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      08-21-2013, 10:25 AM   #1
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Robbing the E92 M3 and E46 of suspension components

First off I'd like to say that this wouldn't have been possible without the work that was done by Orb, Mr5 and Harold from HP Autowerks over on e90post. These guys did the preliminary R&D work for retrofitting some of these components on the E9x platform and inspired me to do the same on the E89.

To reduce costs BMW leveraged several exiting parts from their bin when building the suspension for the E89. Up front the tension struts and swaybar endlinks are the exact same as used in the non-M E9x platform. In the rear, the lower wishbones (camber arms) are lifted from the E85 platform while trailing arm brackets are the same as the E46. This opens up the possibility of improving the suspension performance on the E89 by using the same "parts bin" approach".

Note, I assume no responsibility for damage to your car if you perform the upgrades outlined. Always have suspension components installed by a professional who can also do an alignment at the same shop. DO NOT drive your car without an alignment after performing this upgrade.

Since I haven't seen any of this information posted here before I decided to do the research and be the guinea pig. I wanted to maintain the OEM electronic dampers but improve the overall handling experiance. Initial results are....

Front Suspension:

I've used the tension struts from the E92 M3 along with stock M-Adaptive struts and Eibach lowering springs (1.2" drop). The M3 wishbones are the correct length (maybe a tiny bit longer), but unfortunately have the headlight leveling sensor attachment on the wrong side of the car. The main difference in the M3 tension struts is the rubber bushings which are much stiffer than the stock hydraulic isolators. To correct the geometry of the front sway bar with the lower ride height I plan on installing adjustable swaybar endlinks for the E90 from HP Autowerks, but will let the car settle a bit before installing.

Here are the part numbers for the M3 bits:

Left tension strut with rubber mounting 31102283575
Right tension strut with rubber mounting 31102283576

Since several bolts/locking nuts need to also be replaced I would suggest ordering all the M3 components as a complete kit from HP Autowerks along with the endlinks.

Installation is fairly straight forward. Here are the torque specifications:

Tension strut to steering knuckle
(replace with new) 165 Nm (122 ft-lb)

Tension strut to subframe
M12 8.8 (replace with new) 68 Nm (50 ft-lb) + 90 degree
M12 10.9 (replace with new) 100 Nm (74 ft-lb) +90 degree


Rear Suspension:

In the rear I replaced the stock lower wishbones with adjustable E46 camber arms from Turner Motorsport and Eibach springs (0.8" drop) on the stock M-Adaptive shocks. On the camber arms I opted for rod-ends over rubber bushings to reduce deflection with a small sacrifice in ride quality. Although the E85 and E46 don't share the exact same part number for the camber arms, the Turner arms work fine as the length can be adjusted. In addition, other compatible parts include Turner trailing arm bushing limiters which use the stock bushing but incorparate aluminum shims on both sides of the bushing to limit travel.

Unfortunately the actual bushing where the trailing arm mounts to the chassis is unique to the E89 otherwise an upgrade to the E46 M3 bushing may also be an option. I may still grab a set of the E46 M3 bushings to do a proper comparison as both the balljoint and hub bushing share part numbers with the E46.

Installation of the camber arms is a fairly invovled job as the rear diff needs to be partially lowered in order to remove the inner bolts.

Here are links to the parts on Turner's website:

http://www.turnermotorsport.com/p-96...-shim-kit.aspx
http://www.turnermotorsport.com/p-35...reettrack.aspx

Alignment:

It is absolutely crutial to get a full alignment after completing this upgrade. Here are the OEM alignment tolerances for the E89:

Front Camber -0.1 to -1.1
Front Caster 6.5 (fixed)
Front Toe 0.02 to 0.22
Front SAI 14.2 (fixed)
Front Inc. Angle 13.6 (fixed)
Rear Camber -1.9 to -2.8
Rear Toe 0.05 to 0.25

For my car I was looking for the following targets post suspension upgrade:

Front Camber -0.5
Front Toe 0.06
Rear Camber -2.5
Rear Toe 0

Actual alignment results were very close to the targets.

