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05-02-2017, 01:32 AM | #1 |
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Drives: 2008 BMW 135i (E88 N54 6AT)
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Complete M3 swapover, or just fix the shortcomings of stock?
When I bought my 135i, it was a coin-toss between this car and a Supercharged 450rwhp E46 M3 SMG convertible. I love my car, but I’ve been struggling with buyers remorse since the purchase.
I’m now FBO with a JB4 tune, so about 400rwhp. My end-game is 500rwhp – upgraded turbos, direct injection meth and a fuel-it stage 2 for E30 blend. My current limitation is that I can't even get 400rwhp down with the stock suspension/diff (let alone going for more). My previous experience has been 100% AWD. I’m just learning how to handle a high-powered RWD, and thus far have tested the 135i on the street with pretty average tires and found its handling near the limit to be bloody unpredictable. Stickier tyres are a good answer, but they actually make the problem worse - an unpredictable car on a corner at 100km/h is a lot more dangerous than on that's unpredictable at 50km/h. So, in a previous thread, I asked “what would it take to make a 135i handle like a Porsche boxter”. With this criteria, I’ve been spec’d: Wavetrac LSD, M3 Control Arms, M3 Front & Rear Sway Bars, M3 rear subframe bushes, ECS rear trailing arms, M3 lower camber link conversion kit, Megan Racing rear kit (rear wishbone, guide rod and tie control replacement) and four BC ER Coilovers. Now, I get power mods. I’ve always understood them. But suspension is new to me. I’ve spent the last week reading everything I can and from what I’ve found installation looks like this: Balance the car on scales to get static corner weights with 25% of the car’s weight on each corner. Adjust ride height as low as possible without it causing issues, adjust spring rate to as low as possible such that the car doesn’t bottom out on harsh bumps, adjust dampening to match car and driving conditions, adjust rebound to match car and driving conditions. Get sway-bars which are the right size to provide the best balance of body roll / grip without lifting inside wheels. Adjust caster, camber and toe in/out for best results. Test, adjust, retest, readjust. Any change to any one of the above variables will affect all others. I will track this car, but probably about twice a year. I won’t be insured on the track (it’s just not possible in Australia) and I can’t afford to write it off. So, I’ll never be putting this car on the track competitively. … now, I live in a provincial area and don’t have a great workshop, so I’ll be paying labour for installation of all this kit. In the past, I’ve found when you’re paying labour it’s better to just spend a lot more and get the right parts all at once and have them installed ONCE, than it is to do mods bit-by-bit, but I’m really not comforted by anyone who says they’ll do the alignment for me for a couple of hundred dollars on their laser alignment system. So, here are the questions: 1) Can you do this sort of major suspension swapover then just dial-in the recommended settings from the forums or OEM spec and expect to see a drastic improvement in handling? 2) Is doing this going to be noticeably better than just upgrading the LSD, bushes and control arms of the stock setup? 3) Can a normal regional mechanic or tyre/suspension shop adjust everything above on their laser alignment equipment and give you a car which is _almost_ as good as what you’d get from an expert? 4) Basically: Given the circumstances, am I just better off addressing the 135i shortcomings (LSD, bushes and control arms) and spending the money I save on meth, stage2 lpfp and an upgraded oil cooler? |
05-02-2017, 08:22 PM | #2 |
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1) Yes, definitely
2) Yes, the stock springs and shocks are purposely soft to compensate for the rock hard runflats, hence the handling will be soft and wallowy until they are upgraded. 3) Yes, provided you give him what settings you'd like.. 4) No. Handling upgrades should always be done before adding power, otherwise you end up with a dangerous, unstable beast ianc |
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05-02-2017, 09:51 PM | #3 |
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From one circuit track guy to another this is what I would change:
Use whiteline (or nothane in Aussie might be even cheaper) instead of M3 rear subframe bushings. They are essentially same in function but slightly cheaper for the part but most importantly VASTLY easier to install. As far as arms. I would get M3 front tension and camber arms. In the back I would get M3 guide rods, and Megan toe links only. If you really feel like upgrading the upper camber arm go M3. Skip the rear trailing arm that will do nothing except actually add a bad failure mode to the rear if you hit something. Also skip the lower rear camber arm. If you swap to that lower M3 arm you will need to buy a coilover kit with M3 rear struts and 135i fronts. Keep the 135i rear lower arms and just buy 135i coilovers. Also replace the upper strut mount in the rear, many of use Monroe upper mount kit because it cheap (like $20 usd) and is much less compliant than stock . For coilovers I personally would get something other than BC. One of the Koni single adjustable kits, or KW, or ST coilovers kits will be only a little bit more money but much nicer set. Use the money I saved you above in arms and bushings to get nicer coils. As for the questions: 1) Yes 2) Yes 3) Someone that knows the chassis well is always best. However the final settings really depend on the desired response, street ability, etc. If you just want to use a generic spec from the web (which is probably fine if you don't have a preference of your own) then likely a generic shop can do it. I would find one that has scales and can properly corner balance the car for you though. 