Electric Water Pump
02-13-2003, 09:58 PM
#16
Not a Guru on the coolant system .
I think it was Jay, or Dennis -at SITO- who mentioned that the thermostat was more than just a thermostat.
John -944-,
Mentioned something along those lines.
Jay, Dennis -others-
Correct me if I misunderstood you, but the short version -as I understand it - is no thermostat, no COMPLETE circulation as the small end of the thermostat is a sort of circulation guide/block. Without it the coolant just hangs around the block. (?) In reality, I'm wondering about that as it seems the small end would move after the core coolant was warmed sufficiently to make the oil happy, the driver warm and then open up to the radiator for full circut coolant loop . So if there is a constant push from the pump, wether hot or cold, the loop should be completed without a thermostat. Unless of course in the process of opening it blocks one port and opens another...Enlighten me someone.
I don't doubt that the electric pump could push the coolant thru the system but I am curious to the full function of the thermostat, and what happens when you remove it.
As to the Impeller it would -seemingly- just add to the load on the electric pump, more amps, and provide no benefit. I'm not saying that the impeller couldn't be removed. If there isn't a 'c' clip[ holding it on you would have to press the shaft out then press the shaft or impeller off.
I think you would lose the pressure seal needed to keep the pressurized /hot water from leaking. At the same time if you were using the re-installed shaft to provide an idler pulley shaft to use the same belt, small ocillations would only add to the leak possibilities. The rebuilder could help, I guess.
I agree on the belt being the same size.
Jim,
See your point. Takes power to make power, that pump is costing you power somewhere. Still it might be more efficient even if it does push the alternator/battery to the edge of maximum efficiency. How about a larger pulley and belt combo. Cavitation?
Me? I wouldn't tinker around for HP unless I could get 8 - 10 % plus HP. With a smog sys. dump, loss of weight and parisitic drag on both water pump & smog pump hardware and the addition of a header system should go maybe 20 -25 more HP. That would be worth a shot.
BJ , apparently, is just looking at a waterpump swap. The initial swap really gains him little as he sorts out the system. To me it would not be worth it.
I think it was Jay, or Dennis -at SITO- who mentioned that the thermostat was more than just a thermostat.
John -944-,
Mentioned something along those lines.
Jay, Dennis -others-
Correct me if I misunderstood you, but the short version -as I understand it - is no thermostat, no COMPLETE circulation as the small end of the thermostat is a sort of circulation guide/block. Without it the coolant just hangs around the block. (?) In reality, I'm wondering about that as it seems the small end would move after the core coolant was warmed sufficiently to make the oil happy, the driver warm and then open up to the radiator for full circut coolant loop . So if there is a constant push from the pump, wether hot or cold, the loop should be completed without a thermostat. Unless of course in the process of opening it blocks one port and opens another...Enlighten me someone.
I don't doubt that the electric pump could push the coolant thru the system but I am curious to the full function of the thermostat, and what happens when you remove it.
As to the Impeller it would -seemingly- just add to the load on the electric pump, more amps, and provide no benefit. I'm not saying that the impeller couldn't be removed. If there isn't a 'c' clip[ holding it on you would have to press the shaft out then press the shaft or impeller off.
I think you would lose the pressure seal needed to keep the pressurized /hot water from leaking. At the same time if you were using the re-installed shaft to provide an idler pulley shaft to use the same belt, small ocillations would only add to the leak possibilities. The rebuilder could help, I guess.
I agree on the belt being the same size.
Jim,
See your point. Takes power to make power, that pump is costing you power somewhere. Still it might be more efficient even if it does push the alternator/battery to the edge of maximum efficiency. How about a larger pulley and belt combo. Cavitation?
Me? I wouldn't tinker around for HP unless I could get 8 - 10 % plus HP. With a smog sys. dump, loss of weight and parisitic drag on both water pump & smog pump hardware and the addition of a header system should go maybe 20 -25 more HP. That would be worth a shot.
BJ , apparently, is just looking at a waterpump swap. The initial swap really gains him little as he sorts out the system. To me it would not be worth it.
02-13-2003, 11:32 PM
#17
Burning Brakes
You should never run the engine without a thermostat. It acts as a three way valve. When the engine is cold, it is closed towards the radiator, but allows coolant to circulate in the block. When the engine get hot, it opens and allows coolant to flow through the radiator, and also closes off the recirculation passages in the block. Taking the radiator out causes some coolant to continously recirculate in the block - and that coolant can easily flash to steam. <img border="0" title="" alt="[Eek!]" src="eek.gif" />
The idea of an electric water pump has been cussed and discussed before. Basically, the water pump desing in the 928 engine is hard to beat. YMMV.
The idea of an electric water pump has been cussed and discussed before. Basically, the water pump desing in the 928 engine is hard to beat. YMMV.
