Larger/Heavier Flywheel?

[RH77]

I'm not sure if this has come up at all, but would a larger flywheel enhance FE?

The rationale is to sustain momentum, especially in city driving. (Kinda thought of this from reading an article on F1 racing, which then turned to recalling the hours of playing Gran Turismo and the "Lighter Flywheel" mod).

RH77

[AndrewJ]

I don't think it'll help.

A flywheel is just going to help engine momentum, if you're using P&G then you don't really want more engine momentum.

Plus, from a more theoretical standpoint, a flywheel is an energy storage device. So you're storing your gasolines energy in kinetic form.
You're also losing energy through mechanical friction (of the flywheel) and you're losing energy every time you have to spin the heavier flywheel up to speed.

Same thing as lighter wheels really. I know there's some debate about lighter wheels, but I don't think anyone's in a big rush to go put heavier wheels on their car for the sake of FE.

I can appreciate the "whatever's good for racing is bad for FE" idea, but I don't think it applies in this case.

[tasdrouille]

I would surely works, as its worked in the past. There was the golf ecomatic which used a flywheel to store energy, shut the motor down at stops and help relaunch the car with the flywheel momentum. The car acheived 16% better FE.

[trebuchet03]

1. It won't increase thermal efficiency - so if you're putting energy into a FW, it's not going to make running the engine any more efficient
2. At steady state - there's no difference
3. You can shift earlier without dropping rpm as much
4. You'll be able to go further while engine braking

So for 3 and 4, I don't see that big of benefit... If you're going to coast, EOC or throw it in neutral.... I don't see 3 as a big deal - 99% of the time you'll be in or out of gear, not shifting...

For 4, you can get the same benefit by adding dead weight to your car...

If the FW can be disengaged while not "charging" or "discharging" that energy... That would be beneficial for city driving

[RH77]

Good info guys -- just brainstorming...

[bennelson]

Do a web search about flywheels.

There is some really interesting research using large flywheels as energy storage devices.

Think regenerative breaking where slowing down transfers energy into a big flywheel. It spins very quickly. The energy could then be transfered mechanically back to the wheels again, or could run a generator/motor to drive the car.

Really interesting stuff, wish I could think of a good web page about it.

Now this is not a flywheel as in the thing at the end of your engine. It is a HIGH RPM device made of fancy space age stuff.

[trebuchet03]

Originally Posted by RH77

Good info guys -- just brainstorming...

[diesel_john]

not any help on the engine except for what Frank said.
But, off by itself sitting in a partial vacuum, hooked to only a motor/generator. a high speed flywheel, humming along from regen. don't need as big of engine.

[AndrewJ]

Originally Posted by bennelson

There is some really interesting research using large flywheels as energy storage devices
Really interesting stuff, wish I could think of a good web page about it.

The main problem seems to be safety. Having a massive flywheel (the only kind that'll store enough energy) is quite a safety concern. That's the main problem with energy storage.

Batteries can short out.
Gasoline can blow up.
Flywheels can run off and trash everything.

Oh well.

[RH77]

Originally Posted by bennelson

Do a web search about flywheels.

There is some really interesting research using large flywheels as energy storage devices.

Think regenerative breaking where slowing down transfers energy into a big flywheel. It spins very quickly. The energy could then be transfered mechanically back to the wheels again, or could run a generator/motor to drive the car.

Really interesting stuff, wish I could think of a good web page about it.

Now this is not a flywheel as in the thing at the end of your engine. It is a HIGH RPM device made of fancy space age stuff.

Kind of like the Medium-Duty Hybrid Trucks with hydraulic pressure build-up on slow-down/stop. The hydraulic fluid pressure gets the vehicle moving from a stop, then the hybrid system starts the Diesel engine and takes over. In this case the spinning wheel/disc acts as a "torque storage device"?

Instead of brakes (hey, sometimes ya gotta use them) the device would spin from momentum and store that energy to get started again. I'm sure other devices would take priority for installation.

RH77