Offroad-Express

Hi All

About to start doing some seat time in my Prado rear chop and setting up the rear radiator fan trigger points.
I am running a 1KZT and have a digital gauge in the water out housing on the block.
Using std 86C thermostat.
Plumbed into a huge fully shrouded Nissan TD42 radiator on the back tray with AU Falcon dual fans.
It pulls the temps down fast !.
Just wanting to see what others in similar setups have set the fans to come on at.
Thus far I have it at on at 95C and off at 85C .
But reading various forums I could run it a bit hotter....As the thermostat is only just opening at 86 the block would probably end up settling out at 90 plus... no point trying to cool the water more than I need to....
So far during cert testing it only starts to get hot and trigger the fans at highway speeds... Around town it only comes on every now and then. Will look at having a little wind deflector on rear bar and get a bit of air flow down rear window... all play stuff once I can legally hoon around the neighbourhood.
So what max temps with safety margin can I run my Diesel coolant at?
I plan to put some remote thermocouples around the system and get some readings at various points..
Block, rad inlet, rad outlet, etc etc I have access to some cool 4 channel data loggers.

Interested in anyone thoughts...

Calvin

1kz is bottom thermostat so no point turning fan on at anything close to thermostat temp. engine exit temp should be well above thermostat temp. if you have a 10c split switch then i would be inclined to set it 100c on, 90c off.
try not to cool the water in the radiator below thermostat temp as that can cause temps to bounce which is not good for the head and head gasket.

Thanks Tweake.... I can set the on off trigger point and spread to anything I like....Auberins digital gauge switching a relay for the fans.
So can have it trigger on at 100 and off at anything lower...
Yeah Thats my thoughts re having the fans come on to close to thermostat temp....

i would set it fairly close. just far enough apart to stop it constantly turning the fan on and off. a 5 deg difference is a lot of heat energy.
also have a bypass switch so you can turn the fan on constantly.
see what your normal running around unloaded temp is like as thermostat will dictate that temp.
i would be aiming for 90 running temp and fan on 95ish. that should give plenty of head room for when its under load, radiator full of mud etc.

tweake wrote:1kz is bottom thermostat so no point turning fan on at anything close to thermostat temp. engine exit temp should be well above thermostat temp. if you have a 10c split switch then i would be inclined to set it 100c on, 90c off.
try not to cool the water in the radiator below thermostat temp as that can cause temps to bounce which is not good for the head and head gasket.

Lol . How are you going to cool the engine if your feeding water back into it at thermostat temperature .

sirLachlan wrote:

tweake wrote:1kz is bottom thermostat so no point turning fan on at anything close to thermostat temp. engine exit temp should be well above thermostat temp. if you have a 10c split switch then i would be inclined to set it 100c on, 90c off.
try not to cool the water in the radiator below thermostat temp as that can cause temps to bounce which is not good for the head and head gasket.

Lol . How are you going to cool the engine if your feeding water back into it at thermostat temperature .

they have bottom mounted thermostat not a top mounted one. water going to radiator is a lot higher than what the thermostat rating is. ie 86c thermostat give probably 95c out of the engine with moderate load.

if water going back into the engine goes below 86c (in this case) the thermostat shuts and there is NO flow through the radiator. no point cooling the radiator down any more as the radiator is not cooling the engine any more.
if you cool the radiator a lot, when the thermostat opens again the surge of cold water suddenly cools the engine a lot. that sudden drop in temp is what stuffs up head gaskets and heads (cast iron and alloy heads cool at different rates).
its a problem that some rear mounted radiator cars have.

I plan to take the truck for a run with no fan trigger points set and see what temps it reaches ( safely ) at highway speeds.
It may even out at an acceptable temp.... Then I can set fans to come one when it goes higher than the acceptable temp....
See what happens...
Yes the thermostat is supposed to be fully open at 95...

With the AU Fans you can wire them up with 3 relays so that they operate in the factory dual speed configuration.
Run in series to go half speed and then switch to parallel for full speed .
You then use a dual switch thermo switch like the Tridant TFS214.
I run mine with a 3 way switch as well that allows, off / auto / full on bypass

The idea as I understand it is the thermo switch wants to be in the return bottom pipe close to the block .Lets the radiator do the work of cooling rather than the fan . Low speed fan is for general driving /idling and high speed for load .
My fan is barley on at all during highway driving , low speed only at idle or around town .the full speed AU Fans move some serious air and drop temps fast even under load .

From memeroy it's only something like 7 amps draw at low speed and 15amps at high . But the inrush current can spike over 30amps

yep, the falcon fans will drop paj1's temp from 95 to 60 in a matter of minutes at full noise, and with a 50mm core radiator the fans dont even turn on at anything over 50kph.

as above via thermo switch and three position switch for auto/off/manual
found i didnt really need to wire them with the series option to run at half speed as the time i need them both running generally they need to be at full speed anyway

All good stuff guys thanks I did see the two speed fan relay setup. And will probably set it up that way later once I get some temp results with the data loggers.
With my radiator in the rear it doesnt get much if any airflow so during highway speeds or load situations i suspect the fan will work more than slow work.
Just need to get my cert plate back and run it thru a Wof....then it's test time.

While I await my cert plate I got some relays and have wired up for two speed.
Also ordered an Auberins PID controller so I can trigger slow then fast speed at the desired temps.. Will wire in an override switch to full on.