Sorry Bigsteel didn't see the question. It is a clone of the CY engine. If I remember right it is a HY. I don't have the motor anymore to verify the HY though.
Had the differential out to replace a drive cup and thought I would post of pic of the 1/5th differential next to a Kyosho STRR 1/8th differential I had laying around.
Kyosho doesn't have the biggest ring gear around but cup is the same size as other 1/8th scale. You can really tell the difference when you are gently fondeling the differentials in the palm of your hand..........