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Head cooling on cylinder #5 - solutions?


TimZ

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I sketched up this diagram of the cooling system to help me visualize how the cooling system flows. I thought it might help other people here. Let me know if I screwed something up. Constructive criticism and suggestions for improvement are welcome and expected :).

 

s30_cooling_system.jpg

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Only two things I note:

"Recirculation Line"---there are two, one internal and one external, and they go to the inlet side of the pump.

"Heater Core to Pump" line should also be on the inlet side of the pump.

 

I only make this note because this past weekend I was assisting with a Toyota 18RG Water Pump Swap, and indeed they have lines that go to the pump volute, AND others that go to the inlet of the pump---what is present in those two areas is quite different!

 

Basically, adding the internal bypass line and making the other two lines all go to what looks like the 'lower radiator hose line' would be more technically correct.

 

"Gnaank gnaaank! Lewis, the Alpha-Betas took our pocket protector collection and set on fire!"

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Update on the 260 Retrofit to #5/6.

I Seafoamed the engine via tank of gas, and will Seafoam in the intake this weekend---this will remove any 'deposits' on the back of the valve that may be contributing to any detonation I am hearing.

 

On the tank of gas after the first Seafoaming, I have added a full can of NOS Octane Booster, and from what I can hear, the Detonation has gone away entirely. I will test again tonight on the way home, as it's another scorcher (95+) on the way home, to confirm that a 'boost' in octane will also solve my detonation issue.

 

Then I will probably be sent out of the country till it's cold, and I will have to wait a year to see temperatures that will mirror what I currently experience, but lets keep our fingers crossed that I get a chance to do the mod and report on the detonation results.

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Hey, it was as much to see if the 'octane booster' really did anything at all, and to confirm something other than filling my tank with 100 octane VP Racing gas (at $7 a gallon for COMMUTER DUTY) would indeed solve the knockies.

 

If the Octane Booster didn't work, the double-check would be gritting my teeth and doing a 100 Octane Fillup. I mean I do it for MSA Weekend, but doing it to merely drive to and from work is...yeeech! Kinda over the top, eh?

 

Just had to confirm that there was nothing mechanically causing a problem that wouldn't be cured 'no matter what'---more data supports more logical and pertinent conclusions.

 

I mean, the stuff was effectively adding $1 a gallon to my cost of fuel. Had 'OFF ROAD USE ONLY' emblazoned all over the can, so I felt real good putting it in the tank to drive to work. Like running C16 'just because'!

 

"I commit my Weekly Crime!"

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Well, I just completed the cooling line modification to my 260Z E88 w/N42 valves, (Geez, the last guy saved me a lot of time and trouble, not to mention money!) using copper water line and flare fittings, I like the way the color stands out against the black and silver scheme I have going on...Might even paint the car a coppery color. (The new GM burnt orange comes to mind...)

 

 

Photos in a bit...

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Hey, it was as much to see if the 'octane booster' really did anything at all, and to confirm something other than filling my tank with 100 octane VP Racing gas (at $7 a gallon for COMMUTER DUTY) would indeed solve the knockies.

 

If the Octane Booster didn't work, the double-check would be gritting my teeth and doing a 100 Octane Fillup. I mean I do it for MSA Weekend, but doing it to merely drive to and from work is...yeeech! Kinda over the top, eh?

 

Just had to confirm that there was nothing mechanically causing a problem that wouldn't be cured 'no matter what'---more data supports more logical and pertinent conclusions.

 

I mean, the stuff was effectively adding $1 a gallon to my cost of fuel. Had 'OFF ROAD USE ONLY' emblazoned all over the can, so I felt real good putting it in the tank to drive to work. Like running C16 'just because'!

 

"I commit my Weekly Crime!"

 

How about the "other" octane booster that really does do more than 0.2 octane boost? I can't recall who makes it but it's like the parts store derived bottles in appearance. It really does add at least a few octane to it. Gah, too late in the day to remember stuff...

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Thanks for the suggestions. How about this one:

 

s30_cooling_system_a.jpg

 

 

Only two things I note:

"Recirculation Line"---there are two, one internal and one external, and they go to the inlet side of the pump.

"Heater Core to Pump" line should also be on the inlet side of the pump.

 

I only make this note because this past weekend I was assisting with a Toyota 18RG Water Pump Swap, and indeed they have lines that go to the pump volute, AND others that go to the inlet of the pump---what is present in those two areas is quite different!

