Just picked up a lightly used Racecapture Pro mk2 – can’t wait to hook up the basics and take it for a test drive at TNIA next week!
I’m really interested in connecting some suspension travel sensors to the unit this winter. Wondering what you GRMer’s would recommend for inexpensive but effective sensor options.
I’ve been brainstorming what it would take to build my own budget “string pots” out of some junkyard throttle bodies & TPS’s, but I’m interested in whatever other low cost options might be out there.
If it makes any difference, the car has macstruts on all 4 corners, which will hopefully make implementation pretty straightforward.
I've looked into this for use with my own car and a Racecapture Pro Mk1, and I think the best route is to put optical distance sensors under the wheel wells and use them to measure the distance to the top of the tires. This way you not only avoid fabrication on the sensor itself (as with DIY reel-type stringpots), but also on any mechanical linkages between the suspension and sensor (as with simple rotary stringpots using TPS/headlight sensors etc). I think an optical distance sensor also makes the best steering position sensor (installed on the rack, pointing at a target plate attached to a rod).
The only downside is that the optical sensors can get dirty, but you could make covers for them for when they're not in use, and they're not all that hard to clean anyway.
Volvo uses height sensors with mechanical linkage on all the wagons with that horrible 4C suspension. I have no idea what kind of signal they output, but I'm pretty sure there should be a few of them in the junkyard. All the XC70's from about 2006 have them, I think, and all the R models have as well. Also, Airride has a generic height sensor they sell with their kits.
I picked up some ride height sensors off some GM SUV for next to nothing on eBay. Loads of factory options out there, you just have to add a little tab to the suspension arm.
Heck, this one's under $30 brand spanking new.
Listen to these guys, you'll never build (or even buy) a string pot that will move fast enough, have the fidelity, or stay in calibration for that task.
Some of the older crane models we used to build equipment for (previous job), they used string pots on the Outriggers to determine the correct load chart. As slow moving as those are, they still required constant recalibration and failed often.
The lot where I typically autocross is borderline rallycross in areas… I’m not sure an optical sensor mounted above the tire would endure the onslaught of gravel that my fender liners regularly experience. This is one reason I started thinking about diy stringpots initially… they could be easily remote-mounted where they would be protected. I figured something like bicycle shifter cables would make a reliable/durable linkage between the suspension and an old throttle body… but it sounds like maybe I’m over-estimating the potential for reliability in such a system. Plus, it’d look stupid. :)
Now OE ride height sensors… that’s something I hadn’t even considered. Apparently these things are on practically everything now. A little bit of extra math to map out sensor travel vs. actual wheel/shock travel… but using a part that’s literally designed for the job seems ideal. Plus they look fairly compact, and could be mounted well inboard of the tire to avoid getting sandblasted. HMMMM. I will see what I can find at the junkyard! Hopefully most are variable resistor based and not hall effect or similar… only 3 pulsed inputs on the RCP so hall effect sensors are out for suspension position.
The ones they have on the mag ride equipped GM cars should have the fidelity you need as they're part of the system that makes the mag ride work. They're not expensive and they're OE durable.
