Logging Issue

Attached is a Screen Shot of what happens only when the WMI Relay is activated. Checked the wiring, have resister spark plugs etc. etc. Could it be that I need a Diode across the relay ? I have just before the WMI Pump.

The straight lines are a loss of USB comms, usually takes some serious noise to cause that with the G4+, it was quite robust comms and I've only ever had dropouts on very high boost cars with CDI.

Is the WMI pump being PWM'd or just on/off? If so, what are you using to drive it? Does anything else happen at the same time the WMI is enabled that would increase ignition noise such as ignition timing or boost increase? Do you have anything plugged in to the CAN1/RS232 port?

The WMI pump is being PWM'd via a "normal" type SS relay. The relay is activated by MAP @ 140kpa and timing does increase but not until about 160kpa. Nothing is connected to the CAN1/RS232 port.

Ok, suspect it must be the unsuppressed kickback from the pump that is upsetting things, most of those generic industrial SSR's dont have any snubbing and arent designed to PWM inductive loads. You could try a big diode on it, I dont have enough experience or knowledge to suggest an ideal one but I would probably try just a switching diode first. Look for something with a forward current rating similar to what the pump normally pulls and a max reverse voltage of at least say 200V.