Chin splitter

[Performance nut]

Is anyone using an APR chin splitter? If so, what wing (if any) are you using in the back?

Reason I ask is because I got a really weird response from APR about the GTC-200 wing.

As far as the proper GT wing and splitter setup for this car it is the GT-250 spec wing. the GTC-Drag is not designed for the vehicle and the downforce data on our site is not applied to this wing. this wing only has 3 adjustments and is what it is labeled as a Drag wing. the GT-250 is a Track Wing this is designed to sit in the correct locations for proper function and downforce. The wing comes with all necessary hardware for proper installation.​

So the GTC-200 wing fits our car and it is about the same height as the GT350 spoiler. The CFD they performed may change based on the car's design, probably not a huge amount but I can see it may be changed. But the part that you distinguish between a drag wing and a track wing has me confused.

Downforce is downforce. The only thing I don't know is how much downforce our cars need at what speeds to have better traction on a road course. Based on that, you could select the right wing and AOA. Usually this is trial and error but usually there is that guy who knows these things.

The front splitter is to get rid of the lift I feel at speed but I don't want to induce an unbalanced downforce by only adding the splitter without a wing. Personally I don't like the GT-250 because it is just huge and my car is not a dedicated track car. At the same time, I don't want to induce significant oversteer in my car by adding too much downforce in the front without countering it with rear downforce.

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[OKC S550]

I think your worry of inducing unbalanced downforce is a little mis-guided. I have a front splitter and a GT350 TP spoiler on the rear. I have had my car upwards of 135 mph on track and it felt perfectly stable. I believe there are several others on here that have a front splitter and have not paired it with a big wing. I am no expert on downforce so this is all anecdotle information along with personla experience.

I do think there are 3 or 4 guys on here that have the APR GT-250 or Kognition wing (similiar size/shape) on their cars and I have seen a couple GT350's with them as well. I would be inclined to believe what APR is telling you but again I am no expert.

 

[Performance nut]

I think your worry of inducing unbalanced downforce is a little mis-guided. I have a front splitter and a GT350 TP spoiler on the rear. I have had my car upwards of 135 mph on track and it felt perfectly stable. I believe there are several others on here that have a front splitter and have not paired it with a big wing. I am no expert on downforce so this is all anecdotle information along with personla experience.

I do think there are 3 or 4 guys on here that have the APR GT-250 or Kognition wing (similiar size/shape) on their cars and I have seen a couple GT350's with them as well. I would be inclined to believe what APR is telling you but again I am no expert.

At risk of sounding confrontational, stable is a relative term. Some guys like some oversteer, others like understeer. I could drive your car and have a completely different opinion. Not meant to slight your setup, just my point of view.

Though you bring up valid points. Like I said, most of the time this is based on trial and error, tuning the system to get where you want. Though I have a feeling guys are running their setups to achieve similar characteristics. If no one is using the GT-250 over 10* AOA with gurney flap, seems that the GT-250 is an overkill. However, if everyone has their adjustable wings adjusted to high AOA to get the most downforce possible, seems that I may wish to reconsider my position on the GT-250.

My feeling is that the GTC-200 may not have been designed with the S550 in mind and not the best option out there, it will offer the same if not better handling characteristics than most of the non-adjustable spoilers on the market currently. I may be wrong though which is why I am looking for more experienced insight.

I do appreciate your feedback. If I may ask, which splitter are you using?

 

[ddozier]

If you are looking for another option for a wing check out G-Stream they offer a competition proven wing and S550 mounting system for their wing.
http://www.g-stream.com/C800.html

My first question is what is your goal for the aero package?

Not wanting to sound like an over protective parent but you are headed down a slippery path here if you are doing a splitter, wing, canards, and rear diffuser. It takes lots of time to dial in a aero and suspension setup, lots of trial and error, lots of data to collect and analyze.

