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05-09-2018, 12:29 PM | #67 |
Track? What Track? I was just riding along . . .
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Dogbone I sound like I'm giving you a hard time, and for that I apologize. To me, your data makes me infer there are negligible periods of material understeer (or oversteer) during your track runs. I definitely see periods of very light front brake pressure absent brake pedal input and no comparable episodes in the rear brake pressure. What that says to me is, you're not activating MDM in any material way. You're driving the car with the requisite skill to maintain relative traction across the wheels within the MDM envelope of intervention.
Imagine instead if you were relying materially on MDM to let stay on the gas during understeer conditions without just driving off the outside edge of the corner. What would happen then? What I want to see before I can understand exactly how MDM works is an oversteer/understeer metric, variations in that metric, and caliper pressures in response. The oversteer/understeer metric would be derived from the acceleration and yaw sensors indexed to the steering angle sensor. It takes a fair amount of processing power to collect and display that metric. Then I want to perform experiments putting the car through a range of understeer scenarios and see what the rear brake activations look like. I can (theoretically, given enough time) wear a single rear brake pad down to nothing in MDM without ever touching the brake pedal. Put the car on a sprinkler-wet skidpad going counterclockwise, maintaining constant steering angle, and then accelerate to the point just shy of terminal understeer. MDM will be grinding away on the left rear brake until I run out of gasoline and stop. Also, I don't have data showing what was going on in my car back when I was using MDM as my nanny and I hadn't learned car control yet. Was I under-braking in the brake zone and tossing the car in too hot, letting front tire friction and heavy MDM activation of the brake pads slow me down enough to get to the apex? Was my acceleration off the apex so over-eager that MDM cut fuel, instead of even attempting to moderate the rotation with front brake application? I'll never know. And one other thing that's completely unrelated to my line of analysis, but about which I'm curious. Your system is measuring X bar of pedal input triggering measurements of Y, Z, psi, and omega. I cannot determine from just the graphs whether there are any functions to be derived from those relationships, but I do see an awful lot of variation. Is that all associated with tire torque variations arising from independent suspension/pavement conditions at each wheel? Or is there MDM-induced variation that's driving up the rear pressure numbers incrementally and eating more pad? My comments here are just spaghetti at the wall, not a rigorous engineering evaluation in any sense. I'm just trying to illustrate some of the ways in which I perceive there is much more to the analysis than: Dogbone's measured experience = MDM doesn't get into the rear brakes much. |
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05-09-2018, 12:44 PM | #68 |
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I guarantee you dogbone has an accurate understanding of how MDM works.
I smoked a set of new brake pads in two track days, mostly because I track with MDM on, and the tracks were hard on the brakes. Took me forever to kill the rear brakes, without finishing a single set of rear pads. Rotors and calipers finally gave up.
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05-09-2018, 06:49 PM | #69 |
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subscribing.. fun thread.
OP - trail brake more, and if you can, soften all your suspension then start adding stiffness back in. see what the results are. i have the same issue btw - mid corner understeer in slow (40-60mph) corners. after reviewing with a friend, we are debating if its lack of camber (im running -3) up front. |
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05-09-2018, 08:09 PM | #70 |
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Two more days to 3 days on the track.
I can't wait to try everything on the thread and the weather looks decent. I drove to client sites every day this week talking technology this and technology that.....and when I get home Thur night.....i will be looking forward to get up at 5am and go driving in circles for three days. If you were looking for sanity in this thread, you are either insane like me, or you need to read Jane Austin instead. |
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05-10-2018, 09:46 AM | #71 | |
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You want to question what I post? Great. Question it. I have no ego when it comes this stuff. I say over and over again on this forum, I am not a motorsport industry expert. I have been learning as I go, and sharing what I have discovered. Not many others are sharing their data here on the forum. But if you're going to say stuff like, "...I perceive there is much more to the analysis than: Dogbone's measured experience = MDM doesn't get into the rear brakes much.", then you need to stop perceiving, go strap a data logging device to your CAN bus, you need to go drive a shit-ton on track and collect dozens of days of hard data that proves something different---because it will take many days and many brake pads to prove your claims. Or, at the very least, you need to provide links to someone else's data. (Good luck finding that.) After you do that, I am HAPPY to listen to any of your conclusions. In fact, I wish more people would do exactly that----post up their data charts. Then there would be more to discuss! But until you do that, all your fancy "psi, Omega" terms and all your other theoreticals and questionings are just a bunch of arm chair grand-standing with nothing to support it. I'll take my data any day over your butt dyno. And-----now I'm done with this thread. |
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05-10-2018, 01:55 PM | #72 | |
Track? What Track? I was just riding along . . .
