Nannies?
05-16-2019, 03:27 PM
#46
Rennlist Member
ESC-OFF and TC-OFF for everything but street driving and rain events.
ABS, e-diff and torque vectoring cannot be turned off. The GT3 still controls power/overrun delivery through the e-diff, so not all the nannies can be disabled.
Launch Control program is only available with TC-ON (regardless of ESC setting).
99% of the GT3 drivers should leave these nannies on forever.
ABS, e-diff and torque vectoring cannot be turned off. The GT3 still controls power/overrun delivery through the e-diff, so not all the nannies can be disabled.
Launch Control program is only available with TC-ON (regardless of ESC setting).
99% of the GT3 drivers should leave these nannies on forever.
05-16-2019, 07:57 PM
#47
I believe that doing the fastest lap available for a given car is to have it at it's grip limit. Generally speaking. With nannies off you can explore that limit and even be a step beyond it if your inputs are correct. If not you spin and eat the gravel. With nannies on they would step in on many occasions unnecessarily. Often I find ESC kicking the front brakes where it is not really necessary and thus slowing the car down. I am not talking here stupid going hot into turns.
05-16-2019, 10:54 PM
#48
Rennlist Member
More tail happy is easy to dial in with the bars, obviously- just soften the front and/ or stiffen the rear. That said I get easy rotation without changing anything on a number of corners. It's course/ corner dependent, but driving style could also be the key depending on what you're doing. One guaranteed way to get the tail out is to trail brake into a tighter, longer corner to weight the front and lighten the rear. You'll get some amount of slip angle at the back depending on how aggressive you are, then transition to the throttle and dial in your desired angle.
Coming from older semi-trailing arm 911s this all feels very natural because it's practically the only way early cars get around tight corners quickly. With the 991's multi-link, rear steer, PTV, etc it's very quick regardless, but I do find those systems make dialing in the desired amount of drift relative child's play once the rear starts to slide. It's almost as if some invisible magnet helps prevent the rear from getting too far out of shape under power- it certainly flatters compared to even the 997 GT3 RS, etc.
Coming from older semi-trailing arm 911s this all feels very natural because it's practically the only way early cars get around tight corners quickly. With the 991's multi-link, rear steer, PTV, etc it's very quick regardless, but I do find those systems make dialing in the desired amount of drift relative child's play once the rear starts to slide. It's almost as if some invisible magnet helps prevent the rear from getting too far out of shape under power- it certainly flatters compared to even the 997 GT3 RS, etc.
I believe we were at the same recent PCA autocross, or there was another Pastel Orange GT3 there that day.
I had the car aligned to these settings and found the rotation to be almost on par with the 718s, especially with trail braking + throttle method: 2.5 camber all around, 0 toe front, .2 toe in rear, bar in middle front and rear. You can adjust bars to suit your style but I left them at the factory setting. Stock Cup 2s at 32/34 pressure. I run with the sport PASM mode also but found it too stiff for the street and would probably have done worse at PIR with it on had it not been repaved.
I had the car aligned to these settings and found the rotation to be almost on par with the 718s, especially with trail braking + throttle method: 2.5 camber all around, 0 toe front, .2 toe in rear, bar in middle front and rear. You can adjust bars to suit your style but I left them at the factory setting. Stock Cup 2s at 32/34 pressure. I run with the sport PASM mode also but found it too stiff for the street and would probably have done worse at PIR with it on had it not been repaved.
You were in the chalk RS I assume? You almost had top time. Your setup is good to know, you also have a little extra front tire which helps, but the settings are 90% of it. I tried trail braking, gentle on, hard on the throttle and nothing really worked so I just drove around it as best I could. Ran the same pressure as you, Sport PASM on- off was slower. Of course to keep the thread on target all aids off.
Last edited by montoya; 05-16-2019 at 11:10 PM.
05-17-2019, 12:08 PM
#49
Rennlist Member
Andrie Hartanto, one of the most talented drivers here in the Bay Area, has told me that he can drive just as fast of a lap with the system off or on. The only difference is that he has to slightly alter his driving style. This is a guy who knows how to maintain slip angle at corner entry, mid, and exit like it's nothing. We are talking about road courses, though, not autocross. I can't speak for autocross.
My $.02 on ESC and TC turned on with the new 991 GT3 and GT3RS. My personal preference is to drive these cars with both systems turned off in the car. My reason behind this is that I don't like how they keep the car from slipping and sliding in some parts of the track when I want to feel what the car is doing. Part of my reasoning behind this approach is my driving style and comfort level with how I drive a car on the track. A great example of this is Turn 1 at Road Atlanta. This is a high speed right hand turn that has a slight downward sloping grade on turn in down to the apex. At the apex Turn 1 then transitions to a much bigger uphill grade where the car finds grip suddenly. So when I go into Turn1 with a 991 chassis I want the front of the car to be slightly in an understeer situation and if it is understeering I want to be able to feel the tires sliding slightly. With the ESC on it limits this feel the closer to the limit I get. When the system is interacting with the car to keep the slip to a minimum it numbs the feeling of the car and the grip available in the car. And in Turn 1 at Road Atlanta where there are changes in elevation on the track the car goes from no grip (turn in to apex downhill) to lots of grip (apex to track out uphill), the level of grip changes quickly on the car. Yes the system Porsche has designed in the car will accommodate this but when close to the limit of the car the system can interact a little too much.
