3 ms·
Heh, I should have said "just a matter of software to retard the timing/throttle and per wheel braking". Sure being software the quality of the implementations
by sliken 5y ago
Heh, I should have said "just a matter of software to retard the timing/throttle and per wheel braking". Sure being software the quality of the implementations vary (looking at you Honda, BMW (depending on year), and Toyota).
Sure the Tesla has an advantage over ICE cars in that it can produce positive or negative torque near instantly on either axle. But braking is a good substitute. I didn't really fully understand differentials till I built one for an RC car and played with it enough. If you turn the car upside down you can immediately tell that dragging your finger on one wheel, speeds up the other wheel, thus the dangers of an open differential (my WRX had two limited slip differentials and one open slip). Open differentials + braking give you the best of both worlds. You get a cheap, less drag, lighter differential, but you can still transfer torque from the slipping wheel to the non-slipping as needed.
Most don't realize that most cars (when it's slippery) are one wheel drive (fwd or rwd with an open differential), some are rear or front wheel drive and have limited slip so they are 2wd. AWD can be 1, 2, 3 or 4wd when slippery, depending on the configuration of open and closed differentials. My WRX was 3wd (1 open and 2 LSD). Hardcore offroad vehicles have locking hubs or full sync mode for very slipper conditions, but it's hell on tires if used on a normal road since every turn will scrub tires for the difference between inside and outside curve distances.
However if you google snow testing and the 3 cars I mention above you'll find a report basically saying the Subaru was awesome in the snow, predictable, could climb, turn, and brake as well as traction allowed. The toyota and honda however were pretty terrible in comparison despite all being a similar price, similar power, similar tires, and AWD. I was amused to find that Subaru's were really better in the snow.
I spent a year of commuting through six 7,200 foot peaks every weekend and went through many snow storms, blizzards, freezing fog, etc. My WRX did awesome, except when the snow was so high it would life the car off the tires. It didn't use anything active for traction control, but was awesomely predictable in the snow. I thought rally drivers had inhuman skills in their ability to drift sideways through corners and stay in their lane.... till the WRX and found it easy to do the same. Great fun.
Sure my old WRX couldn't do torque vectoring, or even active traction control, but was so predictable that it didn't particularly matter if there was some slipping. It also communicated exceedingly well, one treacherous night descending from 7,200 feet or so into Carson City I was at 10 mph or so, any slower and I'd slide to the inside of corners. I could tell not only that the ABS was going off, but which wheel. I tuned my speed as a result so I'd slow so one wheel would occasionally trigger, but not so slow that I'd slide to the inside of corners. Pretty eerie with the slow rumble of the boxer engine near idle, silence from the heavy falling snow, and the noise of the ABS floating between the 4 wheels. As you might imagine it had my full attention.
As you can probably tell despite my m3p being faster and more advanced in many ways, I still miss my WRX.
- giantg2 5y agoI don't doubt that the WRX did well. I'm just saying the systems in the highly powerful EVs are highly advanced and are able to control the massive torque via torque vectoring. Sure the open diff is great for driving downhill in the snow and using brakes (and many other conditions), so the Tesla might not do as well at that, but the torque vectoring will do better than the open diff when putting down massive amounts of power.
- sliken 5y agoHeh, maybe, at least at default settings I find the more advanced systems tend to be overly conservative, so in slippery conditions they reduce power, slip, repeat... till you are at a crawl. The subaru on the hand just shrugs, slips a bit, but does what it's asked. The M3P for instance isn't particularly good at donuts, even in track mode, at least with the settings I tried. I've definitely been in scary situations where not being able to slip would have meant getting stuck. In my m3p I've even gotten stuck trying to get into my driveway, even with "slip start" mode enabled. Had to get a running start just to get over the curb of my almost flat driveway that my subaru (either the forester or wrx) would have just slipped a bit and gotten up.
- giantg2 5y agoUsually donuts require traction control to be off.
- sliken 5y agoIndeed, track mode allows for different traction control settings, and different front/rear bias (by percentage). Just haven't found something that works particularly well, granted it's more just for fun than anything practical.