an idea about a new guage cluster

[Greg]

OK, so here is my question then:

So you hook up your computer to the connector by connecting to the pins on whatever port you are inputting from.

Then you write your program in basic or C or whatever to read the input signal from the pins so you are reading what signal the gauge on the car should be getting.

And sure, you can save that into a variable or array or whatever and even write a nice program to graph it over time or whatever the hell.

But then how do you calibrate the signals easily? How do you know what value the car is sending to the speedo @ what speed.

The calibration is where I think you would kill LOTS of time.

(and aren't the speedo's on 3G's analog/cable controlled anyway so wouldn't you need to rig a vehicle speed sensor to get a digital signal?)

Let me know if I'm wrong or how you'd do it?

[Immeraufdemhund]

responding to your statements on "break" at a time
1. I'll hook up the car jacks into a bread board and have that convert all the signals to the appropriate voltage and have it output the appropriate signal to the appropriate pin on a parallel port. (i'm using the parallel port because it's the biggest that is common)
2. Correct, i'll be writting an OS in C and have that read the signals and respond accordingly.
3....umm..maybe, there might be ways around that and just use real time graphing.
4.This is correct, it is going to be tricky. I'm going to make the "car" customizable. The user will have to input the year, and make, for me (87 lxi hatchback) and the tire size. I know some people are doing swaps, but that will be a future project. I might implement a different tranny, because the gear ratio is just a number, and thown into an equation it gives me another number. I'm still wondering how i'm going to "calibrate the car", I might just get with a friend who has an accurate speedo and have him drive at increments of 10mph and see if it's correct.
5. Calibration shouldn't be too hard because it's all just a formula. Getting the correct input values is what is goign to be a little difficult.
6. from what i know the cable in the back controls your odomoter. That will be my only concern. I'm thinking of jury rigging something like a speedo from a bike. (hook up a magnet on your spokes and have that figure out everything). Or i could just use the speed and a timer to get the milage.

As far as i know the only thing mechanical is the cable in the back, The rest of it is electrical. Shouldn't be a problem. Help any? Any suggestions?

[Greg]

Hey man, don't get me wrong. It's a cool idea and very ambitious, but it will be tough. It has a lot of potential (probably more for newer cars that are EFI and have more things controlled by the ECM -- like ignition timing).

But it would be a bitch to truly calibrate everything.

OK, say you do calibrate the speed by figuring out what values it gives at what speeds. It's probably a linear formula (y=mx + B), and you could get the formula by plugging the values at different speeds into a graphing calculator or just doing the math by hand or whatever.

But it will be a trick to get it precise, like within 1% error.

Now, even if you get the speedo good, then you have to think about the tachometer, fuel gauge, temp gauge, etc..

For the temp gauge, I would probably get a multimeter that has a temp probe (my crafstman $50 multimeter, eg, has a thin wire w/ a tiny ball at the end that gives you a digital reading of the temp at the ball end).

If you wanted to be really precise about this shit, you could drill a tiny hole in the bottom of your radiator (like 1mm), next to where the sensor is threaded in, put the probe wire in the hole and seal it w/ some temporary means (like some rtv, just to keep the leak down to a minimum while doing measurements), get readings from the meter & from the temp sensor @ diff coolant temperatures, and then seal up the pinhole with some epoxy.
And then isn't there another coolant temp sensor in the block or head somewhere?
You can do this w/ digital thermometers too.

For the tach, I'd maybe rig something to my crank pulley like your magnetic bike speed sensor or something optical maybe. I'd do this while my instrument cluster was still stock, and calibrate the readings to the tach at that point. Then I would get readings from it afterward.

You know what, I'd even do this FIRST, while everything was still stock, and then get my speed readings by driving it @ a certain RPM in a given gear and doing the math w/the wheel size & gear ratios. I'd get my tach formula accurate first and then just figure out the speedo from there. Or at least I would do it that way and THEN have someone w/ a good speed gun do some tests to see if it's accurate and tweak the equation.

With any linear relationship you only need 2 points to get the formula, but I'd take 4 or 5 or more just to see if there is a tight linear fit.

And I can't think of any reason why the readings from these things wouldn't be linear, but what if they aren't??? Then you have to mess around w/fitting parabolic equations to the measurements, etc.

Writing the code will be the easiest thing. I did some C/C++ programming back when I was in high school (shit, like 7 years ago and I don't remember jack), and this coding will be SIMPLE. Getting the right formula is the tough part.

Well, email me @ [email protected] if you ever get it done & tell me your process. It's cool shit, but I'd never put the time into it myself.

[dosh8er]

you just don't understand....

oi veah!!
[old country style]

The honda... the thing you're driving.. has a computer that interprets all the data from hese various wires/leads.. you know that thing called a speed sensor amplifier?!? think a second...
i'm gonna crawl into my car w/ a multimeter, some time, lots of paper, and a calculator and figure it out..

everything takes some time... i mean.. shit.. you can't just drop a turbo onto a 3g w/ the drop of a hat.. it's a process..

lemme know if you get any more major breakthroughs, Immeraufdemhund (BTW, for those who don't speak german.. that literally means 'always on the dog')

[Xulfiqar]

3rd Gens came with a digital cluster. You can find that on the web along with the controller unit. The genuine one on the Ex-R model is really neat.

We have em here in Pakistan for abt 300 USD (used) along with the controller and installation.

[Immeraufdemhund]

GOSH DUDE THAT BLOWS, YOU GUYS GET EVERYTHING!.. well for us americans who don't get all the cool things, we'll show you easteners.....dosh...did you have to break my secret!

[Immeraufdemhund]

umm, about the amp. I've never messed with amps, and i barely know how they work. How does it amplify the signal, does it just boost the amps?