Exhaust driven Alternator

[scho]

Soak enough heat though, and the catalyst might lose some of its effectiveness.

Either way you go, you have to give something to get something. Hence, it's a really fun puzzle.

[theholycow]

Yeah, you'd have to soak the heat downstream where there's nowhere near as much of it, there's no room for equipment, and you'll still change the exhaust gas density which would produce some backpressure I guess...

[GasSavers_RoadWarrior]

You'd just end up with a real need for a coffee can exhaust tip, let it spread out as it slows down, such that you get the same momentum per unit length of pipe. At the hot end, you have small volume, small mass, at high speed, giving you x momentum, at the cold end you have large volume, larger mass, low speed, giving you the same x momentum..

[scho]

I don't know the answer to this, so I'm going to ask. Do you need to have your alternator running all the time? That is to say, could you go without it for short periods of time (ie. acceleration, idling, etc.)?

If you could, then you might be able to get away with adapting the electro clutch to the alternator as it is, and then only run it when you are at peak efficiency. And even then, it can cut in and out if the system is charged and happy. And then like every other system out there, when charge gets low, it just reverts to an always active state and constantly puts charge into the system (in the case of low charge or poor battery function).

How hard would it be to put an electro clutch on an alternator? Can't be that tough.

[dkjones96]

The clutch is easy, the pulley is hard. The vast majority of clutch pulleys are large diameter which isn't what you want on your alternator, especially if you are going to be only using it when you need it. It'd be MUCH easier to make your crank pulley clutched but unless you went with an electric water pump(or have one of the few cars with a timing belt/chain driven pump) that's an extremely dumb idea.

Why not wind yourself a lightweight rotor and accompanying stator and run direct drive? Make it high voltage, low current and run the 3 phase through a transformer(or 3 single phase) then rectify and regulate as usual. You'll move some of the heat generation from the windings to the transformers so heat soaking the alternator won't be as much of an issue. Making a stator that will hold together at 40-50k rpm will be the hardest part.

Use something like microwave transformers(can be had for free) and have peak alternator output be around 5kv.

[scho]

So it would effectively be slowing down the rate at which the alternator is spinning.... good call. And those pulleys are so damn small on alternators. The only other option beside clutching the crank pulley would be to make the crank pulley even larger to compensate for the gearing change. And a huge pulley would be heavy, which once again would be an extremely dumb idea.

Someone has to make a small clutched pulley somewhere in the world.

[GasSavers_RoadWarrior]

I'm not sure that spinning a clutch pulley would really be any less load on the motor than spinning the armature of the alternator with the field coils turned off, which the ECU will do from time to time, depending on load and state of charge... If one does a lot of highway driving, one could wire up a relay across the TC lockup solenoid, and use it to trip out the field coils such that you second guess the ECU and only charge when at light load cruise... but you'd have your battery light on all the time.. and you'd only get about an hour out of the battery in a wet day stuck in city traffic.

[thecheese429]

Originally Posted by onegammyleg

But seriously , the whole idea of running an ALT from exhaust gasses is not a very good one.
As pointed out in other posts , exhaust gas flow would be too little to turn it at idle or light throttle and it is likely that you rwould need a gear box to reduce the rpm to the ALT.
But that would again make for low output at any normal driving speed at lite throttle.

Even IF it did mechanicaly work, th epower needed to turn the ALT is not free.
The 1 or 2 HP (?) needed to turn it (at full output) would be shown as a restriction on the exahaust.
I would guess that the motor would run worse with that setup than just running a conventional belt drive.

What you need is to get FREE power !!! (or almost free is good too)

How about , running an electric clutch on the ALT pully.
So that it only locks up and starts charging at idle or deceleration.
The clutch can be switched in or out with a simple vac pressure sensor., and the parts to do the clutch can be salvaged off a air con compressor.
CHEAP MOD

KaChing , almost free power

Hmm, brilliant idea. I'll have to look into that one. I might try that with the power steering pump except with a speed lockout, not vacuum.

[theholycow]

Originally Posted by RoadWarrior

spinning the armature of the alternator with the field coils turned off, which the ECU will do from time to time, depending on load and state of charge...

Put more simply: No clutch is necessary because the alternator gets turned off when it's not needed already; it still spins when off but there's no load on it.

[scho]

That's a good point. Without a load, it's not all that bad.

Once again showing that it's hard to improve on what the automakers have sunk millions into researching.