Hello,
Could anybody please show or tell where the water return line from the turbo ends up being plumbed to?
Both the engines I bought were disassembled so I never had a chance to see. I know it connects to the hardline behind the head, but since all of my water lines are deleted, it does not help me much in seeing where it finally ends up.
There really are only three possible locations it could be plumbed to; the big fitting on the back of the block above the starter, the main water inlet, or the water outlet on the intake runners. I am curious which one the turbo coolant ends up being sent to in a stock setup.
Thank you.

Here are the three locations.


Number 1 is actually most likely not it, because I would think water goes out of it, not in. So it is probably either 2 or 3.
In 2, the water from the turbo would not pass through the radiator before entering the motor, but since it is not a large volume I am not sure if it would matter.
In 3, it would enter before the radiator, but I am not sure how much pressure the water pump creates, so perhaps it would not let the turbo coolant flow.

Just noticed that on one of the intake manifolds I have all the lines are actually still attached, and the turbo water return actually plumbs into a hardline that connects to all three places.
I believe I will plumb it to number 2.

Nope, it runs to the line in the back of the intake manifold. It's the highest point in the system and also has an air bleed on it. This serves multiple purposes. Obviously the first is to bleed the air from the system. The second is convective cooling of the turbo after the engine shuts down. As the coolant in the turbo is heated, it rises up to the manifold. When it reaches the manifold, it is cooled because the manifold is a much lower temperature As it does this, colder coolant is drawn out of the block into the CHRA, thereby cooling it.

Thank you, great information. In that case I will plumb it to location 3.
I have an aftermarket manifold and all the extra water lines and accessories will be deleted, though I hope it will still work better than not having the turbo water lines hooked up at all.
My radiator is custom and sits lower than the manifold, so I actually plan to attach a filler neck to location 3, but it should be no problem to splice the turbo line in there.

Location 3 won't work, I should have clarified. After it cools in the back of the manifold, it drops down into the hard coolant line that runs under the intake manifold. This ultimately ends up at the large pipe that #2 is connected to. Do you still have the hardline pipe that goes under the manifold? If you plan on having a heater, you HAVE to have it. Location 2 is the only place for the coolant from locations 1 and 3 to return to the water pump. Locations 1 and 3 are on the "pressure" side of the water pump. The big pipe that location 2 is connected to is the ONLY place in the system that is under "vacuum" (it's not really vacuum, it's just lower in pressure than the rest of the system, so the coolant will flow towards its)

People often get it in their heads that they want to eliminate a bunch of the coolant lines for the sake of simplification. The issue is that there really isn't much you can eliminate and have the system work properly. Really, the only thing you can eliminate the throttle body cooling, and if you have a non-water cooled turbo, the lines associated with that. (Though from experience, finding a banjo bolt plug is impossible, so you end up just having to loop the lines).

Matej wrote:Here are the three locations.

Actually quite a bit can be removed if you can remove the heater, which I could as I live in a country with a tropical climate.

What I gathered from my research while I was simplifying the cooling lines:
- #2 and the big pipe where it's tee'd to is always under suction as that's the inlet to the water pump

- When the coolant is cold and T-stat is closed, coolant flows from the head (#3) to the water pump inlet (big pipe below #3) via the stock "bypass" plumbing.

- When coolant is hot and T-stat opens, the bulk of the coolant from the head will flow past the open stat into the radiator via the T-stat housing outlet, and then back into the water pump inlet via the lower rad hose, this is how the coolant is cooled. There will still be some flow in the "bypass" plumbing as the T-stat doesn't cut off flow completely.

What I did to simplify the lines (heater not required):
- Unscrew the stock fitting at #1 and blanked it off with a plug (1/2" BSPT IIRC)
- Connect #2 to turbo with a line running round back of the block.
- Tee #3 into the big pipe below it (water pump inlet)

float_6969 wrote:Nope, it runs to the line in the back of the intake manifold. It's the highest point in the system and also has an air bleed on it. This serves multiple purposes. Obviously the first is to bleed the air from the system. The second is convective cooling of the turbo after the engine shuts down. As the coolant in the turbo is heated, it rises up to the manifold. When it reaches the manifold, it is cooled because the manifold is a much lower temperature As it does this, colder coolant is drawn out of the block into the CHRA, thereby cooling it.

Fantastic explanation. More knowledge!

If you want to ditch the heater, then yes, there is A LOT you can eliminate. Most people aren't in that situation though.

Izento wrote:Fantastic explanation. More knowledge!

Thanks! I'm full of useless information, LOL!

Hey float I have taken off my heater lines but still want water to the turbo any information you could give me would be great my head is about to explode

The fitting on the exhaust side of the block is the water outlet for the turbo. That should route to the coolant inlet of your tubo. From the outlet of the turbo, you need to make a line that goes all the way back to the other side of the motor and connects to what CCB has circled as #2, or the big pipe that #2 is connected to.

I've got 3 hooked straight to 1 dose that even work

That does nothing. 1 can be capped/plugged, but 3 HAS to connect to 2.

Sorry to be a pain float, at the moment it goes from #3 straight to #1 and that's like a y then goes through a oil cooler to #2 so could I t off somewhere near that #1 piece for the water return from the turbo because it's heading to #2 anyway

That was the most confusing thing I've ever read. That being said, I'm pretty sure the answer is no. You could try to tee between the cooler and #2, but if yours is like my oil cooler, there isn't enough room for a T.

