken my car up to 155 MPH (in a straight though undulating line, on Hwy 95 headed toward Nevada from Oregon), and the reason I did that, for the first and so far only time in my life (though I would do it again under those "perfect storm" conditions - NO TRAFFIC), is because the faster the Stinger went the more planted it felt.

 

[AA95101]

You missed an option in your poll, hurts performance

Im not saying any do but I have seen situations where aftermarket "aero" can cause high speed instability

 

[RogueIV]

There's also no "NO" option. Also all the specific rear diffusers for the Stinger are just for aesthetics. None of them properly go under the car more than the back bumper cover.