991 highspeed cornering characteristic question
10-08-2018, 01:37 AM
#1
Pro
Thread Starter
991 highspeed cornering characteristic question
specifically i have a 991.2 4 GTS. I have a dozen or so track days (+1 wet) under my belt and to my surprise, the 991s (don't know about other generations as this 911 is my first) are more understeer than oversteer prone. I find it very hard to nearly impossible to get the rear end to lose grip unless I trailbrake late and force my rearend to get light inducing a rear slide. I'm pretty happy with this setup as it makes the car pretty dang safe to drive and learn on the track.
my question is:
there are two fast corners at my track, both in between 3rd and 4th gear speeds, that i feel i can floor it into and out of the corner, but I am always a bit sketchy (and frankly scared) at these speeds so i'm always backed off a bit on the throttle. If my experience from slower corners are correct, if I just floor the pedal and the tire starts losing grip, I would understeer, correct? If it induces understeer, I feel like I can back off and correct myself, and become wiser to the limits of my car and be able to take these corners with more confidence. can the characteristics possibly be different at higher speeds and can it possibly oversteer? If it oversteers and my rear slips out, I am not confident enough to manage a drift at such a high speed.
your insights greatly appreciated in advance
my question is:
there are two fast corners at my track, both in between 3rd and 4th gear speeds, that i feel i can floor it into and out of the corner, but I am always a bit sketchy (and frankly scared) at these speeds so i'm always backed off a bit on the throttle. If my experience from slower corners are correct, if I just floor the pedal and the tire starts losing grip, I would understeer, correct? If it induces understeer, I feel like I can back off and correct myself, and become wiser to the limits of my car and be able to take these corners with more confidence. can the characteristics possibly be different at higher speeds and can it possibly oversteer? If it oversteers and my rear slips out, I am not confident enough to manage a drift at such a high speed.
your insights greatly appreciated in advance
10-08-2018, 04:22 AM
#2
Rennlist Member
The factory tunes the suspension for understeer as it's "safer" for people who don't know how to manage oversteer. You can get closer to what you're looking for with an alignment change and even better with adjustable "Lower Control Arms" so that you can tune in more negative camber up front.
10-08-2018, 10:45 AM
#3
Rennlist Member
Yes, the car will understeer until you get it aligned for the track (dealerships usually don’t do this, you will need an Indie shop that specializes on porsche track/race cars). From the factory my camber was near zero both front and rear.
10-08-2018, 11:45 AM
#4
Rennlist Member
Just remember, tuning for corners has it's opposite and equal effect on straight line handling. You can take things too far and reduce straight line braking and stability. Make sure you explain your true needs to whomever does your alignment so they can help find the right balance.
10-08-2018, 12:28 PM
#5
Instructor
specifically i have a 991.2 4 GTS. I have a dozen or so track days (+1 wet) under my belt and to my surprise, the 991s (don't know about other generations as this 911 is my first) are more understeer than oversteer prone. I find it very hard to nearly impossible to get the rear end to lose grip unless I trailbrake late and force my rearend to get light inducing a rear slide. I'm pretty happy with this setup as it makes the car pretty dang safe to drive and learn on the track.
my question is:
there are two fast corners at my track, both in between 3rd and 4th gear speeds, that i feel i can floor it into and out of the corner, but I am always a bit sketchy (and frankly scared) at these speeds so i'm always backed off a bit on the throttle. If my experience from slower corners are correct, if I just floor the pedal and the tire starts losing grip, I would understeer, correct? If it induces understeer, I feel like I can back off and correct myself, and become wiser to the limits of my car and be able to take these corners with more confidence. can the characteristics possibly be different at higher speeds and can it possibly oversteer? If it oversteers and my rear slips out, I am not confident enough to manage a drift at such a high speed.
your insights greatly appreciated in advance
my question is:
there are two fast corners at my track, both in between 3rd and 4th gear speeds, that i feel i can floor it into and out of the corner, but I am always a bit sketchy (and frankly scared) at these speeds so i'm always backed off a bit on the throttle. If my experience from slower corners are correct, if I just floor the pedal and the tire starts losing grip, I would understeer, correct? If it induces understeer, I feel like I can back off and correct myself, and become wiser to the limits of my car and be able to take these corners with more confidence. can the characteristics possibly be different at higher speeds and can it possibly oversteer? If it oversteers and my rear slips out, I am not confident enough to manage a drift at such a high speed.
your insights greatly appreciated in advance
The cars will understeer anytime you release the brake too soon and apply excessive throttle.
Consider moving your brake points (both initial braking and brake release) later and deeper into the corner and brake less; maintain a higher speed going in and through the corner. Ideally, you should not be able to apply any throttle prior to the apex if you are braking late enough and maintaining a high enough corner speed.
Rotating the car becomes easier as you learn to brake less and learn to manipulate the balance of the car.
10-08-2018, 04:26 PM
#6
Rennlist
Basic Site Sponsor
Basic Site Sponsor
Join Date: Jun 2008
Location: Durham, NC and Virginia International Raceway
Posts: 18,680
Received 2,836 Likes
on
1,670 Posts
It sounds like you normally don't trail brake late enough.
