I always enjoy reading non-F1 tech questions here on F1T, so hoping some knowledgeable people chime in.
I'm looking for decent information regarding the practical design and tuning of AWD drivetrains, but I can't seem to find any "broadly accepted" literature about it. For comparison, when reading into suspension design, there's always a book or 5 that everybody seems to recommend to read-up on to get a decent basis.
But, even better, perhaps there's people willing to add some useful insights/experience into this thread? Any info will be greatly appreciated!
My main point of focus is the effects and design choices of different differential types / torque split scenarios for an AWD rallycross vehicle. We've been racing in pseudo-rallycross classes for over 10 years (100% gravel/dirt tracks), but all of our experience is with FWD cars. Over the years we settled on a salisbury-type diff (metal plate LSD) with some preload and what most people call "1.5 way" ramp angles to allow sharp turn in and good corner-exit traction.
We're currently in the early phases of designing our new car/chassis for the 2019 season which will see us step up to the AWD class.
Our proposed chassis at this moment: front longitudinal engine, central seq. gearbox with centre diff/transfer case, front/rear diffs in separate housings. Ballpark figures 550BHP / 1100kg. Weight distr. approx 55/45 front/rear.
What we're uncertain about at this moment are particularly the centre and front diff types, as well as maybe any difference in final drive ratios between f/r?
Centre: torque biasing, Rear: Salisbury, Front: Salisbury is what my gutt feeling says.
-Perhaps front could be more benificial to use the torque biasing type?
-Perhaps centre diffs in gravel-only situations might as well be 100% locked connecting front:rear 1:1?
-Could it be benificial to run the rear axle at a slightly higher speed compared to front?
-What about viscous centre diffs?
As far as electronically controlled diffs, I'm of the opinion these aren't worth the large chunk of our time when concerned with developing a new car. Waaaay to much other areas where we're supposed to gain laptime for the first year(s) before adding in the complexity of active diffs. Unless we're missing out on *the* holy grail?
(I've been told the (non-WRC) driver-controlled diff settings in subarus and lancers only switch between 50/50, 66/33 and 100/0 torque split depending on which mode (tarmac-gravel-snow) the driver selects. Which would basically render it useless for our gravel-only purpose imho.)
Obviously, we'll test the heck out of the thing once it's ready to go vroom in 1-1.5 years time. But I wasn't planning on buying a lifetime supply of differentials....
thanks for any input!