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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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#11 | |
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According to my research..
Competition ZCP/ Stock OEM = Progressive Purple Label ZHP Rack= Linear " On the topic of progressive racks, I think different racks were designed with different amounts of progressiveness. Its my theory that the unquestionably progressive 330 rack is "more linear" than the E46 M3 "quite progressive" rack. " http://www.m3forum.net/m3forum/showthread.php?t=544445 |
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#13 | |
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Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car |
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#14 | ||
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The "unquestionably progressive 330 rack" is unquestionably linear. I measured mine prior to installation. It has 50mm/rev, 3 turns lock to lock and 150mm total travel from side to side. I checked the 50mm/rev directly at center and on both ends. The Z3 non-M rack is also fully linear. It has 53.5mm/rev, 2.7 turns lock to lock and 144.5 mm total travel. It's a little faster, but as you can tell from the total travel, it will hurt your turn radius a bit. I'll go get my regular E46 M3 rack from PE on Monday and measure it. Quote:
That would mean that both the ZCP rack and the 330 rack are 50mm/rev, but the 330 steering knuckle has the outer tie rod location a little closer to the control arm bolt. If that's true, saves me the effort and money of trying to find a ZCP rack.
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Peter Mechanical Engineer Last edited by Volke; Thu, Jul-12-2018 at 04:18:25 PM. |
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Yellow tag is supposedly more feelsome than the ZCP rack, as well. If you want further details, PM him a link to this. I can't seem to find it.
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Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car |
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#16 | |
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If the regular E46 M3 rack is 46mm/rev and that results in a 15.4:1 ratio and we assume that the ZCP rack has the same total rack travel as the regular M3, we can calculate the mm/rev of the 14.5:1 ZCP rack since we know they both use the same steering knuckle. Doing so yields ~48.9 mm/rev. That tells us that the 330 rack is faster than 14.5:1 when installed on the E46 M3. In fact, we can calculate it to be be ~14.17:1. Of course, all this depends how accurate that 46mm/rev measurement is. If that number is actually 47mm/rev, then the ZCP and 330 racks would come out about even and I'll be very happy I don't have to try to find a ZCP rack. I'll take some good measurements off my M3 rack next week to verify. I'll start a new thread to solicit measurements from the community once I have the measurements off my E46 M3 rack. The community should be able to populate the the info for each rack pretty quickly. That way we can have a definitive guide for rack swaps on the E46. Also, I'm not really concerned about the torsion bars and feel. You can offset the effect of a smaller torsion bar by lowering the power steering system pressure which I've already figured out how to do.
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#17 | |
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I can't imagine lowering the power steering pressure increasing feel-- just adding weight/decreasing assistance.
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Current Cars: 2005 IR/IR M3, 2001 LMB/blk M5, 03 530i, 04 M3 wagon, and some boring stuff Past cars: 04 M3, 96 M3, S50B32 e36 M3 CM race car |
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The torsion bar is effectively a torsion spring that controls how much torque needs to be applied to the steering column to open the valving inside the steering rack and send pressure to the steering cylinder. The power assist reduces how much of the load from the tires is transferred back through the column to the steering wheel. If you remove the power steering all together, there's no reason a rack with a smaller torsion bar would have worse feel than one with a larger bar, so decreasing the pressure should help reduce the difference in feel between the two. If the torsional rigidity of the column was that much of an issue even without power assist, then an aluminum steering guibo should improve feel greatly. This place has a pretty good explanation of how power steering works. http://www.agcoauto.com/content/news/p2_articleid/214
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Peter Mechanical Engineer Last edited by Volke; Thu, Jul-12-2018 at 10:11:01 PM. |
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fwiw,
i found the 330 rack to offer abit less in terms of feel, compared to std. the rack was also tighter, and i dialled in a tad of toe in up front to save my tyres. so that could have influenced the outcome. |
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#20 | |
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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 Last edited by terraphantm; Fri, Jul-13-2018 at 01:30:10 AM. |
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