Also, you should not be able to just floor it in the first half of the corner.
The cars will understeer anytime you release the brake too soon and apply excessive throttle.
Consider moving your brake points (both initial braking and brake release) later and deeper into the corner and brake less; maintain a higher speed going in and through the corner. Ideally, you should not be able to apply any throttle prior to the apex if you are braking late enough and maintaining a high enough corner speed.
Rotating the car becomes easier as you learn to brake less and learn to manipulate the balance of the car.
Also, you should not be able to just floor it in the first half of the corner.
The cars will understeer anytime you release the brake too soon and apply excessive throttle.
Consider moving your brake points (both initial braking and brake release) later and deeper into the corner and brake less; maintain a higher speed going in and through the corner. Ideally, you should not be able to apply any throttle prior to the apex if you are braking late enough and maintaining a high enough corner speed.
Rotating the car becomes easier as you learn to brake less and learn to manipulate the balance of the car.
I would not combine his suggested remedies. I would do one OR the other.
Moving the entir brake zone in, such that you leave enough brake for the corner entry, is the best advice. Slow at the maximal rate, but move the zone in.
I don’t agree with the idea of ‘braking less.’ Too nebulous, not repeatable and depends too much on subjective valuation of “how much is too much?”
__________________
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
10-08-2018, 11:07 PM
#7
Burning Brakes
Should also take a look at sway bar settings if that is equipped in your car.
Trending Topics
10-09-2018, 01:46 AM
#8
Pro
Thread Starter
Thank you for all your comments. I think I need to clarify my question, and it's probably my lack of knowledge on the proper terminology.
The corner in question is not a corner that needs braking prior to entry. It is more of a false-straight where i'm pretty much floored third gear going into fourth. There is a bend (corner) during this false-straight that gets me pretty much max side-G'ed. I feel like I can floor it through here but I just don't have enough confidence and end up letting go of the throttle a bit. If experience from slower corners tells me correct, if I did floor through this bend and I did lose traction, I would push and understeer, but I'm reluctant to try it (for lack of confidence). I don't want my rear end to go loose on me instead at this high a speed. So to clarify my question, if I were to lose grip on this high speed false-straight with a bend, would I most likely understeer? I've never induced oversteered in my car unless I was in a trailbrake situation, but I've never pushed the car at this high a speed.
Hope that makes sense. Thank you.
The corner in question is not a corner that needs braking prior to entry. It is more of a false-straight where i'm pretty much floored third gear going into fourth. There is a bend (corner) during this false-straight that gets me pretty much max side-G'ed. I feel like I can floor it through here but I just don't have enough confidence and end up letting go of the throttle a bit. If experience from slower corners tells me correct, if I did floor through this bend and I did lose traction, I would push and understeer, but I'm reluctant to try it (for lack of confidence). I don't want my rear end to go loose on me instead at this high a speed. So to clarify my question, if I were to lose grip on this high speed false-straight with a bend, would I most likely understeer? I've never induced oversteered in my car unless I was in a trailbrake situation, but I've never pushed the car at this high a speed.
Hope that makes sense. Thank you.
10-09-2018, 02:20 AM
#9
Burning Brakes
Lets start with the correct explanation of what understeer and oversteer.is because I think that is where the disconnect is.
Understeer is when your taking a turn as you apply gas the car wants to push you to the outside of the track thus not allowing achieve full throttle as quickly as one would desire and feeling like the front tires are not doing there job because the backs ones are pushing harder then they are.
Oversteer is when your taking a turn the back feel like it wants to slip away from you making the turn feel very uncomfortable thus forcing you to take a turn slower, but allowing you to achieve full throttle faster.
Some people like the feel of Understeer because it is more safe since the back end won't slip away, and others like some Oversteer so they can rotate the car as needed around turns.
On that note it sounds to me that your taking a turn that you feel can probably be achieved at full throttle but not sure and still not comfortable enough to do so.
I can name many tracks where I didn't have the nerve to go full throttle through certain areas that I also felt the same feelings.
After time the speed will come just keep driving the right line.
If we had more data like what g-force you were pulling at that turn along with what kind of tires are you running, and possibly some video that could at least shed some light for us.
Understeer is when your taking a turn as you apply gas the car wants to push you to the outside of the track thus not allowing achieve full throttle as quickly as one would desire and feeling like the front tires are not doing there job because the backs ones are pushing harder then they are.
Oversteer is when your taking a turn the back feel like it wants to slip away from you making the turn feel very uncomfortable thus forcing you to take a turn slower, but allowing you to achieve full throttle faster.
Some people like the feel of Understeer because it is more safe since the back end won't slip away, and others like some Oversteer so they can rotate the car as needed around turns.
On that note it sounds to me that your taking a turn that you feel can probably be achieved at full throttle but not sure and still not comfortable enough to do so.
I can name many tracks where I didn't have the nerve to go full throttle through certain areas that I also felt the same feelings.
After time the speed will come just keep driving the right line.
