If I take a log of my DIYPNP with the engine off, I'm seeing the MAP signal fluctuate constantly by ~0.5Kpa with occasional spikes of 1-2Kpa.

I assume this isn't normal and I'm also assuming it's not related to grounds because I've seen the same thing with it plugged into mains power with the mains adapter.

Also, in my log, the TPS and MAP signals go completely flat for a period (there is still some change on the TPSdot trace) and then the noise returns, which is odd.

So is that 'normal' noise or should I expect the traces to be _dead_ flat when the engine is off?

Attached is a picture of where the MAP trace goes flat.

 

A tiny amount of noise is pretty normal - real electronics seldom give dead flat signals on a real car.

 

It is because of the max an min of you y-axis. You should set fixed max and min and the line will be flat.

The mapdot max and min is only 2 points apart in your screenshot - so an alteration of 1 point is a spike.

 

Thanks, that's what I wanted to know.

The range of the MAPdot trace there is over 300 btw.

The range of the TPSdot is over 150. The larger of the two negative spikes in the TPSdot trace is ~-29 while the TPS trace is dead flat. I'm guessing the TPS fluctuated by a very small amount (<1%) but it must have happened within an extremely short period of time to generate that kind of TPSdot.

(TPS lag factor is 50)

Anyway, I just wanted a sanity check that these fluctuations are reasonable.

Still think it's odd that the MAP and MAPdot traces flatten out for that period.