Another reason I don't use either of these on my car is because of excessive brake use and heat in the brakes, mainly with ESC. If you are leaning on the system a lot then a lot of heat is put into the brakes because the system is active in the majority of the turns on the track. Luckily at a track like Road Atlanta you have a long back straight to help cool the brakes before heading into the biggest braking zone. The car will slow itself down lap after lap but I can tell you the brakes are smoking hot with the system off and with it on they are even hotter. Hotter brakes means hotter tires which is why a lot of guys see tire fade after 15 minutes into a 30 minute session at a DE. TrackCar backs some of this data up when he switched from steel brakes to the Surface Transform rotors. The carbon in the rotors dissipates the heat better than the steel rotors bringing less heat into the tires than steel. Also the way most carbon brakes work is off of pressure and not heat which is the opposite for steel brakes.
A lot of people have commented on the difference of BMWs ESC/TC systems compare to Porsches systems. One thing I think needs to be added to each of these comments is the BMW system in the E46 is over 15 years old. This technology is like trying to use a Nokia 9120 as a smartphone today. What was cutting edge technology at the time is no longer leading edge stuff. It is now obsolete. This is the case with the BMW systems from the E46. On the BMW M2 and newer cars this is somewhat more relevant to the topic. I can attest to the systems in the newer BMWs as being more intrusive on the track in dry weather than the Porsche systems. In the M235i Racing that I have raced at Spa in the past couple of years I know this first hand. In the dry on racing slicks this system severely limits track time being overactive and slowing the car down with any slip of the tires. That is with the system in the Dynamic mode too. Add a wet track to this and the dynamic mode is nice because it does allow the car to slip a little and then grab it back if it gets too far out of line but it does slow the lap time down overall. So even in this system modified for racing the BMW is too intrusive.
05-17-2019, 01:24 PM
#50
Good post Seth, thanks. One technical point/ question:
Can you clarify what you mean by "the way carbon brakes work is off pressure not heat"?
My perspective is all brakes work off heat- they are simple devices that convert kinetic (mechanical) energy into thermal (heat) energy. So the energy from the speeding car gets transformed into heat, the differences between brakes determining how hot they get (depends on their thermal mass) and how quickly they cool (depends on their heat dissipation- surface area, venting, etc). Carbon ceramic brakes typically have less thermal mass than steel (mostly because they are lighter) but they make up for it by shedding heat faster due their much larger surface area, allowing them to stay slightly cooler on average. That's the amateur physicist in me speaking anyway. I suspect your comment on "pressure" is more from the practical usage side, but I was hoping you could clarify what you mean by it?
BTW having owned both an E46 and 1M I could discern no improvement in the ESC systems over those generations. It's almost like BMW was willfully making the system bad either to satisfy lawyers or so that you'd be forced to switch it off.
TrackCar backs some of this data up when he switched from steel brakes to the Surface Transform rotors. The carbon in the rotors dissipates the heat better than the steel rotors bringing less heat into the tires than steel. Also the way most carbon brakes work is off of pressure and not heat which is the opposite for steel brakes.
My perspective is all brakes work off heat- they are simple devices that convert kinetic (mechanical) energy into thermal (heat) energy. So the energy from the speeding car gets transformed into heat, the differences between brakes determining how hot they get (depends on their thermal mass) and how quickly they cool (depends on their heat dissipation- surface area, venting, etc). Carbon ceramic brakes typically have less thermal mass than steel (mostly because they are lighter) but they make up for it by shedding heat faster due their much larger surface area, allowing them to stay slightly cooler on average. That's the amateur physicist in me speaking anyway. I suspect your comment on "pressure" is more from the practical usage side, but I was hoping you could clarify what you mean by it?
BTW having owned both an E46 and 1M I could discern no improvement in the ESC systems over those generations. It's almost like BMW was willfully making the system bad either to satisfy lawyers or so that you'd be forced to switch it off.
05-17-2019, 04:07 PM
#51
Rennlist Member
Good post Seth, thanks. One technical point/ question:
Can you clarify what you mean by "the way carbon brakes work is off pressure not heat"?
My perspective is all brakes work off heat- they are simple devices that convert kinetic (mechanical) energy into thermal (heat) energy. So the energy from the speeding car gets transformed into heat, the differences between brakes determining how hot they get (depends on their thermal mass) and how quickly they cool (depends on their heat dissipation- surface area, venting, etc). Carbon ceramic brakes typically have less thermal mass than steel (mostly because they are lighter) but they make up for it by shedding heat faster due their much larger surface area, allowing them to stay slightly cooler on average. That's the amateur physicist in me speaking anyway. I suspect your comment on "pressure" is more from the practical usage side, but I was hoping you could clarify what you mean by it?
BTW having owned both an E46 and 1M I could discern no improvement in the ESC systems over those generations. It's almost like BMW was willfully making the system bad either to satisfy lawyers or so that you'd be forced to switch it off.