To get a bit of additional camber in the front, the alignment pin can be removed from the top of the strut mount. This allows you to slide the top of the strut in towards the engine a bit more. As a future upgrade I will likely install camber plates and have confirmed that Ground Control has them available for the E89 (should be the exact same mounting as the E9X anyway).

I will be taking the car on the track in the next week to see how the handling feels at the limit. I plan to add in the H&R adjustable rear swaybar soon, but wanted to get a chance to test just some of the upgraded components first.

I've attached a few pics of the install...
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      08-21-2013, 08:23 PM   #2
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thanks for sharing.

Any thoughts on the advantages of this vs. an aftermarket setup meant for E89 ?
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      08-22-2013, 03:18 AM   #3
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Congrats and thanks for the heads up.

What's the point to switch to the M3 front struts since if I read correctly no decrease in front camber resulted by them alone?
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      08-22-2013, 10:29 AM   #4
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nicknaz/janissa,
I'll try and address both of your questions the best I can. First, in regards to this setup vs an aftermarket setup for an E89, there is no complete aftermarket suspension setup for the E89 platform currently available. If you are talking about a coilover setup, which I'll address below, that still leaves a lot of other suspension components stock.

A suspension is very complex with a number of components that each individually play a part in how the car handles and feels. Springs and shocks control the vertical movement of the wheel when cornering or driving over any kind of bump. Other components, like the control arms and bushings, are also important. If the bushings used are too soft (which the stock hydraulic isolators are) they can deflect under load. This deflection can change the geometry of the suspension, even if just slightly. In a full blown race car many of the bushings are eliminated and solid joints used instead but the ride would be so harsh on the street that you'd never want to drive it. So everything is a compromise, trying to find the right balance of stiffness and comfort.

Here's a quick summary of the various components, stock weaknesses and possible solutions. Every single one of these items will have some impact on the overall suspension and handling:

Front tension struts:
Stock - soft bushings which will deflect under load
Upgrade - replace with ones from E9x M3 which have stiffer rubber bushings.
Effect - less deflection in front toe with a little more vibration transferred into the steering wheel. Will help reduce under steer.

Front wishbones:
Stock - soft bushings that will deflect
Upgrade - none currently as the headlight leveling rod is on the opposite side on the E89 and E9x. Still working on some possible solutions here

Front upper spring perch / guide plate:
Stock - no real "issue" other than stack height and lack of adjustment.
Upgrade - replace with ground control or Vorshlag camber plates.
Effect - camber and caster adjustment. lower stack height on the camber plate will give more travel in the strut when lowered

Front springs / struts:
Stock - no ride height adjustment. minimal adjustment to rebound possible (comfort vs sport mode)
Upgrade - fully adjustable coilovers or lowering springs
Effect - lower/adjustable ride height (also allows for corner weighting). adjustable compression and rebound can be made stiffer at the sacrifice of ride quality.

Front sway bar end links:
Stock - no real "issue" at stock ride height. Incorrect length when car is lowered causes geometry to be off.
Upgrade - adjustable sway bar end links
Effect - sway bar geometry restored so that frame mount and end of bar on same horizontal plane increasing effectiveness

Front sway bar:
Stock - a little on the soft side which can lead to under steer and limited roll control
Upgrade - replace with H&R 27mm sway bar
Effect - reduction in under steer, better roll control and turn in response

Rear lower wishbone:
Stock - no adjustment for camber, soft rubber inner bushing which can deflect under load
Upgrade - E46 adjustable rear camber arms with inner bushing replaced with rod end (solid mount)
Effect - large adjustment range for rear camber. slightly rougher ride with rod-end, but no deflection under load.

Rear trailing arm bushing:
Stock - lots of deflection under load will cause rear toe to change during hard corners
Upgrade - E46 rear trailing arm bushing limiters. These are just shims that are installed on both sides of the bushing greatly reducing deflection
Effect - rear toe maintained under hard cornering, no impact on ride quality

Rear trailing arm upper ball joint:
Stock - no issues, part used in E89 is the same as E46 M3 which is already fairly stiff
Upgrade - none

Rear trailing arm lower ball joint:
Stock - rubber bushing that will deflect under load
Upgrade - none. unfortunately BMW used a different size lower bushing in the E89, in the E85 and E46 this could be replaced with the better upper ball joint.

