Measuring coolant flow
 

Anybody aware of a relatively cheap device for measuring the flow rate in a cooling system on a car? One that does not insert itself into the flow? I have seen devices but for much larger pipes and they are big bucks. I am trying to debug overheating issues on a project car and would like to identify my flow rates at various RPM's. I get nice high speed cooling but low speed is a killer.

thanks
Fred emmerich

Google about for "ultra sonic flow meter".

Looks like there must be certain size particle of a minimum concentration in the fluid or bubbles to make it work. I wonder if a cooling system qualifies?

You may need to add some "particles" for the ultra sonic to work.

When I worked in automotive testing we had flow meters that basically consisted of a pipe with a little turbine inside that was attached to a rev counter of sorts. You'd have to hack up a radiator hose to install it, and they aren't cheap, so probably not what you're looking for.

Edit: On second thought, you could get a pretty good estimate of coolant flow by measuring the temperature of the fluid going into and coming out of the radiator. If you come up with a situation where the energy input to the system (quantity of fuel burned) is known and fairly constant for at least a few minutes, you could calculate the corresponding mass flow through the radiator. If you can figure out your fuel rate at highway speed, you could take measurements that way.

Looks like an opportunity for an inventor. If I remember correctly, sound velocity is affected by fluid velocity and direction, pressure and temperature. Hmm, maybe that's in a Newtonian fluid. Do the names Stokes-Navier apply?

Pump laws - A differential pressure detector/gauge/meter around the radiator ? DP is proportional to the square of (volumetric) flowrate ? (its been a few years...) Bueller ?

While I personally love the "temperature difference' measurement method- it requires some good baselines and if there is an electric fan, that will mess with your results in the short term.

If this is on a car - what will flowrate tell you ? I've yet to see a car manual that gives expected coolant flowrates (it'd be cool if they did....) if you actually had flow, could you use it to diagnose the problem component ?

I am trying to measure flow rate as function of RPM. You can measure pressure drops across an orifice but this works mainly in gas, not liquids. The turbine is a common method but is accurate in a small range of flow rates. If you knew the accuracy of your home gas meter you would be shocked. In my gas lab we tested all sorts of meters and if the flow has not stabilized, all bets are off.

Back on subject, I am hoping to see how my mechanical water pump is working and then compare against an electric pump. I t have low speed cooling issues and I want to make sure I don't lose cooling at high RPM. I am pretty sure there will be a big overlap on performance.

BTW this project is a 914 with a Chevy 327 with 400HP in it. Pretty hot motor. Literally.