Downforce Experience, Concept for Driving the GT3RS
12-30-2023, 09:19 PM
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Downforce Experience, Concept for Driving the GT3RS
I’m going to make a cheat sheet for you guys on GT3 vs RS and where the aero makes the most difference. In non-downforce cars- like most normal road cars...the more speed you carry means the less grip you have to negotiate a corner. Pretty logical as we are all taught about the "100% Rule" of the "Friction Circle"
Downforce means as you go faster, the bigger the circle gets, and therefore the more overall grip the tires will have. It's not quite linear, but it's logical. Once you understand how downforce works, you'll not want to drive regular cars on track anymore other than for S***s and Giggles.
That being said- There is a lot of guesswork for the guys coming from the GT4 or GT3 or 9913RS drivers that goes into how the aero will affect the 992 GT3RS but it’s pretty simple:
good aero cars start to really get more planted/ solid around 75-80 MPH from the front end. this shows up on road cars (previously in Senna, P1, ACR-E) as the front bite or instant input entering neutral (swervy/ non braking) corners without hesitation. You can test this a bit by doing lane changes on the highway.
*typically* 911’s- even cup cars- have a slight resistance to turn in without a deceleration or pitch change. without a slight weight transfer, the car will take a tiny bit to shift weight before turning. This is because there is so little weight on the front axle. This is especially obvious to anyone that’s tracked a shelby, a viper or a bmw. their engine is on the front axle so the car doesn’t need braking to have front grip on initial turn in. The issue with those cars is they break loose from the rear throughout the corner.
911 limit cornering for most corners does require some significant weight based reaction to shift weight to the outside front wheel. This is a rear to front shift (weight transfer under brakes) or trail braking to get weight on both outside wheels (you see lots of cup cars with 1-2 wheels off the ground jumping apex curbs). 911 turning modality for years was about getting the car REALLY slowed down and REALLY turned and then REALLY getting on the throttle. Rear engine helps control under braking and stability under acceleration.
Formula cars (F4, F3 and up) and LMP3, 2, etc are set up to turn with downforce and remain driveable even when the driver is under high G loading. In something like an Atlantic series race car, this means the steering wheel is really light, same as in an early LMP3 car. Your body is slammed into the carbon fiber so requiring a massive steering input effort is going to require super strength...and not ideal. LMP and Formula cars are harder to drive in slow corners as a result of this. Road based race cars just drive like crappy road cars into hairpins...they're heavy but basic- just mechanical grip like your street car in the hairpin.
Downforce acts as additional weight - in the 3RS that means you already have weight on the outside tire @ 75-80 mph even at neutral body /neutral roll. This is palpable/ tangible via the steering wheel weight and a quicker reaction to input. You still execute weight transfer or trail braking but some of that is happening so early in the corner you feel more confident and it requires either less latency or less time on the brakes to achieve the change in balance. In some cases you're going to get better reaction from the car and less time turning, so less tire wear- and much less sliding, so the heat of the tires is more even across the carcass.
Downforce adds grip to the car (by pressing down onto the tires) so when you *give the correct input* there is increased force on the tires and suspension on the side you need. this is the invincible feeling that people describe.
F1 cars make enough DF that their apex / minimum speeds generate 4-5G consistently. LMP1/2 cars are 3-4G consistently and LMP1 could occasionally pop a few 5G corners.
Likely that adding some compression to the corner (like T6 Laguna, T1 Sonoma), you can see the GT3RS @ 2G + for short peaks. 1000-1500 lbs of downforce is pretty serious especially when all the weight is on only 2-3 of the tires through a corner.
The key here is understanding how the DF kicks in at higher speeds. 100+MPH corners mean the airflow is really working hard on the rear via the diffuser and the wing and the aero flaps on the front are maxing out. 120MPH and it's really working. 140MPH and there is no sliding at all. Eventually the tires start to become an issue due to overall force potentially wearing out the sidewalls.
