Water Pump Rotating Fin Design Question.

[project_tsi]

Hey all, I have a question about the internal fin desing of water pumps. My question is about which is better, if one design is better then the other, that is.

Take a look at the pics below. Notice the difference in the actual fins that pump the water?

Picture 1 is of the type that has a sort of "cover" over the actual fins, and picture 2 has the actual "open" type fins. Both pics are of 1G 4G63 water pumps.

So, is one design better then the other? What style is OEM? I honestly can't remember right now, and can't find any info on it that I need.

I think I know which design is better but if some knows for sure please let me here it.

Either way both pumps are reffered to as "junk" pumps in the auto parts world. Reason being is that both pumps trap the junk that the coolant system has in it, in its fins.

Rep given for good, accurate, factual information!

 

[GVR4592]

The closed impeller design prevents cavitation and aeration at high rpms and is generally more efficient than the open design.

 

[Old Mitsu Tech]

Very good. Not too many people know what the definition of cavitation and ventilation are.

 

[kanderson111]

What he is describing as cavitation is when cavities form in the liquid you are pumping. This will cause a loss of efficiency, a loss of volume, and a decreased amount of pressure. You could also experience noise and vibration. The pump without the vane cover is more prone to experience recirculation than the one with the cover. Recirculation can cause the above problem.

Thought I would mention that cavities would be in the presence of air pockets. Hope this helps

 

[project_tsi]

So the design in pic 1 is better? I was wrong then. I just picked up a new water pump and purposely bought the style in pic 2 b/c I thougt it was better. Oh well I guess, not much I can do about it now, its already on the engine.

 

[Sharkcus]

I would also like to add that the stockers have the "open fin" design. I recently replaced mine. However, I am not 100% sure, I will go home and check. It is hanging on my wall.

I do know that every aftermarket one I have purchased was closed. Unfortunatly, I haven't seen any gains/losses with either. I hope that helps.

 

[laserspeeddemon]

The bottom one is stock, I've replaced 2 waterpumps already, both were orginal waterpumps when removed.

As to which is more efficient, I can't comment, because I honestly have no clue. I would have said the 1st design, but only in theory, not factual.


GVR4592, can you give me a good link to read up on. I would like to learn more about it. Or better yet, I can get my hands on both of them and run an expirement.

 

[BaddAssGst]

Man, you guys are good. I've ran both, actually just replaced the top style with the bottom style. I've noticed no difference but that's not to say there isn't any.

 

[GVR4592]

GVR4592, can you give me a good link to read up on. I would like to learn more about it. Or better yet, I can get my hands on both of them and run an expirement.

I really don't know of any links with that information. I'm sure the info is out there. I just remember fighting with water pumps on a few circle track cars I helped build and the closed impeller design helped out immensely. At low rpms the car would get pretty hot and at high rpms (7000+) the car would get hot. The open impeller isn't efficient enough for low rpm (caution laps and pit stops) use and it causes cavitation at higher rpms. It's just a very shitty design.

 

[BaddAssGst]

I really don't know of any links with that information. I'm sure the info is out there. I just remember fighting with water pumps on a few circle track cars I helped build and the closed impeller design helped out immensely. At low rpms the car would get pretty hot and at high rpms (7000+) the car would get hot. The open impeller isn't efficient enough for low rpm (caution laps and pit stops) use and it causes cavitation at higher rpms. It's just a very shitty design.

Would you also say this holds true for normal daily driven cars?

 

[Enraged78]

The closed impeller design prevents cavitation and aeration at high rpms and is generally more efficient than the open design.

I had a long conversation about this with a friend of mine who has spent the last 30 years building and dynoing race engines, mosly V8's. GM 350's are known for cooling problems, specifically due to the cooling system cooling one side of the motor better than the other. GM originally had an open impeller design on their pumps, very similar to the second water pump in your picture. In later years, they went to a closed impeller design, also very similar to the first pump in your picture. Many GM folks upgraded to the second design for its improved flow abilities, which helped the cooling problems facing the motor. The basic premise is that an open impeller will cause much more turbulance in the water than the closed design, and turbulance impedes flow. It doesn't really make much sense to look at it, but you can't argue with the results.

