For example if I'm calling this URL :

mywebsite.com/mysefurl?classe_energie_refrigerateur=A%2B%2B

getVar give me
classe_energie_refrigerateur=A

If Joomsef is disabled :
classe_energie_refrigerateur=A%2B%2B

WTF ????

Why does JoomSef filter my variables values ??? Why ???
Is there some antihack variable filtering ? How to disable it ?

Ok, I've found a workaround :

just disable "Prevent non-SEF variables from overwriting the parsed ones:".

It's just a workaround preventing Joomsef overriding correct vars with "cleaned" ones in sef.router.php into JRouterJoomsef::setRequestVars();

I hope it can help someone else.