Disabling ABS for extreme tracking/trialing?
01-18-2019, 02:45 AM
#16
Racer
01-18-2019, 10:19 AM
#17
The later model car ice mode is referring to a hard pedal and inability to apply more brakes. This is due to the much more complex ABS controller hardware and software programming and includes accelerometer inputs. In simple terms the controller determines the car is braking outside the programmed rates and does not allow more brake force.
The 993 ABS controller is much simpler and only looks to keep all of the wheels turning at the same rate. Once you get into the ABS controlling the brakes, the rate of slowing drops off dramatically and the only solution is to get out of the brakes and then back on. However by the time this is all completed the optimum brake timing is shot.
The 993 controller is relatively slow at coming out of ABS control, which is what the racing ABS controller tries to address.
My experience with the 993, on a relatively smooth track, is if you are getting into the ABS you are probably braking too much at the end of the braking event.
Mike
The 993 ABS controller is much simpler and only looks to keep all of the wheels turning at the same rate. Once you get into the ABS controlling the brakes, the rate of slowing drops off dramatically and the only solution is to get out of the brakes and then back on. However by the time this is all completed the optimum brake timing is shot.
The 993 controller is relatively slow at coming out of ABS control, which is what the racing ABS controller tries to address.
My experience with the 993, on a relatively smooth track, is if you are getting into the ABS you are probably braking too much at the end of the braking event.
Mike
01-18-2019, 11:36 AM
#18
The later model car ice mode is referring to a hard pedal and inability to apply more brakes. This is due to the much more complex ABS controller hardware and software programming and includes accelerometer inputs. In simple terms the controller determines the car is braking outside the programmed rates and does not allow more brake force.
The 993 ABS controller is much simpler and only looks to keep all of the wheels turning at the same rate. Once you get into the ABS controlling the brakes, the rate of slowing drops off dramatically and the only solution is to get out of the brakes and then back on. However by the time this is all completed the optimum brake timing is shot.
The 993 controller is relatively slow at coming out of ABS control, which is what the racing ABS controller tries to address.
My experience with the 993, on a relatively smooth track, is if you are getting into the ABS you are probably braking too much at the end of the braking event.
Mike
The 993 ABS controller is much simpler and only looks to keep all of the wheels turning at the same rate. Once you get into the ABS controlling the brakes, the rate of slowing drops off dramatically and the only solution is to get out of the brakes and then back on. However by the time this is all completed the optimum brake timing is shot.
The 993 controller is relatively slow at coming out of ABS control, which is what the racing ABS controller tries to address.
My experience with the 993, on a relatively smooth track, is if you are getting into the ABS you are probably braking too much at the end of the braking event.
Mike
ABS 5 3 channel used in 993
ABS5 4 channel w/ ABD used in 993
PSM 5.3 used later
PSM 8 latest
01-18-2019, 12:26 PM
#19
Rennlist Member
What level of competition are you into? Perhaps if max effort sprint race team I would consider deleting ABS. With multiple driver enduro I would keep it. Now if your taking sprited laps at Laguna the 993 ABS is not a liability like other later model cars. Ask Viper Bob he use to track the hell out of his 993 Turbo at Laguna.
01-18-2019, 01:35 PM
#20
Technical Guru
Rennlist Member
Rennlist Member
Its not that you can't apply more brakes, you literally have no brakes. The ABS controller gets confused by the frequency of the ripples in the pavement and thinks your slipping even though you aren't even close to locking up. Then it tries to cycle the brake pressure but instead of cycling it doesn't apply any pressure. Possibly because it thinks your not slipping and then slipping again, following the frequency of the ripples? In the early 90s there was a highway off-ramp (395S in Webster, MA. USA) that was rippled prior to the intersection. If you tried to brake on the ripples in a 964 with stock shocks & springs it would always happen.
01-18-2019, 05:11 PM
#21
Banned
Thread Starter
Understood, but that doesn’t definitively address whether it happens or not. Am I pro level? I still have some improvements, but I’ve had my fair share of experience both in shifter kart and car to know how to manage a zone without something else being the cuprit of poor braking (ie. poor handling setup, tires, etc) and adjust accordingly.
