N54 Cooling - Temp Control Logic and what are your temps during extended track use?

scrllock

Sergeant
Dec 17, 2018
267
152
0
Ride
2011 335xi
Haha, no, though I've been fighting leaks for months, just recently replaced my rad with an oem one and trying not to second-guess it too much.
The concern is over-cooling, particularly since I drive the car at subzero temps on the highway. Lots of reviews of the csf unit with thermostat warnings, no heat, etc. Unclear to me if that's specific to the AT version however, or if any of the coolant logic discussed here could be used to negate this.
And yes, it works similarly, there's a "heater core" that transfers heat between the oem trans cooler and the radiator. The trans cooler kits I've seen plug it off and run independently, but I would probably try to have it in sequence with a t-stat to accommodate winter here.
 

Asbjorn

Lieutenant
Mar 10, 2018
854
602
0
European, based in China
Ride
Z4 N54 DCT
Haha, no, though I've been fighting leaks for months, just recently replaced my rad with an oem one and trying not to second-guess it too much.
The concern is over-cooling, particularly since I drive the car at subzero temps on the highway. Lots of reviews of the csf unit with thermostat warnings, no heat, etc. Unclear to me if that's specific to the AT version however, or if any of the coolant logic discussed here could be used to negate this.
And yes, it works similarly, there's a "heater core" that transfers heat between the oem trans cooler and the radiator. The trans cooler kits I've seen plug it off and run independently, but I would probably try to have it in sequence with a t-stat to accommodate winter here.

Please show/link to an example/log of a CSF equipped N54 that can't get up to temp in freezing ambient temps. Personally I have had no such problem, and since we have an electric water pump that can turn off or slow down to heat the engine, as well as a thermostat that can close the main radiator, I am not sure it is possible (even if the csf radiator was an actual significant upgrade, which is really isn't)?

Sounds more like examples of the thermostat failing?
 
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scrllock

Sergeant
Dec 17, 2018
267
152
0
Ride
2011 335xi



Those are the ones I was able to quickly find that were firsthand accounts. I'm sure it's a little bit of exaggeration that's spread, but it gets down to -28C (if i'm converting properly) here sometimes, and a working heater is a must-have QoL item.
 

Asbjorn

Lieutenant
Mar 10, 2018
854
602
0
European, based in China
Ride
Z4 N54 DCT



Those are the ones I was able to quickly find that were firsthand accounts. I'm sure it's a little bit of exaggeration that's spread, but it gets down to -28C (if i'm converting properly) here sometimes, and a working heater is a must-have QoL item.

Very interesting!!

Alot of examples here where coolant wont go above 140-160F, and cabin heater doesn't work. The thermostat should be shutting off the main radiator at those temps, and 140F is plenty hot for cabin heating. So what is going on?

Now because the cabin heater is on, the water pump is running at low speed and the thermostat is off, sending coolant to the engine, heater and transmission heat exchanger connected to the AT core. Now someone mentioned that there's no separation between the AT core and main radiator on the CSF.


This might explain everything. It means that coolant still flows through the entire radiator entering in two places and then exiting through the transmission heat exchanger, even though the thermostat is closed. So the flow that should have gone to the cabin heater, actually enters the radiator instead and exits though the transmission heater. And the entire radiator is active, although at reduced flow, even when the car is warming up, and the thermostat is closed. This also explains why pinching the return line from the transmission heater helps, as more coolant is directed through the cabin heater instead of the entire radiator.

I will try and check my oem radiator to see how it was originally supposed to flow.
 
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scrllock

Sergeant
Dec 17, 2018
267
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2011 335xi
That sounds like a pretty reasonable explanation given what I've read and the solutions people have proposed (most just tape over the kidney grilles it seems). Unfortunately no one that's tried it seems to have logged trans temps. I think @Payam@BMS might have done some with their transmission cooler, but they separate it from the heat exchanger and I think they said they only tested down to near-freezing, not sub-zero. I know this is a little off-topic given track use, but I'd be eager to find a good year-round solution that can keep the heater core and trans fluid adequately warm.
 

Asbjorn

Lieutenant
Mar 10, 2018
854
602
0
European, based in China
Ride
Z4 N54 DCT
That sounds like a pretty reasonable explanation given what I've read and the solutions people have proposed (most just tape over the kidney grilles it seems). Unfortunately no one that's tried it seems to have logged trans temps. I think @Payam@BMS might have done some with their transmission cooler, but they separate it from the heat exchanger and I think they said they only tested down to near-freezing, not sub-zero. I know this is a little off-topic given track use, but I'd be eager to find a good year-round solution that can keep the heater core and trans fluid adequately warm.

I found my old oem radiator. The AT and main cores are indeed separate. Some 6 rows or 13-14% of the radiator is used for heating and stabilizing the DCT.

Now we just need to confirm if the rumour about the CSF AT not having separate cores is true.
 

houtan

Lieutenant
Nov 2, 2017
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135i N55 DCT; PS2
I found my old oem radiator. The AT and main cores are indeed separate. Some 6 rows or 13-14% of the radiator is used for heating and stabilizing the DCT.

Now we just need to confirm if the rumour about the CSF AT not having separate cores is true.
Based on the response i received from csf a few years ago, 7046 has separate circuits as well. I had emailed them asking about plugging up the holes to the AT heat exchanger if I got rid of it one day. This was the response. Not sure if anything has changed since then.
 

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Asbjorn

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Mar 10, 2018
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Finally got around to do a proper A-B test of the second aux radiator I installed behind the FMIC.

IMG_20190823_170030.jpg


I have a ball valve on the hose going to it, making it easy to do back-to-back testing. Here's the results form the test, it seems to reduce peak coolant by 5F:

Weather at the time of logging:
Day, clear
26C / 79F indicated in cluster
25C / 77F indicated on weather app
36% rH humidity on weather app
1011mb pressure on weather app
almost no wind
not far from sea-level.

First test: All coolers on + WI:
Peak iat 111F 44C
Peak dct 217F 103C
Peak oil 262F 128C
Peak coolant 223F 106C

Second test: As test number 1, but with the 2nd aux radiator turned off:
Peak iat 111F 44C
Peak dct 210F 99C
Peak oil 262F 128C
Peak coolant 228F 109C

First test: