In the products results page on line 46 is the line that controls how the search terms are treated. Currently the AND separator is ", " and the OR separator is just a space " ". So if you have more than one work separated by just a space then it will use or and find any matches for any of the terms.
You can change this around so that a dash is the separator for the OR by making it like this:
php:
$WADbSearch1->keywordComparison($KeyArr1,"".((isset($_GET["S_ProductName"]))?$_GET["S_ProductName"]:"") ."","AND","Includes",",%20","-","%22","%22",0);
This will make it search for the entire string in the product name.
So if you want to have it combine the terms with an explicit or you would separate the words by with a - rather than a space (word1-word2), if you want to explicitly use and you would use a comma space like this (word1, word2).
