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How should I route coolant to my GT3076R with megasquirt?


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#1 dpuma8

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Posted 23 March 2016 - 02:44 PM

My thermostat housing has two coolant sensors for my gauges and Megasquirt.  The bypass line is still connected as shown in the 280Z cooling diagram and I have the heater hoses plugged at the block since I pulled out the heater equipment.  I rounded out the coolant plug in the back of the block so I can't use that.  Given my situation, what is the best way to route the coolant to my turbo?  Am I going like this ?  Old Heater hose in back of block>>Turbo>>old heater hose in front of block?

 

Any suggestions?  I would prefer to avoid tapping into the thermostat housing if possible unless that is the absolute best option.


1975 280Z L28E with Megasquirt II 3.57


#2 rossman

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Posted 23 March 2016 - 04:02 PM

I think you answered your own question: "Old Heater hose in back of block>>Turbo>>old heater hose in front of block"



#3 Milenko2121

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Posted 25 March 2016 - 09:31 AM

Just keep in mind the coolant coming out of the block near cylinder 6 has already cycled through the engine. If you end up not using the line for a turbo, you should plug near the head and you should plug the entrance to the water inlet even if you use the line there to cool the turbo because if you route water back to it, you're just putting hot water back into your motor instead of getting nice cold coolant from the radiator. Route the coolant back to the thermostat housing instead. You'll see lower coolant temps with them plugged. If you end up deleting the external bypass, you can drill a small hole in the thermostat to act as a bypass instead to prevent you blowing a hose if you go WOT before the thermostat opens.


Edited by Milenko2121, 25 March 2016 - 09:35 AM.

1977 280zt with '87 Z31t ECU, CLSD and S14 SR Transmission

#4 Tony D

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Posted 25 March 2016 - 11:10 PM

Factory routing for the Z31 was housing below thermostat, turbo, water pump inlet.

Yes, you recycle coolant. That factory bypass line? USE THAT! No more recirculation than you already have, and in fact beneficial to your turbo.

"How?"

Because during running, before the thermostat opens, you route recirculated coolant through the turbo back to pump inlet, aiding in cavitation prevention and hastening warmup.

Once that thermostat opens though, there is only the water pump NPSH to circulate water through there.... No big shakes, water flows center section is cool.

But....

After shutdown, you have cap pressure blanketing the system. No pump suction to draw from the thermostat housing through the turbo back to the inlet...

What you DO HAVE, though, is blanket pressure and radiator-cooled water sitting at the water pump inlet. And the boiling hot turbo heating water upstream in that line...heated water which rises to and out the still-opened thermostat and out to the radiator...drawing cool water from the water pump inlet line through a thermal siphon...introducing the coolest water in the system available after shutdown through the turbo until the turbo housing reaches stasis with the water temperature.


When do you form Coke in the turbo, when running or after a heat-soaked shutdown?

This routing insures cool water being drawn through the turbo with no other devices present, at the time the turbo MOST needs this cooling to prevent temperature rise.

During running, water flows thermostat housing to pump inlet via pressure differential.
After running, water flow reverses and continues, pump inlet to thermostat housing and out to radiator via thermal siphon.

Think about the above for a while before making the hose routing changes suggested otherwise. You got what you need already there. You don't change anything by using the existing bypass line in this manner.
Misanthropic Anthroparion Class 5 Hoarder, aspiring to posthumous fame as my containers are cut open and the market floods with crap I've squirrelled away over the years! I endeavour to persevere...

#5 rossman

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Posted 27 March 2016 - 04:29 AM

Ooh, I missed where you said the bypass is still connected.  Tony is absolutely correct, "USE THAT!"



#6 dpuma8

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Posted 19 April 2016 - 01:02 PM

I was using the hole on the side of the thermostat housing (closest to the left wheel) as my bypass line previously.  The outlet is aimed directly towards the back of the car and is pretty stuck in there.  Is it okay if I make a loop with hose and run the line down near the front of the engine rather than across the fuel injector area?  Is this line going to be pressurized or does it need to be pointing downward and is gravity fed?


1975 280Z L28E with Megasquirt II 3.57


#7 Tony D

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Posted 30 April 2016 - 07:15 PM

Never put loops in water lines, they hold water bubbles and block flow.

 

There is a slope for best thermal siphon after shutdown.

 

There is a pressure differential moving it through when running.

 

After shutdown operation is far more critical to prolonging turbo CHRA life than what it does when running and having copious amounts of oil blown through it.


Misanthropic Anthroparion Class 5 Hoarder, aspiring to posthumous fame as my containers are cut open and the market floods with crap I've squirrelled away over the years! I endeavour to persevere...

#8 dpuma8

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Posted 08 June 2016 - 03:48 PM

Okay, I have been reading about thermal siphoning and I just want to be clear on this.  I have two banjo bolts for coolant on the turbo.  I have the turbo tilted to where the coolant port nearest to the engine is slightly higher than the furthest port.  I should have the bypass line from the thermostat connected to the higher turbo coolant port with the banjo bolt facing upward.  On the lower coolant port, does my banjo bolt need to be facing downward so that the heated coolant will rise through the other line and back to the thermostat housing?

 

Do I have the idea right?


1975 280Z L28E with Megasquirt II 3.57


#9 Tony D

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Posted 12 June 2016 - 01:12 AM

Generally yes... it will come up from the lower radiator hose inlet pipe to the bottom of the turbo, be heated and rise to the thermostat housing and the out into the radiator....


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#10 dpuma8

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Posted 10 July 2016 - 05:02 PM

In the picture, I have the bottom coolant banjo bolt aimed downward (this one goes to the passenger side of the engine block) to hopefully make the other coolant banjo bolt the only line for thermal siphoning. Is there an issue if I have both banjo bolts facing upward and thermal siphoning? With this bolt aimed downward, the steering shaft is in the way.

Any ideas?

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1975 280Z L28E with Megasquirt II 3.57





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