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M3 Track: Racing and DE Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start!


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Old Thu, Dec-07-2017, 08:54:10 PM   #11
Bimmerman325i
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

I currently run:

E36
Mk60 DSC/ABS, non-ZCP/CSL version
Stoptech 332mm BBK x4
Hawk DTC60 x4
Nitto NT01 255/40/17

ABS is not too intrusive, but is there when I screw up or really gotta stop NOW.

I have kicked it into ice mode with same hardware but RE71R tires at autocross, under heavy braking + significant turning. Have not had it happen on track.
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Old Tue, Dec-12-2017, 11:15:32 PM   #12
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

I have a 2001 with Mk20 and find it to be pretty decent for track use. I have not run anything beyond DOT R-comps yet but have never experienced true "ice mode". I can see individual wheel speeds in my ECU, at over 100 times a second, and if the ABS intervenes, it's because a wheel is truly starting to lock up (typically a front, since the rears are driven and have much more inertia associated with them, through the drivetrain). I can't say there has been a situation on track yet for me where the ABS intervened and I thought I could brake significantly harder if it was disabled.

This part is a bit anecdotal, but I could see that the Mk60 system could possibly allow for more accurate lockup "control" meaning all 4 tires are kept closer and tighter to their optimal amount of lockup/slip. I have seen a few times in my data with the Mk20 that, especially in parts of the track that "drop away" during a braking zone for example, that a single tire will begin to lock and may slow down to as much as 15mph slower than the other 3 tires for a very brief moment before the ABS releases it and its speed catches back up. When this occurs, I'll hear just a very slight chirp out of the tire. I would be surprised if better control in situations like this nets you more than only a few feet of braking distance. Unfortunately we will always have physics to deal with..

I think some people are confusing what has been termed "ice mode" as the ABS correctly intervening when one or more wheels is actually locking up due to low traction. In this situation, such as dipping a single tire or one side of the car onto a curb or into dirt while braking, the pedal will pulse and braking time will be increased, but this is to be expected, to a point.

What the Porsche guys call true "ice mode" typically occurs when you get on the brakes hard and fast, and even with plenty available braking traction to all 4 wheels, the ABS system goes into some sort of mode where you get little to no braking at all, usually resulting in a crash. I not only have not experienced this, but I have never heard of it actually occurring first-hand, and have worked with a number of teams that race E46s in endurance SCCA/NASA racing. I'm certainly not discounting it, but I think it is blown out of proportion and is very rare.

I regret not getting an E46 with Mk60, but mainly because I have a Z3 rack and I'm unable to code my Mk20 for the quicker ratio. Plus, M Track Mode would be fun to have sometimes. The DSC is quite intrusive on the street especially with the quicker rack that confuses it, but with DSC off and ABS on, it seems to work great on track.
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Old Tue, Dec-12-2017, 11:30:55 PM   #13
Bimmerman325i
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

Quote:
Originally Posted by BBRTuning View Post
I have a 2001 with Mk20 and find it to be pretty decent for track use. I have not run anything beyond DOT R-comps yet but have never experienced true "ice mode". I can see individual wheel speeds in my ECU, at over 100 times a second, and if the ABS intervenes, it's because a wheel is truly starting to lock up (typically a front, since the rears are driven and have much more inertia associated with them, through the drivetrain). I can't say there has been a situation on track yet for me where the ABS intervened and I thought I could brake significantly harder if it was disabled.

This part is a bit anecdotal, but I could see that the Mk60 system could possibly allow for more accurate lockup "control" meaning all 4 tires are kept closer and tighter to their optimal amount of lockup/slip. I have seen a few times in my data with the Mk20 that, especially in parts of the track that "drop away" during a braking zone for example, that a single tire will begin to lock and may slow down to as much as 15mph slower than the other 3 tires for a very brief moment before the ABS releases it and its speed catches back up. When this occurs, I'll hear just a very slight chirp out of the tire. I would be surprised if better control in situations like this nets you more than only a few feet of braking distance. Unfortunately we will always have physics to deal with..

I think some people are confusing what has been termed "ice mode" as the ABS correctly intervening when one or more wheels is actually locking up due to low traction. In this situation, such as dipping a single tire or one side of the car onto a curb or into dirt while braking, the pedal will pulse and braking time will be increased, but this is to be expected, to a point.

What the Porsche guys call true "ice mode" typically occurs when you get on the brakes hard and fast, and even with plenty available braking traction to all 4 wheels, the ABS system goes into some sort of mode where you get little to no braking at all, usually resulting in a crash. I not only have not experienced this, but I have never heard of it actually occurring first-hand, and have worked with a number of teams that race E46s in endurance SCCA/NASA racing. I'm certainly not discounting it, but I think it is blown out of proportion and is very rare.

I regret not getting an E46 with Mk60, but mainly because I have a Z3 rack and I'm unable to code my Mk20 for the quicker ratio. Plus, M Track Mode would be fun to have sometimes. The DSC is quite intrusive on the street especially with the quicker rack that confuses it, but with DSC off and ABS on, it seems to work great on track.
Ironically my Z3 rack doesn't confuse my Mk60 at all, though I think I may have coded it differently when I did the conversion.

I have definitely had true ice mode kick in on the Mk60, and the prior 3-channel E36 ABS. I will have to pull the data up again for the autox when I got it to happen but basically with full pedal effort, and close to full steering, the car decided it didn't feel like continuing to apply the brakes.

