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Head cooling on cylinder #5 - solutions?


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Tim,

 

PM jgkurz and drag him into this. He's adapted the diesel pump. I only know bits of it... so best to get it staight from the horses mouth.

 

 

OK, Here's what I have used and seen in practice. None of this is my original idea. My friend Oz has been the source for much of this information. So first is the water pump, I use the LD28 water pump which does have a larger impeller. The only modification you have to make it to trim roughly 1/8 - 1/4 inch off the leading edge where the pump mounts to the timing chain cover. I have illustrated this in the below pictures. The LD28 pump is Nissan part number 21010-17SY7. Do not go to a local parts store to buy the LD28 pump. You will just get a regular L28E pump and not the one with the larger impeller. For some reason they don't recognize a difference. I also should say that I have never noticed an improvement with the larger pump. I know the larger impeller moves more water but since I have never had a cooling system issue I can't say for sure that it helped my application. Either way, I think it's a good idea and the principle is sound.

 

I have not done this modification but my friend Oz did this on his Bonneville 280ZX. Basically he drilled and tapped three ports above the exhaust on what looks like cylinder 3, 5 and 6. He joined the three ports into a single manifold then had a separate inlet back into the radiator bypassing the thermostat. His application did not use a thermostat so that would be something to consider for a street application. Even under extreme boost and and environmental conditions, the Bonneville L28 setup never had any cooling system or detonation problems he was aware of. There are many other factors that helped but these modifications were key. The picture I enclosed shows the engine in 1991 trim so things are a little aged but you get the idea. I hope this helps.

 

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3.jpg

 

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  I assume you did try to source the LD pump in Australia, I saw a thread and you mentioned you got it from Japan (?)

My thoughts on the Summary:   - The path of coolant through the L engines results in the rear of the head receiving the hottest coolant having stagnated water flow, insufficient for the he

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I really need to make it up there to see that beast.

Those Hobbs Switches look all to familiar! LOL

 

I'd be honored to have you come up. I'd just need a couple months advanced notice so we could dig it out of the barn. If I ever can get my Z done I plan on bringing it over to my garage/shop. :mrgreen: Probably better if you come up then...

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OK, Here's what I have used and seen in practice. None of this is my original idea. My friend Oz has been the source for much of this information. So first is the water pump, I use the LD28 water pump which does have a larger impeller. The only modification you have to make it to trim roughly 1/8 - 1/4 inch off the leading edge where the pump mounts to the timing chain cover. I have illustrated this in the below pictures. The LD28 pump is Nissan part number 21010-17SY7. Do not go to a local parts store to buy the LD28 pump. You will just get a regular L28E pump and not the one with the larger impeller. For some reason they don't recognize a difference. I also should say that I have never noticed an improvement with the larger pump. I know the larger impeller moves more water but since I have never had a cooling system issue I can't say for sure that it helped my application. Either way, I think it's a good idea and the principle is sound.

Thanks, John - that's exactly what I was looking for. Called Courtesy Nissan and ordered one a couple of days ago. Now I just have to wait and see if the right pump shows up. They did actually find that part number after a search for a Maxima Diesel water pump, so it looks pretty promising.

 

Interestingly, I talked to a tech rep at Evans Cooling last week, and he indicated that I'd probably be fine without making any changes to my cooling system's radiator or water pump. His main concern was whether the rad had a low enough restriction for the new fluid, which is slightly more viscous than straight ethylene glycol coolant. Since I'm running an aluminum rad with a 1.25" tube core, he didn't think that would be a problem.

 

I ordered 3 gallons of NPG-R from Irv Hoerr Racing. The "R" formulation is a bit thinner than the regular stuff, and has an even higher boiling point (400 degF). It also freezes at a higher temperature (-10 degF). Since it has no water, it doesn't expand when it freezes, so storage at such temps should be fine. I'm pretty sure the only way my engine will ever be started at temperatures that cold would be if the garage is on fire... :mrgreen:

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...a small amount of turbulence from the casting sand marks is probably also helpful.

 

Please explain this... I'm not sure I understand why... (genuine question, not arguing...)

 

castingweb.JPG

 

close-upweb.JPG

 

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That's what I was thinking (without really knowing, I never ran my L series long enough to even be aware of such problems) when I suggested Extrude-Honing...

 

Eddy's in the space-time continuum.

?????????????????????????????:confused::confused2:hs:

 

Now you lost me... I thought an Eddie was the area behind a protrusion in the flow, where the fluid is barely moving which would create a localised boiling spot?????

 

What do you mean by "space-time continuum"???

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I think JeffP has run stragiht Etheylene-Glycol in his engine since new, and the head looks like new, no corrosion whatsoever. The boiling point of E-G is up there in the same area as the stated values of the Evans stuff, I wonder what the thermal transfer properties are in comparison?

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A rough surface exposes more surface area to the cooling medium...

 

That part I understand...

 

 

 

...a slightly turbulent flow over the surface should help with heat transfer.

 

It`s that part I'm not sure about...

 

I know that turbulence in the intake charge near the combustion chamber helps atomizing fuel but, what does turbulence do for heat transfer???

 

Thanks.

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A turbulence can help disrupt a barrier that will form right at the surface of the metal/fluid contact area. This barrier can act as an insulator, and keep heat from transferring efficiently.

 

A slight turbulence keeps this barrier from forming, and causing bigger problems.

 

Check out the Grape Ape Racing explanation of what happens when boiling occurs on the metal surface precipitating overheating, and you will be able to follow it better I think.

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Not necessarily a steam barrier, but it can work itself up into that eventually, yes. The barrier layer of the fluid/metal interface zone if undisturbed can act as an insulator. Turbulating it allows cooler water from the 'center of the flow' to contact the highest heat area and take the heat away. Think of a metal pipe, with a blowtorch on the outside heating it. The coolest water is in the center of the pipe. If the walls of the pipe are smooth, the water passing over the smooth piping will boil continually at the point where the torch is applied, while the center of the water really doesn't change temperature.

Now add bumps to the inside of the pipe---like a sand cast iron pipe instead of a DOM Piece of tubing. When you do a thermal profile, the center of the pipe is still the coldest, but the 'hot portion' of barrier flow along the pipe itself extends further into the center of the flow. This is a result of more surface area...but even if this was held constant, the turbulation of the flow at the pipe-water surface would promote that heat-transfer further into the center of the pipe's water flow.

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?????????????????????????????:confused::confused2:hs:

 

Now you lost me... I thought an Eddie was the area behind a protrusion in the flow, where the fluid is barely moving which would create a localised boiling spot?????

 

What do you mean by "space-time continuum"???

 

 

 

You were right, I was quoting a book; the Hitch Hiker's Guide To The Galaxy. Actually, one of the sequels. It's where my user avatar comes from.

 

It was a nerd joke, purposefully obscure and I was hoping to draw someone out on commenting on it. Pardon the confusion. It came up in the book exactly like this, one character made a reference to "eddies in the space time continuum" that they could ride out of prehistoric earth, two million years into the future and back to their own time. The other character was confused, and asked who eddy was and what he was doing in the space time continuum.

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