Vacuum engine to improve fuel efficiency? (after burner engine)

[aerohead]

Originally Posted by Tahoe_Hybrid

why don't cars have Vacuum engines? post Cat to recapture lost energy?
like the Engine Flame Dancer

*The energy source would be really low grade.
*The fin and tube 'boiler' would be such an exhaust restriction as to destroy the thermal efficiency of the engine you're harvesting the exhaust from.
*The 'vacuum' engine is on the order of 1% thermally efficient.

[cRiPpLe_rOoStEr]

Originally Posted by iikhod

And some older saabs used vacuum to move heater/blower air flaps.

Makes me wonder how some vacuum-driven flaps behind the grille could be useful to improve aerodynamics and cut warmup times...

[Piotrsko]

One would think a simple expanding wax system to move those flaps would be better than vacuum. The diesel F250 series is noted for inopportune failure of the distribution sysem on the cab climate control

[cRiPpLe_rOoStEr]

Originally Posted by Piotrsko

One would think a simple expanding wax system to move those flaps would be better than vacuum. The diesel F250 series is noted for inopportune failure of the distribution sysem on the cab climate control

Diesels are not usually known as a good source of vacuum anyway.

[freebeard]

A walking beam and a flywheel. Too much jiggery-pokery.

[Piotrsko]

Originally Posted by cRiPpLe_rOoStEr

Diesels are not usually known as a good source of vacuum anyway.

No they aren't, so the F250 uses a small electric vacuum pump and a 1950's style vacuum heater select box.

[cRiPpLe_rOoStEr]

Originally Posted by Piotrsko

a 1950's style vacuum heater select box

I still remember when manual select boxes were used to control the external air intake for the cabin, and they seemed lighter to operate when the engine was on. Selecting temperature on rotary dials OTOH didn't seem to involve any vacuum control.