Rear upper wishbone inner ball joint:
Stock - rubber bushing that will deflect under load
Upgrade - Turner E46 monoball or Group N E46 bushing
Effect - Group N bushing uses stiffer rubber than stock will reduce deflection; Turner monoball replaces rubber bushing with a bearing that will not deflect.

Rear springs / shocks:
Stock - no ride height adjustment. minimal adjustment to rebound possible (comfort vs sport mode)
Upgrade - fully adjustable coilovers or lowering springs
Effect - lower/adjustable ride height (also allows for corner weighting). adjustable compression and rebound can be made stiffer at the sacrifice of ride quality.

Rear sway bar:
Stock - a little on the soft side which can lead to under steer and limited roll control
Upgrade - replace with H&R 21mm adjustable sway bar
Effect - increase in over steer, better roll control

Rear sub frame bushings:
Stock - rubber bushings that will deflect
Upgrade - none currently. still investigating


All of the above can be broken down into various "stages" (these are just mine, but feel free to define your own):

Stage 1:
- Stock struts/shocks (with adaptive suspension)
- Eibach or H&R lowering springs
- Front M3 tension struts
- Front adjustable sway bar end links
- Rear adjustable camber arms

Stage 2:
- Everything in Stage 1
- H&R front and rear sway bars
- rear trailing arm bushing limiter
- rear upper wishbone inner ball joint replacement (Group N or Turner)

Stage 3:
- Everything in Stage 1 & 2
- Vorshlag or Ground Control front camber plates
- Fully adjustable coilovers
- rear subframe bushings (if available)


Hope this helps....


Bill
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Last edited by wmandra; 09-03-2013 at 12:28 PM..
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      08-22-2013, 12:11 PM   #5
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Agreed, suspension complexity is something that would make me hesitant to go "piecemeal" and essentially do R&D myself (especially with the stock adjustable dampers left in place).

Props for taking it on
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      08-22-2013, 03:04 PM   #6
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I've been waiting to see control arm and bushing upgrades for this chassis. Thank you wmandra! I'm assuming you've switched to traditional tires.
Those front tension links will also improve steering feel lost when switching to non-rft's, deflect less when braking hard and reduce tramlining.
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      08-22-2013, 03:23 PM   #7
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Wow Bill, you leave us all with a load of homework.

A few points for discussion:

- Toeing out at the front under load while cornering (the reason you suggest switching to the stiffer M3 struts) is beneficial in turn in feel so I believe there must be another reason to get the m3 struts. Perhaps they give space to lower front camber however only in conjunction with strut pin removal which alone results in a decrease at -1 degree. I 'm eagerly awaiting your feedback on the struts. If they don't decrease it further I don't see the point in switching them at least on paper before listening to your feedback.

- I would refrain from maxing down rear camber as this would produce huge amount of ''static'' grip at the back thus exposing the small limit of front camber/grip and will result in understeer. Most importantly if you run -2 degrees at the back losing traction sideways is on/off and your tail will feel like a hammer. Combined with the zero toe you won't have the trend to bring the tail back on track once loose.

- A stiffer rear arb will not decrease understeer, it will increase oversteer, this is partly the same, it's the who-comes-first game. I 'm mentioning it because the h&r arb are rear adjustable.

- I was under the impression that the rear bushings/joints had mostly vertical play and role and would not affect toe when under load.

Personally I run the eibachs and h&r sways (middle position rear) on adaptive suspension with 1mm toe in each side at the front, -1.60 rear camber and 2mm toe in each side rear. Next step will be to remove the strut pins but so far I experience close to zero understeer provided I don't slam it into the corner and a very friendly/progressive behavior once the tail looses traction.

Again I 'm looking forward to your feedback through each stage you 're taking and once more thanks for pioneering this stuff.
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      08-22-2013, 07:28 PM   #8
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Thanks for the feedback and comments.

Actually going to end up changing the plan a little bit after 250 miles with the suspension changes. The combination of Eibach springs with adaptive struts isn't working out particularly well in the front. Dropping in AST adjustable coilovers and swift springs in the next few days (already have them in the garage anyway). With the electronic dampers the front has almost zero drop in ride height and the sway bar end links are always under load. The AST's have adjustable sway bar mounts, so hopefully won't need a shorter end link also.

