I'm talking about up in the left hand corner where it tells you how many miles and minutes left in the trip. The time is way off from reality. So my question is how does it calculate that time? And is there a way to change it?

 

I would assume by the distance remaining in conjunction with speed.

 

But using what speed (an assumption in the Nav system, my avg over the trip, based on the road sizes to come (interstate, highway, etc))? For example, I had ~50 miles left to go in my trip yesterday, and it said it was going to take 1hr and 20 minutes. I knew that it would take less than 45 minutes since I would be averaging more than 60 miles/hr.

 

I think it goes by what the speed limit is (or what Honda believes it should be) on certain roads. IE - highways = 55mph, sidestreets = 35mph and so on.

I think I remember reading something somewhere about that.

 

Anyone know if it can be changed? My dad is using a Garmin stuck on the windshield because the time to location is so much more accurate than what the Acura nav says.

 

The readout of miles / minutes to the destination involves predicting the future.
All GPS units know the destination and your current position. It assumes you are going to follow the route the GPS will suggest. It also has to assume an average speed on those roads. Knowing the anticipated route and speed, it can calculate the miles / minutes to the destination.
Some Garmin GPS units have a screen where you can enter the average speed that would be assumed. I don't know if the Honda GPS has a similar screen.
The Garmin GPS may have a better set of assumptions and therefore calculates a more accurate miles / minutes to destination.

 

Guys, I understand how the math works for the Nav system to estimate when I'll arrive at my destination. The question is, what are the variables related to speed that the Nav system is using in the calculation. Then the follow-up question will be, can that variable be changed?

Outside of this, have any of you noticed that on long trips the estimated time to the destination is way off? I just went on a 4 hr trip and it was telling me that it would take 5 hours. Even on short trips (less than 1 hr) the Garmin is within a few minutes, whereas the Acura could be 15 minutes off.