Direct Drive Alternator

[dkjones96]

No power brakes isn't going to save you much other than the weight of the booster.

I'm pretty sure your car uses a vacuum powered brake booster and all that does is get a bit of air sucked out of it into the intake manifold and the pressure outside the booster vs the vacuum inside is where you get your assist from. If you want safety you want that power assist.

Smaller pulley does help. Water pumps on cars take a lot to run especially when the thermostat is closed.

[GasSavers_SD26]

Originally Posted by 101mpg

So - first idea - use a direct-drive alternator off a motorcycle. Does Honda make any of these? I'd stick with a Honda product if I could.

Most motorcycle current is produced from a stator that's mounted to the block in a cover that goes around the generator flywheel on the end of the crank. It's a different item.

Here's a side cover off where one can see the stator and the flywheel still mounted on the crank.



Not a lot of power on a motorcycle.

[bones33]

I agree, use and underdrive pulley, then the smallest alternator that you can get away with and still manage your loads. Even if you need to rely on the battery to periodically supply current (like when the radiator fan comes on) I see the goal is to make just enough juice to cover what you use.

My 1000cc motorcycle alternator is rated at 55 watts, but that's at 5000 rpm. That's no way to achieve good FE. I don't see how this would reliably work on a vehicle used so much.

Now an Insight engine/motor/alternator combo is quite interesting. The power from the Insight drivetrain is plenty for a CRX, even without the battery/electric motor assist. I think early CRX's made like 57 hp, Insight is like 70 I think. The Insight engine is also optimized for good FE in several ways.

[dkjones96]

Originally Posted by beatr911

My 1000cc motorcycle alternator is rated at 55 watts, but that's at 5000 rpm. That's no way to achieve good FE. I don't see how this would reliably work on a vehicle used so much.

Remember that you don't run a 1:1 from the crank to the alternator. Usually it's closer to 2.5-3:1 meaning an engine at 2krpm is turning that alternator at 5-6k. A true hypermiler doesn't usually run the engine that low especially if you are doing pulse and coast driving. It stays closer to 3-4k for the pulse then off for the coast.

[101mpg]

Okay - sounds like the best combo to start with is underdrive pulleys for the alternator and the water pump. Underdrive pulleys being slightly larger - going to have a field day trying to figure that out - sounds like a day or two at the junkyard, less if I have any luck.

Any suggestions on how low I should go on the rating on the alternator?

The CRX came with either a 55 or 60. Should I go all out and try for a really teeny one like a 30? Or try to stay down to 40? I realize I need to change out lights for LEDs, etc. first before I go to a smaller alt.

Any percentage I should go lower on the underdrive pulleys? 10%? 25%? I realize I should see a little gain in power (which also means mileage) if I underdrive both the alt and the water pump. Theoretically I should also see a drop in amperage on the alternator if I underdrive it, correct?

Thanks for all these ideas - I am excited. Now if I can just find a CRX...

But I'm liable to do this to at least my Altima and if it works successfully see if I can tweak my wife's Maxx...

[GasSavers_Ryland]

O-ring chains last many times longer then a bicycle chain, as they have little o-rings between the links to seal in lube, there are also cog belts, like are used as timing belts, they are also much more efficent then a v belt, or ribbed belt, and quite as well.
Honda car alternators are already rather light weight, they don't have a fan to add resistance, and other then replacing the bearings with something exotic like ceramic bearings, or having the then rebalenced, I think the best you can do is improve how it's connected to the engine.

[JanGeo]

Forget the o-ring chain they rob power like crazy - my brother says if you want your bike to go faster put a conventional chain on it and you get about 10% more power to the rear wheel. Unless you can connect the alternator to the cam chain inside the engine stick with belts. Forced air scoop instead of the fan and make sure you don't load it down in hot weather.

Another thing to consider is size of alternator. Chances a small alternator is not going to be as efficient as a big one that is made well especially under full load. Heavier copper wire has less losses amd the spinning of a slightly larger rotor is not going to make anywhere as much a difference as the heat losses will in the windings and diodes. Plus you can charge quicker during alternator/regen braking with a big alternator as an example when I run one of my Hawker 25ah batteries down this winter to cycle it a little and wake it up - I can charge it at over 100 amps for a few minutes which is about 1550 watts or about 2 HP or about 3 HP with alternator losses.

