40 Amp To 16 Amp Charging System

[RSM]

Is the power gain from switching to a 16 AMP from a 40 noticable and worth it ? I realize the lightweight flywheels are more readly available and lighter just wondering if less draw on the charging system free's up any power like the underdrive pulley system for car motors can. Allso I have an EFI motor and they love more juice (electricity) to make them run happy, dose that have any affect on this issue ? thanks randy

[Techno]

Electricly there is no difference. A 16 amp system with a 10 amp load is the same as a 40 amp system with a 10 amp load.
746 watts = 1 hp
If it was drawing the extra 24 amps over the 16 amps system the HP loss-
24amps x14 volts =288 watts=1/2 HP increased load. At the full 40 amps it's only drawing 3/4 HP This changes just a bit with higher voltages.

The difference is at high RPMs. The heavy flywheel won't work. Here you don't have a choice and have to use the light flywheel. One other difference is the charging system on the 16 amp is already a rotating element. And it's light wieght. The 40 has a heavier flywheel. And an alternater depending on the type.

So if high RPM use and gaining a possible 1/2 HP and the imeaserable spool up loss is worth it. At the cost of having to be a bean counter with your electrical consumption.

[Steven]

my 40amp wheel weighs 13lbs. the aluminum 16amp variety i bought weighs 7.01 lbs. ;)

[Jeff_G]

It is not just the weight of the flywheels. The 40 amp has more drag on the flywheel from the heavier coils than the 16 amp system.

For instance some fo the F1 guys used to use a low amp stator (9amp) for qualifying due to the less drag on the flywheel but switch back to the high amp (16amp) for the actual race due to needing the additional charging requirements. The smaller stators could not keep up with the electrical drain in the longer races.

For pleasure use you will not notice any difference. Stick with the 40 amp.

[Techno]

I have to disagree Jeff, if the 40 amp is producing more resistance it's from the increased drain. If both 9 amp or 40 amp supplied 9amps the drag should be the same. If there is no load at all on the 40 amp, like it wasn't hooked up there should be no drag.

If it is legal they could come up with a switching arrangement to disconnect the 16 amp system. They wouldn't be generating electricity so would have no load at all. Switch it back on after the run.

[RSM]

So no matter the AMP the system can put out it is only putting out what's demanded from it at a certain time ?

[KeninSC]

RSM,
That is correct. In the newer systems with the electronic voltage regulators. The older systems with the rectifiers are a "waste type" system. The old systems always put out the full rating of the alternator with the excess being drained into the block (ie:ground). The amount of horsepower required to produce 40 amps at 14.6 volts is neglible though, 1.4HP. 16 amps=0.54HP(with a 50% efficiency rating). There will be a small amount of drag created by the magnets on the flywheel passing by the stator poles even without a load, also neglible. The main advantage/disadvantage of going to a 16 amp flywheel versus a 40 amp flywheel would be less rotating mass at the top of the crankshaft as Techno referred to earlier.

Ken

[CDave]

Wouldn' the engine rev quicker with the lighter flywheel? Less rotating mass to turn.

[Jeff_G]

Techno not true.

The 40 amp charging system uses heavier magnets in the flywheel as well as larger alternator coils. This creates a larger magnetic drag. No matter what the output of the charging system is. A bigger coil lamination = more steel and a bigger magnet to generate the additional amp output and match the coil laminations.

Try to pull a larger magnet away from a large piece of metal. Now try the same thing with a smaller magnet and smaller piece of metal. See what I mean?

In addition on a charging system the stator is outputting, or trying to at all times. Under load a charging system is putting out about 18 to 20 volts from the stator, (voltage flowing out of the regulator. With the regulator taking away the load (no output from the regulator) the voltage can reach 200+ volts at high rpm at the stator. The amp is very low at this time however due to the no load condition. The voltage "sits" there until the regulator outputs the voltage again and the voltage drops.

Less magnetic drag on a flywheel/ stator = more HP. For instance you can take a 9 amp racing stator and cut off all the poles except 2 and the charge coils and pick up around 2 hp on the dyno. Imagine if you cut off the poles on a 40 amp system.

A rectifier charging system is a constant voltage system. All the rectifier does is change the ac voltage from the stator into DC voltage. It charges the battery at all times until the battery is fully charged. Once charged the battery will "boil" this will eventually destroy the battery. With a conventional wet cell battery this "boiling" of the electrolite will lower the voltage somewhat. The system continues to output full voltage and amperage. On a maintance free battery it can not do this (boil the electrolite) and will destroy the battery in short order. That is why you don't use a maintance free battery in a non regulated system.

On a regulated charging system the voltage under a no load system will as previously stated continue to grow. There is no mechanism to bleed off voltage in a non regulated (rectifier) system. The excess voltage DOES NOT go to ground.

Lets look at some possible consequences. Using a 16 amp stator with a 40 amp flywheel the system can produce over 500 volts due to the increased magnet size. This will destroy the stator. If you were to put a 40 amp stator with a 16 amp flywheel (which will not fit by the way) you could not generate enough voltage to fire the charge coils. The magnetic field is not strong enough.

If you look at the charge coils (ignition) on a 40 amp system you will see the laminations are very small to reduce the voltage produced from the heavier magnets. Also on the front of the low speed charge coils is a shunt plate. This acts as a dead shorted winding and to "shield" the coil from the magnets and there fore producing excess voltage. If you did not have this the low speed charge coils could produce 2,000 volts at 6,000 RPM!

This is why the coils are exposed and not encapsulated. The encapsulated coil can not dissipate the heat.

So the mass of the flywheel is not the only limiting factor, but the drag produced by the magnets passing the heavier laminations of the coils will also drag down the system. So this drag along with the load can create the loss of as much as 5 to 6 HP at full throttle.

A charging system for a 16 amp system will have less drag on the motor than a 40 amp system at the same amp output .

The heavier flywheel also pays a higher price in being harder to balance and putting more strain on the motor itselt. Yes a lighter flywheel is easier to balance, will have better acceleration and top end and will rev quicker.

[RSM]

That's an explanation. thanks

[espen]

I agree one of the best posts I have seen for a long time !!!
Reminds me of prof outboard where is he???
Thanks