Peak angular point delay

Consulting in the academic field articles in relation with combustion and the delay angle of peak point, around 5 degree discrepancy occurs between them was revealed. Also, motor noise has much to do with the construction of the crankcase stoutness. There exist clear difference of combustion sound between OS Max 60 FSR and ENYA 60 X motors, both of them had been designed based on Schnurle scavenging method, former had lighter weight and the latter did heavier weight with stout case design. Completely different exhaust notes were discerned in height and middle range operations. Former was shrill and latter was bold and low frequency. The thickness and material quality affect much on the exhaust note. So, lighter and vulnerable crank case do not always have an advantage if some comfortable exhaust is desired.
The lighter is not always the better in model 2 cycle motor designing.
Recognition change has done in my mind in this point.