Brake pressure sensor

Logging driver inputs is a way to get quicker, they say. I don't doubt that for a second. For me though, more frequent driving would probably be more effective. But that didn't stop me from putting in another sensor in the car.

When I actually do drive my car on a track I often find the lack of consistency very frustrating. I want to know why I'm faster in the morning than in the afternoon. I could look for excuses such as track temperature etc. Or I could stop fooling myself and start looking closer to the steering wheel. Can my braking be improved? (yes of course) How and where? That's what I want to find out. Also, in order to make sense of the other data collected from the car's sensors I need to know what the driver was doing.

"Aggressive application of the brakes is something that separates good drivers from average drivers. Most driver inputs to the car should be smooth, [...] but in big braking zones a driver should be very aggressive with the brakes." - Optimum G.

"Some of the most useful information to be had concerns driver performance and coaching. Braking is the one aspect of car control that goes against the accepted wisdom of smooth driver inputs."- Competition Systems.

Pressure sensor

For measuring brake pressure you need a pressure sensor in the range to about 200 bars, preferably with a DIN/ISO brake fitting. As there are plenty of production vehicles with brake pressure sensors you can find them at a decent price on eBay. I bought a second hand Bosch 0265005303 for about €25. The tech sheet was a google away and the electrical connector was available from Conrad.com or Farnell with part numbers:


Tyco PSA 2x3 pol
967 642-1 housing
965 907-1 contact pins
967 067-1 seals

1. GND
2. Output
3. Supply voltage +5V

The sensor was connected to one of the analogue inputs on my DL1 data logger.

Brake lines and flares

I installed the sensor on the front brake circuit right after the master cylinder. I made a new brake line with a tee coupling for the sensor. It was not hard, but a bit messy with the brake fluid dripping.
 
The standard Caterham brake lines are 3/16" with an ISO bubble flare. The nut on the master cylinder side is M10x1. On the front left/right tee split, Caterham thought it would be nice to use a UNF 3/8" thread instead.

There are at least three common types of flares and it seems to be massive confusion about ISO/DIN flares. Note that the DIN flare is flat on the underside with a matching nut. With some patience, you can make flares yourself using a simple €20 tool available from almost everywhere. Youtube is your friend!