When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The ABS control system can add or subtract pressure going to the calipers under a wide range of circumstances including ABS.
So in a sense, it can decrease and increase pressure to the calipers via valving and using pumps? I thought the whole valving idea was to change the brake pressure to the calipers by rapidly pulsing. But with this system, it can add/subtract brake pressure from individual calipers? I though the Electronic Brakeforce Distribution took care of adding/subtracting brake pressure to individual calipers.
EDIT: Wait, I'm stupid, I forgot that EBD is a ABS sub-system... and that in turn is part of VDIM. Sorry, that was really stupid. So now with that out of the way, I heard that VDIM can't be disabled, but some sub-systems of VDIM can be disabled by the 'Pedal Dance' . When doing the pedal dance, is it only VSC and TCS that are disabled, or is it also the ABS and EBD that are disabled? And also, while reading some more threads about the IS F, apparently, doing the pedal dance turns off the E-DIFF, and I was wondering if that applies to 2010 and above models of the IS F, since the 2010 IS F has a TORSEN limited slip. I would assume the 2010 differential is purely mechanical, so it wouldn't need a computer, so you could do the pedal dance and not have to worry about your diff turning into a open diff.
So in a sense, it can decrease and increase pressure to the calipers via valving and using pumps? I thought the whole valving idea was to change the brake pressure to the calipers by rapidly pulsing. But with this system, it can add/subtract brake pressure from individual calipers? I though the Electronic Brakeforce Distribution took care of adding/subtracting brake pressure to individual calipers.
EDIT: Wait, I'm stupid, I forgot that EBD is a ABS sub-system... and that in turn is part of VDIM. Sorry, that was really stupid. So now with that out of the way, I heard that VDIM can't be disabled, but some sub-systems of VDIM can be disabled by the 'Pedal Dance' . When doing the pedal dance, is it only VSC and TCS that are disabled, or is it also the ABS and EBD that are disabled? And also, while reading some more threads about the IS F, apparently, doing the pedal dance turns off the E-DIFF, and I was wondering if that applies to 2010 and above models of the IS F, since the 2010 IS F has a TORSEN limited slip. I would assume the 2010 differential is purely mechanical, so it wouldn't need a computer, so you could do the pedal dance and not have to worry about your diff turning into a open diff.
Now you're on it. It's not possible to know if the eLSD function was removed for the Torsen equipped units. It would be a mistake IMHO, because a Torsen will act the same as an open diff if one wheel loses all traction (inside wheel lift in a turn), and the eLSD prevents that. I proved it to myself on a track day exiting turn 8 at Carolina Motorsports Park. After the pedal dance, the engine tach'd out like I had a bad clutch. With just a long push on the VSC button, this never happened. So more than likely both the engineers and lawyers agreed to leave the eLSD function intact on the 2010 and later models. The only real solution to this is a clutch type LSD (OS Giken, Tom's, Cusco, etc.) which eliminates any need for the eLSD short of a complete LSD failure.
ABS, Brake Assist, and EBD are never disabled unless you have a wheel speed sensor fail. There is no test mode, no off switch, no ability at all to remove or disable these services without removing the skid control ECU.
Originally Posted by New Car Features
ABS (Anti-lock Brake System) - The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface. EBD (Electronic Brake Force Distribution) - EBD control utilizes ABS, realizing proper brake force distribution between the front and rear wheels in accordance with the driving conditions.In addition, during braking while cornering, it also controls the brake forces of the right and left wheels, helping maintain vehicle behavior. Brake Assist - The primary purpose of brake assist is to provide an auxiliary brake force to assist a driver who cannot generate a large brake force during emergency braking, thus helping ensure the vehicle’s braking performance.
Now you're on it. It's not possible to know if the eLSD function was removed for the Torsen equipped units. It would be a mistake IMHO, because a Torsen will act the same as an open diff if one wheel loses all traction (inside wheel lift in a turn), and the eLSD prevents that. I proved it to myself on a track day exiting turn 8 at Carolina Motorsports Park. After the pedal dance, the engine tach'd out like I had a bad clutch. With just a long push on the VSC button, this never happened. So more than likely both the engineers and lawyers agreed to leave the eLSD function intact on the 2010 and later models. The only real solution to this is a clutch type LSD (OS Giken, Tom's, Cusco, etc.) which eliminates any need for the eLSD short of a complete LSD failure.
ABS, Brake Assist, and EBD are never disabled unless you have a wheel speed sensor fail. There is no test mode, no off switch, no ability at all to remove or disable these services without removing the skid control ECU.
