The question needs to be phrased more appropriately then.
We've already gone over the discussion of what "kick in" means... Do you mean initially feel anything? or time to peak?
That question is too broad then. Different chemicals act differently on the brain, and have different lengths of time to where they reach peak plasma levels... If you want o know why that is then you have to really understand the neurochemistry behind how each different drug interacts in your brain... which I can't claim to.
So the answer is that most smoked drugs effect you (relatively) immediately, but each individual drug will have different times for when you reach the peak.
IV'ing may be faster but for all intents and purposes both ROA are making the drug effect you immediately. What differs for every drug is the time for the drug to reach peak plasma concentration. This time may also be different for the same drug depending on ROA. ie time to peak plasma concentration for IV Heroin may be different than time to peak plasma concentration for smoked Heroin