B reg 90 Posted September 20, 2014 Share Posted September 20, 2014 So meant to finish with: So removing restrictir plate may push the NPSH r up to the point that the pump cavitates, flow drops, temps go up, engine overheats. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 20, 2014 Share Posted September 20, 2014 I'm not seeing electric pump cavitation as an issue over the OE pump, as the OE only cavitated at high speed and not in it's proper working range. But I still think the pump should be right behind the point of highest back pressure. From an engineering view the pump should be pushing water into the rad. That google cavitation description is wrong. Cavitation is collapsing air bubbles, as said, but it can take lumps out of stainless steel. Infact, it can pretty much etch anything But mainly in this instance it just stops the pump working right. Flow then drops with greater engine rpm rather than continuing up. You don't have this issue because the electric pump is be kept below the risk point. Like the cooling fan it always works at best speed. So I'd pull that plate. You should see the amps drop and the cooling increase. When I'm designing jacket water cooling systems I'm taking unusual measures to reduce system back pressure as much as possible. And if it doesn't go better, put it back in. Simples Tech bit; The faster you can circulate the water, the better the heat exchanger works, from both Reynolds number in the tubes and an increase in average fin root temperature. Quote Link to comment Share on other sites More sharing options...
B reg 90 Posted September 20, 2014 Share Posted September 20, 2014 I'm not seeing electric pump cavitation as an issue over the OE pump, as the OE only cavitated at high speed and not in it's proper working range. But I still think the pump should be right behind the point of highest back pressure. From an engineering view the pump should be pushing water into the rad. That google cavitation description is wrong. Cavitation is collapsing air bubbles, as said, but it can take lumps out of stainless steel. Infact, it can pretty much etch anything But mainly in this instance it just stops the pump working right. Flow then drops with greater engine rpm rather than continuing up. You don't have this issue because the electric pump is be kept below the risk point. Like the cooling fan it always works at best speed. So I'd pull that plate. You should see the amps drop and the cooling increase. When I'm designing jacket water cooling systems I'm taking unusual measures to reduce system back pressure as much as possible. And if it doesn't go better, put it back in. Simples Tech bit; The faster you can circulate the water, the better the heat exchanger works, from both Reynolds number in the tubes and an increase in average fin root temperature. Idris, How do you KNOW the pump is operating at a point that it will not cavitate? I'm not saying the pump is cavitating, but that know one knows if is it or not unless you know the suction pressure, + Temp + where the pump is operating on it's performance curve. The pump is small enough that you will not hear it cavitate (especially while engine is running). Removing the restrictor plate is a WAG (Wild Arsed Guess) unless you measure what is happening. Adrian Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 20, 2014 Share Posted September 20, 2014 The whole thing is a WAG, that's the critical point. There is no R&D except for that done by experience and feedback by the pump vendor. By removing the OE pump and running an electric pump (that is governed by temperature rather than engine speed) all bets are off on cavitation. It was a problem suffered by a system that no longer exists. For instance, the old system, like many V8's of that era, suffers cavitation and needs to be restricted on the outlet for high RPM. But if you draw it as a set of pressure resistance in a block diagram the plate is a pressure drop up-stream of the rad. It simply adds onto it. That's why removing a four row rad and fitting a three row can fix a cavitation issue. So is the pump pulling water through the rad or pushing it? Because it is a circulating system it does both. Add up all resistance between pump outlet and inlet and at some point it is natural system pressure. For sure there is risk. That's R&D. Currently I have no reason to say that this electric pump is working in a danger zone with only; its own body, the rad and the engine block as back pressures. I cannot claim the orifice plate has more effect on the system than swapping a 2row rad for a 4row or making the new rad double pass. The honest truth on this is one that I have every day. The only engine I've seen with full pump pressure/flow Curves is CAT. Everything else is a build and test job. In this instance I believe that removing the orifice plate will speed up water flow and increase cooling. In response the pump controller will reduce the pump speed to compensate, reducing the risk of cavitation. In my mind it is the control algorithm that makes all the difference on this installation. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted September 20, 2014 Author Share Posted September 20, 2014 WAG ??? ??? Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 20, 2014 Share Posted September 20, 2014 Yeh, you know, building your own 4x4 without a £1m R&D budget. Like, can I run a dry sump pump 1:1 drive ratio when it was built for 2:1, because I can't rev an RV8 much compared to a corsa engine. That sort of thing If it wasn't WAG I'd go do something else that was. Quote Link to comment Share on other sites More sharing options...
qwakers Posted September 20, 2014 Share Posted September 20, 2014 WAG ??? ??? (Wild Arsed Guess) Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 22, 2014 Share Posted September 22, 2014 I thought the restrictor was also to create a bit of pressure in the top of the engine to prevent hotspots / steam pockets in the heads? Changing pump won't change the behaviour of that. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 22, 2014 Share Posted September 22, 2014 It's easier to achieve that by upping the rad cap pressure, as the standard pump doesn't have much head/pressure compared to values on the caps. Or go waterless? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 23, 2014 Share Posted September 23, 2014 I'm not convinced that pressurising the whole system does/would have the same effect as restricting the flow out of the top end. Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 24, 2014 Share Posted September 24, 2014 Depends on the issue and the cap fitted. If you had a 7psi cap you could get a 15psi (if rad can stand it). That's quite a pressure hike over what a restrictor could create. If you already have a high pressure rad cap, maybe restrictor is the only thing left to try? Quote Link to comment Share on other sites More sharing options...
B reg 90 Posted September 24, 2014 Share Posted September 24, 2014 I'm not convinced that pressurising the whole system does/would have the same effect as restricting the flow out of the top end. Good point - had not considered that. Another thought - engines are mass produced. Surface finish variations, casting defects are are to be expected within the water passages. All these will make pressure drop in the water passages fairly variable between engines. Hence designers will make the passages big enough such that the pressure drop changes from the manufacturing tolerances of castings are not significant. They then control flow by sticking in a restriction plate (thermostat) that they can put an accurate cheap hole in to create the required back pressure/system resistance. What I am trying to say is that removing the restriction at the thermostat is a poor decision unless you have data from your engine to back your the decision. As Nigel has a custom engine, with a custom ECU map, it's the kind of thing that I'm thinking he would do based on evidence, not gut feel? Any way, time for another beer.... Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 3, 2014 Author Share Posted October 3, 2014 ooooooooooooooooooooooooooooooooooooO !!EWP +LOuvres + Moi + Hogmorr..... Barely went over 90 degrees, and thats before the restrictor plate had been removed, was quite a warm day and I did some stuff that used to make the engine superheat : https://www.youtube.com/watch?v=GLoBpDjeR6w#t=301 Nige 1 Quote Link to comment Share on other sites More sharing options...
Team Idris Posted October 4, 2014 Share Posted October 4, 2014 It looks to be happy The end of a very long journey then ? (mechanical quest). I enjoyed death-wish-kid as well. It was like 'fast predators, slow children' from family guy. Quote Link to comment Share on other sites More sharing options...
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