4) As the above poster said. In terms of on track, tires, brakes, and suspension are all more important than outright power. Edit: Some other thoughts. I honestly like to try to start with just a proper setup on the coilovers without messing with swaybars. Many times they are simply unneeded with a good set of dampers and correct spring rates. So again I would say take the money you plan to put in swaybars (which is a PITA on labor in the back) and instead spend it on a good set of coilovers. Finally on the power front. Not sure if you have an N54 or N55 but in general a ECU flash tune will be smoother and more predictable on track than a JB4. I run flash tune only (MHD) nice and linear, smooth, and controllable. As you said it's all about control at the limit of adhesion on track. Last edited by WhatsADSM; 05-02-2017 at 10:02 PM.. |
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05-03-2017, 12:39 AM | #4 | ||
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Drives: 2008 BMW 135i (E88 N54 6AT)
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That setup would save me a few thousand dollars! I recon' I'll give it a go. Just to clarify, front camber arms are one and the same as front control arms? As an aside, I've got the JB4 with the Back-end Flash, and I would say it's 1,000 times better than the JB4 alone. I like the JB4 - I don't know how much extra safety it gives me, but I've got the bluetooth gauges and have plans of running stage 2 turbos, meth and flex fuel ... I know you can do all those things with only MHD, but the JB4 seems to have more functionality and protection. I doubt I'd go out and buy one new today, but since I've got it (with the backend flashed using MHD so I get exhaust burble and the new 'sport' cooling features of MHD), it'd seem to be a backwards step to go pure MHD. |
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05-03-2017, 01:54 AM | #5 | |
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05-03-2017, 09:18 AM | #6 | |
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And yes there are two "camber arms" up front stock. Replace both of them with M3. It gives you much better bushings as well as a little extra negative camber from the lower arm. |
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05-03-2017, 09:35 AM | #7 |
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Not equating this to a full M suspension swap, but it is a tremendous upgrade over stock.
Rear: https://www.ecstuning.com/b-trw-part...3322283547kt4/ Front: https://www.ecstuning.com/b-trw-part...1102283577mkt/ Front sway: https://www.ecstuning.com/b-genuine-...31352283965kt/ Subrame bushings: https://www.ecstuning.com/b-superpro.../spf3946k~spr/ 1M strut bar: https://www.ecstuning.com/b-genuine-...51618051973kt/ Rear upper shock mount: https://www.ecstuning.com/b-powerfle...fr5-416x2~pfx/ Dinan fixed camber plates: https://www.dinancars.com/product/d1...0i-335i-335is/ Megan rear trailing arms, if you drop too low stock wont let you set correct tow - https://www.ecstuning.com/b-megan-ra...FUlqfgodQKwIFg Shocks/springs of your choice LSD of your choice (have had great luck with wave trac This set up will blow your mind |
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05-11-2017, 06:12 PM | #8 | |
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05-11-2017, 10:12 PM | #9 | |
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06-05-2017, 06:12 PM | #10 |
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Are these acceptable for the rear subframe bushings? http://www.suspension.com/kdt917
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06-05-2017, 06:40 PM | #11 | |
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06-06-2017, 11:21 AM | #12 | |
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Another option is AKG, they make a similar 2 piece poly bushing as well. |
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06-06-2017, 11:25 AM | #13 |
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Awesome, thank you for verifying. I've been doing a ton of research on here and other N54 sites and I had found another set but they are about twice as much. Definitely not going with the M3 ones as I've read they are quite a bit more difficult to install. Cheers
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06-10-2017, 12:04 PM | #14 |
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I installed all 1M parts from, most came from 2 donor cars with less than 5000miles on them. Front and rear of the car (including steering rack) was less than $1500, making the work quite cost effective
A few pictures here http://s240.photobucket.com/user/Griff50078/story I love the way the car drives now |
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01-27-2018, 08:29 PM | #16 | |
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The same lower camber arm is used in the e9x, 128i, and 135i. A different lower camber arm is used in both the M3 and the 1M. An M3 lower camber arm drops right into an e9x. Therefore an M3 lower camber arm swaps right into any 1 series.
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