Turning VSA off, how does it affect ABS operation?
07-31-2009, 01:41 PM
#1
Team Owner
Thread Starter
Turning VSA off, how does it affect ABS operation?
I've been having problems with the ABS and the new sticky tires. It's way too conservative and kicks in way before the tires are at their limit. I pulled the fuse just to make sure I wasn't going crazy and I knocked off an easy 25% in stopping distances by not using ABS. I've been trying to figure out if there's a problem or if the TL just isn't capable of taking advantage of the sticky tires. Keep in mind I'm well aware that ABS isn't supposed to stop as well as a skill driver with no ABS.
Fast forward to yesterday. I happened to try a hard stop with the VSA disabled and it stopped much harder, not that far off of what I can do with the fuse pulled. Tried it again and the same result. I took it to a different stretch of road with a different surface and same result.
Does anyone know what changes when you turn the VSA off? I know it goes from 4 channel to 3 channel but it also seems much more aggressive.
Fast forward to yesterday. I happened to try a hard stop with the VSA disabled and it stopped much harder, not that far off of what I can do with the fuse pulled. Tried it again and the same result. I took it to a different stretch of road with a different surface and same result.
Does anyone know what changes when you turn the VSA off? I know it goes from 4 channel to 3 channel but it also seems much more aggressive.
07-31-2009, 02:06 PM
#2
Safety Car
Here is my theory.
VSA works by controlling all four brakes independently. By applying the brakes to various corners in a strategically fashion, the VSA attempts to prevent the car from getting sideways (yaw).
But, what if the ABS is utilizing 100% of the available braking force already, How could VSA hope to reduce yaw (going sideways) ? Plus, this is when yaw control would be needed the most. That is, a driver will most likely be attempting an emergency maneuver in the same situation that the ABS was induced. This emergency maneuver would mostly likely induce yaw.
I would hope that Acura had this same question. My theory is that the ABS was designed to not utilize 100% of the braking so that the VSA would have something to work with to reduce yaw.
VSA works by controlling all four brakes independently. By applying the brakes to various corners in a strategically fashion, the VSA attempts to prevent the car from getting sideways (yaw).
But, what if the ABS is utilizing 100% of the available braking force already, How could VSA hope to reduce yaw (going sideways) ? Plus, this is when yaw control would be needed the most. That is, a driver will most likely be attempting an emergency maneuver in the same situation that the ABS was induced. This emergency maneuver would mostly likely induce yaw.
I would hope that Acura had this same question. My theory is that the ABS was designed to not utilize 100% of the braking so that the VSA would have something to work with to reduce yaw.
07-31-2009, 02:59 PM
#3
Team Owner
Thread Starter
Here is my theory.
VSA works by controlling all four brakes independently. By applying the brakes to various corners in a strategically fashion, the VSA attempts to prevent the car from getting sideways (yaw).
But, what if the ABS is utilizing 100% of the available braking force already, How could VSA hope to reduce yaw (going sideways) ? Plus, this is when yaw control would be needed the most. That is, a driver will most likely be attempting an emergency maneuver in the same situation that the ABS was induced. This emergency maneuver would mostly likely induce yaw.
I would hope that Acura had this same question. My theory is that the ABS was designed to not utilize 100% of the braking so that the VSA would have something to work with to reduce yaw.
VSA works by controlling all four brakes independently. By applying the brakes to various corners in a strategically fashion, the VSA attempts to prevent the car from getting sideways (yaw).
But, what if the ABS is utilizing 100% of the available braking force already, How could VSA hope to reduce yaw (going sideways) ? Plus, this is when yaw control would be needed the most. That is, a driver will most likely be attempting an emergency maneuver in the same situation that the ABS was induced. This emergency maneuver would mostly likely induce yaw.
I would hope that Acura had this same question. My theory is that the ABS was designed to not utilize 100% of the braking so that the VSA would have something to work with to reduce yaw.
07-31-2009, 03:19 PM
#4
Safety Car
I just thought of a flaw in my previous theory.
The VSA and ABS are two separate concepts. However, the VSA and ABS are the same physical modulator unit.
In theroy, the ABS could utilize 100% of the available braking force. Then in the advent of yaw, the modulator could strategically *reduce* the braking (reversed logic) to attempt to correct the yaw.
The VSA and ABS are two separate concepts. However, the VSA and ABS are the same physical modulator unit.
In theroy, the ABS could utilize 100% of the available braking force. Then in the advent of yaw, the modulator could strategically *reduce* the braking (reversed logic) to attempt to correct the yaw.
07-31-2009, 03:48 PM
#5
hatecars- are your wheel speed sensors all working correctly?
does it stop dead straight under abs? and works correct in a stomp and steer test?
You know how I love to flush/bleed my brake fluid with fun runs~ so 2-5 times a year
Hows your brake fluid? been changed since last hard run to the mountains or track day style driving?
If running synthetic (I am-gen2) wonder if that changes anything with the ABS parameters and things its measuring for forces- brake pedal effort-
And swapping to SS brake lines and ABS calculations???-
not an expert on abs so I can only speculate and question all possiblities
On the race car there was a prob with synthetic brake fluid at higher operating temps, when it goes away the pedal and effect goes away big time- at a bad time-
so we went back to regular brake fluid, at least when/if it boils we know what the brakes will still do to get thru a session
While not abs equipped car- it still shows a differance in fluids in general
Where is one of the real Acura techs to enlighten us please~
does it stop dead straight under abs? and works correct in a stomp and steer test?