Here are some corners where the 3RS will truly require big ***** to max out your laptimes. This is where the car will be generating enough grip on both front and rear to leapfrog the GT3 and other track day players. Of course anyone who has raced LMP cars or tracked the ACR-X will have this type of thing down easier, or have done it before/ learned... It's somewhat counterintuitive to your self-preservation instinct that you need to drive faster through a corner (slow down less) in order to make the car handle better...but in this car- you're making serious downforce at 100-120mph and it will respond better at 120mph than at 85 through the same corner. For me it was an instructor @ Sonoma in F3 cars explaining I needed to go flat in 4th gear through the Esses ( I was breathing in and out of the throttle through the corners to try and get the front end pointed). I was pretty sketched out, but he said hey listen this is legit flat in this car. You need to go flat, that's all there is to it. So I did, and then I was never scared of a fast corner again.
Thunderhill- T1, T2, T7-9,
Laguna- T1, T4, T6, T9
Sonoma- T1, T3a, Carousel, Esses, T10
Cota- T2 -5, 7, carousel, 19
Road America- T1, 7, carousel, kink, 13
Watkins Glen- uphill esses, 5, 10, 11
Sebring- T1, 11,12,14,15,17
Road Atlanta- T1, 4-6, 12
Barber- 9,10,13, 14
Willow Springs- 2,6,8,9
Buttonwillow- 8 (entry to bus stop) Riverside into Phil Hill (13cw config)
FWIW I’m leaving out the big braking zones as braking in a Gt3 vs an RS for slow entry corners is more logical gains vs gains by carrying tons more entry speed.
Driving an aero car quickly is chasing a few different sensations- since so much of the grip is not dependent on your steering wheel inputs but your speed, it takes some time to digest.
Having driven a bunch of cars, I like to ask a lot of questions beforehand (having not asked questions before flogging a superformance Gt40 almost cost me everything, never again)
So- when I first drove the LMP3 Ligier I was trying to get someone to explain the sensation of being on the limit - what will the steering wheel feel like in my hand to explain that this is all the car can do? It had been almost 10 years since I drove an F3 car. Does the car shudder? This whole “what feeling am I chasing” line of questioning really helps me get the pro or factory driver to format good data.
What I can try to relay so you guys willing to push the car get reinforcement-
when you’re used to barely making an entry @ 80mph in a car- entering at 100+ will make the car easier to drive.
the sensation in the wheel at max aero grip is that the wheel tingles, or has high frequency pulsing from the front tires being taxed but also trying to understeer. it’s like you’re driving on gravel with massive grip.
downforce is palapable with steering wheel weight. you will feel it working in that 80-110 mph window where the pressure is building on the front axle. you will feel much more stable at 125-130mph vs 80mph. less play in the wheel, more direct.
rear downforce is much scarier to trust, it basically requires you to have pushed into a place where the car would normally start over-rotating at 100mph+ and instead it’s splatting to the tarmac, allowing you to add throttle earlier or brake less.
as someone said it feels like you have amazing tires from a grip class above. so imagine that your car is on old tires, and there is that one super sketchy corner you cannot challenge because if you do…it’s 130mph and you are going to lose the back end. 1000+ lbs of downforce/ Aero now empowers you to attack that corner like it’s fresh cup2r or better tires.
There are a lot of ways this plays out, in terms of how you attack a corner.
Scenario A: You normally have understeer and have to slow down a lot to get to the apex, 'slow in fast out'. This corner is 2nd gear now. You might still be too slow, or too tight for downforce to matter much...an example of this is T3 at Laguna Seca, or T20 at COTA. Slow corners are still slow...but you can brake harder, deeper, for less time and maybe save 30-50 ft that way (2-3 car lengths)
Scenario B: You have understeer and have to tap the brake a little/ slow down a little from 5th to 4th or 3rd to make a corner, or do a mini-lift to keep the car on the track like Turn 8 at Big Willow, or Turn 1 at Sonoma. This is where Aero is your buddy and will allow you to potentially roll 10-20mph more speed. This is Turn 2 into the entry to the Esses at COTA.
Scenario C: This is a fast corner and you typically turn in early, counting on the car to scrub speed by putting on all 4 wheels into slight drift across the apex zone in 3rd or 4th gear. If you're in that 100mph range, you might now have ample front end downforce that you don't drift/scrub anymore and can turn in with even more speed. Those of you that have done karts know what type of corner I mean here. This is really a long, slow rotation under control where you're over the limit of the tires but the yaw is slow enough to catch and make useful. The corner opens up on the exit and you can hammer the throttle REALLY early in a downforce car. Perhaps the fast kink at Daytona is an example here.
