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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Fri, Jul-13-2018, 01:42:38 AM   #21
Volke
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Default Re: MK20 ABS unit differences

Quote:
Originally Posted by terraphantm View Post
I don't know if my measurements were accurate enough to say for sure whether or not the ZHP rack is 49mm vs 50mm or M3 rack 46mm vs 47mm. I also never had a ZCP rack on hand, I can't confirm or deny whether there's a measurable difference there.

Edit: In this post (which I believe was closer to when I actually changed steering racks and did the measurements), I said the M3 was ~46.5 mm/rev. http://www.m3forum.net/m3forum/showp...0&postcount=13
Are you absolutely sure the ZHP rack is progressive? I assume it's a yellow tag 712?

My 330 rack measurements definitely said 50mm/rev at center, it had exactly 3 turns lock to lock and 150mm total travel which makes it 100% linear. I don't think mine is a 712 though. I'll crawl under the car when I get it back from the cage fabricator next week. If your rack is 50mm/rev at center and gets faster, it would also be less that 3 turns lock to lock.

EDIT: Let's postpone this discussion for now. I'll start a thread later to document stuff in one place after I have my M3 rack on hand and my car back so I can get my 330 rack part number.
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Last edited by Volke; Fri, Jul-13-2018 at 01:51:52 AM.
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Old Fri, Jul-13-2018, 01:46:22 AM   #22
terraphantm
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Default Re: MK20 ABS unit differences

Mine takes about 2.75 turns lock to lock if I recall correctly.

Edit: This non-ZHP also seems to be about the same L2L. An 04 non-ZHP and ZHP should have the same rack

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Old Fri, Jul-13-2018, 01:55:36 AM   #23
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Default Re: MK20 ABS unit differences

Interesting. Yeah, I'll definitely get a thread started later to get everything sorted and documented in one place. It would be nice to have a definitive guide to rack swaps.
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Old Sat, Aug-04-2018, 02:38:37 PM   #24
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Default Re: MK20 ABS unit differences

Update: I got a chance to measure my E46 M3 rack. It is without a doubt 100% linear and has a rate of 47mm/rev.

Also, based on a picture of a ZCP/CSL rack turned all the way to the left that a friend shared, that appears to be linear too. Using the 47mm/rev of my rack and the published 15.4:1 and 14.5:1 ratios of the M3 and ZCP respectively, we can calculate the ZCP rack to be 50mm/rev. This is the same as the 330 rack on my car. Unfortunately, I can't say what 330 rack part number I have since I bought a BMW reman part and they seem to have removed the original ID tag.

Still planning on starting a separate thread to document all this when I have a chance to do a write up on how to measure the racks and what to look for.

EDIT: Someone measured and confirmed the ZCP rack to be 50mm/rev for me

EDIT 2: The M3/ZCP knuckle has a 130mm leverage arm on steering inputs. The fact that a 50mm/rev rack on the ZCP gives 14.5:1 ratio, and a 50mm/rev rack on a 330 gives 13.7:1 means that the 330 knuckles must have a shorter leverage arm. It should be ~123mm, but there may be some slight rounding errors in the 13.7 and 14.5 numbers.
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Last edited by Volke; Sat, Aug-04-2018 at 02:48:12 PM.
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Old Mon, Sep-03-2018, 07:31:21 PM   #25
terraphantm
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Default Re: MK20 ABS unit differences

Quote:
Originally Posted by Volke View Post
Update: I got a chance to measure my E46 M3 rack. It is without a doubt 100% linear and has a rate of 47mm/rev.

Also, based on a picture of a ZCP/CSL rack turned all the way to the left that a friend shared, that appears to be linear too. Using the 47mm/rev of my rack and the published 15.4:1 and 14.5:1 ratios of the M3 and ZCP respectively, we can calculate the ZCP rack to be 50mm/rev. This is the same as the 330 rack on my car. Unfortunately, I can't say what 330 rack part number I have since I bought a BMW reman part and they seem to have removed the original ID tag.

Still planning on starting a separate thread to document all this when I have a chance to do a write up on how to measure the racks and what to look for.

EDIT: Someone measured and confirmed the ZCP rack to be 50mm/rev for me

EDIT 2: The M3/ZCP knuckle has a 130mm leverage arm on steering inputs. The fact that a 50mm/rev rack on the ZCP gives 14.5:1 ratio, and a 50mm/rev rack on a 330 gives 13.7:1 means that the 330 knuckles must have a shorter leverage arm. It should be ~123mm, but there may be some slight rounding errors in the 13.7 and 14.5 numbers.
I missed this update, good information here. Whether your 330 rack is a purple or yellow rack shouldn't make a difference as far as ratio goes since DSC uses the same coding for both. So your measurements are probably accurate for the yellow tag rack. And with the ZCP also being the same 50mm/rev, that probably makes it the same effective ratio. I guess only difference might be the actual steering feel. It's also very possible the racks are actually the same and the different part number was assigned because of the tie rods.