The feedback through the steering wheel with just the tension struts is noticeable and very welcome. The rear end feels much better now but still room for improvement / adjustment.
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      08-24-2013, 01:58 PM   #9
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Impressive amount of information here, thanks for sharing!
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      08-24-2013, 06:56 PM   #10
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Amazing write up. Congrats on a great project. Well done.
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      08-31-2013, 09:35 AM   #11
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Car handled very well at the track this week. Very balanced with a touch of oversteer. The body roll was a bit much though, so sway bar upgrades will definitely be happening soon. I'm replacing the stock struts/shocks and eibach springs today with AST coilovers and swift springs. Next track day will be in October, so may even get the sway bars done before then.
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      09-01-2013, 12:29 AM   #12
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Coilovers went in today but hit a few snags... Rear springs wound up being about an inch too long to get desired ride height and somehow ended up blowing one of the AST rear shocks. New springs being ordered from swift tomorrow along with a replacement shock. Will probably also go with a slightly less aggressive spring rate in the rears at 600lb/in vs the 800s.

Update:

Turns out the shock wasn't blown... instead the person who did that side neglected to properly tighten everything back up.

Last edited by wmandra; 09-01-2013 at 12:31 PM.. Reason: update
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      09-03-2013, 12:04 PM   #13
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Nice write up here with lots of good information!
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      09-03-2013, 01:01 PM   #14
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Quote:
Originally Posted by jannisa View Post
Wow Bill, you leave us all with a load of homework.

A few points for discussion:

- Toeing out at the front under load while cornering (the reason you suggest switching to the stiffer M3 struts) is beneficial in turn in feel so I believe there must be another reason to get the m3 struts. Perhaps they give space to lower front camber however only in conjunction with strut pin removal which alone results in a decrease at -1 degree. I 'm eagerly awaiting your feedback on the struts. If they don't decrease it further I don't see the point in switching them at least on paper before listening to your feedback.

- I would refrain from maxing down rear camber as this would produce huge amount of ''static'' grip at the back thus exposing the small limit of front camber/grip and will result in understeer. Most importantly if you run -2 degrees at the back losing traction sideways is on/off and your tail will feel like a hammer. Combined with the zero toe you won't have the trend to bring the tail back on track once loose.

- A stiffer rear arb will not decrease understeer, it will increase oversteer, this is partly the same, it's the who-comes-first game. I 'm mentioning it because the h&r arb are rear adjustable.

- I was under the impression that the rear bushings/joints had mostly vertical play and role and would not affect toe when under load.

Personally I run the eibachs and h&r sways (middle position rear) on adaptive suspension with 1mm toe in each side at the front, -1.60 rear camber and 2mm toe in each side rear. Next step will be to remove the strut pins but so far I experience close to zero understeer provided I don't slam it into the corner and a very friendly/progressive behavior once the tail looses traction.

Again I 'm looking forward to your feedback through each stage you 're taking and once more thanks for pioneering this stuff.
janissa,
sorry for the delayed response... been a bit swamped the past week.

Having the front toe deflect under load may seem beneficial to turn in but if you're tracking the car heavily the least amount of bushing deflection the better. Bushings don't always deflect in repeatable ways which makes dialing in the optimal settings just that much more difficult. Most purpose built track cars will opt for solid mounts for this very reason, but it would feel horrible on the street. The M3 tension strut upgrade is a very good compromise. There is no other reason to get the M3 tension struts as all other dimensions are exactly the same as the stock component. The M3 lower wishbones would have a slight increase in negative camber for the front, but they currently won't mount up due to the difference in the headlight leveling assembly (although I have a possible solution in the works for this). One other thing worth mentioning on the tension struts is that they will cause more road vibrations to be transferred to the steering wheel which is a nice added bonus.

Believe it or not rear camber is far from maxed... -2 degrees is actually below the factory spec (even though I'm not tuning to factory specs they're still worth keeping in mind). -2.5 didn't produce any snap over steer on the track but I think that a little more front camber is needed (somewhere in the -1 range). It's also a bit early to come to any conclusions on specific alignment settings as various components are still in the process of being upgraded. Once I have everything fully installed and tested I will then start working to optimize the alignment settings.

