Gear Box Ratio

I have taken for granted that the reduction ratio is 2.43 to 1 on the 912 ULS engine. However I've seen 2.27 also mentioned in the Rotax Mtc. Manual regarding some 912 UL and ULS engines...some engines have slipper clutches some don't, anyone know how to tell which ratio you have? reason I ask is I have a tach. checker and need to know the proper ratio to apply the math. BTW my engine is a 2010 model, 912ULS.

Go to: https://www.flyrotax.com/engine-configuration-search.html

Input your serial number and they will tell you how that engine was configured when it left the factory.

Thanks Dave for the info!