Scenario D: The fast entry corner tightens up and you have to wait a long time on exit to go to power because the car is sliding at a medium/high speed or bouncing (sebring turn 1, turn 17). Downforce here at the right speed will prevent you from sliding on the exit and allow you room to complete the track out with more speed potential.
For my California guys, This mental adjustment is similar mechanically to Turn 6 at Laguna since they added that 30%or 50% a car width of paving. You'll end up going through the corner thinking you're not going to be able to keep it on the track...and then you miss the track out curbing by 5 ft or more.
There are a lot of variables here but at F1 type tracks like Silverstone, or Spa, or long flowing corners like T12 and T1 at Road Atlanta, you will stick better, allowing for more throttle or less braking, which allows for more speed, which means more downforce, which means more grip...it's a great cycle.
This is just the beginning of the discussion because as more of us track the GT3RS, we will really see what it can do in pleb hands (not just bergmeister's and pat long's).
Keep in mind this is all conceptual for you to think about how to approach it, you will still have to take small steps and move in safe increments towards your own limits. But, Porsche has given us a really serious tool...the most downforce for a road car under XXXXXX price, ever.
Downforce means as you go faster, the bigger the circle gets, and therefore the more overall grip the tires will have. It's not quite linear, but it's logical. Once you understand how downforce works, you'll not want to drive regular cars on track anymore other than for S***s and Giggles.
That being said- There is a lot of guesswork for the guys coming from the GT4 or GT3 or 9913RS drivers that goes into how the aero will affect the 992 GT3RS but it’s pretty simple:
good aero cars start to really get more planted/ solid around 75-80 MPH from the front end. this shows up on road cars (previously in Senna, P1, ACR-E) as the front bite or instant input entering neutral (swervy/ non braking) corners without hesitation. You can test this a bit by doing lane changes on the highway.
*typically* 911’s- even cup cars- have a slight resistance to turn in without a deceleration or pitch change. without a slight weight transfer, the car will take a tiny bit to shift weight before turning. This is because there is so little weight on the front axle. This is especially obvious to anyone that’s tracked a shelby, a viper or a bmw. their engine is on the front axle so the car doesn’t need braking to have front grip on initial turn in. The issue with those cars is they break loose from the rear throughout the corner.
911 limit cornering for most corners does require some significant weight based reaction to shift weight to the outside front wheel. This is a rear to front shift (weight transfer under brakes) or trail braking to get weight on both outside wheels (you see lots of cup cars with 1-2 wheels off the ground jumping apex curbs). 911 turning modality for years was about getting the car REALLY slowed down and REALLY turned and then REALLY getting on the throttle. Rear engine helps control under braking and stability under acceleration.
Formula cars (F4, F3 and up) and LMP3, 2, etc are set up to turn with downforce and remain driveable even when the driver is under high G loading. In something like an Atlantic series race car, this means the steering wheel is really light, same as in an early LMP3 car. Your body is slammed into the carbon fiber so requiring a massive steering input effort is going to require super strength...and not ideal. LMP and Formula cars are harder to drive in slow corners as a result of this. Road based race cars just drive like crappy road cars into hairpins...they're heavy but basic- just mechanical grip like your street car in the hairpin.
Downforce acts as additional weight - in the 3RS that means you already have weight on the outside tire @ 75-80 mph even at neutral body /neutral roll. This is palpable/ tangible via the steering wheel weight and a quicker reaction to input. You still execute weight transfer or trail braking but some of that is happening so early in the corner you feel more confident and it requires either less latency or less time on the brakes to achieve the change in balance. In some cases you're going to get better reaction from the car and less time turning, so less tire wear- and much less sliding, so the heat of the tires is more even across the carcass.
Downforce adds grip to the car (by pressing down onto the tires) so when you *give the correct input* there is increased force on the tires and suspension on the side you need. this is the invincible feeling that people describe.
F1 cars make enough DF that their apex / minimum speeds generate 4-5G consistently. LMP1/2 cars are 3-4G consistently and LMP1 could occasionally pop a few 5G corners.
Likely that adding some compression to the corner (like T6 Laguna, T1 Sonoma), you can see the GT3RS @ 2G + for short peaks. 1000-1500 lbs of downforce is pretty serious especially when all the weight is on only 2-3 of the tires through a corner.
The key here is understanding how the DF kicks in at higher speeds. 100+MPH corners mean the airflow is really working hard on the rear via the diffuser and the wing and the aero flaps on the front are maxing out. 120MPH and it's really working. 140MPH and there is no sliding at all. Eventually the tires start to become an issue due to overall force potentially wearing out the sidewalls.
Here are some corners where the 3RS will truly require big ***** to max out your laptimes. This is where the car will be generating enough grip on both front and rear to leapfrog the GT3 and other track day players. Of course anyone who has raced LMP cars or tracked the ACR-X will have this type of thing down easier, or have done it before/ learned... It's somewhat counterintuitive to your self-preservation instinct that you need to drive faster through a corner (slow down less) in order to make the car handle better...but in this car- you're making serious downforce at 100-120mph and it will respond better at 120mph than at 85 through the same corner. For me it was an instructor @ Sonoma in F3 cars explaining I needed to go flat in 4th gear through the Esses ( I was breathing in and out of the throttle through the corners to try and get the front end pointed). I was pretty sketched out, but he said hey listen this is legit flat in this car. You need to go flat, that's all there is to it. So I did, and then I was never scared of a fast corner again.
Thunderhill- T1, T2, T7-9,
Laguna- T1, T4, T6, T9
Sonoma- T1, T3a, Carousel, Esses, T10
Cota- T2 -5, 7, carousel, 19
Road America- T1, 7, carousel, kink, 13
Watkins Glen- uphill esses, 5, 10, 11
Sebring- T1, 11,12,14,15,17
Road Atlanta- T1, 4-6, 12
Barber- 9,10,13, 14
Willow Springs- 2,6,8,9
Buttonwillow- 8 (entry to bus stop) Riverside into Phil Hill (13cw config)
FWIW I’m leaving out the big braking zones as braking in a Gt3 vs an RS for slow entry corners is more logical gains vs gains by carrying tons more entry speed.
Driving an aero car quickly is chasing a few different sensations- since so much of the grip is not dependent on your steering wheel inputs but your speed, it takes some time to digest.
Having driven a bunch of cars, I like to ask a lot of questions beforehand (having not asked questions before flogging a superformance Gt40 almost cost me everything, never again)
So- when I first drove the LMP3 Ligier I was trying to get someone to explain the sensation of being on the limit - what will the steering wheel feel like in my hand to explain that this is all the car can do? It had been almost 10 years since I drove an F3 car. Does the car shudder? This whole “what feeling am I chasing” line of questioning really helps me get the pro or factory driver to format good data.
What I can try to relay so you guys willing to push the car get reinforcement-
when you’re used to barely making an entry @ 80mph in a car- entering at 100+ will make the car easier to drive.
the sensation in the wheel at max aero grip is that the wheel tingles, or has high frequency pulsing from the front tires being taxed but also trying to understeer. it’s like you’re driving on gravel with massive grip.
downforce is palapable with steering wheel weight. you will feel it working in that 80-110 mph window where the pressure is building on the front axle. you will feel much more stable at 125-130mph vs 80mph. less play in the wheel, more direct.
rear downforce is much scarier to trust, it basically requires you to have pushed into a place where the car would normally start over-rotating at 100mph+ and instead it’s splatting to the tarmac, allowing you to add throttle earlier or brake less.
as someone said it feels like you have amazing tires from a grip class above. so imagine that your car is on old tires, and there is that one super sketchy corner you cannot challenge because if you do…it’s 130mph and you are going to lose the back end. 1000+ lbs of downforce/ Aero now empowers you to attack that corner like it’s fresh cup2r or better tires.
There are a lot of ways this plays out, in terms of how you attack a corner.
Scenario A: You normally have understeer and have to slow down a lot to get to the apex, 'slow in fast out'. This corner is 2nd gear now. You might still be too slow, or too tight for downforce to matter much...an example of this is T3 at Laguna Seca, or T20 at COTA. Slow corners are still slow...but you can brake harder, deeper, for less time and maybe save 30-50 ft that way (2-3 car lengths)
Scenario B: You have understeer and have to tap the brake a little/ slow down a little from 5th to 4th or 3rd to make a corner, or do a mini-lift to keep the car on the track like Turn 8 at Big Willow, or Turn 1 at Sonoma. This is where Aero is your buddy and will allow you to potentially roll 10-20mph more speed. This is Turn 2 into the entry to the Esses at COTA.
