VEMS Community Forum
Technical => Wiring & Sensors => Topic started by: [email protected] on February 27, 2007, 02:25:10 pm
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Grounds are a much under estimated part of any ECU installation, just count the number of ground wires on your standard ECU if you don't believe me ;D
Because of the way we isolate the delicate sensor grounds from the noisey ignition and control grounds it is ESSENTIAL that the grounds are grouped correctly. It's always best to explain using an example, and thanks to Damo we have the perfect example of a good grounding setup:
(http://www.vems.co.uk/VEMSLoom/DamoIsWellGrounded.jpg)
Wires are all joined securely 10 to 15cm outside of the unit. It is possible to use a longer wire after the join (of >6mm2) if a suitable grounding point is not within reach.
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so where should it be grounded to, i have the battery in the boot and i have run a 35mm2 positive , grounded the negative in the boot but also run a 25mm2 negative cable to ground next to the ecu from the battery then intended to loop through to the cylinder head, is this wise
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Theres a big cluster of ground wires next to the ECU.
I'd use that.
The trouble with multiple ground wires is the possabilities of ground loops, strange things that I don't understand, but fear in the same way as I fear Sharks.
Rob
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The trouble with multiple ground wires is the possabilities of ground loops, strange things that I don't understand, but fear in the same way as I fear Sharks.
I feel compelled to say, that is the funniest thing ive ever read. It makes me laugh every time.
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I have to agree with you - it's excellent.
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Grounds are a much under estimated part of any ECU installation, just count the number of ground wires on your standard ECU if you don't believe me ;D
Because of the way we isolate the delicate sensor grounds from the noisey ignition and control grounds it is ESSENTIAL that the grounds are grouped correctly. It's always best to explain using an example, and thanks to Damo we have the perfect example of a good grounding setup:
(http://www.vems.co.uk/VEMSLoom/DamoIsWellGrounded.jpg)
Wires are all joined securely 10 to 15cm outside of the unit. It is possible to use a longer wire after the join (of >6mm2) if a suitable grounding point is not within reach.
Where would you connect the sensor grounds?
I say this as looking at phatbobs guide and the vems manual it shows the sensor grounds being wired pin 26 (either directly at pin 26 or 20mm from the common ground point along the branch to pin 26)
so looking at the above picture, would it be ok to wire your sensor grounds to that ring terminal? if so that would be good for me a my ecu is a solid metal case and i was going to put a screw\bolt through the case and then connect all the grounds with the use of ring terminals to it.
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You connect the sensor ground to the common ground, the 20mm part has turned out to be not necessary.
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Rob,
will it be ok to join the sensor ground wires at the ring terminal point?
im doing a loom for stuball's v8 capri (dnb doing ecu),
at the ring terminal point it will be where i go up to 6mm cable to run to the back of the head,
(http://www.vems.co.uk/VEMSUserManual/VEMSGrounds.png)
or do i need to run the sensor earths direct to the vems at pin 26? (as you say the 20mm up is not needed)
also i see on the wiki (your post) you show this,
(http://www.vems.co.uk/VEMSUserManual/vitalEarthModSmall.jpg)
where do i need to do this? or where i do the solder join to 6mm be ok?
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Rob,
what would you consider to be the "best" method of wiring the sensor grounds (in an ideal world)? ie all directly at pin 26, all at the common ground point, or 20mm from the common ground point. I know you said the 20mm part wasnt necessary, but is that because you can "get by" by wiring at the common point or because it really makes no difference at all.
Thanks.
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The 20mm point was one of those things that came about when someone who was not a native english speaker told me that the sensors should ground 'not more than 20mm from the common' - or words to that effect. It turns out that anywhere between common ground and 20mm up the wire to the pin26 is acceptable.
But...
If you cut into the wire that leads to that ground pin you can add a stress riser that could potentially break - and that would cause the P259 chip to pop - pulling the VR chip voltage down and stopping your fuel pump, easy enough to fix, but not a fix you want to have to make.
So I go for the common grounding point, using an additional wire with its core exposed mid way which I wrap around the twisted wires (http://www.vems.co.uk/VEMSUserManual/vitalEarthModSmall.jpg) then solder - this gives me two sensor ground wires to fix my sensors to.
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cheers rob, will report back with pictures tonight to see if it passes your inspection mate ;D
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Is it ok to ground coilpack ignitors (Mitsubishi ones) to the same point where the ECU is grounded to?
It would enable to make my wiring alot neater and simplify my Rev counter wiring as well.
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I would ground that directly to the head, and make sure that the grounding on the block is excellent.
Rob
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The pinnout shows, that there is a pin in the econseal 18 plug that needs to be grounded (pin 17), but it is not shown in this topic neither the user manual. Should I connect it to common ground?
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EC18-pin17 is connected internally to signal ground, for convenience. It's for the analog signals and RS232 communication.
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You connect the sensor ground to the common ground, the 20mm part has turned out to be not necessary.
So you do not need to separate the sensor grounds from the common ground? You can bundle them all up together? I thought it was best to remove the sensor grounds from the main grounds to isolate the noise, but maybe I misunderstood.
Also, my factory trigger wires have the extra ground wire wrapped around the inside. Do I ground this to the common ground, or to the sensor ground? Does it make a difference?
Sorry, just trying to make sure I do it right the first time :)
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You do not.
The shield and negative on the VR sensors connect to analog ground, which in itself connects to the main grounds.
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Thanks for the clarification Gunni!
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OK, I haven't been able to work on my project for a bit but I am going to try and get the wiring wrapped up.
I can bundle all grounds to one point from the ECU (and sensors that have a ground including shields). From there I can just use one ground (much larger wire) to the chassis? I am no longer using the factory harness which had multiple ground points.
Also, on the factory harness the ignition coil pack ground had a beefier wire that went to the same chassis point as the grounds from the ECU.
Sorry if this is beating a dead horse, I am just making sure I can ground properly and not have noise interference.
Thanks.
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Sounds about right.
You can put that beefy wire to the same grounding point on the chassis.
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I would ground that directly to the head, and make sure that the grounding on the block is excellent.
Rob
Solid True just see BMW S62 factory dedicated IGN grounds. Basically every coil have own ground wire connected to head.
There are also capacitors(if I am right) connected so IGN stream.. each bank have own.
(http://i70.photobucket.com/albums/i107/jamiepeers/Vanos%20Overhaul/P2090437.jpg)