[GasSavers_bobski]

Why are people focusing on the alternator? When it isn't actively charging the battery or providing power to the electrical accessories, the rotor windings are switched off. That means there's no magnetic field present, and next to no drag on the engine. As was said before, if you want control over the alternator drag, figure out how the ECU control wire works and make the alternator's existing electronics work for you.
Further, all the suggested drive modifications I just read through still draw power from the engine's crank, meaning additional fuel will be burned to make them work, so you'll see little, no or even a negative impact on your fuel economy.

If you want to improve fuel economy, come up with a way to capture the huge amounts of waste energy the engine throws away through the cooling and/or exhaust system.
One idea that came to me a while back was to use a turbocharger's exhaust turbine to drive an alternator or generator, which would in turn directly drive motors installed in otherwise unpowered wheels. Converting to electricity rather than using some kind of mechanical transmission system results in a CVT kind of effect. This is known as an electric transmission and is common place in diesel freight trains, and less directly in electric (power line driven) passenger trains.
The turbine would only be spooled up when there's sufficient hot exhaust flow... That is, when you're accelerating or cruising at speed. The lack of batteries would not only save weight, but eliminate the huge energy losses inherent in the chemical charging/discharging process. If regenerative braking were really important, some kind of low capacity, high charge/discharge rate battery could be charged by the wheel drive motors and provide assist in the short period it takes the turbine to spool up when beginning to move from a stop.

[JanGeo]

Why alternators? Well first off they are easy to use since they are already there and most of the time the belt drives the water pump anyway so getting them to work more efficiently is a plus. Regen with engine braking is going to work to some degree if you control it anyway. Wheel motor is a great idea but getting them connected to the wheel, the added weight, the battery capable of taking hundreds of amps / thousands of watts when braking with the motor are all going to cost a lot of money - think Prius 10-20kwatt motor and a $2000 battery and it doesn't really slow down the car very fast with regen alone.

Turbo charger driven alternator is CUSTOM and does load the exhaust stroke of the engine so you don't get it for free and also adds stress to the oil for its cooling. The BIG reason you are not going to get it to work is because in a high mileage vehicle there is little exhaust to provide boost to run the turbo and definately none at idle when you can use it.

The final important note is that all lead batteries need to be stored fully charged or else they age rapidly so shutting down a car without that final charge at idle before turning it off is going to shorten the battery life. I alway get a kick out of how stupid some car manufactures are when they leave headlights on after the car is shut off and then power them down minutes after you leave the vehicle. Take a perfectly fully charged battery and run it down a little before leaving it sit for an indetermanent amount of time.

[GasSavers_bobski]

Originally Posted by JanGeo

Turbo charger driven alternator is CUSTOM and does load the exhaust stroke of the engine so you don't get it for free and also adds stress to the oil for its cooling.

Yeah, nobody seems to be selling turbo-generators, but a quick look around google shows someone has already been working on this kind of system, so it's far from impossible. As for loading the exhaust stroke, exhaust pulses routinely leave the combustion chamber at super-sonic speeds, which is one of the reasons turbos are more efficient when placed close to the engine's exhaust outlets - the pulses smooth out and slow down losing energy as they travel down the exhaust. Anyway, while a slightly higher static pressure in the manifold might provide some impediment to the pulse, I doubt it's going to make much difference to the piston, especially considering the pressures already present in the cylinder.
Cooling-wise, that's true of your every-day turbocharger as well, but that doesn't stop anyone from using them on cars.

Originally Posted by JanGeo

The BIG reason you are not going to get it to work is because in a high mileage vehicle there is little exhaust to provide boost to run the turbo and definately none at idle when you can use it.

Oh, yeah... I forgot... Nobody ever puts turbo kits on their 15 year old beat up Honda.
I can think of an existing device that makes next to no power at idle: The gasoline engine. So just why would you want boost or forward propulsion when sitting at idle? It seems to me that the common practice is to open the throttle when you want power.