Video on hydraulic hybrid BMW

[David]

For us performance minded folks, hydraulic hybrids offer a way to recover energy quickly under braking and use it to accelerate up to speed more efficiently than with battery power. It's been used on some city driven delivery trucks and now someone has put it on a (somewhat) performance car:

[old man neri]

Now this is interesting.

[Porsche-O-Phile]

Very interesting indeed.

A couple of concerns though:

1. Hydraulics mean liquid and liquids create (eventually) leakage problems and weight issues (they're heavy). Don't know if either is a show-stopper, but something to consider...

2. I wonder this about all hybrid vehicles - do their engines use oil accumulators or something? I imagine all the stop/start cycles of the engine shutting off and then being forced back on (with immediate load demands) could lead to premature wear and failure since the lubrication isn't circulating. Wouldn't it be akin to starting your car engine cold and flooring it right away? Not the best thing for it.

Just curious. Very interesting concept though. I think I've seen something similar with pneumatics - can't remember where though.

[porsche4life]

Originally Posted by Porsche-O-Phile

2. I wonder this about all hybrid vehicles - do their engines use oil accumulators or something? I imagine all the stop/start cycles of the engine shutting off and then being forced back on (with immediate load demands) could lead to premature wear and failure since the lubrication isn't circulating. Wouldn't it be akin to starting your car engine cold and flooring it right away? Not the best thing for it.

+1 I had that exact same concern Jeff. Looks like a killer idea tho.
Also wouldn't all that liquid act as uncontrollable ballast and screw the handling?

[tcar]

I've seen it used on trash trucks, start and stop every 40-50 feet. They do not shut off the engine, tho (Diesel). Basically idles all the time. Supposedly saves over 60% fuel costs.

[David]

The fluid would be under very high pressure when compressed and probably under low pressure when uncompressed (with a bladder and nitrogen) so uncontrolled fluid ballast shouldn't be a problem.

Leakage would be a concern, but hydraulics have been used for a very long time so repair shouldn't be much of a problem.

It will obviously weigh more than no hybrid system but it should weigh considerably less than electric hybrid and the energy recovered should make up for the weight.


Cars and trucks give up so much energy as brake heat, that it seems like something should be done to recover it.

Maybe F1 technology will bring flywheels to street cars, but whatever we end up with, it seems silly to give up so much energy as heat.