The short answer is no. One grid-cell can only use one processor, so it won't help to give more.
The longer answer is that the one thing you could do is to run multi-instance to run more than one case at the same time. You probably wouldn't want to run multiple sites this way with differences between start and stop times, but that might be useful to do simulations to calibrate parameters. But, the other disadvantage with this is that if any of the cases fail -- it will shut the other instances down. So in the end, I'm not sure this is helpful.