[Thecastle]

I've been searching in vain to see if anyone has a low temp thermostat for the N63TU3? The t-stat design on the TU3 appears to be the 1st time it seems in 20 years BMW has changed the V8's T-stat design, so the older low temp's don't appear to be compatible.

I've done this mod on the last 3 BMW V8s I've owned. I had really good success with this MOD on my N63TU and S63 booth going more than 100K miles with no coolant leaks, no expansion tank replacement, or valve stem seals, or turbo lines etc..

I'd like to add this mod to my 2022 M550i, as I see the cars are prone to coolant leaks. Every 10C you can lower the operating temp according to my Ph.D. organic chem buddy reduces the chemical reaction speed by 1/2. Aka the speed at which plastic / rubber etc break down from heat.

[WretchedRefuse]

I've done the same thing in the past but don't plan to with my N63TU3. Lowering the operating temperature would reduce the expansion of piston rings, which could reduce their sealing ability. After that, water that blows past the rings into the engine oil won't evaporate as quickly at lower temperatures. Besides these obvious concerns, our engines in general are calibrated so precisely that there could be other unanticipated consequences of never letting the engine reach "full" operating temperature.

[Thecastle]

Originally Posted by WretchedRefuse

I've done the same thing in the past but don't plan to with my N63TU3. Lowering the operating temperature would reduce the expansion of piston rings, which could reduce their sealing ability. After that, water that blows past the rings into the engine oil won't evaporate as quickly at lower temperatures. Besides these obvious concerns, our engines in general are calibrated so precisely that there could be other unanticipated consequences of never letting the engine reach "full" operating temperature.

I get it the mod is not for you, as not all mods are. Variety is the spice of life, and I would question if your concerns would outweigh the potential benefits. There is always a trade in any engine change, I think for me given my experience with this and having had no coolant leaks, no oil burning, V8 cars that never realized the concerns you bring up, it seems to be a good bet to lower maintenance costs.

Besides maintenance costs reduction, other potential benefits are a risk reduction of LSPI and chances of hotspots forming that leads to detonation. These concerns are why the ECU commands the t-stat fully open using a heating element during hard running and lowers operating temps, often to the ~90C level.

The key benefit is to engine component longevity. Every 10C reduction in temps results in degradation rates falling by ~1/2 according to my organic chem friends, which directly translates into enhanced lifespan of the plastic cooling components.

Engine coolant temp is not fixed, "full" operating temperature is really a range. A modded t-stat operating near the bottom of the normal range should not be a major concern. The car does illuminate the check engine light if it fails to reach normal temp-range.

Ring sealing with this mod is likely a non-issue. As Combustion gas pressure is primary what forces the piston ring against the cylinder wall to form a seal, followed by ring tension.

Oil dilution is only a concern if contamination levels exceeds the manufacturers tolerance for it. Removal speed of dilution is predominantly a function of climate and driving time/habits effecting oil heating. If you take a lot of short trips in cold weather, especially with start/stop enabled and never getting the oil to temp will result in more dilution. Hence some of the reason for current oil formulations to deal with increased dilution to support start/stop and other C02 reduction techniques.

Oil temp and coolant temps are not directly correlated in the N63TU3 as there is an oil cooler t-stat to regulate oil temps independent of coolant. A large amount oil heating is from the friction of moving parts acting on the oil, not a transfer of heat from the coolant. So changing the coolant t-stat won't have a direct impact on oil temps. In fact the oil coolers purpose is to remove excess heat from the oil to the coolant.

I've never encountered anyone including myself that had issues with piston sealing or oil dilution attributable to this MOD. But I sure have run into cooling system failures on these forums, and valve stem seals etc. I've had this mod on 3 BMW V8 cars for a cumulative 250K miles. I can certainly say there are benefits namely the valve stem seals last a lot longer and there aren't any coolant leaks. Never had any oil consumption on my t-stat modded 2011 X5M (S63) or 2016 550i (N63TU) 105K miles just traded in. My 3rd was a 2008 4.8i X5 (S62), and it did develop bad valve stem seals at 80K miles but it didn't get the t-stat until after it was repaired.