Good point on the rear sway bar. You are correct in that it will increase over steer (or help correct under steer) rather than decrease under steer. I'll be going with the H&R bar also at some point but want to get several other components sorted first.

The rear bushings will have deflection opposite whatever direction force is applied to them. The rear trailing arm bushings will have the biggest effect on toe as that is the toe adjustment point in the rear. This is why I chose to use the bushing limiters. The deflection reduction and impact to ride quality by going to a tie-rod end on the camber arm probably isn't noticeable, but I prefer solid mounts where possible.

The biggest overall change will come from swapping out the dampers and springs for coilovers, but that's a whole separate post that I'll have to type up later.

Bill
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      09-12-2013, 07:40 AM   #15
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Great write up! I've been looking into this as well but have got no where near as far as you - well done!

I have fitted the M3 front lower arms, including front wishbones, and made a new bracket for the headlight leveling sensor attachment, as you stated it is on the wrong side of the car. Easy done with a hose clamp and small angle bracket.

I am going to slowly work through the proposed upgrades you have listed, so again thanks for this write up!
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      09-12-2013, 08:48 AM   #16
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Quote:
Originally Posted by Ramjet View Post
Great write up! I've been looking into this as well but have got no where near as far as you - well done!

I have fitted the M3 front lower arms, including front wishbones, and made a new bracket for the headlight leveling sensor attachment, as you stated it is on the wrong side of the car. Easy done with a hose clamp and small angle bracket.

I am going to slowly work through the proposed upgrades you have listed, so again thanks for this write up!
Ramjet,
Any chance you can post a pic of your leveling sensor setup? I'm currently investigating the possibility of flipping the inner bushings between left and right, but haven't had a chance to give it a try yet.
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      09-17-2013, 08:42 AM   #17
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As many have mentioned, great write up!!! This is the type of thread we need more of.

I love the fact you now have road feel through the steering wheel and reduced understeer/promoted over steer.


Does the car feel twitchy? Do you feel any loss of comfort that's unacceptable? Do you regret any stage of the mods?

I came from an e46 330i and had full suspension mods, control arms, Coils overs, sway bars, end links, trailing arms, camber plates. I loved all the mods and it could still be a great daily driver.

Do you feel with all the mods in hand the z is still good for long trips?


Sorry for the long post, and thanks!
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      09-17-2013, 01:32 PM   #18
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jts1981,
Car does not feel twitchy at all. Had it out on NJMP Lightning track on Sunday and the car was well balanced and had a ton of grip. I don't regret any stage of the mods, but a few things to keep in mind:

- EDC warning comes on every time I start the car. When it becomes annoying enough I'll get the KW module to fix this.
- I had a 2 1/2 hour drive to and from NJMP and the ride was fine. Rough / bumpy roads get annoying and have to drive slower on them.
- I'm running fairly aggressive spring rates (392lb/in front, 672lb/in rear) because I will be tracking the car a lot. For just street use or 1-2 track days a year I would recommend softer springs (something like 280lb/in front and 560lb/in rear).
- I do daily drive this car.

I'll do another post in this thread on springs / shocks sometime later this week. Next up is going to be the rear H&R sway bar, won't have it in time for Pocono this weekend but it will be on before VIR in October

Bill
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      09-18-2013, 09:02 AM   #19
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Bill,

Thanks for the quick response! Sounds like this isn't your first rodeo. We appreciate all your knowledge and thanks for sharing!

Im happy to see someone build a proper suspension to harness the N54.

I have a question about LSD. If you switch to an M3 LSD would you also have to change to a 1M program? Forgive me if I'm wrong but doesn't the e89 have a computer controlled diff, while the M diff is mechanical? Would the ecu need to be modded to keep the system, engine power delivery and traction, in harmony? I worry the stock program and mechanical diff would fight each other with the computer cutting power. This is all speculation by the way.

I think your suspension set up, with fmic, upgraded oil cooler, ecu tune, and LSD would make for an incredible self made Z4M.

