I've got a DL1 datalogger in my Miata, which I'm using to try to improve the nut behind the wheel for autoxing. Currently it's wired up to TPS, RPM, and brake on/off, plus the built-in GPS and accelerometers.
I didn't expect much out of wiring it up to brake on/off, so I wasn't surprised when it didn't give me much, it was just easy to do. I'm thinking it's time to put in a proper brake pressure sensor.
race-technology sells a Bosch sensor here: http://www.race-technology.com/brake_pressure_8_977.html
It's $290, which seems like a lot. I see brake pressure sensors available online from $40 on up -- presumably some of those are simple on/off sensors rather than the desired linear range however.
Does anyone have a specific recommendation for this?
Just about any 2000 psi transducer will work- as long as it has a 0-5V output (or whatever the DL1 needs) your golden. AIM sports has a nice MSI sensor I've used before & AEM electronics also has some cheapish sensors ($150 ea I think).
Just make sure its a transducer (output is 0-5VDC corresponding to 0-2000psi) not a switch.
Subscribing. If they really can't be had for under 3 digits, just wiring up the brake light switch doesn't look so bad...don't forget you have accelerometer readings as well.
Accelerometers FTW.
The only way I see pressure data being useful beyond rate of deceleration (remember - pressure will change with grip)... is when base lining bias settings for track & conditions on you setup sheet. You can do that with manual gauges from Longacre for $60 and a couple tee fittings.
Perhaps the accelerometers are enough for this on an road course where you can do the same course for multiple laps, take some time to download and analyze the data, then go out and try to apply the lessons, and repeat. I'm trying to use it for autocrossing, where I only get 4 runs and there's really not enough time between runs to look at the data.
As such, what I'm trying to do with it is to ask local fast drivers to take a fun run or two in my car so I can datalog how they do it. Then I can compare their lap to mine and try to use the data to figure out what I could be doing better.
For that method, the accelerometers and GPS will happily tell me where they're faster than me, but reasoning back to why is trickier. For example, a different line is obvious in the GPS trace, but differences in technique for applying power out of the corner while unwinding the wheel is a lot harder determine. Similarly, analyzing trailbraking is difficult with the accelerometers, because there are deceleration vectors coming both from brake input as well as from tire scrub. Autox is about transitions which often involve multiple driver inputs at the same time, and the accelerometers are the outputs of all of those interactions.
It seems to me that for this kind of analysis, having datalog access to the driver inputs to the car will provide information that is more directly readable. TPS is easy, because there's a nice electronic representation of it in the car that I can just tap, but brakes and steering don't come pre-equipped like that in a Miata. Steering angle is probably more useful than brake pressure, but brake pressure is a lot more obvious and straightforward how to install so I figured I'd do that as my next step. :)
In reply to codrus:
Gotcha... I tend to think of instrumentation in terms of monitoring things I need to set up for race day. Dive, roll, damper speeds, etc. I use only accel/decel, time and distance to find where I'm losing time. Sometimes I overlay someone else's data but I can see right away where it happens.
The "Why" - even if you quantify it with data, you usually already know the few variables in your driving that are available and even if you discover an anomaly by looking at the data... you still have to drive/practice to be able to do it yourself. Knowing where to try something else is usually enough. Don't get me wrong... I do love cool instrumentation - but adding hundreds of dollars of sensors to your car to sample other drivers inputs can often be circumnavigated by sitting in the right seat while they lay the smack down on your lap time. :)
