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05-04-2015, 06:58 AM | #177 | |
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05-04-2015, 09:21 AM | #178 | |
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05-04-2015, 12:21 PM | #179 |
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1) the car doesn't ride on the bump stop in a maximum lateral-g steady state turn (but can when a bump is encountered in a turn)
2) the bump stop prevents any part of the suspension from bottoming out (notably the springs) under the "worst case" bump event My front suspension violated 2) last year in that it could coil bind under some reasonably probable conditions. Therefore I was not using the bump stops properly to prevent this. |
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05-04-2015, 04:07 PM | #180 | |
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1) The simple corner characterization of a turn-in followed by a constant radius at constant speed followed by acceleration and unwinding the wheel at the exit would imply that the minimum (apex) speed would be sustained for a bit before accelerating. This isn't what is shown on most corners, because I am driving them "parabolically" to fill out the edges of the friction circle. This implies a measure of trail braking on virtually every corner and it represents the true "racing line" for many corners. 2) Corner 1 (red) has identical apex speeds between the red and blue runs but the red run picks up the throttle a bit faster, then has a lazier transition to brake. 3) Corner 2 (red) is a carousel, so there is a section of constant speed. On the red run I find a way to get on the throttle sooner, which improves my run down the next straight. 4) Corner 3 (red) is driven parabolically on the blue run but as a carousel with a section of constant speed mid corner on the red run. The red run has a slightly higher apex speed which is a gain, but a slightly weaker acceleration on exit for no net difference between the two approaches. 5) Corner 4 blue run is driven with a downshift on corner entry which permits a stronger acceleration on exit and use of an upshift in lieu of a lift on the entry to the second half of this corner. This produces a gain over the red run's 3rd gear with a lift approach. 6) "Corner" 5 blue has a higher entry speed on the red run, less lift mid segment and more commitment to the approach to corner 6 for a net gain for the blue run in this section. 7) 7 blue is a true corner but 8 red is not because it can be driven flat. The blue run handles this section better with a higher apex speed at 7 which provides and enduring benefit all the way to 9, where again blue has a higher apex speed. This is where the laps diverge to different paths but the elapsed time to this point is identical for both laps. In truth they are not strictly comparable in terms of effort. The blue run was a 100% race effort. The red run was a fast lap with a passenger. This hints at a net improvement in the car since last year. What is never apparent in reading this kind of data is the effect of elevation change, track camber change and general track condition on the result. These factors often affect the actual speed attainable on any given corner or the braking available in a braking zone, or the acceleration available out of a corner. |
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05-05-2015, 05:28 AM | #181 |
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05-08-2015, 12:45 PM | #182 | |||
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05-08-2015, 12:46 PM | #183 | |||
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I had previously read that post and noticed that you mentioned a tyre rate of "approximately 2000 lb/in" but in the above quoted post you used "2200 lb/in" so I was wondering how you had come to use 2200 lbf/in rather than 2000 lbf/in? And from which table did you draw the 2200 lbf/in value from? |
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05-08-2015, 12:48 PM | #184 | ||
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I had built in a lot of assumptions into my calculations, some of which I know may not be as close as what is preferred but, for the purposes of my example, they would have to suffice. As an example, all my suspension components have been replaced with M3 and aftermarket and I use medium compound R-comp / semi-slick tyres on the track that can handle (or should be matched with) a higher spring rate. I realise theory is just that and it's no substitute for real-world experiences but it's a good starting point to know in what direction I need to head. Being outside of the US, the cost involved in testing even a small range of options is exorbitant, given our poor exchange rate and high shipping costs, so theory and research play an important part in attempting to get it right the first time. There are two or three 135i race cars in the national professional categories but I don't think they'd provide me with the details of their suspension setup. I'd think those secrets would be tightly held. Other than at a professional level, there aren't many 135s, going to the same extreme, being raced here. From my research, I have come across several other US-based 135i race cars that have published their spring rates and they were as follows: Front / Rear 650 / 700 560 / 800+ 550 / 850 700 / 850 Using the second and third spring rates, since they have the most commonality, equate to a front/rear spring rate of 100/150 N/mm, which would have a 0.45 Hz difference, which is more than my target range but it worked for these cars. To get back to a maximum 0.3 Hz target ride frequency difference, the spring rates would need to be increased to a 100/180 N/mm pairing or decreased to 90/160 N/mm. All in theory, of course. |
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05-08-2015, 12:49 PM | #185 |
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Do you have anything else that you could add in reply to my posts about
static spring load, spring preload and stroke and spring compression? |
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05-09-2015, 08:41 AM | #186 | |
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http://bndtechsource.ucoz.com/index/...alculator/0-20 |
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05-09-2015, 12:20 PM | #187 | ||
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I had also come across that link last year when I was looking to calculate contact patch area and factors that could impact its size and shape. |
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05-11-2015, 09:40 PM | #188 |
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AIM Solo DL V2
I have previously documented the installation of my AIM Solo DL data logger:
http://www.1addicts.com/forums/showp...0&postcount=60 When I did this, I didn't bother connecting it to power as the Solo has an internal battery with a decent battery life. I have run the battery flat a couple of times though so I decided to make that connection in the fuse box using a Littelfuse "Add-A-Circuit". http://www.littelfuse.com/~/media/co...fhm02fha02.pdf That process has been documented elsewhere on the Forum, but I want to add a few details. My original installation located the Solo beside the LH A-pillar. What I noticed was that the off-center location showed up in the data when doing skid pad testing as an error in path radius of half the car width. Although this might be splitting hairs, the device should really be located on the vehicle centerline. So while relocating the wiring and connecting to power, I moved the harness to the center of the car. That required a small notch to be filed in the center air vent. I took power from the switched power circuit "8" in the fuse box behind the glove box, using an Add-A-Circuit device. As there are no convenient grounding studs in the vicinity, I added one to the steel dash support structure. It is worth examining the internal wiring of the Add-A-Circuit to understand the right and wrong way to insert it into the fuse box. If you are adding to an existing active circuit the device will work in either orientation, but the correct one keeps the original and new circuits isolated from each other. The other orientation does not. If you are inserting the device into an empty space on the circuit panel, it will only work if inserted properly. When using circuit "8" as a power source, the bottom pin in the box is the live one and the top one the load, so the new circuit wire should be on the top side of the Add-A-Circuit when it is inserted. |
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05-30-2015, 05:36 AM | #189 | |
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Did you end up fitting the matching front bar? |
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05-30-2015, 06:53 PM | #190 |
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I had no issues with the rear H&R bar fitment. I am still on the OE front bar. I feel I have enough total roll stiffness with this arrangement, and I like the handling.