The above quote is dead on. The first water pump is more efficent, and should move more water per revolution.

I have also had both styles of pump in my car, and was constantly using DSMLink to monitor water temp, before and after the build of my forged 7-bolt. I guess we have a very good cooling system, as the temperature of the coolant did not change at all with either pump. Moving to a 1G water neck and thermostat housing (when I did a 1G head swap) dropped temps a few degres, changing out the stock thermostat to a 180*F unit helped even more, and removing the 2G oil/coolant heat exchanger took even more off. The car runs between 178*F and 193*F now. Before all these mods, it ran between 204*F and 217*F. During break-in, we had pulled the thermostat, and the engine ran at about 130-160*F.

Matt.

 

[Turbocharged]

The basic premise is that an open impeller will cause much more turbulance in the water than the closed design, and turbulance impedes flow.
Matt.

High flow rates cause turbulant flow and turbulant flow is desirable for heat transfer. Are you familar with Reynolds number?

The closed impellar design is more efficient than the open impeller but I am unsure which is more likely to cause cavitation. Cavitation will occur when pump pressure falls below the vapor pressure of the liquid being pumped. This is more likely to occur at high flow rates.

Propylene glycol has a low vapor pressure compared to water. Vapor pressure increases with increasing temperature. This all means that you are more prone to cavitation if you are running a high water content and your coolant temperatures are excessively high.

Where are the mechanical engineers at? I was told in school that ChE's would never have to design pumps because that was an ME's job...

 

[Turbocharged]

I just noticed that the top pump has a plastic impellar. If that pump cavitates, the impellar may be destroyed. It will certainly be damaged.

 

[kanderson111]

I just noticed that the top pump has a plastic impellar. If that pump cavitates, the impellar may be destroyed. It will certainly be damaged.

I don't think you looked at it closely enough. It looks like steel, just with a black color to it. I've used many pumps of this design and none of them ever had a plastic impellar.

 

[Staytuned]

I have had a plastic impeller on my water pump before and I would never go back to one ever again.

Read here and see pics. http://www.dsmtuners.com/forums/showthread.php?t=180967

 

[Marc91GSX]

I had a long conversation about this with a friend of mine who has spent the last 30 years building and dynoing race engines, mosly V8's. GM 350's are known for cooling problems, specifically due to the cooling system cooling one side of the motor better than the other. GM originally had an open impeller design on their pumps, very similar to the second water pump in your picture. In later years, they went to a closed impeller design, also very similar to the first pump in your picture. Many GM folks upgraded to the second design for its improved flow abilities, which helped the cooling problems facing the motor. The basic premise is that an open impeller will cause much more turbulance in the water than the closed design, and turbulance impedes flow. It doesn't really make much sense to look at it, but you can't argue with the results.

The above quote is dead on. The first water pump is more efficent, and should move more water per revolution.

I have also had both styles of pump in my car, and was constantly using DSMLink to monitor water temp, before and after the build of my forged 7-bolt. I guess we have a very good cooling system, as the temperature of the coolant did not change at all with either pump. Moving to a 1G water neck and thermostat housing (when I did a 1G head swap) dropped temps a few degres, changing out the stock thermostat to a 180*F unit helped even more, and removing the 2G oil/coolant heat exchanger took even more off. The car runs between 178*F and 193*F now. Before all these mods, it ran between 204*F and 217*F. During break-in, we had pulled the thermostat, and the engine ran at about 130-160*F.

Matt.

I am not sure about the exact year that they made this change but it still did not solve the problem entirely. They completely changed the entire cooling system in 1992 whne they introduced the Gen 2 small block ( unlike in DSMs they actually improved the design in the 2nd gen engine). The Gen 2 used a reverse cooling system that cooled the heads first and then the rest of the block. They also went to a completely enclosed water pump with a revised design of the impeller in the first picture.

I told you that because I had a 93 trans am with the Gen 2 small block in it. I had cooling problems from the get go because I bought the car used and the original owner had replaced the water pump with an aftermarket unit. The unit it was replaced with had an open impeller design and when I changed it back to the OE pump I never had another problem.