Nitrous solenoids being "pulsed" when key switched to on

[rubberbudgie]

As the subject says, when the ingition key is switched to on, the nitrous and fuel solenoids are being triggered for a brief moment causing a small amount of fuel and nitrous to be injected into the manifold which causes a nasty "pop" when you start the engine.

I'm using AUX8 (A34) to connect to the relay that controls the solenoids. I'm thinking it's got something to do with the polarity and output mode but am not sure so was wondering if someone could shed some light on this for me or point me in the direction of where I may find some documentation for this?

Thanks.

[rubberbudgie]

Either the question I asked was too hard for anyone to be able to answer or nobody from Motec checks these forums very often.

[IDP]

I have used the M800 for Nitrous without trouble.

What settings are you using for the outputs? I'll have a look and compare to mine.

[Scott@FP]

Why don't you have a Master switch that kills power to both solenoids unless its engaged?

Say a DPDT switch that both activates solenoid relays and provides ECU with the 'armed' status?

[incontrolsteve]

As with most products, at the point of energisation of the ecu the outputs are switched low, so you will get a small pulse during this time,if you have power at the solenoid at the same time, until the ecu is booted up and "running" the output will remain low. Only a few msec, but enough to pulse your outputs. The way to stop this would be to make sure your power to the solenoids is supplied after the ecu is turned on. A PDM or intelligent power supply could do this for you, or even a separate power switch to isolate the solenoids.

[SprinterTRD]

Or just run the power to the solonide off the fuel pump relay.

[MarkMc]

Any relay that the ECU is controlling should NEVER be powered before the ECU or you will have exactly this problem, the same goes for ignition.

[rubberbudgie]

Awesome - thanks so much for the information and solutions, totally makes sense. I knew there had to be a logical explanation for what was happening, the fact that the solution is so simple is an added bonus!

[Martin]

Are you supplying the relay with a "highside" signal to energize it?