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Couldn't sleep the other night, so started coming up with ideas for future projects. One that came through my mind was a rear (mid?) engined, AWD, Bike Engine Car.

My though process was to have the Engine mounted longitudinal behind the driver/passenger, have a sprocket running a chain from the motor to the rear diff, and then a drive shaft going forward to a front diff. IFS and IRS so the diffs can be solid mounted.

Any thoughts? Would obviously want to use a bigger motor. Leaning towards something with higher torque to turn everything, would be pretty easy to adjust the gearing also by swapping out your drive sprocket. Drop the tooth count, and you could have a sweet off-road buggy, up the teeth and have a track rig... Just thinking out-loud at this point.

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Cheers,
Logan

Chain drive off the sprocket and an automotive differential means you're doubling up your final drive. That might be able to work 'ok' off road, but will be shifting a lot. For on road though, can a 'rear' sprocket fit on the engine?

You make no mention of a center differential. Once again may be 'ok's off road, but not so well on road.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Don't have a motor in mind immediately, but yeah, you would need similar sized sprockets on the motor and drive shaft to make it streetable.

A quick search, you could use an offset front sprocket to get you to 24 teeth, and a smaller 36 tooth rear. (assuming that would be large enough to clear the drive shaft.) would give you a 1:1.50 ratio, then throw that on some ford 8" 2.73's and you'd end up with a final of 4.09... Not too far off from what some bikes would already be pulling, the higher RPM you can rev a Bike motor to and you're still getting freeway speeds in 4th or 5th gear.

And the center diff is something I did not think of at 2am... there would be the need to reverse the drive shaft direction. Would you be able to run the front diff upside down?

_________________
Cheers,
Logan

For a BEC... consider this layout:

Use a pair of the lightweight differentials from one of the light "AWD" cars. Some of them are tiny, since the center diff is designed for an 80/20 or 90/10 torque split.

Turn your chain drive bike engine sideways. Connect the center differential to the other two diffs, with one upside down so all the wheels turn in the correct direction.

The bike engine would fit easily in the middle, and they're narrow, so they would add very little extra length between the rear of the cockpit and the rear axle centerline. Depending on the engine and diff dimensions, you might also be able to put it in front - DAX sold some AWD BEC cars built that way.