Custom wiring harness for EFI engine

[Wedg1e]

Just some of the front to rear wiring on a Range Rover.

View attachment 376889

Ah, so about the same volume as a classic Rangey which had 5 Lucas wires

 

[rcx132]

Just some of the front to rear wiring on a Range Rover.

View attachment 376889

And that's why bus based systems like Canbus were introduced ! There comes a point where using a bus is simpler than traditional wiring.

 

[Robotstar5]

And that's why bus based systems like Canbus were introduced ! There comes a point where using a bus is simpler than traditional wiring.

I would imagine it has canbus as well on a 5 year old car?

 

[Wedg1e]

And that's why bus based systems like Canbus were introduced ! There comes a point where using a bus is simpler than traditional wiring.

Yeeees... and then they come up with the sort of silliness where the central locking modules have to be 'coded' to the body control module - and still needs 5 wires between the two (Landrover, I'm pointing at you).
WTF was wrong with simply reversing the polarity on a DC locking motor?

 

[rcx132]

Yeeees... and then they come up with the sort of silliness where the central locking modules have to be 'coded' to the body control module - and still needs 5 wires between the two (Landrover, I'm pointing at you).
WTF was wrong with simply reversing the polarity on a DC locking motor?

I see. Maybe if the bus system was more standardised then it would be easier to deal with.

I've drawn up the wiring diagram for the custom loom, it's a serious amount of wiring for a 90's engine with 12 sensors/controllers.

 

[Cato]

I see. Maybe if the bus system was more standardised then it would be easier to deal with.

CAN BUS is completely standard and universal in its application. The problems/variations come when manufacturers get hold of it and start using it to connect their own weird/wonderful/pointless gadgets and ECUs. They have to allow third party access, but they don't have to make it simple and try to use as many of the loopholes as they can to prevent full access. Security and safety are their top two favourites as blocks to allowing access. So it frequently ends up as a complete dog's breakfast.

 

[bricol]

I do remember the fun I had with a Rover K-series ECU wiring and sensors. Could not get it to fire and run. About midnight one day, laid in bed, had a thought . . . into the garage, in the PJs, pulled the cam cover off . . . ah-ha! No flippin' reluctor on the after market cam . . . tune out cam position sensing in the ECU and twenty years later, it still starts and runs well.

 

[Wedg1e]

I do remember the fun I had with a Rover K-series ECU wiring and sensors. Could not get it to fire and run. About midnight one day, laid in bed, had a thought . . . into the garage, in the PJs, pulled the cam cover off . . . ah-ha! No flippin' reluctor on the after market cam . . . tune out cam position sensing in the ECU and twenty years later, it still starts and runs well.

See, I'd have been the same... except I don't wear PJs

 

[Wedg1e]

CAN BUS is completely standard and universal in its application. The problems/variations come when manufacturers get hold of it and start using it to connect their own weird/wonderful/pointless gadgets and ECUs. They have to allow third party access, but they don't have to make it simple and try to use as many of the loopholes as they can to prevent full access. Security and safety are their top two favourites as blocks to allowing access. So it frequently ends up as a complete dog's breakfast.

When I first heard about CANBUS, it was talked of as a 2-wire system. Power down one (heavy-duty) 'ring main' and data down the other, ground via the chassis.

 

[Pete.]

I see. Maybe if the bus system was more standardised then it would be easier to deal with.

I've drawn up the wiring diagram for the custom loom, it's a serious amount of wiring for a 90's engine with 12 sensors/controllers.

View attachment 377032

What are the triangles in this diagram?

 

[Wedg1e]

I'd presume earths?

 

[m_c]

When I first heard about CANBUS, it was talked of as a 2-wire system. Power down one (heavy-duty) 'ring main' and data down the other, ground via the chassis.

Full spec CAN bus is two data wires plus power wires.
However that's only for high and mid speed CAN bus.
You can also get a low speed single wire CAN system, but you also get LIN bus which is another one wire system.
In terms of automotive, you also get MOST bus, but that's an optical system aimed at Media (Media Orientated System Transport)

CAN bus is just the protocol for communication, the actual implementation can vary quite a bit.
It's not that unlike ethernet, but whereas with ethernet where data packets have to acknowledged and get resent on collision, CAN doesn't have to be acknowledged, and the packet with most priority overrides lower priority packets automatically, so although collisions still occur, the priority packet always gets sent with no delay.
It's quite a clever protocol when you actually look at it in detail.

 

[Pete.]

I'd presume earths?

If they are then it's highly advisable that each sensor has it's own signal ground back to the ECU if it has the pins to accomodate it (which it should), to avoid the ground offset problems that can come with shared returns.

 

[Wedg1e]

If they are then it's highly advisable that each sensor has it's own signal ground back to the ECU if it has the pins to accomodate it (which it should), to avoid the ground offset problems that can come with shared returns.

I was thinking that some of them might need to be screened cable as well.

 

[m_c]

If they are then it's highly advisable that each sensor has it's own signal ground back to the ECU if it has the pins to accomodate it (which it should), to avoid the ground offset problems that can come with shared returns.

Certainly signal grounds are typically direct from the ECU, and changing that could lead to problems.

I was thinking that some of them might need to be screened cable as well.

They might be.
I would be replicating whatever the original wiring consisted off.

 

[rcx132]

What are the triangles in this diagram?

View attachment 377071

Yep the triangles are earths. Diagram was drawn using genetic software so there aren't proper symbols available. Not sure what the best software is for wiring diagrams? I resorted to draw.io (now diagrams.net).

 

[rcx132]

CAN bus is just the protocol for communication, the actual implementation can vary quite a bit.

So is Canbus the way of sending messages but doesn't define what the messages mean ? Not unlike serial then? If so then who or what standards defines what the messages mean ?

 

[rcx132]

If they are then it's highly advisable that each sensor has it's own signal ground back to the ECU if it has the pins to accomodate it (which it should), to avoid the ground offset problems that can come with shared returns.

Ah, is that why the ECU has multiple grounds? I was meaning to ask about that. Thanks.

 

[rcx132]

I was thinking that some of them might need to be screened cable as well.

Yes the Oxygen sensor is screened on the original loom. I'll add that to the diagram.