I don't think a TORSEN differential can be electronically controlled. It is mechanical, from what I've seen, and it's been around since the 50's. Also, all TORSEN differentials seem to all work the same way, but just with different ratios. Now, onto my question. You said that Brake Assist can't be turned off, even with use of the center console screen? I would have thought there was some way to turn it off, but maybe I'm thinking of PCS, because I do know you can turn PCS off.
EDIT: Also, when classifying differentials, and when looking at the TORSEN website, they never display a 'electronic TORSEN', but usually only TORSEN. Here is a link to their website: https://torsen.com/how-it-works/. I can't find any information that suggests that a TORSEN differential would be electronically actuated :/
I don't think a TORSEN differential can be electronically controlled. It is mechanical, from what I've seen, and it's been around since the 50's. Also, all TORSEN differentials seem to all work the same way, but just with different ratios. Now, onto my question. You said that Brake Assist can't be turned off, even with use of the center console screen? I would have thought there was some way to turn it off, but maybe I'm thinking of PCS, because I do know you can turn PCS off.
EDIT: Also, when classifying differentials, and when looking at the TORSEN website, they never display a 'electronic TORSEN', but usually only TORSEN. Here is a link to their website: https://torsen.com/how-it-works/. I can't find any information that suggests that a TORSEN differential would be electronically actuated :/
I could be mistaken but I think what was meant regarding the eLSD function remaining intact on 2010+ models was that the selective wheel braking would still remain active, even with a mechanical diff. So in a situation like the one @lobuxracer encountered with inside wheel lift during a turn which caused one wheel to completely lose traction, the selective wheel braking would activate to brake the spinning wheel, sending power to the wheel that has traction (essentially acting like an e-diff) to prevent the mechanical diff from acting like an open diff.
I think you're mistaking Brake Assist with PCS. PCS is a system that uses radar and cameras (not sure if this generation of IS also had cameras) to detect potential or unavoidable collisions with cars ahead. This can be fully disabled.
Brake Assist does not use camera or radar but rather monitors the speed you switch from the gas pedal to the brake pedal. It also monitors how quickly and how hard you've pressed the brakes. Using these cues, Brake Assist can determine if you're in a panic stop situation and will automatically apply 100% braking force if you didn't apply enough braking pressure (studies show most humans do not apply enough braking force during panic situations and therefore aren't able to avoid accidents that would've otherwise been avoidable had full braking force been used). This cannot be disabled.
You're right, the differential is not electronically actuated, but this diff behaves just like an open diff with a wheel off the ground so it needs the same kind of help an open diff does when this happens. The eLSD uses the brake caliper on the spinning wheel to invoke the normal operation of the diff as if both wheels had traction. You're thinking way too hard about this stuff, it's a lot simpler than that. TVD is the only electronically actuated LSD I know of on the market, and I'm not a big fan compared to a good clutch type diff. I've owned them all and lived with them all, and so far the best option is to scrap whatever the OEM gave you and put an OS Giken spool in the differential. It eliminates the need for 68 pounds of clutches, wiring harness, and ECUs to make TVD work, and actually delivers better results.
You're right, the differential is not electronically actuated, but this diff behaves just like an open diff with a wheel off the ground so it needs the same kind of help an open diff does when this happens. The eLSD uses the brake caliper on the spinning wheel to invoke the normal operation of the diff as if both wheels had traction. You're thinking way too hard about this stuff, it's a lot simpler than that. TVD is the only electronically actuated LSD I know of on the market, and I'm not a big fan compared to a good clutch type diff. I've owned them all and lived with them all, and so far the best option is to scrap whatever the OEM gave you and put an OS Giken spool in the differential. It eliminates the need for 68 pounds of clutches, wiring harness, and ECUs to make TVD work, and actually delivers better results.
So it's not electronically actuated, but rather applies the brakes to the one wheel that goes off the ground. So even with VSC turned off, this feature would still work? Like what was said, when the pedal dance is used, and TCS and VSC are disabled, the eLSD is turned off. So does this system require VSC to operate?
EDIT: Even if the TORSEN does have the eLSD feature enabled, eLSD can be turned off by the pedal dance. I think I understand now. Thanks for the help guys!
I could be mistaken but I think what was meant regarding the eLSD function remaining intact on 2010+ models was that the selective wheel braking would still remain active, even with a mechanical diff. So in a situation like the one @lobuxracer encountered with inside wheel lift during a turn which caused one wheel to completely lose traction, the selective wheel braking would activate to brake the spinning wheel, sending power to the wheel that has traction (essentially acting like an e-diff) to prevent the mechanical diff from acting like an open diff.