Haha yeah sorry mate I'm not the best at writing it down!
So you're saying that I can cap off one of the lines at #1 but keep the oil cooler line going from #1 to #2 ! Then the turbo return line goes to a tee off #2!
And then #3 will tee off #2 as well!

Yes!

Thanks mate

No worries, glad to help!

Here is a diagram of the water system from the manual. It appears that the turbo return line is plumbed to #2.


I should have mentioned that my car will not have a thermostat, so in my case it will be better to simplify the lines to the bare minimum since the water system will only have one cycle, instead of cold/hot/in-between. Running temperature will be achieved through the use of a restrictor and fan control.
Speaking of which, what is an optimal operating temperature for the CA?
Thanks!

Good luck with the engine temp control w/o a thermostat. A couple of people have tried to run without one using the method you're talking about or similar, and AFAIK, they all ended up putting a thermostat in there. The CA is not like the SR and doesn't require much in the way of cooling. I think the issue that you're going to run into is that to have a restrictor sized small enough to allow the engine to heat up properly, won't be big enough to keep the engine cool when needed. Maybe running an electric water pump would work (one person had a post about doing this, but then they fell off the forum and we never heard if it worked), but the use of restrictors and fan control probably won't do it. I'm not trying to discourage you, but I wanted you to know it's been tried before and others haven't had luck.

Optimal engine temp is hard to say. I've tried the 3 available thermostats, 165°F, 180°F & 195°F. I tried all of them when running E85 though. The issue when running E85 that I found was that the fuel didn't like the engine at 165°F. It seemed to run rough. It also sucked in the winter. It was NOT enough to keep me comfortable when it was really cold. I theorize the E85 didn't atomize well at that engine temp and would condensate on the port walls. The 195°F got the oil temps higher than I liked just running on the highway (220-230°F no oil cooler). I can't image what they would have been beating on it. The 180°F thermostat seemed to let the engine run well and the oil temps running on the highway were more where I would have liked them (205°-215°, no oil cooler). All of that being said, If I didn't have the running issues with the 165°F thermostat, and I wasn't driving in the winter, I would use that thermostat. In theory, the cooler engine temperature should help to suppress detonation/pre-ignition.

I dont mean to thread jack, but I too have a similar question.

I have a 510 and the turbo is reverse mounted...

One coolant run line goes from the CHRA to the lower outlet (3/8" size) on the exhaust side. the upper 1/2" hole is plugged.
The second line goes from the CHRA to the #3 outlet.

Is this incorrect, or will this work? The coolant flow is confusing on these motors.

Thank you!

float_6969 wrote:I think the issue that you're going to run into is that to have a restrictor sized small enough to allow the engine to heat up properly, won't be big enough to keep the engine cool when needed.

The issues people usually experience under high load after removing the thermostat on an SR/KA/RB/whatever motor are actually due to not running a restrictor small enough (or not using a restrictor at all). It causes the coolant to pass through the radiator too quickly thus not being able to cool off. Even when the thermostat is fully open, it still acts as quite a significant restrictor.
I have yet to attempt it on the CA, but if it does not work out I will just go back to using a thermostat.

jaredperry wrote:I dont mean to thread jack, but I too have a similar question.

I have a 510 and the turbo is reverse mounted...

One coolant run line goes from the CHRA to the lower outlet (3/8" size) on the exhaust side. the upper 1/2" hole is plugged.
The second line goes from the CHRA to the #3 outlet.

Is this incorrect, or will this work? The coolant flow is confusing on these motors.

Thank you!

That doesn't work. Every coolant port on the block is an outlet EXCEPT for #2. EVERYTHING has to come back to the #2 port somehow.

Matej wrote:...I have yet to attempt it on the CA, but if it does not work out I will just go back to using a thermostat.

Keep us updated please!

But does it really matter what way coolant flows through the turbo as long as the inlet and outlet are as you described, Float?

As far as the water inlet and outlet on the turbo, they are not directional.
The curious thing is that Garrett recommends the center cartridges on their turbos to be tilted and to plumb the inlet into the lower water port and the outlet to the one that is higher, yet on CA's and SR's and probably other Nissan motors the feed line is plumbed into the higher port from the factory. I wonder if it would be beneficial to switch them, or if Nissan did it on purpose.

The tilting is for the purpose of convection cooling post shut down, and to ensure that no air is trapped in the center section. I know on my CA, it was plumbed as is should be. You know all of the cooling ports on the block (with the exception of the large radiator hose) are "cold" water, right?

What's crazy is that I don't have a 5/8" port on #2

What would really happen if I had lines run from #3 into the turbo then out the turbo to the 3/8" bspt fitting to the lower rear of the motor. I don't understand why my water neck doesn't have the 5/8" nipple.

float_6969 wrote:The tilting is for the purpose of convection cooling post shut down, and to ensure that no air is trapped in the center section. I know on my CA, it was plumbed as is should be. You know all of the cooling ports on the block (with the exception of the large radiator hose) are "cold" water, right?

From the factory the feed line always comes plumbed into the higher port. Perhaps back then the benefits were not yet as thoroughly explored.


If using braided lines, it would probably be best to switch the feed to the inside and use the higher outer port as the return, or re-clock the center section to tilt the other way.