Digital Instantaneous MPG readout for rear-window?

[OG VX]

Hello all,
I think a neat way to let people know why I'm driving a bit slower than the rest of the pack, plus spread the word about hypermiling, would be to create some sort of digital readout of my (instant) mpg for the back window.

I'm not much on electronics, nor wiring. But, I can imagine this could be possible by either converting a VSS signal to a numerical data/signal of some sort (maybe through a Speedohealer, or similar) that could be sent to an LED screen, or one of the older dot-type (think basketball scoreboard) screens.

Ideally, I'm picturing about a 9"x9" black box, with bold white letting at the top stating "CURRENT MPG", with a dual-digit red-dotted LED light box below it to display current instantaneous mpg.

What are your thoughts? Any ideas/input on how I can pull this off, I would greatly appreciate it.

[3n3rgystar]

I thought about this idea, but displaying what current hypermilling technique was being used. Then I thought if someone was reading it and wrecked that it would be a bad idea because of liability. But something simple like current MPG might not be as distracting.

[cowmeat]

Cool idea, I think at one point or another we all consider doing it.

I thought about putting one on the Turtle, maybe a small green led readout in the back window, but then I figured some dumb ass would rear-end me trying to read it, and I'd be back to the drawing board. I'll just stick to putting on my ecomodder stickers (if Daox ever sends them to me)

When I was driving the Black widow I couldn't have done it anyway, because half the time the car was rolling it was off, lol! It would have looked like a cheesy motel sign, on, off, on, off . . . . .

[jcp123]

The thought has definitely crossed my mind, I had flights of fantasy adapting a Cadillac DeVille HUD to do it.

[j12piprius]

Originally Posted by OG VX

create some sort of digital readout of my (instant) mpg for the back window.

Great idea. I would like that for trip average mpg.

[Fat Charlie]

My idea had been to wait until after August (done!) and get one of those euro oval stickers with its best tank and "Best Tank MPG" or something in the border. Screw your 26.2 sticker, I've got a 54.3 sticker.

[dirtydave]

I went and put

40MPG
<----
pass me bro

on my back window for weeks and all the people I drive near have realized to just pass my POS KIA. The only people I have problems with now are the brodozers.

[Fat Charlie]

Here it is. If they're tailgating, they can read it and figure out what to do on their own.

[Occasionally6]

Perhaps something like this:

32x16 Red Dot Matrix Display | Freetronics

[Hersbird]

If I saw an instant readout sign on the back of a car I'd pull in tight to the draft and see if I could make it go up!