I think you're mistaking Brake Assist with PCS. PCS is a system that uses radar and cameras (not sure if this generation of IS also had cameras) to detect potential or unavoidable collisions with cars ahead. This can be fully disabled.
Brake Assist does not use camera or radar but rather monitors the speed you switch from the gas pedal to the brake pedal. It also monitors how quickly and how hard you've pressed the brakes. Using these cues, Brake Assist can determine if you're in a panic stop situation and will automatically apply 100% braking force if you didn't apply enough braking pressure (studies show most humans do not apply enough braking force during panic situations and therefore aren't able to avoid accidents that would've otherwise been avoidable had full braking force been used). This cannot be disabled.
Yeah I was figuring the PCS and Brake Assist were 2 different systems.
That's not at all how ABS or other systems work on the IS F or other Lexus vehicles. It's not just valving, there are active pumps involved. VDIM wouldn't be able to control wheel speed as it does without active pumps working the brakes. Note the pumps in the schematic diagram below. This is an extract from the 48 pages in the 2008 IS F New Car Features explaining how all these systems work. Computers in the car have ACTIVE control over the braking system without the master cylinder doing anything. I know this well because VDIM intervened on my behalf on my very first track day and caused me to cook my brakes (Carbotech XP-12 full race pads) in the fourth session of the day because VDIM was applying the brakes through a couple of turns and it wasn't possible to hear any warnings with windows down and helmets on. I later discovered those same turns couldn't possibly be negotiated at full throttle the way VDIM permitted me when it was turned on. I no longer drive with VDIM on at the track for this reason. You learn very little with it injecting itself into the equation.
It's called the ABS control, but it manages anything to do with brake caliper pressure not invoked by the driver. So, yes, ABS, EBD, VSC all use this.
What I mean is, is all of what was shown in the picture in a central control box, or is that supposed to be spread out across the vehicle? I found a part called the brake actuator. Is this image depicting the inside of a brake actuator, or is the ABS module something different?
Everything inside the dotted line is a single unit next to the master cylinder. This pic is a BMW unit, but the Lexus unit looks very similar.
So it is the dotted line in that picture represents the brake actuator box? (Btw, the brake actuator is basically a shortened name for the ABS/EBD/VSC module if you want to call it that), and about the lines up top, are those the output lines or the input lines? Judging by the diagram, I would say input lines, but then there would have to be 4 input lines, where as there are only 2. By looking at a diagram on the Lexus Parts website, this is what the top looks like:
What I'm trying to ask is, are the 4 round holes (in the square) input holes, or output holes, or are they even holes at all?
EDIT: So I did find this one listing on ebay... those holes appear to be output holes. Are the input holes these things?
(in the red square)
This is the unit in my IS F. The four tubes in a line coming out of the top go to the calipers.
The inputs are visible in this shot, they are the OTHER two connections to this device.
The official nomenclature for this device in EPC is ACTUATOR ASSY, BRAKE. In TIS it is called Brake Actuator. That's what it does, and nothing more. Those functions you referenced are handled by electronic devices, so this device is really no more than a brake actuator.
This is the unit in my IS F. The four tubes in a line coming out of the top go to the calipers.
The inputs are visible in this shot, they are the OTHER two connections to this device.
The official nomenclature for this device in EPC is ACTUATOR ASSY, BRAKE. In TIS it is called Brake Actuator. That's what it does, and nothing more. Those functions you referenced are handled by electronic devices, so this device is really no more than a brake actuator.
wait wait, so the Brake Actuator ASSY isn't the same as the ABS? Or does the Brake Actuator ASSY contain the ABS/EBD/VSC?
EDIT: So actually, the Brake Actuator ASSY is technically just the ABS/EBD/VSC system under a different name. I think I got the idea now. They just summarize the ABS/EBD/VSC module as a Brake Actuator, right? Since I think I get that, are the 2008-2014 IS F Brake Actuators all the same? The reason I ask this is because of 2 diagrams I saw. Let me show them: The first one is the '2010 - 2011 Lexus IS F Brake Actuator: https://parts.rallyelexus.com/p/Lexu...cation=9007412
Notice the top outlet orientation. Now look at the secondary diagram (which looks like your Brake Actuator):
Now the reason why I am confused is that I found a listing on Ebay that looked like the first diagram, but then your one looks like the second diagram. I though 'Well maybe the years are just different', but I can't seem to find any evidence which supports that idea. The thing is, the Lexus Parts websites show the same diagram for 08-14 cars. Maybe they just messed up on their diagrams? I figured I would bring this up because I am heavily confused. Maybe the IS F 2008-2009 models had the sort of actuator your car has, and then 2010 and up have the type that I saw on Ebay?
02-05-20, 06:38 PM