[WretchedRefuse]

Thanks for the info. Please post if you're able to find a low-temp thermostat. If you do, I'd be interested to see how it works out, especially if you normally send in your used oil for analysis. I'm guilty of doing lots of local driving without letting my car fully warm up, and I haven't had any problems up to ~30k miles. The oil seems to be pretty robust.

[M550bernina]

Originally Posted by Thecastle

I've been searching in vain to see if anyone has a low temp thermostat for the N63TU3? The t-stat design on the TU3 appears to be the 1st time it seems in 20 years BMW has changed the V8's T-stat design, so the older low temp's don't appear to be compatible.

I've done this mod on the last 3 BMW V8s I've owned. I had really good success with this MOD on my N63TU and S63 booth going more than 100K miles with no coolant leaks, no expansion tank replacement, or valve stem seals, or turbo lines etc..

I'd like to add this mod to my 2022 M550i, as I see the cars are prone to coolant leaks. Every 10C you can lower the operating temp according to my Ph.D. organic chem buddy reduces the chemical reaction speed by 1/2. Aka the speed at which plastic / rubber etc break down from heat.

There is a place that will modify one for you, but you have to send yours in or buy a new one and send it to them.

[Dasky_spas]

To the op- you can get your tstat lowered and you are wise to choose so. Our cars run excessively hot for emissions purposes. 105c operating temp is crazy! I used a guy from Bavlogic to modify the oem tstat. I sent him a spare and he lowered it to 95c without issue. It could be set lower to 90c but you could run the risk of an engine code due to the dme thinking the tstat is stuck. My oil and coolant stay closer to 90c now.

[Thecastle]

Yeah thats probably a good bet. I've purchased 3 t-stats from BAV after purchasing some bad hambug(er) tech ones from ECS and having to re-do the t-stat swap.

the N63TU3s use a different design. I'll reach out to him

[Gandalf the Grey]

very interested in your end results.
A 90 or 95c thermostat sounds acceptable for a street car.
Does anyone know what the lowest degree the computer requires for setting fuel trims as being at fully warmed up?
(I have a 2023 M550xi)

[WretchedRefuse]

Here is a video on a related subject as it pertains to the B58. Aside from the fact that he is repeating some of my concerns above, does anybody know if the N63TU3 also has a heat management module? If so, maybe an engine tune (max cooling mode) instead of replacing the thermostat is how to reduce operating temperature. I think that BM3 has this option for the N63TU3.

[Dasky_spas]

You don't want to do max cooling mode. If you want to run cooler, you have to reduce the tstat threshold. That's it.

There's also PWR heat exchangers coming out that I'm testing.

You can wrap your downpipes and put heat tape around your charge coolers.

[kosmokratur]

I tried to find one for the TU2 a couple years ago. I was told the ECU would "catch it" and throw A code. I'd like to get one if I cAn find it!

[Dasky_spas]

https://www.bavlogic.com/?page_id=4004

[Gandalf the Grey]

I sent www.bavlogic.com an email and asked if they can do a thermostat for the N63tu3.
20 plus days and I have not seen a reply.

[Dasky_spas]

Originally Posted by Gandalf the Grey

I sent www.bavlogic.com an email and asked if they can do a thermostat for the N63tu3.
20 plus days and I have not seen a reply.

Email again. He's back.

[Thecastle]

I emailed him, and after a very long delay... He commented he did a t-stat for a 2020 BMW M550i, but he wasn't sure if it was the same for a newer+. I believe it should be, 2020 was the 1st year with the N63TU3 which uses a different t-stat design than any previous BMW V8. I'm still having coolant leak problems so I didn't want to mess with this until this is all resolved on the car. But I'll pursue this again when I'm sure its fixed, just had the oil/water cooler replaced on my car.

[Thecastle]

Originally Posted by WretchedRefuse

Here is a video on a related subject as it pertains to the B58. Aside from the fact that he is repeating some of my concerns above, does anybody know if the N63TU3 also has a heat management module? If so, maybe an engine tune (max cooling mode) instead of replacing the thermostat is how to reduce operating temperature. I think that BM3 has this option for the N63TU3.

It does, and long term it won't work. At least that was the experience with previous generations. Using the heating element for extended periods of time causes it to burn out. So tuning works but its not a long term solution.

