Does the HP Spoiler with Gurney Flap Actually Generate Downforce?

[Junkyard Dog]

And if so, how much?

I have a hard time believing something bolted to the trunk lid actually generates enough downforce to matter.

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[Sofa King]

From what I understand they do in fact hove some downforce... how much or if enough to matter, I don't know. I've always been a bit curious about the downforce from factory as well as aftermarket spoilers (splitters too). Most people get them for looks... I'm not big on spoilers for looks, but for performance increase... maybe. Of course, engine add ons use HP numbers (dyno charts) to show performance increase... it would be nice to see downforce numbers to determine if the spoiler/splitter is a performance increase.

 

[timd38]

I does something because my fuel mileage takes a hit on the highway when I have the Gurney flap installed.

 

[Gregs24]

It reduces lift a bit I suspect and adds drag! The under floor strakes probably do more.

 

[robvas]

Supposedly takes 2mph off in the 1/4 mile

 

[gbadger]

Ford hasn’t released any numbers but if you look at reputable aftermarket wing companies that have gurney flap attachments they publish their data. The gurney flap adds a significant amount of downforce on those wings. I can’t imagine the flap on the HP spoiler is much different.

 

[gbadger]

Here is some data of other spoilers with and without flaps. The flap is pretty significant. Similar car, different spoiler, should be ballpark.

https://www.herrodperformance.com.au/2020-mustang-r-spec-gurney-flap/?utm_source=chatgpt.com

 

[Junkyard Dog]

Here is some data of other spoilers with and without flaps. The flap is pretty significant. Similar car, different spoiler, should be ballpark.

https://www.herrodperformance.com.au/2020-mustang-r-spec-gurney-flap/?utm_source=chatgpt.com

Surprising. Thanks for sharing the link.

 

[Gregs24]

Here is some data of other spoilers with and without flaps. The flap is pretty significant. Similar car, different spoiler, should be ballpark.

https://www.herrodperformance.com.au/2020-mustang-r-spec-gurney-flap/?utm_source=chatgpt.com

Or you could just put 60kg of sand in the trunk which would give you additional 'downforce' at all speeds

 

[Junkyard Dog]

Or you could just put 60kg of sand in the trunk which would give you additional 'downforce' at all speeds

Along with corresponding extra lateral force pulling on the rear of the car to the outside of the turn, lol!

 

[Kevi]

Or you could just put 60kg of sand in the trunk which would give you additional 'downforce' at all speeds

Somehow I don't think dead weight would help as much in a corner as down force.

 

[Gregs24]

Somehow I don't think dead weight would help as much in a corner as down force.

indeed (it was tongue in cheek), but those figures for the spoiler at speeds of 200kph+ (120mph) are marginal at best. What you would gain in a corner from an extra 60kg of rear downforce (very fast corners at that) you would almost certainly lose down the straight from the drag. Never mind that the additional rear downforce may actually increase understeer in those corners!

Downforce per se is no use unless it is efficient downforce and a huge gurney is NOT efficient!

Without a wind tunnel it is all just finger in the air stuff, but underfloor downforce from the strakes that Ford designed using a wind tunnel will almost certainly do more.

So the answer to the thread title is YES it will generate downforce but also a lot of drag and may make the car slower over a lap!

 

[gbadger]

It’s going to be course dependent and however you have setup the suspension on your car, tires, etc.

 

[gbadger]

Also, just making sure we are on the same page. This is not for drag racing. This is entirely a road course thing, high speed sweeping turns (Sebring, Daytona, etc)

 

[A.alansari]

I remember I've seen steeda drag test their red dark horse and the gurney flap slowed the car a little bit

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