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I don't think you're seeing this the same way that I am. Right now the engine is leaned over towards the drivers side, but is offset towards the passenger side. Turning the engine 180*, but keeping the output shaft along the same longitudinal axis (co-linear) with the current layout, would keep it offset to the passenger side but lean it over further towards the passenger side. This would actually be a further improvement in equalizing weight distribution, in addition to a reduction in unnecessary complexity.

In a word, yes. The torque moment in question that is exerted on a solid axle is entirely reacted within the chassis on an IRS. Although technically I believe that it's the left side that gets 'pushed' into the ground and the right side that gets 'lifted', causing the right side to be more likely to slip...which causes the excess wear.

good catch there driven5 i was oversimplifying far too much to make sense in the light of day. bias, as i understand it, isn't a true "split" of applied power but a "tendency" for one side to slip before the other, a small but telling difference, one side tries to play catch up if you will. units such as the torsen have occurrences wherein they lift one wheel and the other wheel goes into "open" mode because the primary wheel is using all the torque to spin as fast as it can. .. not bloody likely on a pavement pounder i'll admit. what i haven't experienced is this happening on turns in both directions so does that occur irregardless of which side lifts? it's much easier to lift the right wheel than the left with my 200 lb butt in the drivers seat. .. another argument for an electronic controller on the diff, what i've worked with used a pwm driver, pretty easy to construct with a visit to the local radio shack.
but then of course i could be HUGELY mistaken about how a torsen works. .. and it wouldn't be the first time i should've shut up while i was ahead.

Yes that effect will occur on whichever side happens to lose traction first traction.

The differential naturally sends equal torque to both tires determined by the amount of torque reaction between the pavement and the tire. What happens when one tire loses traction is that less of of the torque is being reacted between the pavement and tire, resulting in the tire with more traction being sent the equal amount of torque as is being reacted on the slipping side. The difference in torque between what is being applied from the engine/transmission and the combination of the torque reaction from both tires, is applied against the already slipping tire...Causing it to slip even worse. A helical differential, as in TORSEN (TORque SENsing) or Quaife ATB (Automatic Torque Biasing), is able to take the torque reaction from the slipping tire and multiply that torque back against the tire with more traction, by the "bias ratio". An open differential and a helical limited slip will both only provide no propulsion when the slipping wheel has absolutely zero traction. Hopefully the wording of all of this makes sense...If not Wikipedia actually has some surprisingly good descriptions of how each of these work in the "differential" and "limited slip differential" pages.

Which is why I decided to go with a clutch type LSD for my racecar build, I don't want to slow down every time one of the driving tires leaves the pavement.

For my street build, however, I am going with a torsen.

Moti

Why worry about differentials? Just use sierra 4x4 differentials front and rear, and call it a day.

Hell, maybe pull the center differential out of the transfer case and use that too. Or just detach the transfer case from the transmission(does it unbolt, or would you have to cut it out?), and use it whole.

Maybe I'm missing something...but with the rear mounted engine spinning it's driveshaft the wrong way, why not just put an intermediate gear between the driveshaft and center differential to get it spinning the right way? As pictured, there are two gears in the center section already, just stick another, equally toothed small one in.

Or, as I'm prone to do, am I underthinking things again?

i've considered how to do something like that, so far the only issue is needing a 6" or so pulley/sprocket on the trans output so the center diff diameter is compensated for. an r160 diff carrier diameter is about 4 1/2", an r180 would probably be a better choice for strength if not an r200 since it gets full motor output and 4 tires worth of traction applied to it. parts to do it are either available or easily machinable so its just a matter of someone jumping off the deep end and going for it.

Here is part of a post I wrote a few years ago over on locostbuilders.co.uk. It was an idea I never got to followup with, but think it would still be one of the easiest ways of going AWD with a bike engine:

The engine in my car is a Yamaha FJR1300, a bigger bored, shaft engined cousin of the R1. I have a spare engine on the bench which I am considering turbo-charging. While stripping this engine, I noticed that it has a counter shaft assembly below the transmission which drives the 90 degree shaft drive. It is called the middle drive assembly. Think of it as similar to the R1 but with an extra shaft below the sprocket output. This extra shaft is the reason that the drive rotates in the opposite direction, the reason why my rear axle is flipped upside down to compensate.

Anyway, this middle drive assembly runs the complete length of the engine, and has a side cover on each side of the engine casing. The assembly can be easily removed by taking off both side covers and pulling it out.

My idea is to fabricate a longer middle shaft with splines on either end, and machine new side covers with bearings and oil seals.
This would allow the engine to be mounted longtitudinally like most BEC's but with a drive output facing the back and the front of the car to enable a AWD drivetrain. I believe there is also room at the rear of the engine casing to fit a small centre diff where the rightangle drive unit currently is.
Taken from: http://www.locostbuilders.co.uk/viewthr ... ?tid=82315

Now that sounds like one interesting, possible path to an AWD BEC!

Corrected link: http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=82315

My biggest concerns would be what speed is that shaft being driven at & how do you integrate a functional clutch? A couple of possible ideas pop to mind but I don't have enough info to evaluate them, lol.

Actually the shaft is after the clutch, so the bike clutch and gearbox can be used as standard. The shaft speed if i remember was in the realm of being OK once a suitable pair of diffs were found for each end of the car.

Here is a picture of the engine, with one of the new side covers built, the other side of the engine would be similar with the shaft running right through.

Definitely keep us posted! If what you're doing does work, I will eventually build a car based around that platform. This may represent a path to a light weight, turbocharged AWD middy. All three of my motoring addictions combined in one car!

And hopefully the clutch and transmission will hold up!

True, but well worth the experiment. You would never be able to treat the car like a dragster or the transmission would go boom. My AWD addiction comes from it's ability to apply power on corner exits. In my Evo I can be on the power earlier & more aggressively then a 'vette or viper with comparable compound tires, despite having skinnier contact patches.

This is the most plausible AWD concept I've heard so far. Maybe consider a honda rear end, they generally have a center diff built in and a ~2.5:1 ratio.

Which Honda rear ends run gear ratios that tall? Finding light differentials with ratios taller than ~3:1 has been challenging.

I think they do this to bias the torque to the front. Interesting...

If the center diff is built in, maybe the unit isn't usable without AWD though, so just useful for this application.

Any pictures available?