[Dasky_spas]

Originally Posted by Thecastle

I emailed him, and after a very long delay... He commented he did a t-stat for a 2020 BMW M550i, but he wasn't sure if it was the same for a newer+. I believe it should be, 2020 was the 1st year with the N63TU3 which uses a different t-stat design than any previous BMW V8. I'm still having coolant leak problems so I didn't want to mess with this until this is all resolved on the car. But I'll pursue this again when I'm sure its fixed, just had the oil/water cooler replaced on my car.

I have a 2019 m850 so that will have same tstat as '20+ m550. You can look up the part number to confirm.

[Thecastle]

The 2019 M850 has a different engine than the 2020+.

They do not use the same thermostat. Recalling form memory the N62/N63/N63TU/N63TU2 all use the same t-stat so your fine getting one of the modded ones they sell. The N63TU3 which is in the 2020+ is a different design. This one would have to be custom made.

[M550bernina]

Originally Posted by Thecastle

The 2019 M850 has a different engine than the 2020+.

They do not use the same thermostat. Recalling form memory the N62/N63/N63TU/N63TU2 all use the same t-stat so your fine getting one of the modded ones they sell. The N63TU3 which is in the 2020+ is a different design. This one would have to be custom made.

The TU3 first came out in 2019 and was put in the M850.

2020 was the first year they put it in M550

[enemigo13]

sure that 2019 M850i has the same engine as 2020+, it is TU3. 8er never ever came with TU2.
About coolant temp targets, N63TU3 targets in eco pro mode to 110C which is surely high. in normal mode it targets to 95C, in high load scenarios target is 85C. not sure if 95C is way too high, imho right operating temperature.
About "new" thermostat - the same part no is in N63TU2 so it is here for nearly 10 years.

Originally Posted by Thecastle

The 2019 M850 has a different engine than the 2020+.

They do not use the same thermostat. Recalling form memory the N62/N63/N63TU/N63TU2 all use the same t-stat so your fine getting one of the modded ones they sell. The N63TU3 which is in the 2020+ is a different design. This one would have to be custom made.

[Thecastle]

So I bothered to look up the p/n's for various engines on the t-stat. It does look like the TU2/TU3 share a t-stat now. There was more than 1 part number for the TU2 at some point BMW revised the t-stat p/n on the TU2 to the same version also used in the TU3. Apologies for any confusion. So a recalibrated T-stat does appear to be available. It looks like the TU2/TU3 went to a plastic body t-stat instead of an aluminum body in previous V8's. Do not know if the previous TU/etc is compatible.

The N63TU3 - 11538685978
N63TU2 - 11538685978 or 11538602282 (old p/n)
N63TU - 11537586885
N63 - 11537586885

I'll run the engine monitoring to see what the actual temps are that the engine targets running at. The N63TU (previous car) was calibrated to fully open at 105C, and would run at 105-113C in normal driving at full temp. I've been having so many cooling system problems with my N63TU3 that I've not bothered with this project until now.

[enemigo13]

N63TU2/TU3 thermostat is with position sensor, so ECU knows how much it is open now. I've changed target coolant values in eco driving from 110C to 100C now it runs at about 100C deg max. I did not touch high load targets as it is 85 and map which is described as "normal" driving, target 95C. If someone will tell that setting target from 110 to 100 will burn off thermostat quickly - I must admit that N63TU2 has same part no thermostat and stock coolant targets are lower than TU3.

Originally Posted by Thecastle

So I bothered to look up the p/n's for various engines on the t-stat. It does look like the TU2/TU3 share a t-stat now. There was more than 1 part number for the TU2 at some point BMW revised the t-stat p/n on the TU2 to the same version also used in the TU3. Apologies for any confusion. So a recalibrated T-stat does appear to be available. It looks like the TU2/TU3 went to a plastic body t-stat instead of an aluminum body in previous V8's. Do not know if the previous TU/etc is compatible.

The N63TU3 - 11538685978
N63TU2 - 11538685978 or 11538602282 (old p/n)
N63TU - 11537586885
N63 - 11537586885

I'll run the engine monitoring to see what the actual temps are that the engine targets running at. The N63TU (previous car) was calibrated to fully open at 105C, and would run at 105-113C in normal driving at full temp. I've been having so many cooling system problems with my N63TU3 that I've not bothered with this project until now.