Quote:
Originally Posted by justpete
The heat flux into the coolant must be shed via the radiator or temps will climb, that's what I meant by balance. And I'm not including oil cooling at all, just engine cooling and disregarding other thermal rejection pathways.
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Yes, I get what you're saying. Makes perfect sense. What I was pointing out was that, on our cars, there is very minimal "heat flux" into the coolant (unless you're an AT which comes with an oil to water heat exchanger). What little heat the coolant does pick up from the massively increased oil temps (290f+) is for the most part handled by the stock radiator.
We cant measure inlet coolant temps at the radiator, but we can measure radiator outlet coolant temps at the water pump. All data indicates coolant temps post radiator don't really increase that much beyond what you see on the street. Therefore, no limp modes due to coolant temps on track like oil. Hence why everyone has an obsession with increasing OIL cooling not coolant.
"Cooling System
The cooling system of the N55 is enhanced with additional oil cooling.
Two different types of oil cooling systems are used depending on the model and application. In the “hot climate” version, heat transfer from the engine oil to the engine coolant is avoided by separating the oil cooler from the engine coolant circuit. The other version uses an auxiliary radiator in combination with an oil to coolant heat exchanger bolted to the oil filter housing. The auxiliary radiator enhances cooling efficiency by adding surface area to the cooling system."
Since the 135i manual didn't come with the heat exchanger, that last part about increasing cooling capacity is irrelevant. Automatic cars might benefit from a radiator upgrade though since more heat is indeed being exchange into the coolant.
Quote:
Originally Posted by justpete
Anyone who's had a compromised radiator knows opening the heater to coolant flow will drop the temps.
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Yes, absolutely! Again, my point was that it's not really necessary since most people's coolant never overheats past normal. This further supports why everyone takes a priority of upgrading oil cooler capacity over the radiator.
As you point out yourself, you can simply dump heat through the heater core if your coolant temps start climbing too high. You effectively already have a second radiator in the car
I do agree a dedicated track car could benefit from increased cooling capacity, but not before tackling the oil temperature issue. In opposite effect of what your saying, running a larger oil cooler should also help keep coolant temps down!!!
Quote:
Originally Posted by justpete
A bypass thermostat is one that recircs the oil back to the engine and gradually with increasing temp allows an increasing amount of the flow to pass through the downstream oil cooler. It doesn't bypass anything but the oil cooler, iow.
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I'm guessing you're referring to the very expensive improved racing oil thermostat. It is definetly a nice thermostat that operates like stock but at a lower temp. I was referring to people deleting the stock thermostat without adding back something like the improved racing thermostat.
Even 215f isn't that much lower than the stock 230f. Hardly worth $180 imo since it basically does nothing. I say this because I don't think ANYONE has a big enough oil cooler in place to keep oil temps below 230f on track... besides, the cars dme is literally designed to operate between 230 and 260. Tons of dme parameters are actively seeking to operate within that range. Again, all opening the thermostat at 215f does it delay the inevitable...