Drag data acquisition

hi I’m stepping up the set up in my car for drag racing and want some help with what I need to log for things like traction control eg. So it is a heavy car with twin s480 turbos and a dart ls 427 next, t400, full clip 4 link rear end, haltech 2500 with traction control expansion module. I’m thinking tail shaft speed sensor, rear shock travel, g meter, and front laser ride height. What do you guys think?

You want a front wheel speed input from the wheel least likely to lift off as well.

If I was running front laser ride height and tail shaft speed, what would the need of front wheel speed be for?

Unless you have a very advanced integrating fuction based on the accelerometer data you have no reference for target wheel slip? No GPS?

Or are you programming a target G and tailshaft speed/accel is closed loop to a slip ratio based on that? I don't know how advanced they are now. What is the parameter that PID targets?

This is the first time I have set anything up like this so I don’t really know, but I was thinking comparing g meter versus tail shaft speed. I was going to try and keep it basic to start with but I am re-wiring the hole car so it would be good to add everything now even if I’m not using it all straight away.

I would be taking (accelerometer balanced as most modern loggers do) gps or front wheel speed to try to get as accurate a slip ratio chanel as possible (if you are traction limited), certainly in road and circuit applications slip ratio is what you target for best acceleration.

If your car has the front wheels off the ground for a significant portion of the track then you probably want to closed loop on front ride height just having an initial overshoot off the line then one wheel touching just enough to steer if you are not power/traction limited in the first half track. Really need to work out what you limiting factors are by gear or time/speed and control strategy may change in each gear.

They are quite expensive, but there are ground speed sensing senders commercially available for motorsport.

Examples are

https://www.kistler.com/en/product/type-csf2a/ or

http://www.advantagemotorsports.com/Sensors.htm (near bottom).

One of the issues with getting an accurate slip channel into the ECU is that a proper drag slick will grow in rolling diameter as the terminal speed increases. this makes it hard to compare rear wheel speed to front wheel speed, or even ground speed for that matter. Couple this with the fact that traction control is illegal in many racing classes and the next option is to profile the drive shaft speed vs time. The Haltech does this with their REM and it's normally referred to as 'torquen management'. Basically it's a form of passive traction control where you profile the theoretical ideal relationship between driveshaft speed and elapsed time, and if the driveshaft speed rises above the profile it indicates wheel spin and the ECU can retard timing or cut spark to control it. This does require you to have data from a good pass to start with and then you can manipulate the profile to suit.