Sharing some of my knowledge from a recent venture into alternator wiring and control when using an aftermarket ECU.
Background
The CH uses a 4pin alternator, with connectors labeled FR, G, S, L. There is a separate stud for the main positive cable and grounding is done via the body/engine block. (RP27)
The CE 4g93 and early 4g94 use a 2pin alternator with connectors labeled S and L. There is a separate stud for the main positive cable and grounding is done via the body/engine block. (RP19)
When you use an aftermarket ECU, you'll need a way to trigger this alternator correctly and the info you need is not in one simple place.
The easy way (2pin 80amp)
The two pin alternator is more expensive to purchase new, however the effort to wire in is much less. If you already have one, no work needed. It simply needs a direct 12volt positive connection to the battery on the S pin and connection to the ground side of the battery warning light on the cluster to the L pin. This will already be there from factory. These are low current carrying wires, FSM specifies 0.5mm^2. The alternator will run at its maximum output at all times, regulated to 14.6-14.8volts.
The other way (4pin 90amp)
In my example I am using a Haltech PS1000, with the factory 4pin alternator.
As above, S & L are connected to sense and the warning lamp.
FR should be connected to ground.
G can be left floating (unplugged).
This will have the alternator operate 14-14.3 volt at idle & 14.6-14.8 volt above 2000rpm. More than fine for a rudimentary setup. This will not raise the idle if loads are high and voltage starts to dip. This will not reduce the charge rate in case of over voltage nor optimise charging.
Fault finding
The 4pin will NOT charge properly without the FR/G circuit. It will only charge up to 12.3 volt.
The sense circuit is required for general voltage limits.
Notably if there is a break in the Sense wire only, the alternator will charge at an extra 0.5volt of it's regular maximum output and will trigger the battery warning light. A nice failsafe option.
Future notes:
If anyone understands the PCM control better, please do share. I have done my best to understand this system within a limited scope, all info pointed toward a 5v positive control on the FR terminal and ecu ground on G terminal. This does not control the alternator. I would love to be able to trigger an idle speed raise and optimised charging rates (like smart charging).
Background
The CH uses a 4pin alternator, with connectors labeled FR, G, S, L. There is a separate stud for the main positive cable and grounding is done via the body/engine block. (RP27)
The CE 4g93 and early 4g94 use a 2pin alternator with connectors labeled S and L. There is a separate stud for the main positive cable and grounding is done via the body/engine block. (RP19)
When you use an aftermarket ECU, you'll need a way to trigger this alternator correctly and the info you need is not in one simple place.
The easy way (2pin 80amp)
The two pin alternator is more expensive to purchase new, however the effort to wire in is much less. If you already have one, no work needed. It simply needs a direct 12volt positive connection to the battery on the S pin and connection to the ground side of the battery warning light on the cluster to the L pin. This will already be there from factory. These are low current carrying wires, FSM specifies 0.5mm^2. The alternator will run at its maximum output at all times, regulated to 14.6-14.8volts.
The other way (4pin 90amp)
In my example I am using a Haltech PS1000, with the factory 4pin alternator.
As above, S & L are connected to sense and the warning lamp.
FR should be connected to ground.
G can be left floating (unplugged).
This will have the alternator operate 14-14.3 volt at idle & 14.6-14.8 volt above 2000rpm. More than fine for a rudimentary setup. This will not raise the idle if loads are high and voltage starts to dip. This will not reduce the charge rate in case of over voltage nor optimise charging.
Fault finding
The 4pin will NOT charge properly without the FR/G circuit. It will only charge up to 12.3 volt.
The sense circuit is required for general voltage limits.
Notably if there is a break in the Sense wire only, the alternator will charge at an extra 0.5volt of it's regular maximum output and will trigger the battery warning light. A nice failsafe option.
Future notes:
If anyone understands the PCM control better, please do share. I have done my best to understand this system within a limited scope, all info pointed toward a 5v positive control on the FR terminal and ecu ground on G terminal. This does not control the alternator. I would love to be able to trigger an idle speed raise and optimised charging rates (like smart charging).