what is the best software to design car engine and get diagram ??

سلام. اون کارم فکر می کنم تو کتیا می تونی انجام بدی ولی محدود تر از نرم افزارای تخصصی .بگرد محیطشو پیدا کن

Okay, there is two type of CADing... one is modeling and another is designing... the difference between "modeling" and "designing" is in modeling you just create the concept of any object... just a rough model to make a understanding about your object's concept... but in designing you model that object with optimum specifications which means it includes accurate dimensions, assemblies, flow simulation, analysis etc...

If you are just a beginner, I would suggest to use Autodesk 3ds Max for modeling... it's quite handy, has a user friendly work station and it's one of the most versatile softwares for modeling and animations.

For intermediate level, I think Dassault Systèmes SOLIDWROKS is best for getting acquainted with actual designing which means you will get good concept about your car's dimension, engine assemblies and car's flow simulation for analysis.

And if you're looking for something very big, something much much more advanced... I suggest you go for Dassault Systèmes CATIA