I made a craddle to install Vems under the dashboard. This is not too far from the ignition and injection ecu from where i would get the signal sensors.
<phtos coming>
Noise from Vems
Next I made the harness between injection ecu Mplex and Vems following the documentation instruction concerning the "grounds";
Everything is coming from Mplex (ground, 12V etc) through and 8 poinst external connector: triggers signal is one wire shield on the Vems side
Then I bench test it.
- trigger errors at low speed
- no trigger errors when crank trigger shield is ground on the Mplex side.
- no trigger error when using fliyng single wires to connect Vems
- 200mv 2kHz noise on any grounds of the Vems
- no noise on the Mplex side
- Vems noise independent of rpm.
- 0 ohm between Ground 5,32,21,22
- 0.4, 0.5ohm between Ground 26 (senor groung) and the others (so GND5 and GND26 are not connected hard).
To debate ..
- I conclude that there is a noise radiated by the multiple ground wires coming out the genboard the more wires, the more noise)
- that it is better not to shield the trigger on Vems side
- besides I do not understand much the physics or the maths of the recommendation: "all 4 GND5 (power-ground) pins must be connected to GND (EC36pin26) with short wires max 40cm (1.3 feet) from EC36 connetor to avoid damage caused by GND5 voltage jumping too high above GND (when ignition transformers, injectors or other loads are driven) ..." from "GenBoard/Manual/GroundConnections .
Why not make a hard connect Ground 5,32,21,22 (good section). (This will save some pins) ??