Battered by the better burger wars among higher-end competitors including Five Guys, Wendy's has decided to remake and upgrade its 42-year-old hamburger. In doing so, the company spared no details in research and planning.

Wendy's consulted a pickle chemist, executives went cross-country on a burger-eating tour, and customers were quizzed on their lettuce knowledge and preferences.

The result is Dave's Hot 'N Juicy, the new burger named after Wendy's founder, the late Dave Thomas. The burger has more cheese, a thicker beef patty, a buttered bun, crinkle-cut pickles, and red onions instead of white onions.

Hot 'N Juicy patties are still square, like Wendy's classic hamburger, and the 6,600-restaurant chain hopes the new burger will help the company better compete against McDonald's, Burger King and other new better burger competitors, including Five Guys.

Sales at Five Guys increased 38 percent last year and the chain has received high ratings from fast food industry surveys and long lines from customers coast-to-coast.

Wendy's Hot 'N Juicy hamburger is now available nationwide.

Wendy's started working on a new burger in 2009 as part of its Project Gold Hamburger project after hedge fund magnate Nelson Peltz bought Wendy's and combined it with Arby's. The union between Wendy's and Arby's didn't last, but Project Gold Hamburger survived, resulting ultimately in Dave's Hot 'N Juicy.

Wendy's chefs tested different concepts, ingredients and styles in the Project Gold Hamburger quest, sampling different lettuces and even round burgers. But in the end, the natural square won out, in keeping with Wendy's tradition, as did iceberg lettuce, since taste testers preferred that over green-leaf lettuce.

Tasters did say they wanted a thicker burger, though, and Wendy's ultimately changed everything about it's classic burger but the ketchup. Wendy's dropped the mustard, opted for whole-fat mayonnaise, and reduced the pickle and onion serving sizes to better emphasize the beef flavor.