Turbo Speed Measurement Issues

[mantonakakis]

Hi all,

I built my own board to control the HE351VE and interface with a MegaSquirt2 and Nextion display, as well as read various sensors and control some other actuators (like boost control solenoids).
I'm using the MAX9924 in A2 mode to read the turbo shaft speed, and using the FreqMeasure library on the recommended input pin. However, I'm having issues in certain ranges reading the turbo speed. At idle with low shaft speed (1000-3000rpm turbo speed), I am seeing some huge spikes. I might be able to attribute those to poor signal quality at such low speeds. At WOT and full boost, I'm also seeing weird readings, where for a single sample I am getting a spike of about 10,000rpm.
I'm hoping to rule out some potential hardware issues first.

Does VR sensor polarity into the MAX9924 matter?

[hakcenter]

Do you have any back pressure equipment to verify a steady environment for the turbo ?
This is the second HE351VE I've heard of that has unstable shaft speeds, yet I just tuned Dooley and his turbo was rock solid shaft speed.

Can you provide some pictures of your soldering, verify your pinning on the max chip on the adapter board prior to soldering to the main board ?