I have not gotten Mk60 to freak out on track, however; only the E36 system was dumb enough to go into ice mode (braking for turn 6 at laguna, for reference). Both instances weren't ABS functioning so much as the pedal was firm, engaged, and the car essentially stopped decelerating. VERY scary. I agree that it happens super rarely since the combination of inputs required to confuse the unit is pretty strange.
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Old Thu, Dec-14-2017, 05:13:20 AM   #14
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

Quote:
Originally Posted by BBRTuning View Post
I have a 2001 with Mk20 and find it to be pretty decent for track use. I have not run anything beyond DOT R-comps yet but have never experienced true "ice mode". I can see individual wheel speeds in my ECU, at over 100 times a second, and if the ABS intervenes, it's because a wheel is truly starting to lock up (typically a front, since the rears are driven and have much more inertia associated with them, through the drivetrain). I can't say there has been a situation on track yet for me where the ABS intervened and I thought I could brake significantly harder if it was disabled.

This part is a bit anecdotal, but I could see that the Mk60 system could possibly allow for more accurate lockup "control" meaning all 4 tires are kept closer and tighter to their optimal amount of lockup/slip. I have seen a few times in my data with the Mk20 that, especially in parts of the track that "drop away" during a braking zone for example, that a single tire will begin to lock and may slow down to as much as 15mph slower than the other 3 tires for a very brief moment before the ABS releases it and its speed catches back up. When this occurs, I'll hear just a very slight chirp out of the tire. I would be surprised if better control in situations like this nets you more than only a few feet of braking distance. Unfortunately we will always have physics to deal with..

I think some people are confusing what has been termed "ice mode" as the ABS correctly intervening when one or more wheels is actually locking up due to low traction. In this situation, such as dipping a single tire or one side of the car onto a curb or into dirt while braking, the pedal will pulse and braking time will be increased, but this is to be expected, to a point.

What the Porsche guys call true "ice mode" typically occurs when you get on the brakes hard and fast, and even with plenty available braking traction to all 4 wheels, the ABS system goes into some sort of mode where you get little to no braking at all, usually resulting in a crash. I not only have not experienced this, but I have never heard of it actually occurring first-hand, and have worked with a number of teams that race E46s in endurance SCCA/NASA racing. I'm certainly not discounting it, but I think it is blown out of proportion and is very rare.

I regret not getting an E46 with Mk60, but mainly because I have a Z3 rack and I'm unable to code my Mk20 for the quicker ratio. Plus, M Track Mode would be fun to have sometimes. The DSC is quite intrusive on the street especially with the quicker rack that confuses it, but with DSC off and ABS on, it seems to work great on track.
This is fantastic data proofed response. Appreciate you taking time to write out full explanation and your personal feelings. As to your first point looking at data logs and single wheel locking up is exactly what I had a notion could happen. (Hence me raising this topic) So I picture that same scenario, but running with slicks would be immensely heightened and occur more frequent.
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Old Thu, Dec-14-2017, 06:48:39 PM   #15
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

While we're on the subject, in case you feel like geeking out a bit, here's a screenshot from a straight-line braking zone into the final (left) turn at Buttonwillow. I picked this particular example since I braked a bit late and too hard into the turn and the ABS was very active during the entire braking event.

The 2nd trace from the top shows the 4 individual wheel speeds. "NL" is "non-driven left" (front left), "DR" is driven right (rear right), etc. You can pretty clearly see the individual wheels start to lock. I highlighted the data at one of the larger lockups. You can see the car is going approx 88mph, but the front right is at 77. That entire dip only lasts ~110ms, or 0.11 seconds. You can see one final front left lockup (dark red) as I just start to turn in, since at that point the front left has less load on it. Also interesting to see the front left seems to be free-wheeling a bit near at the exit of the turn, although this obviously isn't related to ABS. Also, very slight amount of inside rear wheel spin during corner exit (salmon? color).

What is interesting to note is in the 3rd trace, "Acceleration X", showing longitudinal decel G. It's relatively flat and consistent throughout the braking zone, meaning the decel rate is pretty constant. You can't expect it to be perfectly smooth, especially since the track itself isn't perfectly smooth, but if this was very jagged or wavy it would indicate the ABS was causing inconsistent braking rate which would extend braking distance. You can see the decel-G transition into accel-G as the Accel-Y lateral G force picks up (turning in, and then straightening out by the end of the screenshot).

Now, if only I had data just like this from an Mk60 car I might actually be able to this weekend as I'm hitting the track with a friend that has a 2004, same data package on the car and same brake kit. Hopefully he gets into ABS a few times and we get some cool Mk60 data to look at!

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Old Thu, Dec-14-2017, 07:51:18 PM   #16
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Default Re: MK20 vs MK60 Dilema ; Deal breaker?

Here's some Mk60 data, though not ice-mode related. I'm not at the computer with the data logs, so this is from an email I sent to a buddy after the same autocross I mentioned above. Image quality is....poor, sorry, and there are two runs being compared at the same time.

The data clearly shows the diff is dying and is allowing way too much relative spin exiting corners, leading to oversteer.



Data key: top trace is throttle position, then steering angle, then LR wheel speed then RR wheel speed. The red boxes highlight spikey uneven wheel speeds across the differential in sweepers/acceleration zones where it's not putting power down.

Our theory was the clutch packs were worn to the point that it doesn't really work like an LSD anymore, and combined with unloading of the suspension in roll, the inside tire is burning up (Left tire mostly) and then once the car settles, it shocks the diff, causing oversteer (note the steering angle backs off very close to these spikey wheel speeds). This proved to be the case once a diff with new clutches was installed.

Data is cool. I'll try to remember to pull this data for the ice mode run tonight, but....star wars premiere likely means I'll forget.
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