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I know there are tons of readers and software on the market, but what I really need is something to convert signals of my1970s sensors (fuel level, speed, coolant temp, etc) to OBD compliant signals. I realize certain components like a pulse generator might be required. I'm ok with that.

Any info converting standard, pre-OBD signals to OBD is welcome!

NOTE: The vehicle I'm working on is a Chevrolet Corvette, but the principles should be same for all pre-OBD vehicles.

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What is it exactly that you are trying to accomplish? –  Larry Mar 21 '11 at 5:17
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4 Answers

Off the top of my head, the easiest way to get there would be using some sort of hobbyist microcontroller board, such as an Arduino. You'll need to add encoders since most of the data you'll be receiving will be analog.

Since the CPU for your board will include timing by default, you can calculate time-based measurements (RPM, MPH, etc) from that.

Disclaimer: I have not tried something like this before, so am a bit hesitant to start pointing you in any particular direction without at least some expert feedback.

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It's funny you mention that. It's exactly what I'm doing right now. I've had so many problems with it so far, that I thought I would see if there was anything like this conceptual converter. –  Kilhoffer Mar 15 '11 at 21:11
    
Yes, this is definitely not a wholly amateur project. However, searching around the web gives me some decent results; most are doing the same thing you're doing, just not all at once. –  pixelbath Mar 15 '11 at 21:24
    
Oops, accidentally submitted before finished. Anyway, it looks like most of the sensor output is fairly simple: 0v-5v (or 12v, in some cases). These should be fairly easy to read; what sort of problems are you having with this? –  pixelbath Mar 15 '11 at 21:26
    
Well, right now I'm having a hard time with speed and tach. Speed shouldnt be too bad once I get a pulse generator. It should output 8K pulses per mile. From there, it's all math. But the tach I'm not sure about. I should have coolant temp covered with what I have now, but I need to find out the resistance values the fuel level sender issues. I have a pending question on here for that one, too. –  Kilhoffer Mar 16 '11 at 1:33
    
Overcame some hurdles last night. The only thing I have left to read is the pulse generator for speed and whatever it is the tach reads. Any suggestions on how to read and interret the tach are welcome! –  Kilhoffer Mar 16 '11 at 14:52
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You'll definitely have to figure out something for the speed sensor. A mid-70s anything will have a cable driven speedo so you'll have to rig up some kind of VSS.

I have a feeling the aftermarket has already produced a solution for this.

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The solution is to get a pulse generator and monitor it. 8K pulses per mile is what most put out. –  Kilhoffer Mar 16 '11 at 1:33
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OBD-II didn't become standard until 1996; some 30+ years later. And to make matters worst, the CAN2.0 spec (ISO15765) was sort of solidified in 2008 even though it was around a bit longer. Still, with CAN, it's just a signaling spec. You still need something known as a DBC file to decode CAN data..

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Sounds like a lot of work for little gain. Consider doing slightly more work for much greater gains with something along the lines of an AEM EMS: http://www.aemelectronics.com/engine-management-systems-9/plug-play-engine-management-systems-ems-10/

Not the only game in town, but it is probably the most popular. Probably 90% of the standalone EMS installations I've seen are AEM...

EDIT

Obviously most of the kits are aimed at being plug & play into certain wiring harnesses, but muscle car guys do also use it. Have to rig up your own harness and sensors, just like you would with any EMS installation.

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