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10-10-2014, 09:25 AM | #43 | |
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It's all based on rate of change of wheel speed differential/brake applied pressure once these trigger then it uses G sensors to change the strategy. You are probably pulling over 1 g and railing the sensors as well as unexpected rate of changes. you may need to switch to a Bosch motorsports ABS setup or try removing every other tooth on the rings to get the rates back in range ( speedo might be wrong). Brake bias without lockup or slip while an issue to the butt dyno shouldn't screw up the ABS obviously getting it balanced makes everything easier to control. Need some really got data logging to see where then we can look for the why. DougW |
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10-10-2014, 12:42 PM | #44 | |
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I can still log the CAN system with the Hydra EMS in there since that computer is also retained. I'm going to be working with someone to design an ideal brake kit for the car. We are going to first start with getting the mechanical bias without ABS close to ideal before turning the ABS back on. I'm hoping this could help prevent a rapid lock up of the fronts which may be causing the ABS to shut down. |
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10-10-2014, 01:44 PM | #45 | |
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10-10-2014, 03:19 PM | #46 | |
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10-10-2014, 04:44 PM | #47 |
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Is there any reason why you cant bypass the ABS module and plumb in a manual bias valve? Is it classing? Because, being a track beast, it seems like that would be the preferred setup.
Hell a quick valve with a lever in the cockpit like F1 uses might be pretty useful. |
10-10-2014, 06:06 PM | #48 |
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This is a standard euro city car problem when running wide tyres & BBKs. Shut-off is basically the system going "I have no idea what's going on, I think I'm making things worse! Over to you & good luck". It was very important for this to happen quite early with euro city cars as if you tried braking hard on a surface with detached gravel you'd effectively have 0 braking with ABS on.
From the sound of it the system in your car is acting like a very early Bosch DBB system with seriously sticky tyres, in my case going from 145 wide eco tyres to 215 wide soft track day rubber (sticky enough to allow the car to endo!). I found someone with the kit to remap my ABS ECU which allowed me to keep it but input appropriate parameters for the brake & tyres I was running. I have no idea if this is possible with the BRZ system or not & what software is required. The system I dealt with naturally had a brake bias of something ridiculous like a 95/5 F/R split without and DBB intervention. So when the system was disabled completely it'd become almost impossible to brake hard, thankfully when the system gave up it did at least leave the brake bias at a saneish setting. The two parameters that usually needed to be changed due to sticky tyres were the maximum wheel deceleration & the maximum pressure release cycle length. The latter is what caused the ECU to give up with sticky tyres. Because the wheels weren't really slipping the release values was way too low to reduce the braking enough so that the ECU thought everything was okay. Sorry for the lack of useful info it's been so long since I dabbled in all this it's mostly been forgotten. I also doubt that most of what I knew is actually useful with modern ABS systems. |
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10-10-2014, 06:44 PM | #49 | ||
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I do run cockpit Tilton bias valves on my STi so I can fine tune my brake bias even with the ABS. This is what I plan to do with the FRS (tame the fronts). Keep the ABS but plumb in driver adjustable valves. First however we need to fix or get much closer with the bias via the rotor/caliper. Quote:
That is why I'm going all the way vs. just swapping compounds around. Also keep in mind I trashed over $2k in tires in two weekends so while I do agree I could probably get something OK with pad compound swaps I feel like it's not a real fix for my level of racing. For you track day guys it's probably all you need until you go with a front BBK to help with brake fade. It's at that point you're going to want to make sure those rears are doing their share of the workload. |
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10-10-2014, 06:49 PM | #50 | |
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We need a computer hack ASAP over here |
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10-13-2014, 03:20 PM | #51 | |
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10-13-2014, 03:43 PM | #52 |
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10-13-2014, 04:08 PM | #53 | |
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Since you pointed it out, I decided to do some digging and it looks like the crap Subaru brakes I was referring to, are also made by ADVICS. So the Subaru brakes I hate are made by a company partially owned by Toyota. Toyota is also part owner of Fuji Heavy who own Subaru. So yeah, all the incest is complicated and difficult to sort through these days. Point is, the modern Subaru brakes feel like shit to me compared to the older Toyota brakes I was used to. When I first test drove the FRS and got on the brakes, the first thing I thought about were the brakes in my Subaru which I hated till I swapped out for Hawks. Any idea which Toyotas used to have Akebono pads? http://www.autonews.com/article/2009...ness-to-advics http://www.advics.co.jp/eng/company/enkaku.html https://www.google.com/search?q=advi...cs+subaru+pads |
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10-13-2014, 05:01 PM | #54 | |
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The pads are usually the biggest factor in brake feel. Fortunately, pads and discs are not that big of a deal to swap out. There are lots of options out there for these cars.
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10-14-2014, 04:18 PM | #55 |
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So the car pretty much has front wheel brakes until it's decelerating very hard.
That would explain why my car understeers under braking in the canyon, but nowhere else: no grip.
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10-28-2014, 12:45 AM | #56 | |
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In any event it was good to see someone else experience the extreme front bias when the ABS fails. Click on the link in the quote to watch his video and see how he struggles to stop even at relatively slow speeds. The key is going to balance the brakes without the ABS on. |
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