its to quieten accessory NVH - per Nissan engineer in Nissan NA. I had a lengthy discussion with him regarding this. He says Nissan specifies it as a NVH dampner not a crank dampner. Even I4's of various tipres have this rubber ring and its a NVH dampner - nothing more.
Harry
Formerly yellowzxtt
" If it doesn't make it faster, i don't care " Please visit www.ztuner.com to GO FASTER