In general it is best to develop a cars mechanical grip to its limits first then work from there to develop an aero package that will maintain a balance at the speed range you will be in for a given track. Often to maintain this balance requires a rework of the spring rates as the aero load is increased, this may mean a change in shock package as well as bar rates. You also have to consider ride height as well as alignment changes as the suspension is loaded beyond the physical weight of the car. It will be difficult at best to know what to change to improve lap times if all these items are done at once or if there is no test data to verify the performance of an added part. Most consumer aero mods sold are nearly worthless and do little more than increase drag as speeds increase. Some are downright dangerous at speeds above 100mph due to their mounting systems.

Dave

 

[Performance nut]

If you are looking for another option for a wing check out G-Stream they offer a competition proven wing and S550 mounting system for their wing.
http://www.g-stream.com/C800.html

My first question is what is your goal for the aero package?

Not wanting to sound like an over protective parent but you are headed down a slippery path here if you are doing a splitter, wing, canards, and rear diffuser. It takes lots of time to dial in a aero and suspension setup, lots of trial and error, lots of data to collect and analyze.

In general it is best to develop a cars mechanical grip to its limits first then work from there to develop an aero package that will maintain a balance at the speed range you will be in for a given track. Often to maintain this balance requires a rework of the spring rates as the aero load is increased, this may mean a change in shock package as well as bar rates. You also have to consider ride height as well as alignment changes as the suspension is loaded beyond the physical weight of the car. It will be difficult at best to know what to change to improve lap times if all these items are done at once or if there is no test data to verify the performance of an added part. Most consumer aero mods sold are nearly worthless and do little more than increase drag as speeds increase. Some are downright dangerous at speeds above 100mph due to their mounting systems.

Dave

No, you are totally good. My goal is to reduce lift in the car. It unnerves me quite a bit sometimes to the point that I will not push as much as know I can. It feels like it is more up front than in the back. Problem is I don't know what is too much in the front so a ln adjustable wing seems like good insurance.

As far as mounting goes, the splitter looks like it mounts to the chassis for the most part. The wing I am wondering what it will do to the trunk as I am unsure how much force it can take before it fails though chassis mounting is not an option for me. Canards was something I saw and was curious if it could substitute a splitter because I was concerned with ground clearance as well. However, another forum member runs the same splitter I want to run and he is lower than I am and has no issues.

 

[ddozier]

No, you are totally good. My goal is to reduce lift in the car. It unnerves me quite a bit sometimes to the point that I will not push as much as know I can. It feels like it is more up front than in the back. Problem is I don't know what is too much in the front so a ln adjustable wing seems like good insurance.

As far as mounting goes, the splitter looks like it mounts to the chassis for the most part. The wing I am wondering what it will do to the trunk as I am unsure how much force it can take before it fails though chassis mounting is not an option for me. Canards was something I saw and was curious if it could substitute a splitter because I was concerned with ground clearance as well. However, another forum member runs the same splitter I want to run and he is lower than I am and has no issues.

I would start with the splitter, test and see if it meets your needs and does not mess with the balance of the car. I ran my splitter without a wing or diffuser for several events and did not have an issue. The other thing to consider is a diffuser will actually add to the total available downforce and also reduce drag at the same time. If you run the splitter and find the rear loose I would then add the diffuser, test again and if the rear is still loose (not likely) then try a wing.

Dave

 

[OKC S550]

At risk of sounding confrontational, stable is a relative term. Some guys like some oversteer, others like understeer. I could drive your car and have a completely different opinion. Not meant to slight your setup, just my point of view.

Though you bring up valid points. Like I said, most of the time this is based on trial and error, tuning the system to get where you want. Though I have a feeling guys are running their setups to achieve similar characteristics. If no one is using the GT-250 over 10* AOA with gurney flap, seems that the GT-250 is an overkill. However, if everyone has their adjustable wings adjusted to high AOA to get the most downforce possible, seems that I may wish to reconsider my position on the GT-250.

My feeling is that the GTC-200 may not have been designed with the S550 in mind and not the best option out there, it will offer the same if not better handling characteristics than most of the non-adjustable spoilers on the market currently. I may be wrong though which is why I am looking for more experienced insight.

I do appreciate your feedback. If I may ask, which splitter are you using?

