Any ideas on a steering angle sensor I could retrofit into my racecar? The intarwebsz seem to focus on repairs to BMW sensors, so maybe that's not the best place to start! 
This would wire into my RaceCapture unit once it finally ships... seems like the next thing to add once TPS and brake pressure are known from a driver training standpoint.
Seems like the easiest would be to make a potentiometer behind the steering wheel.
Now, it would only be able to give you 360 degrees of detail, but for race data collection you're probably not using more than that anyway.
Basically make a long coil of wire, place in a circle on back of steering wheel. Get two sprung brushes and place them on steering column, one touching the circle if wire, the other touching maybe the steering shaft or whatever. Resistance between the two brushes will vary with wheel position.
Robbie wrote: Seems like the easiest would be to make a potentiometer behind the steering wheel. Now, it would only be able to give you 360 degrees of detail, but for race data collection you're probably not using more than that anyway. Basically make a long coil of wire, place in a circle on back of steering wheel. Get two sprung brushes and place them on steering column, one touching the circle if wire, the other touching maybe the steering shaft or whatever. Resistance between the two brushes will vary with wheel position.
Good advice here.
I would agree that the steering wheel is probably the best input point. however, I would look for some kind of off the shelf position sensor.
Could also use a linear position sensor on the steering rack inner tie rod. I'd think adding something there would be easiest to incorporate on something not originally equipped with one. Calibrate rack positions with steering wheel angles and done.
DIY string pot wrap it around the column.
In reply to RXBeetle:
Dude- I know this will sound stupid, but I have never heard of instructables. You have changed my world! 
I'm not understanding the "back of the steering wheel" suggestions. If you mean in "back" of the firewall (as in, wrapped around the steering column linkage), well, OK, that sounds possible. If you actually mean on the back of the steering wheel (as in, where your fingers grip), it sounds awful.
RXBeetle's link to the home made string-pot displacement transducer shows how to build it for probably less than $10. The first picture in the instructable shows it attached to a pneumatic cylinder in essentially the identical configuration it would take to attach it to a steering rack.
No need to involve the steering wheel. Linear motion feedback direct from the steering rack.
I've looked into this heavily, and I think the best solution is an infrared distance sensor on the rack and a target plate on the base of a tie rod. It's simpler and more reliable than anything else out there, although not as accurate as a linear potentiometer.
SVreX wrote: In reply to RXBeetle: Dude- I know this will sound stupid, but I have never heard of instructables. You have changed my world!
+1 for instructables
and I thought Lunchables was cool
I don't know about steering angle sensors, but I knowabout instructables. There is a giant range of usefullness on that site going from brilliant all the way down to dangerous and idiotic with everything in between.
Robbie wrote: Seems like the easiest would be to make a potentiometer behind the steering wheel. Now, it would only be able to give you 360 degrees of detail, but for race data collection you're probably not using more than that anyway. Basically make a long coil of wire, place in a circle on back of steering wheel. Get two sprung brushes and place them on steering column, one touching the circle if wire, the other touching maybe the steering shaft or whatever. Resistance between the two brushes will vary with wheel position.
You can get multi-turn pots.
The simplest steering wheel angle position sensor assembly I have ever seen is to use a rotary potentiometer with a pulley attached (340 degree or so) and connect it to the steering column using a rubber band or similar connection. The difference in diameters gets you a very easy to center system with enough range of operation but not too much loss of resolution. The upside is the potentiometer can be a relatively cheap unit and can be hard mounted, with no chance of limiting the steering range if you have 'a moment' and need more steering angle.
I am using a similar system but with delrin gears cut to allow full steering range.
Simplest? My idea is the only one with no moving or wearable parts 
Simplest for steering wheel motion, not rack motion, but yes IR to tie rod works too.
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