Jump to content
SAU Community

Recommended Posts

I've done everything, koyorad, oem pump, oem fan. Pressure test coolant system, vacuum bled cooling system, new headgasket, head crack tested, new radiator shroud, new oem fan clutch. 

Literally the only thing left is the electric fan on the front. It may be lazy so I'll look for a replacement. 

Any other suggestions? On a 40 degree day or can reach 95 degree with aircon on if waiting in traffic for long enough. Then I turn ac off it comes back down. 

Anyone else's r33 does this? I think it always has but since I've got gauges I'm more aware of it. 

Link to comment
https://www.sau.com.au/forums/topic/480594-r33-gets-hot-only-with-ac-on/
Share on other sites

2 hours ago, joshuaho96 said:

Is this why all the oil cooler kits on the market have laughably low thermostat crack temps like 70C? 

They work the same way that water thermostats do - i.e. they do not limit maximum temps they are designed to regulate minimum temps so that the engine is not operating below its efficiency temperature. Some are set at 70/ 80 deg C some are adjustable.

19 hours ago, KiwiRS4T said:

They work the same way that water thermostats do - i.e. they do not limit maximum temps they are designed to regulate minimum temps so that the engine is not operating below its efficiency temperature. Some are set at 70/ 80 deg C some are adjustable.

I was under the impression that you want to hold engine oil temps at 100C and coolant around 90C, so a 90C thermostat seems more reasonable? Pretty much every oil cooler kit for RBs has a thermostat crack temp of 70C which is kind of ridiculous.

Crack temp and hold temp are not the same thing. There's a whole mass and energy balance thing going in between the engine dumping heat into the oil and the cooler dropping it out. Just because the TS cracks at 70 does not mean that the cooler has any hope of holding the oil at that temperature. The factors at play are the "effective HTUs" of the core, which is comprised of the oil temperature and the cooling power of the ambient air flowing across it (more oil T drives HTUs up, less oil T drives HTUs down, likewise, more and colder ambient air flow drives HTUs up and vice versa). Against an ambient air T of, say 35°C, you only get ~half the HTUs out of the core at 70°C oil T as you would with 100+°C oil T. So even though you may see the 70°C crack T as being horribly low, it actually gives quite a soft start to the cooling power, which ramps up as the oil gets hotter (both because the TS opens more and as the hotter oil drives more heat transfer out of the core).

On 6/14/2020 at 11:23 PM, GTSBoy said:

Crack temp and hold temp are not the same thing. There's a whole mass and energy balance thing going in between the engine dumping heat into the oil and the cooler dropping it out. Just because the TS cracks at 70 does not mean that the cooler has any hope of holding the oil at that temperature. The factors at play are the "effective HTUs" of the core, which is comprised of the oil temperature and the cooling power of the ambient air flowing across it (more oil T drives HTUs up, less oil T drives HTUs down, likewise, more and colder ambient air flow drives HTUs up and vice versa). Against an ambient air T of, say 35°C, you only get ~half the HTUs out of the core at 70°C oil T as you would with 100+°C oil T. So even though you may see the 70°C crack T as being horribly low, it actually gives quite a soft start to the cooling power, which ramps up as the oil gets hotter (both because the TS opens more and as the hotter oil drives more heat transfer out of the core).

That makes sense, and explains the trend of electrically heated thermostats. But the OEM coolant thermostat cracks at 76.5C or so and under normal driving with good cooling it shouldn't greatly exceed 85-90C. In comparable conditions I would imagine a 70C thermostat on the oil cooler to lead to oil that never gets past 100C unless you exceed the cooling capacity of the system. Oil should be hotter than coolant so wouldn't you want to run an 80C or 85C thermostat?

22 minutes ago, joshuaho96 said:

But the OEM coolant thermostat cracks at 76.5C or so and under normal driving with good cooling it shouldn't greatly exceed 85-90C. In comparable conditions I would imagine a 70C thermostat on the oil cooler to lead to oil that never gets past 100C unless you exceed the cooling capacity of the system. Oil should be hotter than coolant so wouldn't you want to run an 80C or 85C thermostat?

Not really. Remember, the thermostat does nothing to cool the fluid. It just lets it through. Logically, if you covered all except for 10% of your radiator with cardboard, the fact that the thermostat cracks at 76° won't do anything to stop it from overheating. It is the cooling capacity of the cooler that determines that.

And so, the size of the coolant radiator and the size of the oil cooler core and the relative amounts of heat that need to be dumped out through these and the relative capacity to dump heat are somewhat unrelated. You put a little oil cooler on and it will do wonders, up to a point. Then it won't be able to cope. Bigger cooler will keep oil T under control until some higher load. Then it too won't be big enough.

