Hello again

Now that I've set up iGO perfectly, I've had several trial navigation to known places.
As in any other navigation software I use the profile "fast" and "car" (I am talking about IGO nextgen for Android with latest HERE maps.)
The calculated routes are terrible, because "fast" is not faster or at least as fast as "short", it's significantly slower.

After a few tests I found out that the dependent variable for the route calculation is the set 'maximum speed' in the vehicle profile. With "130 km/h" the fast routes are not fast, with "70 km/h" the routes are totally different and a lot better...

What is this phenomenon and what is the optimal maximum speed to get "good" routes then?

To any moderator, yes I used the forum search 'route calculation' in iGO forums and there is nothing like that to find.