No worries, and I agree the feeling of stability is certainly relative to the driver.

It is interesting they say it wasnt designed for the S550. If you google that wing you will see it on a lot of different cars, including an S197 Mustang, so it makes me wonder what car they did design it for. I like the wing on Mike Maiers Mustang, it is lower profile and I'm sure it is functional as well. https://mikemaierinc.com/2017/02/new-blue-ford-mustang-s550/

I have the SBS performance splitter (you can find them on Facebook). Made by a guy in Oklahoma and its really just a piece of plastic but seems to work.

I'm with you on the GT-250 wing, its just a little too big for my taste but if that what it takes to get decernable downforce on these cars then I guess thats what we are "stuck" with.:shrug:

 

[Eritas]

The GTC-200 is a parachute. APR's "3D" wings are all garbage (200-300-500). The 250 is a much more effective and efficient wing. You can order it in different span/widths.

I would go with a wing or GT350TP spoiler before being concerned about a splitter.

 

[OKC S550]

I would go with a wing or GT350TP spoiler before being concerned about a splitter.

Interested on why you think this

 

[Eritas]

Interested on why you think this

Cars need a center of pressure behind the center of gravity for ultimate grip and stability. This means you need far more rear downforce than front whether the car is Front-engine, mid-engine, or even Front-wheel-drive.

Look at any racecar and the rear wings are substantially larger than the front splitter, if the car even has one. FWD touring cars (World Challenge, BTCC, WTCC) even have significant wings on them, because all cars need more rear downforce than front. You won't see a professional racecar with a massive splitter and no rear wing.

 

[OKC S550]

Cars need a center of pressure behind the center of gravity for ultimate grip and stability. This means you need far more rear downforce than front whether the car is Front-engine, mid-engine, or even Front-wheel-drive.

Look at any racecar and the rear wings are substantially larger than the front splitter, if the car even has one. FWD touring cars (World Challenge, BTCC, WTCC) even have significant wings on them, because all cars need more rear downforce than front. You won't see a professional racecar with a massive splitter and no rear wing.

This makes a lot of sense. I'm still trying to learn all of the nuances of aero and the ways it can affect the car at speed.

 

[Eritas]

It's considered a "black art" because most people don't have access to wind tunnels that cost $2K-$10K per hour to see how much downforce each part/wing/setting makes on a given car. Even then, changing one aspect almost always has an effect on other parts of the car.

I don't think you can go wrong with a quality wing like a GTC-250 or G-stream and then try different angles of attack to increase rear grip and stability. From there, you can work on a front splitter and adding front downforce to further improve lap times and grip, but also adding more rear downforce accordingly.

Most wings tend to stall around 15-20* and people tend to forget to take the angle of air flow off of the roof and rear glass into consideration IE ( a lower mounted wing will likely see 7* of downward airflow coming off of the roof, so a wing set at 0* relative to the ground is seeing a true 7* Angle Of Attack.

 

[Performance nut]

The GTC-200 is a parachute. APR's "3D" wings are all garbage (200-300-500). The 250 is a much more effective and efficient wing. You can order it in different span/widths.

I would go with a wing or GT350TP spoiler before being concerned about a splitter.

So how do you tackle lift in the front? Not disagreeing with you, just saying the front lifts way more than I would like.

On a side note, I noticed some serious nose resistance recently. Felt like I was pushing a ton of bricks. Are hood vents part of the strategy to relieve that pressure? Is that part of the lift issue?

 

[Eritas]

So how do you tackle lift in the front? Not disagreeing with you, just saying the front lifts way more than I would like.

On a side note, I noticed some serious nose resistance recently. Felt like I was pushing a ton of bricks. Are hood vents part of the strategy to relieve that pressure? Is that part of the lift issue?

Reducing rear lift/adding rear downforce is a priority over reducing front lift/adding front downforce.

Soft OEM front springs and very little front rebound damping exaggerate the front suspension going into droop under acceleration and lifting the nose. Running stiffer springs and a lower ride height can help this. Purely high speed front lift is a somewhat different problem, in which hood vents and front splitters do address and help.

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