You know how I love to flush/bleed my brake fluid with fun runs~ so 2-5 times a year
Hows your brake fluid? been changed since last hard run to the mountains or track day style driving?
If running synthetic (I am-gen2) wonder if that changes anything with the ABS parameters and things its measuring for forces- brake pedal effort-
And swapping to SS brake lines and ABS calculations???-
not an expert on abs so I can only speculate and question all possiblities
On the race car there was a prob with synthetic brake fluid at higher operating temps, when it goes away the pedal and effect goes away big time- at a bad time-
so we went back to regular brake fluid, at least when/if it boils we know what the brakes will still do to get thru a session
While not abs equipped car- it still shows a differance in fluids in general
Where is one of the real Acura techs to enlighten us please~
07-31-2009, 04:17 PM
#6
Team Owner
Thread Starter
hatecars- are your wheel speed sensors all working correctly?
does it stop dead straight under abs? and works correct in a stomp and steer test?
You know how I love to flush/bleed my brake fluid with fun runs~ so 2-5 times a year
Hows your brake fluid? been changed since last hard run to the mountains or track day style driving?
If running synthetic (I am-gen2) wonder if that changes anything with the ABS parameters and things its measuring for forces- brake pedal effort-
And swapping to SS brake lines and ABS calculations???-
not an expert on abs so I can only speculate and question all possiblities
On the race car there was a prob with synthetic brake fluid at higher operating temps, when it goes away the pedal and effect goes away big time- at a bad time-
so we went back to regular brake fluid, at least when/if it boils we know what the brakes will still do to get thru a session
While not abs equipped car- it still shows a differance in fluids in general
Where is one of the real Acura techs to enlighten us please~
does it stop dead straight under abs? and works correct in a stomp and steer test?
You know how I love to flush/bleed my brake fluid with fun runs~ so 2-5 times a year
Hows your brake fluid? been changed since last hard run to the mountains or track day style driving?
If running synthetic (I am-gen2) wonder if that changes anything with the ABS parameters and things its measuring for forces- brake pedal effort-
And swapping to SS brake lines and ABS calculations???-
not an expert on abs so I can only speculate and question all possiblities
On the race car there was a prob with synthetic brake fluid at higher operating temps, when it goes away the pedal and effect goes away big time- at a bad time-
so we went back to regular brake fluid, at least when/if it boils we know what the brakes will still do to get thru a session
While not abs equipped car- it still shows a differance in fluids in general
Where is one of the real Acura techs to enlighten us please~
I did the stomp and turn with the VSA off. You know, exactly what you're not supposed to do. I hit full ABS and turned as hard as I could with the brake pedal through the floorboard and it turned just fine.
I agree about the fluids. I had DOT 5.1 and it seemed to really allow the ABS to work to it's potential. Rumor has it that the 5.1 is half as thick as DOT 4. However, after I had the subframe replaced and they had to remove the calipers, even though I specified 5.1, the invoice said DOT3. It's not apparent until ABS is in effect.
That's good to know about different fluids and their charicteristics at the limit. I also would rather have a fluid that boils slightly lower but gives you some warning instead of just losing the brakes.
I've got the Wilwoods now but I'm not putting them on until this gets resolved.
07-31-2009, 04:19 PM
#7
Team Owner
Thread Starter
I just thought of a flaw in my previous theory.
The VSA and ABS are two separate concepts. However, the VSA and ABS are the same physical modulator unit.
In theroy, the ABS could utilize 100% of the available braking force. Then in the advent of yaw, the modulator could strategically *reduce* the braking (reversed logic) to attempt to correct the yaw.
The VSA and ABS are two separate concepts. However, the VSA and ABS are the same physical modulator unit.
In theroy, the ABS could utilize 100% of the available braking force. Then in the advent of yaw, the modulator could strategically *reduce* the braking (reversed logic) to attempt to correct the yaw.
Trending Topics
07-31-2009, 05:11 PM
#8
I'd be happy to come abuse your brakes!! Weekend at Willow?
Oh- you meant someone with a gen3 go do the same test- DOh!
Maybe the ABS really likes DOT4 and thats all it likes
doesnt the filler cap say 4 only? if the shop used dot3 you need a flush and dot4 install for sure
You can go up a spec from 3 to 4, but not down from 4 to 3
Do NOT go from 4 to 5.0- thats not compatible systems,,,
but 5.1 can be used in certain dot4 applications
dot= Dept Of Transportation level number- for fluid specifications
Oh- you meant someone with a gen3 go do the same test- DOh!
Maybe the ABS really likes DOT4 and thats all it likes
doesnt the filler cap say 4 only? if the shop used dot3 you need a flush and dot4 install for sure
You can go up a spec from 3 to 4, but not down from 4 to 3
Do NOT go from 4 to 5.0- thats not compatible systems,,,
but 5.1 can be used in certain dot4 applications
dot= Dept Of Transportation level number- for fluid specifications
Thread
Thread Starter
Forum
Replies
Last Post
mada51589
3G TL Problems & Fixes
79
05-03-2022 08:54 PM
