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| 06-29-2023, 06:02 PM | #46 | |
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Derbo Tuning
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I would suggest try it without SPBR VO in the system. I believe your module most likely doesn't have the same under/oversteer values as the US ones and run Euro MDM??
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Journal: Link E9x ZCP Suspension Info: Link Track Chat Discord: https://discord.gg/VsKbTyqBVj SF Bay Area: DM For coding services Last edited by derbo; 06-29-2023 at 06:10 PM.. |
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| 06-29-2023, 06:46 PM | #47 | |
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OK let me disable SPBR then try the GTS settings. Just need to find some time... |
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| 07-01-2023, 04:54 PM | #48 |
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This 100% makes a difference. I’ve now tracked my car once and driven about 2,000 street miles. Pedal travel is lessened and has a nice solid feel to it. Abs activation does not seem intrusive. Activated just when needed on track under heavy breaking. Before coding the pedal was traveling almost halfway to the floor before engaging. Still worked but the brake pedal was not as confident. I guess only more miles will tell if it affects anything negatively. But I see no downsides so far.
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| 10-08-2023, 07:26 PM | #49 | |
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| 10-10-2023, 11:59 AM | #50 | |
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| 10-11-2023, 10:11 AM | #51 |
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Just some food for thought... a more on/off brake pedal feel isn't necessarily a good thing.
I really doubt there is any performance benefit to coding SBPR on an M3. It's not an M3 option and it's meant to change the 128i from base brakes to performance brakes. So, you're basically coding your M3 to use the DSC settings meant for the bias and pressure of the 135i Brembos installed on a 128i (if the coding and values even change at all since the M3 DSC is different). The M3 stock brakes and BBK are massively bigger than the 135i brembos... the master cylinder is different on the M3 and the slave cylinder is also different... The rear M3 brakes have a bit more rear bias which improves handling/trail braking over the more aggressive front bias of the 135i brembos. The 128i has the smallest slave cylinder of the three cars for the front circuit... and stands to reason putting a bigger caliper on the front of a 128i will result in the most brake pedal feel change. I guess if your BBk increases front bias from the stock M3 brakes then you are kind of doing the same thing as putting 135i brembos on a 128i... so, maybe it does feel better. Still way too many variables that aren't being considered to determine if there is really any reason to do the coding change... but i guess if the change gives you more confidence it's a win. A quick google shows these calcs for common BBK options (I did not check how accurate this is): Stock balance is: F/R = 1.74 Stoptech ST40 all around is: F/R = 1.69 Stoptech ST60/ST40 is: F/R = 1.70 Stoptech ST60/stock is: F/R = 1.78 Stoptech ST40/stock is: F/R = 1.77 Several of the popular BBK combos decrease front brake bias vs stock M3 so coding SBPR would be opposite you would want to do. I also question is any of this coding matters when DSC is turned off? Last edited by bbnks2; 10-11-2023 at 10:50 AM.. |
| 10-11-2023, 11:53 AM | #52 | |
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Derbo Tuning
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I went through some rough math calculations. It involved brake piston diameter, brake pad surface area based on pad width, rotor annulus, radius effective, and brake torque. I was purely looking at getting the brake torque number based on the piston surface area to pad surface area, on the useable rotor annulus. After getting brake torque numbers from both axles, I just divided to get the ratio. I got the following numbers:F/R Stock brakes 1.76 ST40/Stock 1.86 ST60/Stock 1.89 AP9660372mm/stock 1.68 Brembo4p 1.90 I dont have the information on the Brembo 6p 380mm but I suspect its similar to the ST60 bias. This assumes same brake pad compound on both axles. This is my rough math with me trying to get the stock brakes to that 1.74 number. With DSC off, your ABS is still affected.
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| 10-11-2023, 12:21 PM | #53 | |
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VO codes simply tell the various modules what their default coded values should be. If the M3 never had a SPBR option the DSC will have no idea what to do with that VO and skip right over it, the same that every other modules does. The simple way to check is make sure SPBR is not in your VO, default code the DSC, read the file back out, add in SPBR, write VO to CAS and NFRM, then default code the DSC again. If none of the coded options changed then the SPBR VO did nothing. |
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| 10-11-2023, 02:30 PM | #54 | |
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I understand that turning off DSC does not affect ABS. That's exactly why I question if the functions we can change in the DSC module impact ABS... They may be models that purely influence the DSC intervention which is all turned off with a 5 second hold of traction control button. I don't think ABS has ever been able to be manipulated with coding. Everyone that has ever messed with ABS flashes new software. I question this because of the claims of different ABS engagement after coding for SBPR which is something that would actually impact performance and isn't just a subjective "feel" of a brake pedal change. With dsc off... the coding changes are probably moot. I am honestly surprised so many people coding for SPBR feel it makes a change but no one has provided a trace file for comparison? Look back at the chart on page two and you can see the "values" for many of these functions is "0" meaning no data meaning they don't even do anything. "Pressure model F/R" is a GTS and 335i function. The data value for M3/1M is 0. Last edited by bbnks2; 10-11-2023 at 02:58 PM.. |
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| 10-11-2023, 11:23 PM | #55 |
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This site is handy:https://upbrakes.com/upgrade_advisor Standard piston sizes are 60mm/46mm.
Raw brake torque has an impact on mechanical bias however the it is often controlled by the ABS module instructed by DSC which literally act as a bias proportioning valve even out of ABS. You're barely ever getting raw mechanical bias, the module's always doing something. If you stray way too far out, it'll mess with the calibration which is why aftermarket tries to stay close. There was a M5/6 MK60 document posted in one of these threads that's worth a read. Anyway, It has been like this since the invention of such device and integration with traction or stability control systems. The reason I asked for GTS is because I wanted to see what other values are different. If you plug their numbers in with the common front pad of 155mm brembo width, and totally guess the rears with the known 380mm disc, common Brembo 4p piston sizes and pad heights. The raw mechanical bias is ~61%, lol. It would not also surprise me if the co-efficients for ABS engagement (or even MDM) were raised considering it's tyre and tyre sizes shipped.
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| 10-12-2023, 11:17 PM | #56 | |
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Derbo Tuning
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https://www.m3post.com/forums/showthread.php?t=699892 I assume you mean this thread? I did the math so long ago I dont remember how accurate or what I did anymore. Its all on a googlesheet at this point. https://www.mathworks.com/help/sdl/ref/discbrake.html
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