02-14-2003, 11:16 PM
#20
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Ed Ruiz.." Basically, the water pump desing in the 928 engine is hard to beat. YMMV." ............HO HO HO HA HA HA ......the belt driven external pump on our 1987 VW fox costs less than $200 new from the dealer and can be easily changed in less than two hours but with only about 80,000 miles and ten years on this engine I have not yet had to change it ....small block Chevy water pumps sell new for $40 and nearly fall off the engine . You have brought " automotive ethnocentrism " to a whole new level . Porsche Dealers used to do tons of 928 water pumps while the cars were under warranty nearly new it has been the higher quality of some of the rebuilt pumps which has enabled a 928 to make it 45,000 -60,000 miles until the timing belt needed changing and the pump got changed as well . If Porsche had tried to make the water pump any more difficult to service I doubt that they could have . With reasoning like this you might as well be saying " building a GTS engine to burn a quart of oil every 500 miles is a good idea !"
02-15-2003, 02:01 AM
#21
Nordschleife Master
I would deffently have prefered a pump mounted on the outside of the engine, NOT connected to the timeing belt.
What Porsche did is a pretty elegent solution to a simple engineering problem. The problem is that an elegent solutions is not called for.
A better system would have been a v-belt or electric power pump, with an idler for the cam belt. This could have been done by useing a serpentine belt to drive the fan/smog pump/altnator/steering pump/compresser/oil pump/H2O pump.
This away when the pump locks up from getting antifreeze in the bearings, it doen't screw up the cam timeing. When the oil pump drags, it makes the serpentine belt squeek, not tears up the timeng belt. This would keep a simple problem from resulting in head dammage, expecaly on 32v cars. Also, the pump isn't underneath everything. When it fails, it's on the top, pretty simple to replace. Same with everything else.
Without something to tear it up, I'd bet the timeing belt would last much longer.
The final addition would be an automatic belt tensioner. You flip the lever, the tension is right. No questions, no guages, no worrys. Something like the later 944 unit. Put a similer unit on the serpentine belt assymboly.
Well, at least thats what I'd do if I redesigned a 928 motor.
It's more parts, but at the end of the day, it's easyer to fix, and cheaper to boot!
What Porsche did is a pretty elegent solution to a simple engineering problem. The problem is that an elegent solutions is not called for.
A better system would have been a v-belt or electric power pump, with an idler for the cam belt. This could have been done by useing a serpentine belt to drive the fan/smog pump/altnator/steering pump/compresser/oil pump/H2O pump.
This away when the pump locks up from getting antifreeze in the bearings, it doen't screw up the cam timeing. When the oil pump drags, it makes the serpentine belt squeek, not tears up the timeng belt. This would keep a simple problem from resulting in head dammage, expecaly on 32v cars. Also, the pump isn't underneath everything. When it fails, it's on the top, pretty simple to replace. Same with everything else.
Without something to tear it up, I'd bet the timeing belt would last much longer.
The final addition would be an automatic belt tensioner. You flip the lever, the tension is right. No questions, no guages, no worrys. Something like the later 944 unit. Put a similer unit on the serpentine belt assymboly.
Well, at least thats what I'd do if I redesigned a 928 motor.
It's more parts, but at the end of the day, it's easyer to fix, and cheaper to boot!
02-15-2003, 03:01 PM
#22
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Barry,
I have to disagree with John's numbers for determining if the pump is worth trying. If anyone can average 60MPH on a daily driver, I want to know were they live. With stop and go traffic you are going to best look at something around 30MPH and that is if you avoid rush traffic on the way to and from work. Even when you are not moving the clock is ticking away at your pump. You might get 30 * 2000 = 60,000. miles, but I would not count on it.
Ell
I have to disagree with John's numbers for determining if the pump is worth trying. If anyone can average 60MPH on a daily driver, I want to know were they live. With stop and go traffic you are going to best look at something around 30MPH and that is if you avoid rush traffic on the way to and from work. Even when you are not moving the clock is ticking away at your pump. You might get 30 * 2000 = 60,000. miles, but I would not count on it.
Ell
02-15-2003, 05:52 PM
#23
Ell,
Ell, bear with me I'm explaining here, not ragging on you. Pattycakes is on the charger...I have some time.
God-forsaken, Midland, Texas!
They put a 4 lane divided system - Loop 250 - running from east to west across the northern part of town all 60mph most people run 70-75mph.
Loop 250 intersects Sh-191, a 4 lane divided -70mph-, and the Northern Part of SH-349, two lane, 55 -70mph -to the east side- as well as BI-20-East, 70mph, to the east of town. This runs directly to IH-20,70mph, on the east. And BI-20-East, 70mph (western side of town) which hits
FM-1788, 2 & 4 lane and connects with the middle of SH-191, yep, same one ,70mph to the north and IH-20, western side, 70mph to the south. 1788 after a 2 lane 70mph stretch hits FM-1787 a two lane - anything goes! - which wanders back to the southern end of SH-349, 70mph. Ell, even the Service/Frontage roads which parallel IH-20, Bi-20-E, and SH-191 are 55mph and everyone travels at speeds equal to or greater than the speed out on the main highways.
