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04-29-2018, 08:12 AM | #1 |
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Hey all track experts.
i just finished my first 2018 track day. I have a theoretical question trying to figure out how to improve the suspension setup to go faster thru the slow turns. The main issue I am trying to address is that I have 2 long left turns and one long right turn that i have got to move the 40+ mph to 50+ mph I know that everything is "it depends" so understanding that, here is my question. My front Hotchkis sway bar is set to the third position at 96% stiffer than stock. If I move it back to the second position, at 73% stiffer than stock, would it help the understeer at slow turns. |
04-29-2018, 08:39 AM | #3 |
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04-29-2018, 08:58 AM | #4 |
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I am already maximizing my trail braking to the best of my ability. I am trying to focus the discussion on mid corner. I am also happy with how the car track out once I am on the gas.
The specific issue that I have is that when I am done trail braking and before I can hit the gas, i am waiting at least a second or two for the car to point in the direction I can hit the gas. I can trail brake further, but that will get me into the 30mph. Keep in mind I have tried many strategies. And for now, what I want to improve is the 2 second I am hanging at 40+ mid corner waiting for the car to come around. I also must add that for the last three sessions i went with traction control off. I finally gather my courage to do so. The first three sessions my MDM was on and the traction control light was on for the entire lap. So I said "it's time" The feeling of improved connection to the car and the pavement is unreal. all of a sudden, everything you do with the gas paddle, steering and brakes has direct effect. Best way to describe is that with MDM on, it is like eating a candy with the wrap still on. somewhat muted taste. Hopefully this make sense to you guys |
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04-29-2018, 09:12 AM | #5 | |
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Also I am not saying trail brake all the way through the corner but be strategic about it. We had a turn at TWS that was slow constant tight radius. The DE line was was to make it a triangle. Brake deep and rotate the car back. My buddy helped me with a much faster line which was to approach it wide and come in at about 1/3 and then trail brake to 1/2 and then throttle steer - chop the throttle as necessary to rotate the car. I crushed everyone in that turn. |
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04-29-2018, 09:17 AM | #6 |
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Knee jerk response is "less swaybar." What else is going on with the suspension (settings)?
When are you getting the mid corner understeer? In both turns, or after the switchback? Is the understeer only in the lefts? Initial impression is less swaybar, maybe more front spring, and make sure the swaybar doesn't have any preload.
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04-29-2018, 10:47 AM | #7 |
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From what speed are you braking down upon entering the turn?
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04-29-2018, 11:13 AM | #8 |
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I am going from 131mph into 40+ mph
I have created a video of a hot lap. I will upload it to youtube and add the link here. here is the braking acceleration heat map: |
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04-29-2018, 06:40 PM | #9 |
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What's your wheel and tire setup?
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04-29-2018, 07:14 PM | #10 |
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Here is the link to a hot lap.
When you hear the tires, I need more traction. After one lap I am catching up to Nismo GTR before turn 3. As soon as we finish righthand turn 3 notice how the GTR takes off and establish a serious gap between turn 3 and 4. I then catch him again at turn 6 and he give me a point by after wheelly hill. What a nice driver. Last edited by rhyary; 04-29-2018 at 07:26 PM.. |
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04-29-2018, 08:08 PM | #11 |
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he takes off because he is in a high powered, awd car. the track appears to be slightly banked there, but flattens out, which may be why you start to feel like the car is pushing while he is clawing away from you at high speed. he is also using more of the track to his advantage.
i'd start treating that particular turn as a late apex turn. brake later and go longer into the corner, then pull it in tighter to that second rumble strip for a faster exit. notice how you're nowhere near the inside of the track on that second set of rumble strip? i think you'll be much better off towards the inside, and even if the car's speed pulls you to the outside as the track starts to flatten out at the exit, you'll be fine. part of the reason why the gtr has a faster exit, is he is closer to the inside and uses more of the available track at that late apex. watch it a few times. btw, i'm just a nobody with a keyboard, so hopefully someone more knowledgeable will chime in.
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04-29-2018, 08:25 PM | #12 |
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>> notice how you're nowhere near the inside of the track on that second set of rumble strip?
Yes! I have. I even opened a whole thread about it with the title "Improving 40mph turns" :-) The GTR opened a gap not in the turn but at the straight line. It is much more powerful car and he was running E85 to get even more power. |
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04-29-2018, 08:53 PM | #14 |
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Its both his car, plus the positioning.
