Deca has a very long half life (this is why I prefer Nandrolone Phenyl Prop, 3 day half life instead of 14 days) so it generally takes most several weeks (4 weeks as another posted is about right for me using nandrolone decaonate) and there for will take longer than about anything you will have in your AAS tool box to kick in. Keep in mind it also takes a very long time to clear your body (Deca's metabolites are detectable for up to 18 months in drug tests , once again because of the long effect of the ester.
Front loading might have some minor effect, but biologically you will get more out of front loading the shorter the hormone ester is. Test Prop will obviously hit harder and faster the test cyp, etc.
This is a little off the question you asked. But you may want to look at going to short esters if speed of impact is what you are looking for. Generally aal i would use anymore are short esters for 3 reasons. 1, there is more hormone per weight in a short ester than a longer one. This really is a small difference, but over a long cycle, it does add up. 2, Short esters act faster and are faster to shut off when you want to and 3. short esters allow you to adjust to unforeseen issues such has side effects you may not have expected, you can change dose levels and have effect from that change in a matter of days. With Deca you mentioned, if you needed to lower the dose if your stop all injections it has about a 30 day roll out untill you get to low enough concentrations to no longer effect the body. Short esters give you a level of control and modification that long ester do not.
Down side to short esters is ed injections (or EOD injections ). I personally do not mind shots at all, so not an issue.
badham