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06-18-2014, 05:27 PM | #1 | |||
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Why you need a LSD if you like cornering!
So a brief explanation of what is going on here Top graph = throttle position 2nd graph = Front left wheel speed 3rd graph = Front right wheel speed 4th graph = Rear left wheel speed 5th graph = Rear right wheel speed 6th graph = steering angle (negative = left, positive = right) Blue/purple thin boxes - compare the left and right wheels, and you can see momentary lockups under braking. Decreasing wheel speeds mean I'm braking the car, and the little sudden dips are the wheels on the verge of locking up, but recovering before they actually do. The wheel speed would go to 0 if it actually locked up. This is shown to demonstrate the accuracy of the equipment we are using, and validity of this test. Red box #1 - under acceleration and turning, notice the wheel speed differences between the rear left and rear right wheels. The rear left wheel is the "inner" wheel in this case, and you can see spikes where it speeds up, and then slows back down as I modulate the throttle. With a mechanical LSD, I would be able to give the car more throttle without the rear wheels going at different speeds or spinning altogether. Spikes on the left rear wheel here indicate that the inside wheel is spinning, rather than gripping. The inside wheel travels a lesser distance than the outer wheel, and should be travelling at a lower speed, not a higher speed. Red box #2 - Notice the dips and peaks of the rear right wheel, compared to the rear left wheel. The spikes up and down are a result of throttle modulation, but I am unable to put down any power, because when I do get on the throttle, I'm spinning the inside (rear right) wheel instead of accelerating. Red box #4 - Note the spikes in the rear left wheel. Same thing; I'm modulating the throttle (top graph) to accommodate the car's inability to put all the power down. If the inside rear wheel were not slipping, I'd be able to corner faster, and put down more power. Red box # - I manage to spin BOTH wheels for once, and need to countersteer.... TL;DR: mechanical LSDs help you power out of corners, and corner faster, regardless of power output levels (note that all the times where I cannot power out are at partial throttle) and driving experience. *edit* Some highlights from others. Quote:
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Last edited by CSG Mike; 10-28-2014 at 02:41 PM. |
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06-18-2014, 06:05 PM | #2 |
AutoX-10/10ths every run
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Thanks Mike, nice writeup.
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06-18-2014, 06:15 PM | #3 |
i'm sorry, what?
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hey mike, as an aside, did you pull the wheel position sensor using the Solo DL or a more advanced unit?
did AiM release a new FRS/BRZ file
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06-18-2014, 06:59 PM | #4 | |
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Quote:
I'm reading this as: you can't do this because the car doesn't have a mechanical LSD. I thought the FR-S & BRZ came standard with a Torsen LSD. Isn't that a mechanical diff? Please clarify if I've missed something obvious. Src: [ame="http://www.youtube.com/watch?v=u0EOrzn7-Qc"]http://www.youtube.com/watch?v=u0EOrzn7-Qc[/ame] |
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06-18-2014, 07:26 PM | #5 | |
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Quote:
Given that the AIM Solo DL now reads Oil Temp and Wheel Speed sensors, we're thinking about doing a group buy if there is enough interest. |
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06-18-2014, 07:26 PM | #6 |
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The car comes with a Torsen, but if you lose traction with one of the wheels, then the differential effectively becomes open. Loss of traction can be lifting a wheel, or spinning a wheel. In this case, the inner wheel is spinning.
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06-18-2014, 07:32 PM | #7 | |
i'm sorry, what?
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Quote:
I just updated! (didn't realize I was on xx.53 and not xx.54) now I have all these fun things too!
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06-18-2014, 07:48 PM | #9 | |
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Quote:
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06-18-2014, 08:02 PM | #10 |
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BUt I thought that if we lifted a wheel the ECU would use the VSC to apply brakes to the spinning wheel.
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06-18-2014, 08:11 PM | #11 | |
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Quote:
Also, that functions by slowing you down; the goal is to go faster |
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06-18-2014, 08:16 PM | #12 | ||
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Quote:
Quote:
I thought that was the whole concept of a LSD. |
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06-18-2014, 08:44 PM | #14 | |
i'm sorry, what?
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Quote:
it's slowing down the spinning wheel so the LSD kicks in and gives power to the one that's not spinning but because this is achieved through electronics and well.. brake actuation, it's really just a hack
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