speeder Posted October 3, 2004 Share Posted October 3, 2004 I have a CSR electric water pump , and at present am running it off a relay controlled by the E-motive's GPO output, being turned on at full speed when water temp reaches 50* C. This works pretty well - but my car has always had marginal cooling performance (big/thick IC, A/C condenser, and no room for a mechanical fan) - I know the problems are caused by the decreased airflow, but am looking to maybe offset this by optimizing water pump speed with an electronic controller. From my days as an SCCA crewmember/pit slave, I remember that we could actually get better cooling on the ITS racecar by installing restrictors in place of the thermostat, with the theory being slowing down the flow to keep the water in the radiator long enough to get optimal cooling. Anyone have any experience/ knowledge in the area of controlling coolant water flow? I think initially I will provide a cockpit mounted pump speed control knob, and just play with pump speed under various conditions until I can rough in an automatic control curve with a CLT sensor. I'll report results. Quote Link to comment Share on other sites More sharing options...
Hugh Posted October 3, 2004 Share Posted October 3, 2004 I've always seen the same results. Slower moving coolant does a better job. This is why pulleys that underdrive the water pump actually cool the engine down during extended high RPM runs. Being a drag racer, I've never really had cooling issues. As long as the car stays cool while idling, the short burst down the track has never been a problem. I had an under-hood air flow problem while idling in my last car that I solved by raising the back end of it an inch (ghetto venting) Supposedly this creates backwards airflow into the back end of the hood off the windshield, but I didn't care about cooling while moving. (the car ain't overheating in 11 seconds ) Your idea of a knob to control pump speed is a great idea. My main concern is current handling of the potentiometer and cables used to accomplish this. Be sure it is a high amperage Pot. and the cables are large enough. Electric water pumps suck a lot of current... and you don't want to start a fire under your dash while the water pump is dying and you are still running down the track. Quote Link to comment Share on other sites More sharing options...
speeder Posted October 3, 2004 Author Share Posted October 3, 2004 My speed controller is electronic - it controls the pump by pulse width modulation of the motor's supply voltage. The cockpit control will only provide a reference voltage to the remote mounted high current controller board. I have long suspected that optimum cooling does not happen proportional to crankshaft speed, and we shall soon see. Quote Link to comment Share on other sites More sharing options...
TimZ Posted October 10, 2004 Share Posted October 10, 2004 I've always seen the same results. Slower moving coolant does a better job. This is why pulleys that underdrive the water pump actually cool the engine down during extended high RPM runs. I've never really bought into this argument' date=' and I think it has been discussed here before. Yes, slower moving water [i']will[/i] absorb more heat, but this means two things - it will be hotter when it exits the engine, and you will see a larger temperature delta across the engine(i.e., the front of the head will be hotter than the back of the head, and by a larger degree). I'm 99.9% sure that the real reason for adding restrictors in the cooling system was to add some backpressure. The reason that you want backpressure is that it makes it harder for the mechanical pump to cavitate at high rpm. Slowing the pump down with an underdrive pulley will also make it less likely to cavitate. Cavitation = no water flow = bad. Since the electric pump no longer changes speed with rpm, cavitation should no longer be an issue. I went the other direction and installed the lowest restriction thermostat that I could find with my CSI pump. This seemed to help marginally. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted October 11, 2004 Share Posted October 11, 2004 All my (limited) experience with industrial heat exchangers has found that higher flow = higher cooling efficiency. I wouldn't be surprised if there was potential to be some unique characteristics with any HTX system that may make for an optimal flow rate however. I'm interested to hear your results with the experiment for sure. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted November 20, 2004 Share Posted November 20, 2004 Bump.... Quote Link to comment Share on other sites More sharing options...
speeder Posted November 21, 2004 Author Share Posted November 21, 2004 I've discontinued work on the pump controller due to electrical interference from the CSR pump into my TEC2's Crank angle sensor. Some very odd things going on there that I didn't want to spend time now to figure out. Went back to a mechanical pump. I'll get back on this some day... Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted November 21, 2004 Share Posted November 21, 2004 Is that what was causing the over heating issue? Was the pump not working correctly or was it freaking out the Tec 2? Quote Link to comment Share on other sites More sharing options...
