Turbo speed sensor calibration

[Lorcan]

Please would anyone confirm the calibration numbers to use for Garrett turbo speed sensors and M800. We have 14 blade turbos so use 14 as the calibration factor in ECU manager, however I've read that the speed sensors only pulse once every 8 blades.

Using a maths multiple of 4 in i2 seems to give a half sensible figure, but 8 gives ridiculous numbers like 160,000 rpm for a GT42 turbo, which it wouldn't do without falling disintegrating.

I've read through the calcs on the Garrett website but maths is not my strongest subject! TIA for any help.

[Lorcan]

Anyone?