Spray M injectors are 8-hole gasoline injectors donated by BorgWarner to the ECN in 2022. The counterbore geometry is very similar to Spray G, but there are differences depicted below.
The Spray M internal geometry is similar to Spray G geometry with the hole position at distance from injector centerline approximately 0.1 mm less. The tip diameter is 6.0 mm for Spray M, compared to 7.5 mm for Spray G.
A comparison of internal measurements of Spray M and the Single-Hole Atomizer nozzle using x-ray computed tomography is detailed in this PPTX file presented at ECN8.11.