Matt Romanowski

I thought people might find my latest sensor interesting. This is a brake fluid temp sensor. It will replace one of the bleder screws and report back the temp of the fluid in the caliper. I already have brake rotor temps with an IR temp sensor, so it will be very interesting to see how much of that energy makes it back to the fluid. I'm also very curious about what the temp the fluid in the calipers really is and when. It will be a long winter!

tedean

Matt, is that a wire or capillary tube leaving the fitting.

924RACR

Interesting.

We usually just put a thermocouple directly into the pad, from the backside (drill a small hole, press in the TC plug, and gap it to somewhere inside the pad so it's not hitting the rotor)...

ProCoach

That would mean a lot more to me. Of course, you can't do anything about it in-session, so tempilaq or temp tape (Alcon strips) work fine, too.

IMO, the only time I could see value in BF temp is in systems that recirculate fluid (a la NASCAR).

Matt Romanowski

That is just a wire. This is just a probe that replaces the brake bleeder. All the temp sensing is done at the tip of the probe.


Or in any car that is boiling the fluid. The temp at the pad/rotor interface can be figured with a thermocouple like Vaughn said or pretty darn close with an IR rotor temp like I do. If you want real brake fluid temps, this is the only way to get it. I don't know anyone that can correlate rotor or caliper temps to fluid temps.

Indy cars run a RTD sensor in the top of the caliper to get caliper temps.

Matt Romanowski

There is a contact rotor thermocouple available that you could do the same with. It would give you actual rotor temp in the middle of the pad. Not sure I would want to see that number!

ProCoach

Hahahaha! True dat.

924RACR

+1 to that!

I've seen that done on some test cars too (mainly trucks, at least in drum brakes) with TC's pressed right into the braking surface, then all that crazy slip plate contact stuff for getting the signals back out.

But you have a good point, IR sensors would be just great too, without the PITA wiring install issues. Of course, in our case, we're paying techs to do the work, and have countless vehicles to instrument, and go through countless pads, so wiring them direct into the pad is enough, then plumb them into the data system... just a couple more analogs out of tens or hundreds... I'm sure you can imagine what some of these cars look like when built for powertrain work, truly hundreds of TCs running around, massive bricks of A-2-D converters... then a little laptop strapped down to log it all... LOL

2BWise

It will be cool to see, but I don't suspect you'll find temps as high as you may think. Shockingly, the fluid doesn't usually see a huge spike in temp that corresponds with pad or rotor temp increases. Let me preface that this is all my experience from 4 and 6 piston calipers. Generally there is so much more material to the caliper and the fluid volume is relatively small so won't see large temperature increases. All my testing has ever shown is that the fluid may, just may, reach the wet boiling point.

Matt Romanowski

My car is extremely easy on brakes, so I don't expect I'll see very high temps, though the rotors are running over 1,400F. We'll see in April when my car (the rolling test bed for lots of stuff) wakes from it's winter hibernation.