Thanks guys for all the inputs! i guess the logical way to go would be to read the tach and make a decision based off of that.
Wildbil, no i havn't as of yet.
The code for the project was mostly written by another member on this forum, as i'm quite new to the world of arduino i'm not that fluent with the language yet and had no idea how to create a state machine, but i will try and implement the tach sense completely myself..
Will update and do a project write up once it is completely finished