Scenario C: This is a fast corner and you typically turn in early, counting on the car to scrub speed by putting on all 4 wheels into slight drift across the apex zone in 3rd or 4th gear. If you're in that 100mph range, you might now have ample front end downforce that you don't drift/scrub anymore and can turn in with even more speed. Those of you that have done karts know what type of corner I mean here. This is really a long, slow rotation under control where you're over the limit of the tires but the yaw is slow enough to catch and make useful. The corner opens up on the exit and you can hammer the throttle REALLY early in a downforce car. Perhaps the fast kink at Daytona is an example here.
Scenario D: The fast entry corner tightens up and you have to wait a long time on exit to go to power because the car is sliding at a medium/high speed or bouncing (sebring turn 1, turn 17). Downforce here at the right speed will prevent you from sliding on the exit and allow you room to complete the track out with more speed potential.
For my California guys, This mental adjustment is similar mechanically to Turn 6 at Laguna since they added that 30%or 50% a car width of paving. You'll end up going through the corner thinking you're not going to be able to keep it on the track...and then you miss the track out curbing by 5 ft or more.
There are a lot of variables here but at F1 type tracks like Silverstone, or Spa, or long flowing corners like T12 and T1 at Road Atlanta, you will stick better, allowing for more throttle or less braking, which allows for more speed, which means more downforce, which means more grip...it's a great cycle.
This is just the beginning of the discussion because as more of us track the GT3RS, we will really see what it can do in pleb hands (not just bergmeister's and pat long's).
Keep in mind this is all conceptual for you to think about how to approach it, you will still have to take small steps and move in safe increments towards your own limits. But, Porsche has given us a really serious tool...the most downforce for a road car under XXXXXX price, ever.
Popular Reply
01-05-2024, 04:12 PM
Race Car
Imagine that, a technical post about driving gets 15 replies in a week.
Should have put ADM in the title
Should have put ADM in the title
12-30-2023, 09:28 PM
#2
Rennlist Member
Amazing insights!
The following users liked this post:
AlexCeres (12-31-2023)
12-30-2023, 10:35 PM
#4
Awesome thread. Cannot wait to track this thing
12-30-2023, 10:52 PM
#5
Rennlist Member
subscribed - I understand al this in theory - it's practice that's going to be fun.
12-31-2023, 05:26 AM
#7
Rennlist Member
What do you think of the tire selection? I've only got to experience Pirelli PZero Corsas and Goodyear Supersport R; no frame of reference as compared to Cup2s since I haven't driven the car with Cup2s; I don't know how the tires fall off. I know Cup2 has peak grip in the first day and then it turns into something resembling hot garbage in terms of grip but the car is so heroic that I can't tell if I could have gone faster with fresh tires or not yet.
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12-31-2023, 11:07 AM
#8
Rennlist Member
Good analysis and guidance CJ 
. I am sure this will help a lot of drivers to be more confident in their GT3 RS's. Hope they will come out in droves to Laguna and Sears in 2024 to exchange experiences and tips. Looking forward to it
. I am sure this will help a lot of drivers to be more confident in their GT3 RS's. Hope they will come out in droves to Laguna and Sears in 2024 to exchange experiences and tips. Looking forward to it
12-31-2023, 11:36 AM
#9
Good analysis CJ. Driving a high downforce, lightweight car is an addictive experience. Also, downforce can only really be exploited in a track so anyone saying they feel it on the road is either confused or should probably be in jail.
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daveo4porsche (01-05-2024)
01-05-2024, 08:19 AM
#10
I have a novice question. If you have a fixed wing that gives you high downforce such as the GT3, I understand this is beneficial with a higher speed approaching a turn. However don't you have a penalty on straight aways with the increased drag?
01-05-2024, 10:58 AM
#12
Rennlist Member
Never did aero, although I once removed the wing and splitter from my 964 and almost crashed two laps in a row.
Thanks CJ!