If we had more data like what g-force you were pulling at that turn along with what kind of tires are you running, and possibly some video that could at least shed some light for us.
10-09-2018, 03:12 AM
#10
Pro
Thread Starter
Lets start with the correct explanation of what understeer and oversteer.is because I think that is where the disconnect is.
Understeer is when your taking a turn as you apply gas the car wants to push you to the outside of the track thus not allowing achieve full throttle as quickly as one would desire and feeling like the front tires are not doing there job because the backs ones are pushing harder then they are.
Oversteer is when your taking a turn the back feel like it wants to slip away from you making the turn feel very uncomfortable thus forcing you to take a turn slower, but allowing you to achieve full throttle faster.
Some people like the feel of Understeer because it is more safe since the back end won't slip away, and others like some Oversteer so they can rotate the car as needed around turns.
On that note it sounds to me that your taking a turn that you feel can probably be achieved at full throttle but not sure and still not comfortable enough to do so.
I can name many tracks where I didn't have the nerve to go full throttle through certain areas that I also felt the same feelings.
After time the speed will come just keep driving the right line.
If we had more data like what g-force you were pulling at that turn along with what kind of tires are you running, and possibly some video that could at least shed some light for us.
Understeer is when your taking a turn as you apply gas the car wants to push you to the outside of the track thus not allowing achieve full throttle as quickly as one would desire and feeling like the front tires are not doing there job because the backs ones are pushing harder then they are.
Oversteer is when your taking a turn the back feel like it wants to slip away from you making the turn feel very uncomfortable thus forcing you to take a turn slower, but allowing you to achieve full throttle faster.
Some people like the feel of Understeer because it is more safe since the back end won't slip away, and others like some Oversteer so they can rotate the car as needed around turns.
On that note it sounds to me that your taking a turn that you feel can probably be achieved at full throttle but not sure and still not comfortable enough to do so.
I can name many tracks where I didn't have the nerve to go full throttle through certain areas that I also felt the same feelings.
After time the speed will come just keep driving the right line.
If we had more data like what g-force you were pulling at that turn along with what kind of tires are you running, and possibly some video that could at least shed some light for us.
10-09-2018, 03:37 AM
#11
Burning Brakes
I'll try to get some video when I'm next at the track. But yes, what you are saying is what I'm asking. I'm running Sport Cup 2s. I just wish I had the nerve to go full throttle but I lose confidence at such high speeds. If I did go full throttle and knew I would most likely understeer rather than oversteer, I would try it because understeer is much easier for me to correct. i hope to join an instructor class one day and get this area answered.
What track are we talking about, and what turn is it?
10-09-2018, 03:58 AM
#12
Pro
Thread Starter
i don't have the specific turn on video but maybe this video of another track in Korea (Inje Speedium) can give reference to the situations i'm referring to.
Turn 6, starting 00:35min, i feel like i can floor it from the middle of the turn into exit of the turn but I'm always a bit hesitant and don't floor until the exit.
Turn 15, starting 1:17min, I want to floor through this entire turn but I'm always alittle less.
If I tried flooring it through these, you think I would push or my rear end would come out?
10-09-2018, 04:07 AM
#13
Burning Brakes
https://youtu.be/S0jITqiZRFE
i don't have the specific turn on video but maybe this video of another track in Korea (Inje Speedium) can give reference to the situations i'm referring to.
Turn 6, starting 00:35min, i feel like i can floor it from the middle of the turn into exit of the turn but I'm always a bit hesitant and don't floor until the exit.
Turn 15, starting 1:17min, I want to floor through this entire turn but I'm always alittle less.
If I tried flooring it through these, you think I would push or my rear end would come out?
i don't have the specific turn on video but maybe this video of another track in Korea (Inje Speedium) can give reference to the situations i'm referring to.
Turn 6, starting 00:35min, i feel like i can floor it from the middle of the turn into exit of the turn but I'm always a bit hesitant and don't floor until the exit.
Turn 15, starting 1:17min, I want to floor through this entire turn but I'm always alittle less.
If I tried flooring it through these, you think I would push or my rear end would come out?
Best advice is to get an instructor or someone familiar with that track to help you learn a good line and keep practicing, the speed will come.
10-09-2018, 04:13 AM
#14
Pro
Thread Starter
Again I don't think this has anything to do with under or over steer, sound more like lateral grip which has to do with car and tire ability, along with weather conditions as I see snow on the track!!
Best advice is to get an instructor or someone familiar with that track to help you learn a good line and keep practicing, the speed will come.
Best advice is to get an instructor or someone familiar with that track to help you learn a good line and keep practicing, the speed will come.
I have amateur experience with trailbrake induced oversteer but in these lateral grip situations, I just don't know what happens if I over cook it. do I push, go side ways, spin out? I want to know how the car will react but too scared to push it. definitely will seek instructor help when I can. thanks
10-09-2018, 08:42 AM
#15
Rennlist Member
If you get a chance work out on a skid pad with an instructor. It will teach you how to induce understeer, safe ways to correct it, how to induce oversteer, ways to correct that, and more importantly, how to control all these techniques so they become tools in your driving skills toolbox.