Navigation Screen

When you say the NAV screen do you really mean the MFD?. I don't see how a moving map could effect your gas mileage.
And the MFD is the nerve-center for all the features of the car. Is it realistic to turn it off for long periods of time.? Just turn the whole car off and save alot of gas.
Gimme-a-break.

Yeah it would save you some gas, about 100/th of a MPG. Someone quantified how many watts of electrical power used would impact a single MPG. It's a whole lotta Watts.

Learning how to drive your Prius, to exploit it capabilities, will have a far greater impact on your MPG.

 

I think a reasonable average energy density for gasoline is about 36.6 kWh/gal. US.

So if you drive 50 MPH for one hour and get 50 MPG, you've gone through 36.6 kWh of gasoline.

In the mean time the Nav system and display probably draw less than 400 Watts altogether. After using them for that same hour, you'll have "wasted" less than 400 Wh. This works out to something less than 0.011 gallons. Assume triple that for various conversion inefficiencies (gasoline to motive to electrical) and you're looking at somewhere less than 0.033 gallons extra for 50 miles. So if you eliminate the NAV and display I suppose you might have achieved, at best, 50.03 MPG saving you 1 gallon of gasoline for every 1,500 miles.

If you drive 12,000 miles per year, eliminating the NAV and display might manage to save 8 gallons per year.

Anyone want to check my math? For some reason I'm not feeling confident about it. I expected it to come out quite a bit less than 8 gallons.

 

Are you sure they pull 400 watts together? My 62" Plasma pull 398 Watts and my 42" LCD pulls around 250 watts (from memory). I'm not sure how the MFD can pull that much?

 

Nope. Not sure at all. Thats why I said, "probably draw less than 400 Watts". Figured there was no way they'd pull more, but wasn't sure how low I could go. If you've got a better guess, the math is simple.

If the entire system pulls 200 Watts, then divide in half. Perhaps 4 gallons per year, and an improvement from 50MPG to 50.017MPG?

 

Since a scan gauge can pull the same info that means the info is being calculated by the onboard computer anyway and the MFD is just simply a touch screen that displays data so there probably isn't any "computing" that anything you're turning off stops (this all is a guess on my part). With regards to the tracking of satellites you may have a point there. It would be my guess that that's powered by the MFD, but then again we don't know if turning the MFD really turns much off... or perhaps it just turns the display off? Regardless, the power pulled by the tracking of satellites is probably relatively small. I'm assuming such because back when I had my external GPS receiver that hooked in to my laptop the external GPS receiver took a couple of AA batteries and they lasted a pretty long time. This was before USB external receivers that are powered by the USB...mine was a serial connection.

You make another good point about the Nav DVD. When using the DVD of my laptop to watch a movie on the plane it does drain my laptop battery much faster... but that's reading a movie sequentially off the disk non-stop. Not sure how much power the Nav DVD pulls when sporadically updating maps for the screen... part of this would probably depend on how much map info is cached elsewhere in the system.

Mike

 

There are many computers in the Prius. Some are necessary to operation, and others are there to provide information to the driver. The MFD screen probably isn't necessary to operation, nor is the NAV computer. Certainly there is some amount of power used to operate the NAV computer and DVD drive. As for the GPS, it doesn't need to "connect to the orbital satellites", any more that your radio needs to "connect to the radio station". The satellites transmit radio signals that are received by an antenna. The GPS computer figures out how far away from each satellite it is by timing how long it took to receive the signal from when it was transmitted, and then translates this into numbers that indicate your location.

I doubt that the total of these computers (MFD display generation and NAV) plus the MFD screen itself adds up to more than 400 Watts (and is likely quite a bit less), but I don't have any reliable information to provide on which to base that assumption. It's mostly just an educated guess.

 

No.

 

It all comes from burning gas. The point is that the power required for the MFD is tiny compared to anything else involved with moving the car. It does save gas to turn off any unnecessary equipment, but the results are generally not worth it.

Tom

 

Not much. It pales in comparison to all of the other energy requirements. You might remove one headlamp instead. That will save you a bit.

Tom