I'm going to try something to hopefully capture more people to this thread. I am going to link directly to this post from the original post so newcomers can jump straight to the new direction of the topic of discussion. So for those that have been following along, please bear with me for the repeat information in this post.
Refocused Topic of Discussion...
I get it, roll eyes, the N54 has been around for 11 years and the cooling topic has been beaten to death. However, I want to bring to light some issues that I still see with our N54 cooling system. To date, everyone has been trying to keep the engine from hitting limp mode, which is great, but more needs to be done than that in my opinion.
Lets step back and look at the big picture. The N54 was developed as a street car, not a performance hot rod like the M3. It was also the first new era BMW turbo motor. Fast forward several years and BMW themselves address the lacking cooling system so they added a PPK such as that found on the 1M and the 335is. In their own literature they discuss how it was challenging developing the cooling system because the radiator frontal surface area had to be shrunk drastically to make room for the FMIC. We have to remember, the design parameters were for a motor they considered a street car motor where efficiency and emissions were high on the priority list. To accomplish this they ran the motor hot to lower emissions and to heat up the oil for better fuel economy (less drag).
Now... here comes the aftermarket world of hot rod turbo motors. This creates a WHOLE different set of parameters for the cooling system. Unlike the original intent of the cooling system, we don't care about running hot for emissions nor do we care about fuel economy. Now, the design logic/parameters built into the stock cooling system no longer apply.
Now that we are pushing 1.5x to 2x the power through it, we have to follow "performance" engine cooling parameters, which is simply keep it cool at all times. But there are details involved with this. We want to do things like keep the motor at volumetric efficiency (VE) which BMW claims is 194F, any higher than that is pointless. We also don't want a drastically fluctuating temp, again, absolutely pointless. lastly, and most important of all, we want max coolant fluid flow through the motor especially at high RPMs and load. That last parameter right there is what I think has been overlooked and what I want to discuss.
Cooling systems have been studied and perfected for decades, Stewart Components sums it up best with regard to coolant flow:
"A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures."
So, we want lots of coolant flow at high RPMs where we are putting the most heat into the motor. We don't want hot spots that temporarily distort cylinder walls, cause detonation, list goes on.
This is where we start talking coolant targets built into the DME. Most of us know there are several different targets for coolant temps. ECO (226F), Normal (219F), High (203F), and High + Map thermostat (194F). And most of us know we can change this with XDF files or MHD. What we don't know (or at least I dont know) is the logic behind these modes. I'm not talking about the logic of ambient vs coolant temp vs throttle position. I'm talking about the logic of the duty cycle of the water pump.
What I want to determine are the times when the waterpump is running at a low duty cycle creating slow coolant flow. Lets imagine we are doing some spirited driving and are running along at 210F. Then we decide to do a pull and take off. We now immediately start putting heat into the cylinders but what we don't know is if the waterpump is at 100% duty cycle to dissipate that heat. Lets remember, the DME logic was designed around a 300 BHP street car. It may not go to instant 100% duty cycle. BMW may have determined it wasn't necessary. But we have 1.5x to 2x the power of stock. If the pump is not at full duty cycle our cylinder walls may start to heat up which aids in detonation causing the timing to get pulled back. Loose all around.
I'm not an engine builder or tuner (or DME coder) so I am not an expert and will never claim to be. I will say I've built racecars both in club and pro racing for over 20 years and have dealt with the lingo and the concepts enough to have a clue. I'm hoping some engine builders, tuners, and more specifically DME coders will chime into this thread. Or anyone who might know the logic for that matter.
I was discussing with
@RSL about logging waterpump duty cycle within MHD. It is currently not an ID we can log but in theory should be easy to add. Again, not a coder so don't know. Logging Map thermostat actuation would be nice too.
@RSL had a great idea to try INPA. Anyways, once we get that information we can start understanding the logic of the DME and perhaps make changes for the better.
Again, sorry about the repeat info to all who have been following this thread.