A little perspective. I have a Neo. Stock oil/water HX under the filter, but with a sandwich plate added for oil T sensor. Aftermarket radiator. No oil cooler otherwise.

  • Neo thermostat runs about 10° hotter than vanilla 25's TS. So, just in completely normal operation, almost** regardless of the season, my oil temp shows ~90°C, which, given the oil-water HX, is pretty much the expected water temperature too. The target coolant T for a Neo is in the order of 90-92°, or something like it.
  • **In summer though, when it is really hot, my oil T will often be up at about 100°C. The oil-water HX can't move any more heat into the coolant, and the coolant is probably hotter too.
  • And when it is really really hot weather, my oil T will be up at 110°C after everything is settled down to a steady state. And I would presume that my coolant is quite a lot higher than 100°C too.
  • And when it is really really really f**king hot weather, my oil T will often peak at ~120°C as I get home after a ~30km drive from work in the afternoon. But that's fine. I'm not thrashing it. I'm just driving it.

All of the above ignores use of air-con. If I have the AC running then the worst case temps in the above list will happen at lower ambient temps.

Another mental note is that all of the above was with a different radiator than I have now. So we will have to wait until summer to find out if the new radiator is worse/same/as good.

1 minute ago, GTSBoy said:

Not really. Remember, the thermostat does nothing to cool the fluid. It just lets it through. Logically, if you covered all except for 10% of your radiator with cardboard, the fact that the thermostat cracks at 76° won't do anything to stop it from overheating. It is the cooling capacity of the cooler that determines that.

And so, the size of the coolant radiator and the size of the oil cooler core and the relative amounts of heat that need to be dumped out through these and the relative capacity to dump heat are somewhat unrelated. You put a little oil cooler on and it will do wonders, up to a point. Then it won't be able to cope. Bigger cooler will keep oil T under control until some higher load. Then it too won't be big enough.

A little perspective. I have a Neo. Stock oil/water HX under the filter, but with a sandwich plate added for oil T sensor. Aftermarket radiator. No oil cooler otherwise.

  • Neo thermostat runs about 10° hotter than vanilla 25's TS. So, just in completely normal operation, almost** regardless of the season, my oil temp shows ~90°C, which, given the oil-water HX, is pretty much the expected water temperature too. The target coolant T for a Neo is in the order of 90-92°, or something like it.
  • **In summer though, when it is really hot, my oil T will often be up at about 100°C. The oil-water HX can't move any more heat into the coolant, and the coolant is probably hotter too.
  • And when it is really really hot weather, my oil T will be up at 110°C after everything is settled down to a steady state. And I would presume that my coolant is quite a lot higher than 100°C too.
  • And when it is really really really f**king hot weather, my oil T will often peak at ~120°C as I get home after a ~30km drive from work in the afternoon. But that's fine. I'm not thrashing it. I'm just driving it.

All of the above ignores use of air-con. If I have the AC running then the worst case temps in the above list will happen at lower ambient temps.

Another mental note is that all of the above was with a different radiator than I have now. So we will have to wait until summer to find out if the new radiator is worse/same/as good.

Right, if the cooler is insufficient then the thermostat crack/full flow temp spec won't be what determines the oil temperature. But for street use when ambient is like 4C I would worry about the oil never getting up to temp on the highway and just turning to milkshake.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
    • But first....while I was there, I also swapped across the centre console box for the other style where the AV inputs don't intrude into the (very limited !) space.  Part# was 96926-4GA0A, 284H3-4GA0B, 284H3-4GA0A. (I've already swapped the top 12v socket for a USB bulkhead in this pic, it fit the hole without modification:) Comparison of the 2: Basically to do the console you need to remove the DS and PS side console trim (they slide up and back, held in by clips only) Then remove the back half of the console top trim with the cupholders, pops up, all clips again but be careful at the front as it is pretty flimsy. Then slide the shifter boot down, remove the spring clip, loose it forever somewhere in the car the pull the shift knob off. Remove the tiny plastic piece on DS near "P" and use something thin and long (most screwdrivers won't fit) to push down the interlock and put the shifter down in D for space. There is one screw at the front, then the shifter surround and ashtray lift up. There are 3 or 4 plugs underneath and it is off. Next is the rear cover of the centre console; you need to open the console lid, pop off the trim covering the lid hinge and undo the 2rd screw from the driver's side (the rest all need to come out later so you can do them all now and remove the lid) Then the rear cover unclips (6 clips), start at the top with a trim tool pulling backwards. Once it is off there are 2 screws facing rearwards to remove (need a short phillips for these) and you are done with the rear of the console. There are 4 plugs at the A/V box to unclip Then there are 2 screws at the front of the console, and 2 clips (pull up and back) and the console will come out.
×
×
  • Create New...