cheftrd Posted November 22, 2004 Share Posted November 22, 2004 I've seen this interference problem on quite a few Electromotive setups. Powerful electric fans near the sensor will also cause them to run erratic. In the past, I've built custom mounts for SBC to keep the Electromotive sensor down near the oil pan. No interference problems with a CSR pump. Quote Link to comment Share on other sites More sharing options...
speeder Posted November 22, 2004 Author Share Posted November 22, 2004 I think I had solved the cooling problem with a different thermostat - but the interference problem made me give up on the electric pump for now. I had made another really stupid blunder with the pump control initially that I would rather not tell about now. Just let it suffice to say I was a primo dummass. Probably the only mistake I ever made. There were getting to be too many issues to deal with and I was anxious to get the new setup running. I did try to completely shield the mag pickup with no change. There is an upgraded pickup available from E-Motive that they claim "may" solve the problem. Like I said, I will eventually get back on this, but it's way down on the list right now. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted December 11, 2004 Share Posted December 11, 2004 I'm with TimZ on this one as I've never bought into the slower water transfers heat better. In developing cooling systems for large off-highway machines I'm pretty sure this is not a consideration ... but I'll check. Preventing cavitation sounds more reasonable to me. If you have an airflow restriction problem then I doubt water flow would really help since that's not the limiting factor - no matter how optimal the water flow is if you dont have the airflow it really wont matter. The counter intuitive thing about centrifugal pumps - flow is proportional to the power of pressure (squared ... cubic ... dont remember) so adding restriction will raise pressure and in the process lower flow much more (again raised to a power). Net result is you reduce the power the pump is drawing (power = pressure * flow) despite raising the pressure! This is an issue on for example electrically driven fuel pumps where if the pressure gets too low the flow skyrockets and consequently you overload and burn up the motor. Quote Link to comment Share on other sites More sharing options...
TimZ Posted December 13, 2004 Share Posted December 13, 2004 I've seen this interference problem on quite a few Electromotive setups. Powerful electric fans near the sensor will also cause them to run erratic. In the past, I've built custom mounts for SBC to keep the Electromotive sensor down near the oil pan. No interference problems with a CSR pump. Sorry I didn't respond to this earlier - for some reason I wasn't getting email updates on this thread. I've had interference problems with the TEC2 also, although I doubt that this is unique to the TEC. I also tried shielding, etc., to no avail. The solution that I found was really quite simple. The magnetic field that the pickup is sensitive to has a polarity. If you change the orientation of the pickup 90 degrees to the interfering magnetic signal (in this case the pump motor's magnetic field), it no longer "sees" it. So, if you currently have the pickup oriented axially (pointing towards the center of rotation of the trigger wheel), you need to make a new pickup mount that orients the pickup facing for/aft at the edge of the wheel instead. It will still get the pulses from the trigger wheel, but it will no longer get the interfering pulses. Quote Link to comment Share on other sites More sharing options...
Guest Droopdude Posted December 15, 2004 Share Posted December 15, 2004 I think I had solved the cooling problem with a different thermostat - but the interference problem made me give up on the electric pump for now. I had made another really stupid blunder with the pump control initially that I would rather not tell about now. Just let it suffice to say I was a primo dummass. Probably the only mistake I ever made. There were getting to be too many issues to deal with and I was anxious to get the new setup running. I did try to completely shield the mag pickup with no change. There is an upgraded pickup available from E-Motive that they claim "may" solve the problem. Like I said' date=' I will eventually get back on this, but it's way down on the list right now.[/quote'] You might want to try sticking a line reactor (half a transformer to filter the supply) on the supply side of your PWM controller, and tie the negative side of the pump motor and controller to a single common point. Another thing to look at is to make sure that the wiring between the PWM controller to the motor is physically isolated from any other wiring, or is shielded. Quote Link to comment Share on other sites More sharing options...
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