With the above said, everyone is different in how they approach a corner as is there desired result of their trip to the track. I’m not an expert in Bosch’s ABS controller for that standard 220/224 (as there are different PN for hydro and vacuum setup), but I do know that it’s hypothetically possible from a technical standpoint. It’s not out of line to surmise that Bosch gave the system more complexity than the 964 as is rightly understood that the 996 is more than our 993’s.
Either way, it sounds like the issue is exhausted as far as can be addressed without an engineer or one stating they experienced “ice mode” on the 993.
Thanks for the input for all that wrote as I’m sure this will help someone else out down the road.
With the above said, everyone is different in how they approach a corner as is there desired result of their trip to the track. I’m not an expert in Bosch’s ABS controller for that standard 220/224 (as there are different PN for hydro and vacuum setup), but I do know that it’s hypothetically possible from a technical standpoint. It’s not out of line to surmise that Bosch gave the system more complexity than the 964 as is rightly understood that the 996 is more than our 993’s.
Either way, it sounds like the issue is exhausted as far as can be addressed without an engineer or one stating they experienced “ice mode” on the 993.
Thanks for the input for all that wrote as I’m sure this will help someone else out down the road.
01-18-2019, 06:01 PM
#22
limiting the discussion to only 1 wheel helps clarify
each wheel has 2 valves that service it
1 inlet this is an electrically driven solenoid
and
1 outlet - this has a motor driven pump associated w/ it
There are 3 modes
1) normal- here both valves are open pressure and fluid from the pedal is directly translated to the caliper through the master cylinder
2) holding pressure - here both valves are closed, no pressure or fluid movement either way
3) reducing pressure - here the inlet is closed and the outlet is open, the associated motor pumps fluid from the caliper back to the m/c
Which mode is in effect is determined by the ABS brain using wheel speed sensor information
It was my understanding that the 964 Cup on/off switch was there so that the ABS could be shut off in the event of a spin where the car was going backward, this confused the brain and resulted in mode 2 or 3 not sure which. 993 apparently doesn't need that switch as it was missing from 993Cup and RSR
each wheel has 2 valves that service it
1 inlet this is an electrically driven solenoid
and
1 outlet - this has a motor driven pump associated w/ it
There are 3 modes
1) normal- here both valves are open pressure and fluid from the pedal is directly translated to the caliper through the master cylinder
2) holding pressure - here both valves are closed, no pressure or fluid movement either way
3) reducing pressure - here the inlet is closed and the outlet is open, the associated motor pumps fluid from the caliper back to the m/c
Which mode is in effect is determined by the ABS brain using wheel speed sensor information
It was my understanding that the 964 Cup on/off switch was there so that the ABS could be shut off in the event of a spin where the car was going backward, this confused the brain and resulted in mode 2 or 3 not sure which. 993 apparently doesn't need that switch as it was missing from 993Cup and RSR
09-17-2020, 06:12 PM
#23
Banned
Thread Starter
A little bit to add...I was recently out at Laguna and whilst hitting the last outside curb going into 8 (Corky), an “oh Shoot” moment occurred. Violent ABS with just the right side hitting middle of the curb. To say the ABS was helping is probably giving too much credit. It certainly engaged, but I’d say if it wasn’t for the rears being set up with more bias, I think I would have plowed into the gravel. Odd feeling for sure. I might have Locked up at the tail end of crest, but am not sure. Hence posting..... Trapping around 102 or so going up the hill. Decent speed. I didn’t touch that curb anymore. Ideally though, you’d want to track far right to setup for a nice entry into 8. With all this said, I was able to engage ABS every time into that turn unlike any other on the course. Ripples up there create havoc for the stock system. Running 15 or so cycled NT 1s probably helped create some slippage to benefit of absolute threshold. Ratio between front and rear was still ok with 235/40 and 275/35.
By the way, thanks Jason, Bill, and the rest for a great discussion.
Jdisteffa’s GT2 abs controller ended up being a “no-joy” with PMS in LA not returning any calls. Maybe Freisinger has some stuff.
By the way, thanks Jason, Bill, and the rest for a great discussion.
Jdisteffa’s GT2 abs controller ended up being a “no-joy” with PMS in LA not returning any calls. Maybe Freisinger has some stuff.