Thanks again!
Jake
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      09-18-2013, 12:38 PM   #20
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Quote:
Originally Posted by jts1981 View Post
Bill,

Thanks for the quick response! Sounds like this isn't your first rodeo. We appreciate all your knowledge and thanks for sharing!

Im happy to see someone build a proper suspension to harness the N54.

I have a question about LSD. If you switch to an M3 LSD would you also have to change to a 1M program? Forgive me if I'm wrong but doesn't the e89 have a computer controlled diff, while the M diff is mechanical? Would the ecu need to be modded to keep the system, engine power delivery and traction, in harmony? I worry the stock program and mechanical diff would fight each other with the computer cutting power. This is all speculation by the way.

I think your suspension set up, with fmic, upgraded oil cooler, ecu tune, and LSD would make for an incredible self made Z4M.

Thanks again!
Jake

Jake,
The M3 diff isn't an option, but aftermarket ones from either Quaife or Wavetrac are. No mods to the ECU would be necessary as the EDL (Electronic Differential Lock) on the Z4 is controlled by the DSC system. Essentially EDL uses the brakes to control wheelspin and "simulate" an LSD. Its actually a pretty good system, not as fast limiting spin as a mechanical unit, but better than a normal open diff like on the 3 series. EDL is so good that I'm not likely to upgrade mine for an LSD anytime soon.
I should point out that my car is the N20 motor with a JB4 Stage 2 and upgrading the FMIC is on my winter todo list. Upgrading the oil cooler is not necessary on this engine - even when pushing the car extremely hard on the track oil temps remained reasonable (way better than the N52). I've also installed a BMS oil catch can though as the stock setup does let enough oil into the vent hose pre turbo that it could cause issues.

Bill
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      09-19-2013, 06:34 AM   #21
jts1981
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Bill,
Interesting fact about the rear diff, both non M compatible and that you favor it.

I tracked my car a few times with the NYPCA but never felt the handling was up to par. Perhaps with the sway bars to reduce understeer the EDL results would be more noticeable.

We race on some bumpy parking lots, like Nassau colleseum and the power just couldn't get down to the ground. That coupled with too much understeer made for some pretty weak lap times.

I'm itching to perform the suspension mods. That set up sounds like a complete transformation from fast cruiser to pure driver's car.

Jake
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      09-19-2013, 12:19 PM   #22
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Quote:
Originally Posted by jts1981 View Post
Bill,
Interesting fact about the rear diff, both non M compatible and that you favor it.
Just to be clear, my preference would be a mechanical locking diff (ie. Quiafe or Wavetrac) but EDL works well enough to make up for the loss of traction in an open diff without EDL that the expense simply isn't justified IMO.


Quote:
Originally Posted by jts1981 View Post
I tracked my car a few times with the NYPCA but never felt the handling was up to par. Perhaps with the sway bars to reduce understeer the EDL results would be more noticeable.

We race on some bumpy parking lots, like Nassau colleseum and the power just couldn't get down to the ground. That coupled with too much understeer made for some pretty weak lap times.
For autocross (especially in bumpy lots and not fully prepared race tracks) I would suggest a lower natural spring frequency than what I am running. On a 28i something like 290lb/in front and 560lb/in rear which is closer to 2Hz. Note, this would be different on a 35i due to the higher weight and different weight distribution.

For reference:

28i Manual Trans: 3263lbs; 47.3/52.7% front/rear weight distribution
28i Auto Trans: 3307lbs; 47.7/52.3% front/rear weight distribution
35i Manual Trans: 3493lbs; 48.6/51.4% front/rear weight distribution
35i DCT Trans: 3527lbs; 49.1/50.9% front/rear weight distribution

For each of these you would potentially have different spring rate setups for street, autocross or track. To determine the spring rate required you have to choose the spring natural frequency based on the application. There are several sources online to help calculate spring rates (Eibach has a good doc available on their website).

Street: < 2Hz
Autocross: 2Hz - 2.5Hz
Track: 2.5Hz - 3Hz

These are just basic numbers you can use as a guideline to get started, it may take several attempts to get it completely dialed in. Given the great weight balance on the Z4 it has a lot of potential... When you get your suspension setup tuned you will find the car has tons of grip available.

Bill
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