But, what is, and when do you get, "snap oversteer"?
I shall quote from thy Wiki:
http://en.wikipedia.org/wiki/Snap_oversteer
"Snap oversteer is when a motor vehicle spins dramatically during a turn (usually un-expectantly). This is most common with mid-mounted engine, rear wheel drive (MR) vehicles. Mid-mounted engine vehicles have a much lower rotational inertia than a vehicles with a front mounted or rear mounted engine. The lower rotational inertia of mid-mounted engine vehicles causes the vehicle to spin much faster than a front or rear mounted engine vehicle. Snap oversteer if unexpected can catch the driver off guard when cornering, ultimately leading to loss of control of the vehicle."
So the problem here is that unfortunately many noobs, even those with much prior driving experience first learn about the 'snap' part in an expensive NSX the hard way. If it is the first time you have encountered it, unless you are Michael Schumacher, you probably won't realize what happened until long after the point of no return. Particularly in traction challenged conditions with inadequate grip capability.
Their are several ways in the NSX to get to see this in action.
Common ways some work themselves into this bad spot is to do a hard 1st to 2nd shift at WOT on crappy tires or with the TCS off on a nice wet slick road totally losing the rear end (throttle oversteer), lifting at or near the limit (lift-throttle oversteer), trailing off on exit particularly on a decreasing radius turn (trailing throttle oversteer), issuing an overly aggressive steering correction without a comparable recovery, or perhaps most common simply getting scared and lifting suddenly at or too close to the limit (throttle-off-oversteer).
The 'snap' is the sudden/drastic/often unpredictable let go of the rear end, leading to that stomach wrenching feeling you get knowing that the opportunity to correct/recover was 2 seconds ago in the past... having now lost total control of the vehicle. At its worst, now having your nose being pretty much pointed in the totally opposite direction of normal travel or finding yourself on the opposite side of the track without any clue as to how you got there. :biggrin:
This would be contrary to a more usual, predictable, relatively easily correctable, oversteer condition which would require less reaction time / driver competency on other platforms.
Technically, the key is that because more of the mass is off the extreme ends [centered along the length of the wheelbase yielding a lower PMI ] means less 'polar feel' for the driver. In some ways it is a contradiction, however think of it this way. A ME RWD platform won't come around faster because of a higher polar mass in the rear as you may think, it actually "comes around faster" if you will because the driver often doesn't feel it until later due to lower polar mass. It responds faster.
It is all about the weight distribution. Think of it like swinging a baton, having more mass toward the center means faster response at the poles. That is obviously good when you want it and expect it and very bad when you don't. Another often used example is standing on a dolly spinning, your rotation speeds up when you brings your arms in.
It does not have to be a mid-engined RWD platform either. A front mid engined platform like the 2K can exhibit similar characteristics just to a lesser extent.
One of my friends killed himself in the first week of owning his blingy new S2000 having traded up from a low power FWD civic... because he did a hard 2nd-3rd shift in the wet on a 2 lane road, didn't catch or whatever, and ended up in the on-coming lane of a semi trailer. Often times the higher hp the vehicle the more frequently this rears its head, which is one of the many aspects that makes the top tier CART racing drivers among others going wheel to wheel out their in the wet freakin' amazing to behold.
Some degree of risk can be mitigated in car setup, such as setting up the vehicle to tend to understeer or be more predictable on the compliance... but it is not as simple as asking about dali sway bar settings. It is the cumulative effect of everything that is relevant to how the car behaves and feels at or near the limit.
Getting back to the root of it. If you want to really know about sway, pressures, or other settings, I recommend everyone find out on a wet skid pad what base characteristics your specific vehicle has, as well as after making any serious suspension /setup change. Then, making small incremental changes from there.
This past weekend I got a fair amount of skid pad time in the NSX at Bremerton, as we wet down the VHT on the drag strip real good, and setup half the skid pad over it while the students were off running auto-x. I did not know what to expect with those mongo Dali bars and all the other changes I made as it was like driving a whole new vehicle to me.
It allowed me to test my machine's characteristics in a safe environment by first establishing the vehicles tendencies (understeer, neutral, or oversteer). Then feeling how a given setup responds when pushed with unusual inputs and/or over drastic surface traction changes before finding out the hard way on the track. Seeing as how it rained the next day, I was very glad I did.
Hope that helps.
