Any program will be more accurate dependant on the amount of info put in and variables that you can add....There are so many things that you can't enter, weather etc....which all play a factor, but is a fun tool, and can make you think about whether something is going to help or not, and if not why or why so little etc.....There is another program other than DD, that supposedly is very accurate, but you have to map everything, by the time you are done, you could have built the motor and tested it....can't think of the name of the software off the top of my head though....
Brian
www.teamcracing.com