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05-10-2018, 05:39 PM | #73 | |
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Do you even track bro? |
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05-10-2018, 06:51 PM | #74 |
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05-12-2018, 07:26 AM | #75 |
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[Update]
well softening the sway bar was a good idea. However, adjusting the JRZ proven problematic to the point of mowing some grass at a high speed. Lap times For reference my best time is 1:37.x and it is in general a fast time at NYST on 200 tires. Yesterday i hit multiple time 1:38, 1:39 and 1:40. But no cigar. Best laptime was not in the cards Track temperature were cold at 70, 80 and afternoon got to 102. Ambient was 50s and sunny JRZ Settings Starting at a JRZ engineers recommended settings created two issues. 1. At the front straight bump the car got unsettled. At the Wheely hill the car landed and was unstable. Both high speed. This is were I made a mistake that could have been disastrous but i got lucky and no issues The mistake I made was to add more rebound to "settle" the car. The thinking was that the car was compressing and releasing too quickly creating a pogo effect. I was increasing rebound to try to slow the return. An astute observer approach me in the afternoon and say my car, especially the rear wheels were off the ground at the front straight at 130mph. Hmm. His recommendation was to REDUCE rebound to allow the wheels to return quicker. It was a spot on suggestion. The Last session yesterday I dialed back the rebound to 1 in the rear and 4 in the front. Changing nothing else. The car was much more settled. I was not going as fast (mostly 1:42/1:43) but it felt better. The last session was open track and I head many many laps with track basically empty. Today I am mounting inexpensive set for a rainy day and will continue working out the suspension. I am happy with the Hotchkis set to front second from softest and rear on the softest setting. The rest of the 40mph problem will come from driving better |
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05-12-2018, 09:02 AM | #76 |
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it sounds like you are happy with the new settings. so now i'll ask this- why didn't you pb? what was better about the 1:37 lap?
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05-12-2018, 04:10 PM | #77 |
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05-12-2018, 04:32 PM | #78 |
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[Update 2]
Today was a second track day out of three. Yesterday I confirmed that my sway bar settings are good and discovered that I was adjusting my rebound the "wrong" direction Today was non stop rain day and few showed up. I had to change my tires to the cheap "closeout" tires I bought from Tire Rack. The tire shop opens at 8 and I was not first on line. I was able to get to the track to catch the 11am session. nobody showed up because of the forecast. so the Motorcycle guys got 30 min, and us car guys got 30 minutes on the hour. Then at 2pm NYST unleashed us to the track until basically I ran out of gas. Getting the option to run open session on the track is my dream come true. I can try what ever I feel like without running out of time. My goal for this rainy day was to run on MDM and not activate traction control. My rear rebound was on 1 and the front was dialed back to 3 compare to 4 yesterday's last session. I run gazillion laps on 2:03 and toward the end ventured into 1:59 with out activating the MDM. It was a divine experience. Since I am coming off 10 years of riding a Ducati on track days, doing a track day in the rain in a car was just as fun as in the dry. Unlike motorcycles. The biggest revelation was actually driving home. My main reason to buy JRZ 4-way was the separation between High Speed dumping (a bump in the road) and Low Speed damping (transition left/right and a wave like surface. NyST is pretty smooth so my dumping (HS) is set to pretty soft and jumping off curbs seems to be fine on a low settings of 3 or 4 out of 14. So far the LS dumping was set to 10 then 9 then 8. Unlike the HS dumping the LS starts high (10) for less effective and becomes more effective going down (1) I was driving home and was thinking, the low transition left and right needs some dumping. So I stopped by the side of the road and changed the front from 8 to 7. This had the effect of pushing the EDC to sport from normal. Hmm, that has potential. So tomorrow forecast is dry and I am going to start the day as is with LS set to 7 front and 8 rear and will see how it feels. . . . |
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05-12-2018, 04:46 PM | #79 | |
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So your rebound settings seem underdamped to me. |
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05-12-2018, 05:55 PM | #80 | |||
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I think his point was that getting the fundamentals down will let you extract the most performance from the car, especially with a sophisticated suspension setup. We can all improve. It pains me when I see guys at the track who continually sink more and more money into the car (or worse yet, buy an even faster one) hoping it will magically fix a bad habit they developed. I'm also in agreement with what roastbeef said: you are very fixated on the suspension which is now a sunk cost. I'd challenge you to drop down one class at the next track day and ask for an instructor to ride-along. What's the worst that happens, they tell you, "wow, great driving, you don't need my guidance -- I'm moving you into advanced"? Quote:
Just to be clear, MDM doesn't always flash the light when it is intervening. As some of the previous discussions have shown, it will do very subtle things like tap a single brake or reduce power very slightly. It's supposed to be largely transparent....which is a good and a bad thing. Good because you still have a safety net and have a computer that can react faster than you, do things you can never do, etc., but bad because it can hide/compensate for mistakes. Additionally, it can cook the brakes, as mentioned above. When the light flashes, that is a more severe event where the computer had to do something drastic. Can you clarify what you meant by "without activating the MDM"?