The first time, it looks like you are close to the apex, but you are actually hugging the inside of the turn and early apex. It doesn't look like you track out as far as he does in your first lap. Experiment with it.
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04-29-2018, 09:48 PM | #15 |
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The turn on the outside is off camber.
So if you take the late apex approach and come out, ignoring the first apex to take the second curb as the real apex, you will be off camber with very little traction. The correct line at turn three is to go into the first curb, on camber, track out a bit mid corner and them come in again into the next curb. NYST is like that on each corner. It has infinite lines with trade offs on each corner. It has been said that out of 18 corners, three are not blind. What you can't see in the video are the angles of the turns. Anyway, great discussion. And I am by no means an expert. So I have no problem trying things including suspension and different lines. |
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04-29-2018, 09:58 PM | #16 |
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sorry, I forgot to answer your question,
i am on 275/30/19 front and 295/30/19 rear. And the suspension is JRZ with 900Lbs/in front spring and 750 rear. If I remember correctly. Wight distribution as follow: LF 926 RF 955 LR 782 RR 765 Cross : 1735 / 50.65% Total : 3428 |
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04-30-2018, 04:08 AM | #17 | |
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Is the weight of the car with or without driver? And I don't recall seeing what model tire you're running. I run JRZ RS Pro. I would consider your front spring choice to be fairly non-traditional compared to what I've seen around over the years. I have a supercharger weighing down the nose of my car and my springs are only 600 up front, 900 rear (stock spring location). My car weighs 3475 with me in it and half tank of gas. I have experimented with higher spring rates on the car and did not like the results. You need the damper to be able to move so it can address the surface features of the track. 900 up front, along with a stiff sway bar, to me, feels like a deadly stiff setup......how is the damper supposed to move with all those restrictions on it? May I ask who made the recommendation to run this spring setup? Or did you base the springs on the weight of each corner? |
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04-30-2018, 06:51 AM | #18 |
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first, I got the springs mixed up,
so 750 front 900 rear. The car does not feel stiff. Rear is non coil over. JRZ recommended staying like the stock config. I have the JRZ 14-52 (4-way) JRZ made the spring recommendations based on informations I gave them for my objectives. It is not my daily driver, but it is comfortable on the street when I dial everything to soft after track day. Weight is with 165 driver and half tank. Tires are currently Yoko ADO8R I will dial back the sway bars. they are still set to when I had the stock ZCP. |
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04-30-2018, 09:06 AM | #19 |
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I agree you may have the car too stiff for a street tire, and you may be asking the tire to act as too much of the suspension's compliance. The car definitely looks extremely stable, you're late in and leaning hard ont he outside front in a few places and I never see any yaw in the video? Still, it's hard to tell without seeing the driver's inputs, and usually understeer at 40mph in a 400+ hp car is a driver issue . Gotta get that outside rear working hard in corners like that, if you're leaning on the outside front you've botched it, usually. It may be that with all that tire under the car you just don't have the confidence to get it dancing, that's a snappy tire anyway and generally speaking, the wider the snappier
My advice, nobody, least of all you (because you've already seen it, Live!), cares about watching the scenery going around track. Point that camera so you can see your hands, preferably synced to a TPS output so you can see what you're doing with the throttle, you seem analytical enough to be able to figure out what works and what doesn't once you can take a look at those "hand-in-hand" so to speak
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Last edited by Richbot; 04-30-2018 at 09:21 AM.. |
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04-30-2018, 09:21 AM | #20 |
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Do you have any sort of datalogging to help with calculating the amount of understeer you have? I think some of this comes down to expectations -- it's very difficult (impossible?) to make a car perfectly neutral.
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04-30-2018, 09:25 AM | #21 | |
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Also, your car has two pedals and it's ok to use them both at the same time
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04-30-2018, 10:38 AM | #22 |
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I do something similar to what ThunderMoose posted. I double apex turns like that but I early apex the first apex. This lets me carry more speed in the first half of the turn. That also means I can't make the second apex so I scrub speed by lifting. This keeps weight on the front and I might do an extra lift just before the second apex to get the rear to rotate. Then back on the gas which stops the rotation and drives me out of the corner.
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