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09-10-2015, 12:40 PM | #191 |
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How is everything performing? Are you making any adjustments?
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09-03-2016, 09:34 AM | #192 |
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Just found this thread linked from an autocross forum, lots of great testing going on here!
I especially love the swaybar testing you've done. I tried something similar because I didn't trust the equations I found online, but my resources for doing the testing were not nearly as good as yours, and I wasn't able to get good data over a few hundred pounds of force, because the wood bench I had it bolted to would twist! You can read about my journey here, if you have some time: http://www.bimmerforums.com/forum/sh...-STX-330-Build Some thoughts on what you're up to, based on extensive autocross testing on my E46: 1. Coil bind or even too much bump stop engagement is death for grip. You seem to know this intellectually, but I'm not sure you're focusing enough on measuring whether and how much that's actually happening on your car. A shock pot tied to your data logger is the best way to do that, but a really cheap/easy way to measure the maximum travel of the strut is to just use a tight zip tie on the strut shaft 2. Tire tech is moving very quickly, and those RE71R's can generate a LOT of grip. The ride frequency ideals that you read about in books assumes a certain level of grip that is a lot lower than what you're working with today. The more grip you have, the more the car will roll, and the more likely you are to see coil bind or bumpstop. 3. It's easy to assume that if your front outside wheel can accommodate all the weight of that end of the car without coil bind, you should be golden, because you probably won't transfer 100% of the load of the front end, and that's true, but often you're braking going into that turn, and so you get some weight transfer from the rear as well, and then you hit a bump and you're screwed. So test, test, test! 4. I'd recommend some testing days where you bring extra springs and bars, test one change at a time, and keep a lot of records of the results. Test the ride height too. You're correct that too low is no good, but too high and you're giving up grip as well. Gotta test to find the right balance. I ended up with 600lb springs and a 30mm bar up front on my car, with older tires that didn't generate as much grip as your RE-71s and a lighter car. (though wider tires and wider wheels) You might not need that much on your car due to strut travel differences, that's hard to say, but I'd just encourage more real world testing. I'm quite sure you can manage more than 1.2 G's in that car. |
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09-14-2016, 12:48 AM | #193 | |
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Any info is appropriate. Great job to op
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///M3... Don't want more power, Just want it to turn sharper one step closer each time. -Ohlins TTX Raceline, PolePostions seats, Akrapovic EVO, ARC-8, 1/2 Cage, Seat Delete, Stoptech BBK, solid Subframe and diff bushing, spherical bearing on everything.
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09-18-2016, 01:38 AM | #194 | |
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///M3... Don't want more power, Just want it to turn sharper one step closer each time. -Ohlins TTX Raceline, PolePostions seats, Akrapovic EVO, ARC-8, 1/2 Cage, Seat Delete, Stoptech BBK, solid Subframe and diff bushing, spherical bearing on everything.
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10-25-2016, 09:54 AM | #196 |
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fe1rx
So I've read through this thread, and I was wondering if you could reiterate a few points. Stock front camber is approx -.5*. I've installed m3 front arms and removed the strut alignment pin allowing me to get -1.5* up front. I zeroed out front toe. According to what your saying, when my coilovers arrive, and I move to -2.5*, I should dial in .1* toe out per side to maintain steering feel due to tire construction? Does dialing in that toe out offset also come with the typical effects of running toe out such as less stable straight line stability? Also, I have no idea if MFactory took anything you've come to realize as limiting factors of mass produced suspension setups into consideration when they developed thier e90/e82 coilovers. I'll have to look into tire fitment/spring perches/and top hats once they arrive. When you moved to a shorter spring did you end up limiting your overall strut travel as a side effect? Last edited by bNks334; 10-25-2016 at 08:43 PM.. |
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10-26-2016, 06:22 AM | #197 | |
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By careful selection of the spring and preload I was able to avoid coil binding that could have become the travel limit. I have a very narrow range of acceptable preloads though. This is something you need to look at carefully with a short spring. |
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03-04-2017, 01:06 PM | #198 |
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Dear fe1rx
I am tracking my 135i e88 twice per month. I have the same MI00 system, and i am about to order my swift springs. My semi slick tyres are 255 35 8.5" r18 front and 265 35 9" r18 rear. Will go for a square setup with 245 649 r18 slicks soon. My camper plates are from Vorshlag. Would you recommend the 60nm in front and the 140nm in the back for my car as well? Thanks in advance for your reply and detailed work! |
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