I can't swear to the rest of Texas but from east of El Paso to the splitter at Ft.Stockton then to San Antonio -south east-, or, east thru Pecos, Odessa,, Midland, Big Spring, Abilene. And from Amarillo south thru Lubbock, Midland, Iraan, or easterly thru San Angelo these speeds hold pretty much true. The speed limits reflect the enormous distances involved. Probably also reflect why they used to hang horse theives here. To be afoot in Texas then or now is truly life threatening.
I have neighbors who drive from here to Dallas for their 13 yr old daughters' soccer match back up to Lubbock for their 17 year old son's Marching BAnd Shootout the next day, and then on to Amarillo for another round robin soccer match same day, then home. This is REAL COMMON out here -stupid, but, common-. The ugly reality is that people out here travel so far so fast that to buy a 2 year old used car with 120,000 on the clock is simply accepted.
So, in a town that isn't 5 miles in diameter, we have a highway system with speed limits that folks in the northeast would die for.
BUT!
You are probably right in one respect...the national average -speedlimit- has got to be lower! I've been here since 93' and this is almost normal to me, now.
John S.
Ell, bear with me I'm explaining here, not ragging on you. Pattycakes is on the charger...I have some time.
God-forsaken, Midland, Texas!
They put a 4 lane divided system - Loop 250 - running from east to west across the northern part of town all 60mph most people run 70-75mph.
Loop 250 intersects Sh-191, a 4 lane divided -70mph-, and the Northern Part of SH-349, two lane, 55 -70mph -to the east side- as well as BI-20-East, 70mph, to the east of town. This runs directly to IH-20,70mph, on the east. And BI-20-East, 70mph (western side of town) which hits
FM-1788, 2 & 4 lane and connects with the middle of SH-191, yep, same one ,70mph to the north and IH-20, western side, 70mph to the south. 1788 after a 2 lane 70mph stretch hits FM-1787 a two lane - anything goes! - which wanders back to the southern end of SH-349, 70mph. Ell, even the Service/Frontage roads which parallel IH-20, Bi-20-E, and SH-191 are 55mph and everyone travels at speeds equal to or greater than the speed out on the main highways.
I can't swear to the rest of Texas but from east of El Paso to the splitter at Ft.Stockton then to San Antonio -south east-, or, east thru Pecos, Odessa,, Midland, Big Spring, Abilene. And from Amarillo south thru Lubbock, Midland, Iraan, or easterly thru San Angelo these speeds hold pretty much true. The speed limits reflect the enormous distances involved. Probably also reflect why they used to hang horse theives here. To be afoot in Texas then or now is truly life threatening.
I have neighbors who drive from here to Dallas for their 13 yr old daughters' soccer match back up to Lubbock for their 17 year old son's Marching BAnd Shootout the next day, and then on to Amarillo for another round robin soccer match same day, then home. This is REAL COMMON out here -stupid, but, common-. The ugly reality is that people out here travel so far so fast that to buy a 2 year old used car with 120,000 on the clock is simply accepted.
So, in a town that isn't 5 miles in diameter, we have a highway system with speed limits that folks in the northeast would die for.
BUT!
You are probably right in one respect...the national average -speedlimit- has got to be lower! I've been here since 93' and this is almost normal to me, now.
John S.
02-15-2003, 07:13 PM
#24
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Average speed:
The '89+ cars have a trip computer functions list that includes "average speed". I sometimes reset this along with "average MPG" when I refill, just to keep an eye on real mileage based on driving style. While my car is a daily driver, it's only driven on the days when I'm home and need to go someplace (and the place isn't Home Depot and it isn't raining, etc).
Drum roll... Average speed for this duty is less than 25MPH. It can and does go up a lot on longer trips, though. Last August's dash to the Devek event netted me a blistering 58mph average, including 80+ on interstate five up through the middle of the state. It seems like there are more and more obstructions to traffic flow these days, even in the high-speed corridors. It's the slowing for road construction, detours, rest stops and gas, hot dog breaks, stuff like that. Oh, and rush-hour traffic in the San Jose area. But you get the idea. Even if I lived where you do, at the end of a freeway ramp where everybody goes 70+, I'd still find that my average speed was a lot less. I guess I'd have a tough time justifying getting on the freeway for tem mile to get groceries, just to keep the average speed numbers up in bragging range.