What are the measurement points you used for the leverage arm?
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Old Wed, Sep-05-2018, 12:43:59 AM   #26
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Default Re: MK20 ABS unit differences

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Originally Posted by terraphantm View Post
I missed this update, good information here. Whether your 330 rack is a purple or yellow rack shouldn't make a difference as far as ratio goes since DSC uses the same coding for both. So your measurements are probably accurate for the yellow tag rack. And with the ZCP also being the same 50mm/rev, that probably makes it the same effective ratio. I guess only difference might be the actual steering feel. It's also very possible the racks are actually the same and the different part number was assigned because of the tie rods.

What are the measurement points you used for the leverage arm?
You make a good point about the 330 DSC coding.

The ZCP and 330 racks definitely result in identical steering ratios.

I measured from the center of the LCA hole to the center of the tie rod hole on my CSL knuckles. It was easy to do since I haven't installed them yet. I confirmed the same measurement on my SLR Speed roll center/bump steer correction adapters for the M3 which are designed to fit on to the regular M3 knuckles.

Side note since there are a lot of misconceptions: The CSL knuckles add 1 extra degree of negative camber, and that's it. They do not affect track width. The reason for this is that adding negative camber on a MacPherson strut suspension by moving the top of the strut mount inwards through the use of camber plates also increases the KPI angle. A larger KPI angle means more caster loss as the wheels are turned left or right. Caster loss results in more positive camber gain as the wheels are turned. This means that for a given static negative camber alignment, the CSL knuckles will maintain more caster and gain less positive camber vs the regular M3 knuckles as you turn left or right.
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Old Sat, Sep-15-2018, 10:40:41 PM   #27
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Default Re: MK20 ABS unit differences

So I was digging through some NCS files, and I found this line in "E46AEDOC.000"

Quote:
-E LEN1 N0301 fuer (LIM,COUP,TOUR,CABR)+(M54B30,M57D30,M56B30)+SA210 ab 04/01 (Lenkuebersetzung i=50)

-E LEN1 N0301 for (LIM, COUP, TOUR, CABR) + (M54B30, M57D30, M56B30) + SA210 from 04/01 (Steering ratio i = 50) (google translate)
Basically a mentioning of an option code for E46 sedans, coupes, tourings, and cabrios w/ one of the 3 liter engines that designates a steering ratio of "i = 50" for cars with the sports package (SA210) built from 04/01 onward.

Does seem to confirm 330s from 04/01 onward got a 50mm/rev steering rack. And I do remember that way back when, early 01 330s were said to have overboosted steering and BMW actually offered retrofits for them (which may well be where this option code comes into play)

Wish we could get proper numbers on all the other racks
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Old Mon, Sep-17-2018, 05:29:13 PM   #28
Volke
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Default Re: MK20 ABS unit differences

Quote:
Originally Posted by terraphantm View Post
So I was digging through some NCS files, and I found this line in "E46AEDOC.000"



Basically a mentioning of an option code for E46 sedans, coupes, tourings, and cabrios w/ one of the 3 liter engines that designates a steering ratio of "i = 50" for cars with the sports package (SA210) built from 04/01 onward.

Does seem to confirm 330s from 04/01 onward got a 50mm/rev steering rack. And I do remember that way back when, early 01 330s were said to have overboosted steering and BMW actually offered retrofits for them (which may well be where this option code comes into play)

Wish we could get proper numbers on all the other racks
Last week I finally started working on writing up a comprehensive steering information thread that will include the measurements I've taken and basic instructions on how to measure racks so the community can help me compile a database of steering racks. I have first hand information on the regular M3, a 330 rack of unknown origin, and a 2.5L Z3 rack I had a chance to measure at Performance Eurowerks, along with second hand information on the ZCP. Spoiler alert, the 2.5L Z3 rack is also 50mm/rev and linear.

It will take me a little while longer to finish writing it since I'm going to include a section on power steering assist and a DIY on how to lessen the assist. Note, I'm not talking about power pulleys which don't actually lessen assist.

I think the overboosted feeling was because of a weaker torsion bar which basically causes the steering assist to apply more easily, but if the earlier cars had higher steering ratios, that would contribute to the light feeling as well.
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Discussing MK20 ABS unit differences in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)