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05-12-2018, 07:37 PM | #82 |
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>> I'd challenge you to drop down one class at the next track day
I have been going with instructors last year and this year and every time I can get one. I like to learn from anyone that offers knowledge. On NYST days we have one car session per hour and three motorcycles sessions. No classes. When I join a track days of other organizations I am typically in the advanced group and I do alright. It is my goal to learn my suspension, one click at a time. And I share my observations on this thread. I hope it is ok with members of this forum. |
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05-12-2018, 07:53 PM | #83 |
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>> . It pains me when I see guys at the track who continually sink more and more money into the car (or worse yet, buy an even faster one)
I bought my Ducati 996S in 2001 and rode it until two years ago. I loved every minute I spent riding it. I did not have a need to buy anything faster or better. I knew it like the back of my hand. Now I have the M3 and I don't need anything else. My intention is to enjoy it as long as I can and know everything about it. I am not really clear why there is a resistance to learn the way I like to learn something. I am not in a rush to figure it out. I want to know how each setting feels. And I will try all the combinations. Why not? |
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05-12-2018, 07:59 PM | #84 |
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>> I am no suspension expert but I typically run about 2x more rebound than compression. So typically 6 clicks (from full soft) compression and 12 clicks rebound and then usually a bit more on both. I run MCS 2WNR.
I am in constant contact with JRZ engineers. The 14-52 is not the same as the other models and you can't extrapolate how to set it up based on other models. |
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05-12-2018, 08:23 PM | #85 | |
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What are your current 4-way settings front and rear? |
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05-12-2018, 09:04 PM | #86 |
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>> What are your current 4-way settings front and rear?
This is what I am starting the dry day tomorrow: Front: Shaft 4, Rebound 4, LS 7, HS 4 Rear: Shaft 2, Rebound 1, LS 8, HS 2 It is softer then JRZ start recommendations. Specifically, JRZ recommend LS on 9. But I have a hunch that once the rebound is good, the LS is what will get me stability I am looking for since NYST is pretty smooth so no need for HS dumping. Will see tomorrow. |
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05-13-2018, 02:24 PM | #87 | |
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Because you are trying to jump into a very advanced topic (suspension tuning, and a 4-way system at that) and then arguing whenever anyone tries to provide an alternative viewpoint. Like the other poster, I'm done posting in this thread since it seems like you're only interested in validation of what you've already made your mind up about. Also, please use the "quote" feature so that your posts are easier to read. This thread is extremely hard to follow.
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05-13-2018, 08:11 PM | #88 |
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[Update 3]
I am happy with the setup. Today was a dry day and it was my second day on a set of tires I bought cheap at Tire Rack. 275/30ZR-19 KUMHO ECSTA PS91 2014 PRODUCTION XL $126.30 295/30ZR-19 YOKOHAMA ADVAN SPORT V105 2013 PRODUCTION XL $166.00 The best lap time I was able to get on these was 1:43.69 which is fine. The Hochkis sway bar setting to softest in the rear and second from softest in the front. Front JRZ were set to Rebound 4, Shaft 4, Low Speed 7, High Speed 4 Rear JRZ were set to Rebound 1, Shaft 2, Low Speed 8, High Speed 2 3PM session track temperature was 96f and ambient low 60s Coming off the track tires temp were (outside, middle, inside): Driver Front: 153, 153, 158 Pass Front: 150, 153, 150 Pass Rear: 131, 137, 133 Driver Rear: 109, 132, 134 The hardest working tire at NYST is the passenger front. I was happy to get fairly even temp On Friday I was on the last day on a set of Yoko ADVAN Neova AD08R and while I was not happy with the suspension setup, my times were 1:38-1:39 with multiple times at 1:40. So I have one more day on the cheap tires I bought to finish them off, and I have a new set of the ADVAN Neova AD08R waiting to be mounted. It will be very interesting to see what the lap times will be with the ADVAN Neova AD08R and the current suspension settings. Here is two laps from today, including the 1:43. The Subaru I am chasing is on slicks. . Last edited by rhyary; 05-13-2018 at 08:19 PM.. |
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