¶ Improving Braking Performance With Bosch ABS
When it comes to going faster around a racetrack , the more usual approach is to add power . However , actually concentrating on the braking performance of the car can yield much bigger gains . We're here with Ashley from 909 Motorsport to talk about the Bosch Motorsport ABS unit . Welcome to High Performance Academy's tuned in Field Report podcast series .
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We've pulled the audio from these tech-filled interviews with some of the industry's most well-known figures and presented it in podcast format for you to enjoy as a quick hit of insider knowledge . So before we get into the Bosch ABS itself , Ashley , can we talk about some of the shortcomings of factory ABS in a modified car on a racetrack scenario ?
Yeah , there's a lot of , I guess , downsides to a factory ABS system . Once you go into a modified car on a racetrack scenario . Yeah , there's a lot of , I guess , downsides to a factory ABS system .
Once you go into a modified car , once you change the weight of the vehicle , the centre of gravity , the braking package on the car , then the factory ABS becomes sub-optimal .
So essentially the factory ABS , as you could rightly expect , is going to be calibrated for a stock standard factory car and once you start modifying all of those parameters you just mentioned , then the calibration doesn't work as intended .
Yeah , that's exactly right , and it's important to note too that on a factory car the biggest thing is stability , safety , driver comfort . Those things come very high on the priority list from an engineering perspective . With motorsport ABS , the primary directive is improving the stopping .
All right . Well , let's just dive into that in a little bit more detail . So it's easy to overlook thinking that all ABS systems are created equal .
But , as you just mentioned , when an OE manufacturer is designing and calibrating an ABS system , it's really designed around the driver being able to maintain directional control of the vehicle , as opposed to absolutely optimal stopping distances , correct ?
Yeah , that's right and I guess they expect in a racing situation . The driver is a high performance driver and they can control the vehicle under racing conditions .
On that note , when something like a Bosch ABS unit is installed and again here the priority here is absolutely optimising stopping distances , maybe at the expense of some of the other parameters like driver comfort etc .
You mentioned there that there is an assumption that the driver is a professional or able to control the car better than the average punter , so does that mean it is a little bit more difficult to control the car when the ABS is functioning in a motorsport environment like that ?
No , I wouldn't say it's more difficult . It's a more predictable pedal and the stability of the car in the racing conditions is predictable . But it does require if you're on a racetrack . I guess it is assumed that you have a level of ability .
So let's talk about what we may notice with a stock ABS system on the racetrack and where the sub optimal performance can come in . What will the driver actually notice ?
The pedal pulsations on the M5 ABS are a lot , lot smoother than most production stuff . You'll find that on some particularly early model ABS units with a big brake package that they can lock tires and everything and they can also actually lock the brake pedal out and not stop the car . So yeah , it's very unpredictable .
That sounds like what a lot of people refer to as ice mode . Am I right there ?
Yeah , it's , I think , a factory sort of setup to maintain stability on slippery surfaces such as ice , and if the ABS unit's working outside parameters , you can come across that actual symptom . I guess yeah .
So in that instance you've still got directional control of the vehicle , because obviously the wheels aren't locked , but not a lot of retardation . No , not at all . Alright , so let's talk about a move to something like a Bosch Motorsport ABS system . It sounds like a fairly extensive setup to install . What is actually involved ? What do we need ?
It's car dependent , but the M5 ABS Club Sport kit is fairly complete . So it comes with a pre-made wiring loom for the car . That's fairly generous , and you install it in the car , give it a power and ground . You have to mount your sensors and things which are all included , and pipe it up . So it's a fairly good start .
The wheel speed sensor is a consideration depending model to model , so you've got to have the sensors mounted in the correct location and the correct amount of teeth and that sort of thing . So it is dependent and we like to try and guide people when they set these up .
¶ Aftermarket ABS System Installation Essentials
Alright . So if you've got a car that has an existing ABS system , is there potential for compatibility with the existing wheel speed sensor rings and wheel speed sensors , or do we need to go to a Bosch specific wheel speed sensor ?
In most cases you need to use the sensors that are supplied with the kit or the specific sensor type , which is a DF11 type sensor that is required . Some very late model cars have got that sensor from factories , such as an R35 GTR , things like that . You can use the factory sensor . So it is a bit vehicle dependent but certainly old vehicles .
You must change a sensor .
The other element we see with most race cars is the move away from a brake booster and a dual style factory master cylinder to what's referred to generically as a pedal box , where we've got a separate circuit for the front and rear brake master cylinders . Is that essential when going to an aftermarket ABS system , or is it just preferable ?
I would say it's preferable . I mean , the system of choice would be to have a pedal box and dual master cylinders so that you could set the system up optimally .
But we have successfully installed the system into production style braking systems , sometimes with an additional bias valve to allow the drivers some control over the bias , and still got the booster systems in them Again . It's not as good as a pedal box , but in some categories it states that the production braking system rusts remain , so it does still work good .
Are you interested in expanding your automotive knowledge ? Start your free lessons with us today at hpacademycom forward slash free . For those who aren't aware , let's talk a little bit about the brake booster , because this is something that generally , as I've mentioned , is removed in a race car .