 

Basically, adding the internal bypass line and making the other two lines all go to what looks like the 'lower radiator hose line' would be more technically correct.

 

"Gnaank gnaaank! Lewis, the Alpha-Betas took our pocket protector collection and set on fire!"

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Close. The lower rad hose doesn't really need to be called out as a box, and the recirc lines should all just go to the thick blue arrow coming from the radiator return.

 

Technically, the Thermostat is not a block valve as drawn, but more properly drawn as a regulator with the flag for the sensing line on the engine side...but I look at this stuff all the time...for work....STOP MAKING THIS WORK!:wc:

 

Some more information on the Diesel (LD28) Water Pump:

 

Flow rate is 30.6gpm at 3400 rpm pump speed.

Driven speed on the diesel is 1.32:1, with a maximum power occurring at 4600rpms, so you may deduce that the 30.6 GPM is being produced at a crankshaft speed of 2575 rpms...which is conincidentally 175 rpms higher than it's peak torque rating speed (2400 rpms crankshaft speed)

 

In an industrial application the torque peak is rated at 2300 rpms crankshaft speed, and is down 9 ft-lbs from the automotive torque peak rating.

 

If you look at the pump drive ratio, and recognise that the diesel is peak HP rated at 4600 rpms, you see the pump speed there is 6072 rpms. I don't know what speed cavitation will happen in this pump, given the NPSH present, but consideration of re-considering the actual drive speed of the pump and actually slowing it down may pay dividends in a more stable flow characteristic.

 

As John Coffee stated, running a 20psi radiator cap would solve all the problems as well...and that may be something to look into; perhaps the non-diesel pumps are experiencing some higher speed cavitation and causing heat buildup problems.

 

But for roadgoing street cars it looks like the diesel water pump may well indeed offer more flow without any penalty at the speeds the engine sees 85-95% of the time.

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As John Coffee stated, running a 20psi radiator cap would solve all the problems as well...and that may be something to look into; perhaps the non-diesel pumps are experiencing some higher speed cavitation and causing heat buildup problems.

 

Tony, I searched for for John Coffey's comments on a 20psi cap but found nothing. Can you post the thread? I run the LD28 water pump and have no issues that I'm aware of. Next Friday I'm going to take the Z out for a track day but with the boost set on stun rather then kill. I'm worried about cyl #5 and 6 under sustained boost. Maybe the 20psi cap would keep flow moving in the head better then my 13psi cap?

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Yes, I mentioned 20psi as I knew you could get caps with that rating relatively inexpensively.

It's not a matter of keeping it flowing in the head, it's a matter of getting enough pump suction head that cavitation doesn't happen when you turn the impeller to fast, or exceed design tip speeds. This can happen with increased temperature at relatively slow speeds as well. It all interacts.

 

But the increased static pressure prevents nucleate boiling like John said, and that is what can cause the cavitation in the impeller as well. (And when the pump cavitates, you cease flowing...meaning heat transfer, or carrying heat away more properly, ceases. Then you start that n-boiling, and from there, all is lost!)

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Yes, I mentioned 20psi as I knew you could get caps with that rating relatively inexpensively.

It's not a matter of keeping it flowing in the head, it's a matter of getting enough pump suction head that cavitation doesn't happen when you turn the impeller to fast, or exceed design tip speeds. This can happen with increased temperature at relatively slow speeds as well. It all interacts.

 

But the increased static pressure prevents nucleate boiling like John said, and that is what can cause the cavitation in the impeller as well. (And when the pump cavitates, you cease flowing...meaning heat transfer, or carrying heat away more properly, ceases. Then you start that n-boiling, and from there, all is lost!)

 

I just bought a Stant 20psi radiator cap for just these reasons... :)

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Here is Rev B! Sorry for making it work! At least you know what you are doing! I have only seen a few flow diagrams so I'm pretty much just making this up as I go along...

 

s30_cooling_system-revB.jpg

 

Close. The lower rad hose doesn't really need to be called out as a box, and the recirc lines should all just go to the thick blue arrow coming from the radiator return.

 

Technically, the Thermostat is not a block valve as drawn, but more properly drawn as a regulator with the flag for the sensing line on the engine side...but I look at this stuff all the time...for work....STOP MAKING THIS WORK!:wc:

 

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  • 2 months later...

Tony,

 

How did your results turn out? Did the 100 octane solve the pinging? Were you going to drill and install the additional cooling? Did that solve the pingin with 93 octane?

 

Just looking for an update

 

Thanks,

Chris

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