Alternator Control

[Taylor]

How are you guys doing it? Its my last thing on the list to get the car back on the street.

In outputs, there is no load vs volts, which is a table i would like to create, but cant.

Its for a honda engine, a 3 wire alternator.

[John Reed]

What engine model is the alternator from? If I am not mistaken, most of the Honda alternators have the regulator built in. Only the Mx00 ecus have the capability (and it is VERY new out) of performing the function of regulating alternator output. Now if you simply want to cut the alternator at WOT to reduce load on the engine, that is a different matter (though make sure your battery system is up to the task).

[RossB]

The Hondas I have seen do have an internal regulator so should not need to be controlled by the ECU. What model Honda is this? Switching off the alternator at WOT can be done on some applications but we have not tested this with the Honda alternator.

[Taylor]

it is a 91 integra, obd0. I have the motec engine harness they make for the hondas.

Here is a diagram.

[Taylor]

anyone?

[NathanS]

From my limited experience with Hondas the input to the alternator is used to vary its output based on what ancillaries are running and engine operation, however if it is not connected the internal regulator maintains the voltage at around 14V.

Unfortunately I never got a chance to scope the signal to see if we could replicate it so have usually left it disconnected.

[Taylor]

ok, ill leave it unplugged and see how it goes.

[RossB]

The connection from this alternator to the ECU is not an alternator control function. There is a diode in the alternator to prevent current flow to the ECU. It is likely that this connection to the ECU is being used as an input to measure the alternator load. So as the internal regulator earths the field winding the voltage on the ECU pin is pulled down, this voltage would be a measurement of alternator load. You could connect this to the Aux Temp input of the M4 to measure alternator load if you wanted to. I would say that the Honda ECU uses this as a parameter in their idle control function.

Leaving it un-plugged should not effect its opperation.