06-03-2017, 06:35 AM | #23 |
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There are threads on the pros and cons.
http://www.2addicts.com/forums/showt...=982936&page=5 This thread is about changing the final drive ratio. Turner Motorsport who knows what they are doing highly recommend the Wavetrac. I am absolutely happy with my choice but haven't compared side by side to other LSDs. http://www.2addicts.com/forums/showthread.php?t=1113986 There is not much that can go wrong changing a diff so warranty wise it doesn't have a lot of implications I think. |
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06-03-2017, 07:38 AM | #24 | |
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So from what I gather with the Wavetrac you had to send them your stock diff for modification since it is a welded ring gear or do they send you a unit and you send back a core? Also, I don't see an M240i application with the 2.81 ratio. EDIT: Nor the Wavetrac option at Turner.
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06-03-2017, 10:47 PM | #26 | |
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06-04-2017, 08:02 AM | #27 |
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"Awesome, thanks!
So from what I gather with the Wavetrac you had to send them your stock diff for modification since it is a welded ring gear or do they send you a unit and you send back a core? Also, I don't see an M240i application with the 2.81 ratio. EDIT: Nor the Wavetrac option at Turner." Yes, Diffsonline did put a diff together according to my specs. You send the original back after the install or there is an additional charge. Turner doesn't do the diff itself but works with diffsonline and wavetrac. They may even run some of the wavetracs in their race cars, not sure. I went with a 3.46 ratio. I was worried it may be too extreme but now that I have experience would even consider going more aggressive. I had a sligthly larger diameter winter tire for a while and didn't like the change in final drive ratio. I should mention that I saw the need for a higher final drive ratio in my other BMW too. Which spins to 14200rpm. I like revs, what can I do . |
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06-04-2017, 08:29 AM | #28 | |
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The reason I ask, is because I did a simulation on Autotest2000 with different final drive ratios, and the results were not in favour of 3.08 or 3.54 over the stock M1/240i 2.81 (auto), both slower on the 1/4 mile. |
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06-04-2017, 01:44 PM | #30 | |
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I would be curious to see what Autotest2000 says about the 6MT going to a 3.23 or 3.46 and how that impacts the M235/M240 over the stock 3.08 gear. The M2 6MT runs a 3.46, but the overall tire diameter is nearly 1" taller than the M235's thus much of that additional gearing is lost. I find the M235's gearing to be just a tab too long. I was thinking on doing a 3.46, but when it's all said and done with an LSD, you're out $3,000+. I have found that the 3/4 series F3X 6mt cars run 3.23 gears as stock and I thought maybe I could just buy the M Performance 3.23 LSD setup from the 3/4 series and swap it into my M235. That setup is only around $1,800 plus I'd get a little more torque multiplication. I would assume the F3X diff is the same housing as the M235/M240s. Why wouldn't it be? That's something I need to confirm some way. |
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06-04-2017, 01:49 PM | #31 |
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I'm curious to those that say the handling and feel is just terrible without a LSD: Are you guys driving in DSC Off? Because that is the only mode where the electronic LSD is in operation. All other modes the diff acts like a true open diff and the nannies are interfering and making things worse in almost every situation. DSC Off makes this car a different animal. Power comes on harder, faster, power is not cut, and the easily rotates when needed. The car is simply more eager and aggressive and IMO, easier to control.
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06-04-2017, 02:46 PM | #32 | ||
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Autotest also has an 'optimum parameter' function, so you can set a test up and it will graph what diff ratio will run the quickest times. But as you say, it doesn't always follow that a higher ratio gives more acceleration. When I picked up my 240, I immediately started looking for a spare diff to convert to LSD. I couldn't find any 140/240 diffs on eBay, but came across plenty of 3.08 versions. I quickly ran the numbers in autotest, thinking that the shorter gearing would be a plus. Turns out the figures were worse. As you mentioned, 1st gear on an auto is already a high ratio, making it higher would almost make it useless for traction and real forward progress. If you have to short shift to get out of it, then all the good work is undone. |
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06-04-2017, 03:14 PM | #33 | |
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One, it is not always practical to drive with DSC off, so even if there is a mode that performs better, you are not always in it when things get loose. I agree with you how DSC interferes. It will try to kill you if you attempt to drift with it on. Two, the e-diff is electro mechanical, and as with everything of such a nature, there is delay in the closed loop feedback together with a poorly weighted response. By that I mean it allows things to get out of control a certain amount, but then its response is usually overly heavy handed, which is not the best for smooth consistent feedback. Once you fit a mechanical LSD, you quickly realise how slow the e-diff is at reacting, it is night and day. |
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06-14-2017, 09:33 PM | #34 | |
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06-15-2017, 02:42 PM | #35 |
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No, but I have just run them.
I set the power in Autotest exactly as a 140i dyno plot, which means I have them set accurately for each 500 rpm point. (358 hp @ flywheel). Setting a 0-100km/h run (62mph) I get the following: Stock diff________2.81________4.55 seconds Alt BMW diff______3.08________4.46 seconds Best ratio________2.54________4.43 seconds (Hits 102 km/h in second gear) When I set the speed to 100 mph so a 0-100mph run, I get: Stock diff________2.81________9.87 seconds Alt BMW diff______3.08________9.77 seconds Best ratio________3.39________9.63 seconds So there you have it. A 3.08 (manual or x35i diff ratio) is marginally quicker than the long legged 2.81. When I used just a single peak hp / peak torque data point, the results were slightly different. Let me know if you want any other ratio's run through the grinder. Last edited by NISFAN; 06-15-2017 at 02:58 PM.. |
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06-15-2017, 07:21 PM | #36 | |
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I emailed Dan at Diffsonline and he said he's done 18 M240i's and the 3.08 ratio has been very popular. He has both in stock, ready to ship if anyone is interested. He'll do either at the stock price (no additional charge).
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06-16-2017, 12:23 PM | #37 |
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Just for street use, new wheels and tires would make a nice cosmetic change. Neither will do a ton for performance.
For track, that LSD will make a noticeable difference and last much longer than a set of tires (hopefully!) But track slicks make a hugeee difference. |
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06-17-2017, 11:40 AM | #38 |
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While I'm sure that LSD would be a great upgrade, don't underestimate the benefit of bigger rubber on this car. I upgraded my setup from MPSS 225/245 to MPS4 S 235/265, I've noticed a dramatic difference in stability. The original setup was a slave to the traction control, with spirited driving, the traction control very often interfered with handling. Now with the new setup, I have to really push it to engage the traction control. IMHO, this car has too much torque for the stock tires, even the BMW 3 series with less horsepower and basically the same weight comes with 255s at the rear.
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06-17-2017, 05:16 PM | #39 | |
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06-18-2017, 01:16 AM | #40 | |
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Last edited by AlpsRider; 06-18-2017 at 01:21 AM.. |
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06-19-2017, 05:27 PM | #41 | |
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09-25-2017, 07:09 PM | #42 |
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Just pulled the trigger on a Wavetrac LSD from Diffsonline. Stepping down to a 3.08 final drive ratio from the 2.81 in the auto. I'll report back once I get it installed.
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09-26-2017, 12:28 AM | #43 |
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09-26-2017, 08:02 AM | #44 |
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Nice! We'll have to compare notes. My OEM LSD gets installed today.
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