Blowby CFM


Has anyone used a blow by sensor/gauge on their engines to monitor the health? i’m just wondering what a normal reading might be?

i got 1.5 CFM out the valve cover breather venting to atmosphere.



Normally its measured with a manometer. You can use electronic ones, but they dont measure CFM.
I dont know what the limit is per BMW.


what is measured with a manometer? measuring pressure in the system can be misleading for working out if there is too much blowby. i’m venting to atmosphere anyway (no sludge in intake ftw)


Suggest you search web for how to do a leakdown test. Cliff notes, dual gage, cylinder at TDC, 100psi on first gage, read leakdown on second. Anything under 5 is excellent.