I know this may sound weird, but instead of making a payment of $1100.00 make your normal payment, and then two weeks later make your payment of $115.00. This will only help you if your lender applies the 2nd payment towards principle. You will have to ask them specifically how they handle payments. What this does is lower the amount of intrest to be paid between normal payments, putting more $$$$ towards your principle and less towards intrest.
Unfortunately, my lender does not handle payments made other than on due date. Therefore I can pay as much as I want during a month, but it will only be applied once during the month. It sucks! Find out how your lender will handle 2nd payments. It will speed up the payoff process even more than what you are already doing.