"Here are some corners where the 3RS will truly require big ***** to max out your laptimes. This is where the car will be generating enough grip on both front and rear to leapfrog the GT3 and other track day players. Of course anyone who has raced LMP cars or tracked the ACR-X will have this type of thing down easier, or have done it before/ learned... It's somewhat counterintuitive to your self-preservation instinct that you need to drive faster through a corner (slow down less) in order to make the car handle better...but in this car- you're making serious downforce at 100-120mph and it will respond better at 120mph than at 85 through the same corner. For me it was an instructor @ Sonoma in F3 cars explaining I needed to go flat in 4th gear through the Esses ( I was breathing in and out of the throttle through the corners to try and get the front end pointed). I was pretty sketched out, but he said hey listen this is legit flat in this car. You need to go flat, that's all there is to it. So I did, and then I was never scared of a fast corner again.
Sebring- T1, 11,12,14,15,17"
Oeftah..
T1 Sebring?
Or scenario D, but either way; What does aero and very hard suspension do over the big bumps at the exit?! I'm a little scared already
"Scenario C: This is a fast corner and you typically turn in early, counting on the car to scrub speed by putting on all 4 wheels into slight drift across the apex zone in 3rd or 4th gear. If you're in that 100mph range, you might now have ample front end downforce that you don't drift/scrub anymore and can turn in with even more speed. Those of you that have done karts know what type of corner I mean here. This is really a long, slow rotation under control where you're over the limit of the tires but the yaw is slow enough to catch and make useful. The corner opens up on the exit and you can hammer the throttle REALLY early in a downforce car. Perhaps the fast kink at Daytona is an example here."
Thanks CJ!
"Here are some corners where the 3RS will truly require big ***** to max out your laptimes. This is where the car will be generating enough grip on both front and rear to leapfrog the GT3 and other track day players. Of course anyone who has raced LMP cars or tracked the ACR-X will have this type of thing down easier, or have done it before/ learned... It's somewhat counterintuitive to your self-preservation instinct that you need to drive faster through a corner (slow down less) in order to make the car handle better...but in this car- you're making serious downforce at 100-120mph and it will respond better at 120mph than at 85 through the same corner. For me it was an instructor @ Sonoma in F3 cars explaining I needed to go flat in 4th gear through the Esses ( I was breathing in and out of the throttle through the corners to try and get the front end pointed). I was pretty sketched out, but he said hey listen this is legit flat in this car. You need to go flat, that's all there is to it. So I did, and then I was never scared of a fast corner again.
Sebring- T1, 11,12,14,15,17"
Oeftah..
T1 Sebring?
Or scenario D, but either way; What does aero and very hard suspension do over the big bumps at the exit?! I'm a little scared already
"Scenario C: This is a fast corner and you typically turn in early, counting on the car to scrub speed by putting on all 4 wheels into slight drift across the apex zone in 3rd or 4th gear. If you're in that 100mph range, you might now have ample front end downforce that you don't drift/scrub anymore and can turn in with even more speed. Those of you that have done karts know what type of corner I mean here. This is really a long, slow rotation under control where you're over the limit of the tires but the yaw is slow enough to catch and make useful. The corner opens up on the exit and you can hammer the throttle REALLY early in a downforce car. Perhaps the fast kink at Daytona is an example here."
Last edited by TRAKCAR; 01-05-2024 at 11:07 AM.
01-05-2024, 02:08 PM
#13
Platinum Dealership
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Never did aero, although I once removed the wing and splitter from my 964 and almost crashed two laps in a row.
Thanks CJ!
"
Sebring- T1, 11,12,14,15,17"
Oeftah..
T1 Sebring?
Or scenario D, but either way; What does aero and very hard suspension do over the big bumps at the exit?! I'm a little scared already
"
Thanks CJ!
"
Sebring- T1, 11,12,14,15,17"
Oeftah..
T1 Sebring?
Or scenario D, but either way; What does aero and very hard suspension do over the big bumps at the exit?! I'm a little scared already
"
All that being said- you know some of those bumps especially in 17 actually help the car rotate, as scary as that is.
Sebring is an animal unlike all the other tracks in USA.
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Diablo Dude (01-05-2024),
TRAKCAR (01-06-2024)
01-05-2024, 02:37 PM
#15
The following users liked this post:
TRAKCAR (01-06-2024)