Is it possible to get status without the Nav on the G coupe?

My buddy's base 350Z has a guage that tells . . . speed, temp, mpg, miles till runout of gas, timer, stopwatch, shift light control, all this non vital but useful information but it seems that it is not available on the G w/o getting the navigation package.

I wonder if it is possible to tap into some wire or computer on the G to get this info or maybe the computer that calculates all that info is on the navi computer itself.

Anyone have any idea?

 

you need nav,which i think sux.i agree this should be available w/out nav.just about every car out there today has this info available.why not on the the g?

 

The Navi unit has a speed sense wire going to it so it always knows how fast you are going. Without the Navi unit it would be my guess that none of those calcualtions would take place. Just a hunch though, I really have NO idea

But, I do know as far as there being a 'wire' to tap into you are out of luck. If anything there will be two wires you need to tap in to, Can-H and Can-L. This is the central backbone for data transfer in the car. Once you make your tap you will need to figure out what data for your can controller to listen for and program it to extract what you need. Then, you would have to have your Can controller send the information to the real world. Not a simple plug and play solution!

 

Pretty sure either that info is part of the cars OBD or you can calculate it using ODB information

What I want to do is calculate that information on my computer in the car and then display it on a small serial LCD
Not certain thats part of OBD though

 

Yeah I guess if you can read in the injector duty cycle in through OBD. I know you can pull out vehicle speed. With vehicle speed you could calculate miles driven and with injector duty cycle you could determine how much gas is being used. I'm not sure if injector duty cycle is availible though???

 

I think this would be a cool mod iif someone can figure it out.
I'm not an engineer, but I'll try and get my buddies to look at the Z wiring schematics off the shop manual and see what they can figure out.

 

You can use OBD II, but its not too reliable particularly on ISO based cars like the g35 that only update 3 or 4 times / sec. The only way to do it with the OBD II parameters is to use the MAF air flow value to determine the rate at which air and fuel is flowing through the engine, then guestimate the current air / fuel ratio based on the other parameters and multiply to get the grams of fuel per second flowing through the engine.

 

How does the MAF sensor relate to fuel usage? I know that you can tell how much air is coming into the motor, so are you just assuming an A/F of 14.7? Since you know the amount of air I would guess you could calculate the fuel usage ONLY if the A/F ratio is known? The A/F ratio is never a constant though and will change. If you know your injector size and duty cycle you could calculate EXACT fuel usage in CCs. use your 3.785 conversion factor and you are in gallons of gas.

What do you think about that?

 

gosh guys, this makes me so glad I did get the nav. With all these numbers flying around, the math scares me back to the many years of calculus.....*shivers*

 

So i guess the computer that calculates all this stuff is on the Nav computer.

 

There are OBDII scanners that perform MPG calculations. Don't know they actually arrive at the value or how accurate they are given the limitations of the OBDII interface in regards to sampling.

 

I haven't gotten around to actually implementing mpg with my own OBD II code, but I have another post on here where what I wanted to do was explained, except search doesn't seem to be working now

But yeah basically you would get the MAF value and assume a constant value of 14.7 or so. This obviously could be widely off depending on your driving conditions so you would then have some logic that would change this constant based on the driving variables that would change your A/F ratio, i.e. hard acceleration that you could determine from the absolute throttle sensor position parameter. I don't remember exactly all the things I looked for but there was only 3 or 4 different conditions that I thought would cover a good 95% of your A/F variations. Not ideal, but OBD II doesn't seem to offer must more that I could figure out how to use for this type of calculation.

Here's the complete list of standard OBD II pids:
http://www.obddiagnostics.com/obdinfo/pids1-2.html

 

Wow, thats pretty crazy. So, basically you are left with a best guess.

Have you looked in to see if injector duty cycle is availible? If nothing else you could electronically monitor the injection rate. The drawback to this is you HAVE to know your fuel pressure, or else your injection rate won't work. Fuel pressues don't change very often, but if you go FI this idea would be shot (but, so would the MAF idea)

The other drawback would be where would you mount the screen? It would be easy for you Non Navi guys but for us guys with Navi we have no place to put a screen. Oh wait, if we already have navi we don't need this!!!!!

 

What we need to find out is how the nav computer calculates it and then work from there