Can you clarify what you mean by "the way carbon brakes work is off pressure not heat"?
My perspective is all brakes work off heat- they are simple devices that convert kinetic (mechanical) energy into thermal (heat) energy. So the energy from the speeding car gets transformed into heat, the differences between brakes determining how hot they get (depends on their thermal mass) and how quickly they cool (depends on their heat dissipation- surface area, venting, etc). Carbon ceramic brakes typically have less thermal mass than steel (mostly because they are lighter) but they make up for it by shedding heat faster due their much larger surface area, allowing them to stay slightly cooler on average. That's the amateur physicist in me speaking anyway. I suspect your comment on "pressure" is more from the practical usage side, but I was hoping you could clarify what you mean by it?
BTW having owned both an E46 and 1M I could discern no improvement in the ESC systems over those generations. It's almost like BMW was willfully making the system bad either to satisfy lawyers or so that you'd be forced to switch it off.
E46 and 1M are both ancient systems. Only fair to compare the E46 to a 997.1 GT3/RS system. For the 1M it is slightly newer but more comparable to a 997.2 GT car. I will say that the newer BMW systems are not as good as the one in the 991 chassis. I drove a M4 GTS at Road Atlanta on old tires for some moderate paced demo laps once only to have to turn the system off because it was intervening at weird places on the track. The way it intervened seemed like the factory alignment could have been off though.
05-18-2019, 12:47 PM
#53
Instructor
Nannies - Swedish Yes, German No. But I digress... I purchased a 2016 RS a few weeks ago, drove it straight to the track, unclear on the alignment specs, though tire wear was relatively uniform. Ride height a bit tall in the rear, wing angle flat so a bit loose under heavy, high speed braking, no idea on sway bars, though car turns in well with virtually no understeer at entry.
SO ... Day one, figure out how to drive an RS. Full auto, PDK Sport, PASM firm. Lots of corners, small track configuration with no really high speed corner entries. Fast car, insanely fun. Nannies engaged.
Day 2, a week later, at UMC (Miller) in Utah. Here is when the nannies kicked in hard. West track, turn 1, high speed corner entry with long, relatively light trail braking - the sensors did not like the pitch, roll, and yaw attitude, and put the brakes on firmly as I was coming OFF the pedal. Rear end steps out, where normally the rear would be settled by now, then ESC adds even more brake, with my foot now almost 90% off the pedal. Ugh! Felt like I threw out the boat anchor.
Solution... ESC Off - lap times improve by over 2 seconds as I was now able to roll smoothly into the 3 high speed corners. No more auto-brake, l no more tail wag. (T1, 3, 9)
Next step - off goes the TC/ESC to see what effect that has on car balance, mid-corner roll through, and acceleration.
SO ... Day one, figure out how to drive an RS. Full auto, PDK Sport, PASM firm. Lots of corners, small track configuration with no really high speed corner entries. Fast car, insanely fun. Nannies engaged.
Day 2, a week later, at UMC (Miller) in Utah. Here is when the nannies kicked in hard. West track, turn 1, high speed corner entry with long, relatively light trail braking - the sensors did not like the pitch, roll, and yaw attitude, and put the brakes on firmly as I was coming OFF the pedal. Rear end steps out, where normally the rear would be settled by now, then ESC adds even more brake, with my foot now almost 90% off the pedal. Ugh! Felt like I threw out the boat anchor.
Solution... ESC Off - lap times improve by over 2 seconds as I was now able to roll smoothly into the 3 high speed corners. No more auto-brake, l no more tail wag. (T1, 3, 9)
Next step - off goes the TC/ESC to see what effect that has on car balance, mid-corner roll through, and acceleration.
05-18-2019, 12:54 PM
#54
Rennlist Member
Nannies on. See no reason to turn it off. I am here for fun. If there is a safety net that is not terribly intrusive and reminds me when I am not doing things right, why not? Just to convince my ego that I am a grown up and dont need a nanny? Nah, I leave my ego at home when I come to the track. My trophy is coming home in one piece with a smile in my face.
05-18-2019, 01:36 PM
#56
practice on becoming a smooth driver, learning to carry your speed through the apex will really let you see the difference with it on or off. the best way to learn the systems response is to do consistent laps in higher gears, carry more speed and allow the system to interact. Then turn it off, carry the same speed and watch the response of the car. Slamming every apex, and smashing the gas makes one feel good, but you miss the interaction of the system. It compensates for you, then when you turn it off, you end up oversteering and or sliding the back of the car. In a perfect world, you would stick the car in 4th and learn to drive it.
05-18-2019, 01:46 PM
#57
All the years of teaching Road racing to students, we made them stay in 3rd and 4th gear until they learn to feel the bike and how it responded. Faster laps, smoother laps. etc etc. i have a hard time getting my own mind in check and letting the car do the work. I also never turn off the nannies, as I am not trying to set record laps in my street toy. so if I had a full blown track car, i would experiment more, but 200k and a wall is enough to for me to keep them on. tires and brakes are cheap, but totals are not. 