Water in- & outlet 4agze ae101

[bozu]

Gents,

I've recently replaced the water lines going to my turbo on my 4agze (AE101) turbo set up and was wondering which way the water is flowing through the turbo.

Some say there is no specific water outlet or inlet on a turbo but I believe there is due to the thermal siphon effect.

Having said this I want to make sure my lines are connected the right way so this effect can occur.

The line from the low side of the turbo is T'ed into a line that on one end is connected to the valve that is operated by the heater control dash. The other end goes to, which I believe is, the external thermostat.

The line from the high side of the turbo is T'ed into a steel line that runs on the right side of the engine (when sitting behind the wheel and looking forward) which I believe is the water outlet from the head. This steel line is then also connected to the external thermostat (with a rubber line).

Can someone tell me which way the water is flowing?

[bozu]

I've sketched up my situation and added arrows for the flow directions. The flow directions are based on the info I could find so far. Please see image below.



I assume the flow directions are correct, can someone confirm this?

Starting at the waterpump which sucks water from connection 1 on the external T-housing and pumps the coolant through the head and out the two head outlets.

Assuming the following I think the lines are connected the wrong way around for the thermal siphoning effect to occur:
- There is pressure between the head outlet on the side of the engine and connection 2 which pumps water into the turbo via the high side.
- There is suction on the low side of the turbo due to the water pump sucking water from the external thermostat housing.

Disregarding the fact that the lines might be the wrong way around I still have doubts that the current set-up actually works (although I've driven it ±5000 km's with no problems so far). Reason being that in my opinion there can be water pressure on both sides of the turbo...

Because in my understanding the thermostat in the external housing only blocks connection 4 so the waterpump can effectively suck water from connection 2 & 3. However if the heater valve is open there might also be pressure in the line between the valve and connection 3 because it is pumped through from the outlet on the back of the engine head.

Although one would also have to take into account the resistance created by the heater core and line diameters. I don't not know when does pressure in the line switches to suction.

Considering the current set-up was working I think switching the lines around would be the solution as the feed will be on the low side and the return on the high side.

Tried to make it as clear as possible so hopefully it is. Any help/input would be appreciated!

[jondee86]

I have no idea what the two small hoses attached at F and C are for ?
Maybe they are for a water cooled turbo... or a heated throttlebody ?



But the principle is clear. Take the "flow" line as close to the head as
possible, and connect the "return" line as close to the pump suction as
possible. This gives the greatest pressure differential to ensure flow
takes place in the circuit.

Thermosyphon action is something quite different, and does not apply in
a pumped system. The last vehicle I saw with a thermosyphon cooling
system (no water pump) was a 1950's Fordson van



Thermosyphon action requires the radiator to be higher that the engine,
so that hot water can rise and flow from the top of the (side valve) head
to the top of the radiator. After losing heat in the radiator, the denser cool
water returns to a connection low down on the block.

Cheers... jondee86

[bozu]

I agree thermo siphon does not occur in a system with a pump when that pump is active.

When the pump is not active i.e. the engine is not running i believe it can occur as my turbo is a high mount.

Also agree on your proposed connection locations to create the greatest pressure differential.

Would you agree though that in my situation i have to switch the hoses around?

[jondee86]

If we assume that all connections to the remote thermostat housing are
at the same pressure, then points 2 and 3 will be at the same pressure.
The only force that will make flow in the turbo cooling circuit is the
pressure differential between the point you tee'd into the bypass line, and
the thermostat housing.

In loose terms, the flow in each circuit will be proportional to the
resistance. And in your case, the resistance of the turbo circuit will be far
greater than the resistance between the tee and the housing. IMHO, you
will get negligible flow in the turbo circuit with the heater valve closed.

To get flow in the turbo circuit you will need to create some resistance in
the tube/hose between the point where you tee'd into the bypass hose,
and the thermostat housing. Probably the easiest way would be to get a
small ball valve from a plumbing store, and insert it in the hose. Then
you can partially close it to force a percentage of the bypass water to go
thru the turbo circuit.

Regarding thermosyphon, this will only occur if the hot water can rise
naturally from the turbo to the radiator, and thus create circulation.

Cheers... jondee86