Work in Progress


It’s been quite a while. Slow progress. Lots of other things to tackle.

Meanwhile, I’ve been “repainting” the current flow diagrams to reflect the decentralised electrics with the respective distributed control units, new switches and devices; and the lack of connection into the central electrics.

For easy reference, I’m leaving the original electrical devices in or near the same current tracks as drawn originally.

Similarly, the colour(s) of connecting wires remain, as much as possible, the same as per the source vehicle. Wire sizes are being reviewed as most of the wires to switches, etc. will no longer be carrying substantial current to drive motors and lamps directly; just a tiny signal and some tiny illumination in the case of dashboard switches.

Here are the first few pages.

In tracks 1 to 14, I introduce J-Front which is the distributed electrical control at the front of the car near the battery, starter and cooling fan(s). Part of J-Front’s function is to operate the starter motor when receiving an authentic signal from J-DC, the unit for driver controls in the dashboard, ignition switch (D), steering column, handbrake, brake pedal switch, etc.

One of the implementable features of the two units in combination and with other signals, is that the engine can be started automatically by the driver briefly turning the key to the start position, making the starting (X) contact. J-Front then operates the starter optimally, just enough to make the engine “kick over” by monitoring the engine speed signal. That same engine speed signal can be used to prevent the starter from trying to crank too long if the engine isn’t actually turning, or from engaging the starter while the engine is already running.

As fail-safes, the driver can hold the key in the starter position as usual and J-Front will keep cranking until the key is released or the battery voltage drops too low. The driver can stop the automatic cranking process by turning the ignition switch to off.

We don’t need no steenking ENGINE START button.

Main electricsIn my research, I’ve found that the Mk2 Golfs with second-generation central electrics (CE2) usually have an ignition key that provides the S contact available in later models, but never wired usefully in the Mk2 Golf. If there’s a rectangular connector on the back of the ignition switch, there’s probably an S contact. The S contact provides battery power to e.g. accessories from the time that the ignition is first switched on after key insertion, until the key is removed from the lock. A very useful signal for lots of stuff.

Also useful is the battery distribution box (BDB) that mounts directly onto the battery, providing for up to 10 fused circuits, two of them via MIDI fuses and the other 8 by MAXI fuses. This is sufficient to provide the major current tracks leading to electrical consumers throughout the car, controlled by the networked controllers.

There are also threaded lugs for attaching the starter and generator leads, unfused as well as a tab for attaching a jump-start cable.

Tracks 15 to 28 shows more of J-Front, this time controlling J293, which is comprised of the 2 fans salvaged from a Mk5 Golf repair job where the smaller fan had stopped turning and the fans had to be replaced as a pair. The usual problem with them is that one of the motor brushes becomes dislodged due to ingested dirt. Opening up the motor by “uncrimping” its top cover and repositioning the brushes after cleaning out the sand, etc is all that is needed before the cover is refixed. (I used some high-temperature, metal-loaded epoxy resin.)

J293 is incorporated into the larger fan V7 is provided with the slow PWM signal that it expects normally for speed control. V177 is driven by J293, at a speed matched to V7.

15-28Driving the ventilation fan for the interior is J-HVAC that incorporates all the heating, ventilation and airconditioning controls and actuators in the cabin. The four-speed fan switch E9 is directly augmented with a resistor network so that the position of the switch can be taken into the control unit as a single, analogue signal.

The ventilation fan V2 is expected to be driven via high frequency PWM to control its speed directly, eliminating the old resistor network.

Unfortunately, the Mk5 fan shroud won’t just bolt straight into the Mk2, being about 60mm too tall. You get an idea of how much bigger a Mk5 is, compared to a Mk2, when trying to “back-port” components. The smaller of the 2 fans is the same diameter as the fan originally in the Mk2.

Fan Shroud V7+V177So the fans need a new radiator shroud; a design for which I’ve designed up to make out of aluminium extrusions and 0.8mm sheet, simply folded and rolled. The new is much lower profile than the deep fan shroud and fan motor originally in the Mk2. However, at the time of writing, I’ve not mocked it up in cardboard to ensure sufficient clearance to components in the engine bay.

It is very inconvenient not to have a full 3D model of an engine bay interior!

Tracks 29 to 42 cover the fuel supply to the engine. J-RBody handles all that in the back of the car, near to the fuel pump. It’s a simple unit mainly because it shouldn’t be doing much given the nature of the stuff with which it’s dealing. Contary to previous publication, the node will not be used to control any tail lights or the luggage compartment illumination.

The unit receives control and keep-alive signals via LINbus and transmits fuel levels and filler flap lock status as required. The fuel pump is stopped if the LINbus becomes silent or if a signal is received that the engine has been switched off. (The virtual KL15 signal goes low.)

Fuel SupplyV-FFlap is a central locking actuator replacing the pneumatic lock of the Mk2. Independent control of that lock provides useful features such as keeping the flap locked while the engine is running (i.e. the fuel pump is running) and under normal operations, moving or stationary.

For convenience, the driver can force the flap to unlatch by holding the door lock knob at the driver’s door up for a second or more, with the engine stopped and the door open. This is not thought to be inconvenient as it is nearly all, already part of a “standard” refuelling process of the car. The flap will relatch when the engine is started or the car is locked.

And so we move onto the final teaser of the evening; tracks 43 to 56 covering the ignition and the first half of the fuel injection system. The main interlocutor introduced here is J-Central which is to be located near the Digifant control (J169) in the air plenum in between engine compartment and windshield.

J-Central provides power (as a proxy for the ignition lock via J-DC) to the ignition amplifier and Digifant control units, as well as monitoring a number of signals to transfer them to the vehicle network realm. It also manipulates some to make the new devices compatible with what Digifant expects to see. The Hall sensor signal from the distributor (G40) is buffered to be used as an engine speed indicator throughout the vehicle network; especially for J-Front to operate the starter.

J-Central also proxies signals from other units such as the cranking and airconditioning compressor clutch activation from J-Front.

Ignition and Fuel InjectionNotable in tracks 53 to 56 is G70, an airflow meter (air mass meter) with intake air temperature sensor to replace the (very expensive) flap-type meter in the Mk2 Golf with Digifant. Translating the signal from the newer sensor to the language of the old for Digifant, requires the engine speed signal so that the air quantity per intake stroke can be represented accurately as an average; a quality mechanically inherent through the inertia of the moving flap in the old meter.

J-Central also provides the additional power required by the hot film sensor of G70.

More to follow. Relatively soon.

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