Searching here I didn't see this one listed so i'm sharing it...
https://seniordesign.engr.uidaho.edu...%20may2005.pdf
Apparently about a decade ago, some university of idaho engineering students turned a 1988 Ford F350 into a hydraulic hybrid, gaining both improved acceleration and apparently 25% fuel mileage increases as well as reduced wear expected on the brakes and such.
I scanread the above and don't understand it all but i'm intrigued. I would be curious how hard it would be to replicate such a project just on a smaller vehicle. I would like to use secondhand parts (maybe forklift parts which I thought used accumulators?) as much as possible to keep the budget down even cheaper... apparently one potential benefit of hydraulics vs electrics is much lower cost even brand new (I see this quoted elsewhere but I don't have any offhand examples).
It could also be possible for a 'hydraulic hybrid' to charge the accumulator while maintaining a steady speed, then engine-off-coast while bleeding off pressure to maintain some speed I should think... giving a constant speed pulse and glide effect.
From what i've read elsewhere electrics cant recover more than 30-40% of the energy of regenerative braking end-to-end, but hydraulics are much more efficient at it. (though they lack the power density, storing seconds of energy not minutes) With no battery pack to die 100,000 miles in it's possible the overall total cost savings would be superior as well, what do you think?