Temp sensitive speed control on the pump:
For the suggestion that it's OK to slow the coolant pump speed at less-than-full temperature, um, I wouldn't do it. One of the things that prevents localized boiling at hot spots in the block is the back pressure provided by the thermostat and the pump speed. American car "fans" often hear that the reason you don't run without a thermostat is because the coolant circulates too fast. Wrong reason, it has to do with the localized boiling and hot spots. Porsche thinks it's enough of a problem that they provide a full-circulation bypass at the thermostat so you can keep full circulation even when the engine isn't warmed up. Helps avoid the hot spots.
Motor and generator efficiency:
For the sake of discussion, electric motors use about 650 watts per HP. Generators make less than 600 per HP typically. The rest is heat. So each conversion costs you maybe 10%. This water pump costs 1/4 horspower give or take, delivers somewhat less. So the power "saved" is really none at better than best.
Making the water pump electric adds another electrical system to a car with known electrical gremlins already. Porsche considered this in my car by putting fan power leads directly to the battery. Want to add something to the electrical system that, if there's a failure that's as simple as a loose connection or a blown fuse, will cause engine death in a matter of seconds?
Temp gauge currently reads the temp of water circulating up to the water manifold. By the time the sender sees hot water with no circulation, the head gaskets are history and some precious metal is warped. Even with your eyes glued to the gauge, you'd be too late.
So, I'm thinking along the KISS lines, guessing that, as complex and elegant the original water pump and system are, there were reasons that Hans and Fritz designed it that way. More reasons than I can think of, I suspect.
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />
The '89+ cars have a trip computer functions list that includes "average speed". I sometimes reset this along with "average MPG" when I refill, just to keep an eye on real mileage based on driving style. While my car is a daily driver, it's only driven on the days when I'm home and need to go someplace (and the place isn't Home Depot and it isn't raining, etc).
Drum roll... Average speed for this duty is less than 25MPH. It can and does go up a lot on longer trips, though. Last August's dash to the Devek event netted me a blistering 58mph average, including 80+ on interstate five up through the middle of the state. It seems like there are more and more obstructions to traffic flow these days, even in the high-speed corridors. It's the slowing for road construction, detours, rest stops and gas, hot dog breaks, stuff like that. Oh, and rush-hour traffic in the San Jose area. But you get the idea. Even if I lived where you do, at the end of a freeway ramp where everybody goes 70+, I'd still find that my average speed was a lot less. I guess I'd have a tough time justifying getting on the freeway for tem mile to get groceries, just to keep the average speed numbers up in bragging range.
Temp sensitive speed control on the pump:
For the suggestion that it's OK to slow the coolant pump speed at less-than-full temperature, um, I wouldn't do it. One of the things that prevents localized boiling at hot spots in the block is the back pressure provided by the thermostat and the pump speed. American car "fans" often hear that the reason you don't run without a thermostat is because the coolant circulates too fast. Wrong reason, it has to do with the localized boiling and hot spots. Porsche thinks it's enough of a problem that they provide a full-circulation bypass at the thermostat so you can keep full circulation even when the engine isn't warmed up. Helps avoid the hot spots.
Motor and generator efficiency:
For the sake of discussion, electric motors use about 650 watts per HP. Generators make less than 600 per HP typically. The rest is heat. So each conversion costs you maybe 10%. This water pump costs 1/4 horspower give or take, delivers somewhat less. So the power "saved" is really none at better than best.
Making the water pump electric adds another electrical system to a car with known electrical gremlins already. Porsche considered this in my car by putting fan power leads directly to the battery. Want to add something to the electrical system that, if there's a failure that's as simple as a loose connection or a blown fuse, will cause engine death in a matter of seconds?
Temp gauge currently reads the temp of water circulating up to the water manifold. By the time the sender sees hot water with no circulation, the head gaskets are history and some precious metal is warped. Even with your eyes glued to the gauge, you'd be too late.
So, I'm thinking along the KISS lines, guessing that, as complex and elegant the original water pump and system are, there were reasons that Hans and Fritz designed it that way. More reasons than I can think of, I suspect.
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />
02-16-2003, 12:30 AM
#25
Nordschleife Master
I'm with John on this one.
I typicaly average between 50 and 60 for most of my trips. Course their 5-6 hours long, but...
Like John said, there's alought of country to cross, and it's almost all empty. Along my traditional route accrost the state, there are plenty of spaces where one could run wide open, w/o a problem. Course I don't do that. Can't realy, what with that rev. limiter of a miss... ;-) Keeps me legal, right?
Enoy!
I typicaly average between 50 and 60 for most of my trips. Course their 5-6 hours long, but...
Like John said, there's alought of country to cross, and it's almost all empty. Along my traditional route accrost the state, there are plenty of spaces where one could run wide open, w/o a problem. Course I don't do that. Can't realy, what with that rev. limiter of a miss... ;-) Keeps me legal, right?
Enoy!
