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      08-28-2011, 09:11 PM   #1
MDORPHN
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Outstanding performance at track (but ABS...)

Just back from two days at VIR. Ran the North Course on Saturday under windy/damp conditions (courtesy of Hurricane Irene) and the Full Course today in beautiful but hot (92F) conditions.

Very pleased with the 1M. I was running PFC01 pads and brakes were outstanding. Still a bit too much mid-turn understeer but I'll shortly be addressing that with some adjustable camber/caster plates. Oil temps went up to around 280 F today running hard in hot conditions so I'll have to keep a close eye on that and, of course, change the oil frequently. And, if need be, I'll move to a larger oil cooler.

The only issue that I'm still puzzling through involves the ABS. Although braking on the straight from high speeds (~145 mph on back straight) was fine, the ABS would actuate when trail braking into turns in lower speed situations -- including turns 3 and 4.

Braking would be fine immediately following application, but seconds (likely milliseconds) later as I'd begin bending into the turn (and without any change in pedal pressure) the ABS would briefly actuate and the car felt like it would be skating for a moment. The ABS would then disengage so normal braking resumed and all would be fine.

A fellow instructor who was behind me said that the car looked like it would momentarily drift sideways when this happened.

FWIW, I was running on the stock tires (Michelin PS2) with all the stability/traction control nannies off. Nonetheless, I'm wondering if at least some of the stability control is restored when ABS is engaged.

Any insights?

Neil
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      08-28-2011, 09:34 PM   #2
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I have no clue. But any issues with the charge pipe?
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      08-28-2011, 09:35 PM   #3
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I have no clue. But any issues with the charge pipe?
Nope, but I'm no longer running the POS stock pipe!

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      08-28-2011, 09:37 PM   #4
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Ah, did you go with the ER one?
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      08-29-2011, 08:33 AM   #5
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Heard from a braking engineer, who advised me that German stability control systems tend to be calibrated to re-enable when you press the brake pedal, even if you have the system "switched off".

This very well may be what I was experiencing. I'm trying to learn more and figure out if there is a work around.

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      08-29-2011, 01:58 PM   #6
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Neil Q.: did you change the brake fluid?
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      08-29-2011, 01:59 PM   #7
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Yes, definitely need to change your fluid if it's broke.
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      08-29-2011, 02:07 PM   #8
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Quote:
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Yes, definitely need to change your fluid if it's broke.

Fixed it...... better now? Sorry for the clumsyness
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      08-29-2011, 02:13 PM   #9
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Yes, definitely need to change your fluid if it's broke.
Motul RBF 600 and stainless steel brake lines, but what I'm experiencing is wholly unrelated to brake fade.

I'm now quite certain that it's due to the "cornering brake control" that BMW fits in many of its new models, including the 1M.

Here is BMW's description:

"Cornering Brake Control (CBC).

For greater safety when braking on curves - Cornering Brake Control stabilises your BMW by applying braking pressure asymmetrically despite physically difficult conditions (e.g. the car swerving towards the inside of the bend when the wheel load changes). Cornering Brake Control (CBC) reduces the danger of vehicle instability that can arise when the brakes are applied while taking a bend at speed. Without CBC, the load shift caused by braking can reduce traction on the wheels on the side towards the inside of the bend, thereby applying excessive load to the other side. This load imbalance may result in a loss of directional control, causing the vehicle to skid out of the curve. CBC counteracts this tendency by asymmetrically distributing brake pressure to the left- and right-side brakes or by reducing pressure (to the rear axle), even if the driver brakes outside the normal range of ABS. The result: a significant improvement in stability and safety when applying light brake pressure, even on bends."


I don't know what is meant by "even if the driver brakes outside the normal range of ABS," but suspect that this explains what I'm experiencing on track. I'd love to get rid of it -- since it interferes with my ability to rotate the car with the brakes -- but figure that would only be possible if I were to totally disable the ABS (which I don't want to do).

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      08-29-2011, 02:25 PM   #10
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I wonder if the system is tied into the sensors that are on each of the front a-arms that seem to sense suspension compression for some reason. You could always disconnect those and see what happens???
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      08-29-2011, 03:30 PM   #11
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MDORPHIN

Are you sure the 1M has the CBC? Never read anything about that.
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      08-29-2011, 04:04 PM   #12
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MDORPHIN

Are you sure the 1M has the CBC? Never read anything about that.
CBC is listed in the AG 1M brochure as part of DSC. It also shows up on the UK website, but not on the USA site.

I guess the question we're trying to get answered is whether or not CBC is disabled when DSC is disabled or does it remain on like ABS.

http://bmw.co.uk/bmwuk/pricesandspec...%3D%3D,00.html
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      08-29-2011, 04:07 PM   #13
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Quote:
Originally Posted by bdaddylo View Post
CBC is listed in the AG 1M brochure as part of DSC. It also shows up on the UK website, but not on the USA site.

I guess the question we're trying to get answered is whether or not CBC is disabled when DSC is disabled or does it remain on like ABS.

http://bmw.co.uk/bmwuk/pricesandspec...%3D%3D,00.html
Well, I had the DSC completely off and the cornering brake control sure seems to explain what I was experiencing.

Neil
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      09-07-2011, 09:30 AM   #14
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I just read that thing about the charge pipe. Did BMW leave the same pipe from the older '08+ N54 135i's or does it have the extended version like the N55? What pipe did you end up getting? Keep us updated about this braking issue!
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      10-30-2011, 12:14 PM   #15
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Neil, you have done a ton of track days now it appears. How is this issue?

What mods have you done to your car now?

I have done one day at CMP in SC and do VIR grand course in two weeks.
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      03-23-2012, 05:31 PM   #16
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This is annoying to me at Autocross. Has anyone found a solution yet?
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      03-24-2012, 05:34 AM   #17
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This is annoying to me at Autocross. Has anyone found a solution yet?
Nobody will touch the ABS brain (for both technical and legal reasons). Only "solution" is to disable the ABS entirely

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      03-24-2012, 06:39 PM   #18
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MDORPHN: Can you reduce the effect by reducing the amount of trailbraking more rapidly with turnin? IS it dependent on how much you are braking?

I havent been to the track with the 1M yet, but I LOVE trailbraking, and think this will annoy me to no end if it is too intrusive.
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      03-24-2012, 07:52 PM   #19
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This is annoying to me at Autocross. Has anyone found a solution yet?
What i have found so far is, if you get late and have to max brke and jerk the wheel you have a good chance of experiencing it.
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      03-25-2012, 07:46 PM   #20
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What i have found so far is, if you get late and have to max brke and jerk the wheel you have a good chance of experiencing it.
I would agree that you'll most likely experience it only if you're on the edge.

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      03-26-2012, 01:38 PM   #21
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It sounds like you are too hard on the brakes on trailbraking, there is no reason for the ABS to even be activated unless the wheels are breaking loose from over breaking.
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      03-26-2012, 01:42 PM   #22
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It sounds like you are too hard on the brakes on trailbraking, there is no reason for the ABS to even be activated unless the wheels are breaking loose from over breaking.
Sometimes I am using the brakes to shift the balance forward and allow the rear tires to slip, thereby helping to rotate the car.

I'd really prefer the car not to work against me!

Neil
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