What's that brake booster for in a factory car and where are the potential downsides ? In other words , why are they so commonly removed ?
I guess it's the driver's variability of assistance that varies with vacuum , and every time they grab the brake it's not exactly the same as what it was last time . So I guess that's where , in a proper racing application , having a pedal box is the ultimate way to go .
You just want that consistency . Every time you hit the brake pedal it's going to feel the same , and that is so important to the confidence of the driver , correct ? Yeah , that's right .
Yeah , let's just come back to talk about brake bias a little bit , because you mentioned there you can utilise the Bosch Motorsport ABS with the factory style master cylinder , but of course then the bias is not adjustable . So in that instance are we relying on the ABS unit to actually do the biasing ?
In other words , if you've got too much rearward bias hydraulically , then the ABS unit is going to have to be working overtime , maybe releasing the brake pressure on the rears more than the front .
Yeah , that's exactly right , and that is certainly not the way to set it up , and particularly in something that's a factory four-wheel drive car like an Evo or a WRX , where they have a cross-link brake system . From factory you would get 50-50 hydraulic braking effort front and rear .
Now let's just actually clear that up Cross link what do you refer to by cross link ? What's that actually mean ?
So that would be the right front and the left rear on the same mass cylinder circuit , and the opposite is true for the other side .
So this is done by OE's to maintain , essentially , if there's a failure , you've got at least one front and one rear wheel that's going to do the braking . Obviously not optimal , but certainly when it comes to a motorsport application , this is as far away from what we want as possible .
Yeah , that's exactly right , and so we change that over when we do the install to a front rear split and then , so that the driver then has a balance of proportioning , and then we fit a valve to the car .
Really all this comes down to , I think , is the fact that a lot of people would assume that you can fit the ABS unit and that's going to do all of the work for you , which , I mean , to a degree is correct .
But essentially , if you can get the mechanical braking package correct or as close to the window as possible , then the ABS is going to be able to do a better job .
Absolutely yeah . And what you will find too is if , for example , a car had too much rear bias and you didn't address that , the ABS on the rear will cut in to stop the car from spinning , losing control , locking a rear wheel , and the driver might not push hard enough to optimise the front braking effort .
So , yeah , it's certainly something you don't want to happen . You want to have the balance as close to possible as you can and have the ABS as an overlay over the top of that
¶ Driving Style With Motorsport ABS
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Can we talk a little bit about driving style with a proper motorsport ABS system ? Is there anything we need to do differently when driving the car ? Particularly , I'm talking here about the maximum braking effort areas on the track , not where we're just brushing the brake to bleed a little bit of speed .
Yeah , sure , and it's a big change for a lot of seasoned drivers that haven't been used to using motorsport ABS to retrain your brain . It's rather than driving like you would without ABS , where you might sort of have a sharp application to drop the nose of the vehicle and then bleed the brakes off . You don't do that with the ABS .
It's a sharp shot application and hold and maintain through the braking zone .
So essentially you want more pressure than you would typically produce so that the ABS can bleed off that pressure to reduce a lock up . But then it's got that excess of pressure there to reintroduce , to get the braking working again .
Yeah , that's right , and you have to be able to have the wheels locked under all situations so that the ABS can modulate , because it can't generate any pressure , it can only take it away .
And I mean that really also comes back to my previous comment that the basic mechanical package of the braking system has to be right before you add the ABS . In other words , you need something with enough brake torque to actually be able to lock the wheels .
Yeah , that's true and it's also important to remember if you have a marginal braking system that's right at the limit before you put ABS on , you're probably going to be over the limit once the ABS is on because you're going to be working those brakes harder .
So this is going to essentially be introducing more heat into the braking package than you would conventionally yeah for sure . Heat into the braking package than you would conventionally yeah for sure , ok . Last thing I want to talk about is the little adjuster that we see with the Bosch Motorsport system I think a 12 position , if I'm correct there .
What is that used for ? How should the driver treat that ? What sort of control does that give ?
Essentially it's a variable slip adjustment , so a wet and a dry setting would be the best way to describe it , and a wet situation . The tyre takes longer to recover , so the algorithms in the ABS allow the tyre longer to recover under those situations when it's modulating the brake .
So this does become a bit of a trial and error sort of adjustment to just see what works best for the driver and the car combination plus the track conditions .
Yeah , that's right , the driver can feel it and we can see it in the data . So we can help people dial that in depending on the situation . But then it's sort of up to the driver as another tunable driver function , not unlike a BIAS or an adjustable anti-roll bar .
Also just in terms of the outputs from the Bosch Motorsport ABS unit . Is there anything there that can be logged by your ECU or any interaction between maybe the Bosch ABS , your ECU or maybe your dash logger ?
Yeah , there's a CAN output so that can be fed into a logger or a display and it logs all the wheel speed channels , brake pressure , the 5x accelerometer in the car . So there's a lot of vehicle dynamics stuff that can be taken from that , not just ABS type stuff .
It's been really great to get some more insight into
¶ How to Connect With 909 Motorsport
the product . Ashley , if people want to find out more about 909 Motorsport , how are they best to reach out ?
You can find us on our website , www.909motorsportcomau .
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