Wrong time estimates for routes calculated by LM+Brouter (car profile)

I am using 3.68.2 and Brouter, for car travel only. While the distances calculated are always correct, the time estimates are always about 2x too long for any given distance (with a know speed/profile). Ran a few simple tests, the factor of ~2 is consistent (example: motorway, almost straight line of 100km is estimated at 2 hours -> as if the max speed on that motorway was 50kmh). So I thought it must be a problem in profiles (max speed!) used by Brouter. I checked with the brouter dev and he answered that LM uses its own profiles, in other words he has no control over it. Searching the LM files on my phone I cannot identify the location of any profile files, nor can I edit them.

In a similar thread another user complaints about much too short time estimates when hiking. However this seems unrelated. His (expected and real) speed does significantly vary with sloop (climbing is not hiking) and that is why the panel responded that this is very difficult to fix.

My case occurs in flat space and on flat roads. It happens even on straight line roads without any intersections, villages, etc. And as the distance traveled by a car does much less depend slope, this cannot have the same origine.

Is there a chance to fix this problem OR let me know if a user can edit the profile values for average / max speed ?

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