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

[Tahoe_Hybrid]

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

[oil pan 4]

Air or vaccum motors are large and put out low power.
Better off running a thermo electronic generator off the waste heat. We know they work, they just aren't cost effective.

[ASV]

there is a 15 psi limit on the pressure differential
between one side of the piston and the other.

I mean yeah you can do some work with that but a 10 to 1
compression ratio really has that beat

[serialk11r]

The answer is anything with a heat exchanger has low power density.

It's going to take a LOT of cooling air to cool down the exhaust stream.

[Ecky]

Check this out:

https://www.motorauthority.com/news/...-racing-engine

One way engineers were able to extract more efficiency from the powertrain is by using a motor-generator unit heat, which recaptures waste heat from the exhaust and converts it to electric power. That wasted exhaust heat spools up a compressor that spins an electric motor, which sends electricity to a battery that powers another electric motor to add torque to the rear wheels. Mercedes also pioneered the split turbocharger, which keeps the unit cooler and allows the car to use a smaller intercooler design with less intake piping.

Exhaust heat recovery works, but it's typically some combination of complicated, heavy, large and expensive. I'm guessing with the Mercades F1 unit, it's mostly complicated and expensive.

[Tahoe_Hybrid]

Originally Posted by Ecky

Check this out:

https://www.motorauthority.com/news/...-racing-engine



Exhaust heat recovery works, but it's typically some combination of complicated, heavy, large and expensive. I'm guessing with the Mercades F1 unit, it's mostly complicated and expensive.

i'm not sure why we don't recover it using a boiler FREE energy that would have been wasted

catalytic converters get to 500-1200C.. FREE wasted energy... basically you can regenerate your battery while your ICE is on


the steam can be recycled 0 water loss steam system


I see there is something called Rankine Cycle how would i add something like this to my suv

[Ecky]

I would be reluctant to put a steam boiler in my 1800lb car. Certainly there are BTUs to capture, but the exhaust piping isn't that hot - I can put my hand on it only a few feet from the engine, because it takes so little energy to push my car around. It might not boil water unless the exhaust gasses had to pass through a heat exchanger, and there's not a good place for this in my tiny exhaust tunnel. R134a, that might work better. Half the year it's below freezing outside and the system might not work at all in those conditions unless it was fully insulated. If It were insulated and it stopped working for some reason, there would be a risk of explosion from heated and expanding gas in a closed loop, so we'd need a purge valve of some kind. Hmm...

This isn't my field, and I don't know roughly how much or little energy it could capture, or have more than the vaguest ideas about how much energy it could capture. We need someone more educated to give an opinion.

[oil pan 4]

Better off with thermoelectric generators.
I don't think anyone has been able to add a steam cycle to anything smaller than about a tractor trailer, last time I read about it.

[cRiPpLe_rOoStEr]

I remember some Mercedes-Benz and Volkswagen cars resorted to vacuum to actuate the central door locks, not to mention some automatic clutch systems which also resort to vacuum as a power source.

[iikhod]

Originally Posted by cRiPpLe_rOoStEr

I remember some Mercedes-Benz and Volkswagen cars resorted to vacuum to actuate the central door locks, not to mention some automatic clutch systems which also resort to vacuum as a power source.

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