In reply to rslifkin :
Meanwhile, many GM and Chrysler product won't even turn the fans on until 230-245 degrees. If Chrysler can figure it out, why can't BMW?
Higher temps not only increase engine efficiency, but radiator efficiency as well. It's easier to move BTUs when the temperature difference between the coolant and outside air is 140 degrees instead of 80 degrees, so the radiators can be made smaller, so the nose can be made smaller, so the vehicle can be more aerodynamic, so fuel economy can be increased.
At least, this made sense before everyone needed an automotive Hoveround to cargo themselves around, making frontal area moot.
In reply to Knurled. :
Ah, but there's a difference. The GMs, Chryslers, etc. that I've seen with 230+ fan turn on points usually still have 195* t-stats or so, so they're running 210* or less most of the time and only get that hot when sitting still for a while without the A/C on. So they don't spend all that much time at 230*. The BMWs that do it run that hot all the time and they also run really high cooling system pressures. The thermostat in mine, for example, is a 220* stat. So temps around 220 up to 230 are normal.
Now put some plastic parts in the cooling system, make the engine bay a bit tightly packed because you sucked up a bit more space for better suspension geometry and still wanted to squeeze a big overhead cam V8 between the shock towers and poof, you get a lot of cooked plastic. Now add that plastic needing to handle 29 psi instead of the less than 20 common to a lot of cars and suddenly it makes sense why the stuff doesn't last as long as it should. Same story with why these engines cook the valve cover gaskets to death frequently too. Doesn't seem to cause any real engine durability issues, mind you. And BMW did it for exactly the reason you mentioned: better gas mileage.
In reply to Tyler H :
I ran a 22RE without fluid in the cooling system for 22,000 miles back in the late 90s. I shut it down at lights and always had the heater blasting (not fun when it was 95 outside) but she held together for over a year until I properly replaced the water pump and radiator.
In reply to captdownshift :
If there was no fluid in it, how was the heater doing anything?
Evens coolent is zero pressure.
rslifkin said:
In reply to Knurled. :
Ah, but there's a difference. The GMs, Chryslers, etc. that I've seen with 230+ fan turn on points usually still have 195* t-stats or so, so they're running 210* or less most of the time and only get that hot when sitting still for a while without the A/C on. So they don't spend all that much time at 230*. The BMWs that do it run that hot all the time and they also run really high cooling system pressures. The thermostat in mine, for example, is a 220* stat. So temps around 220 up to 230 are normal.
Now put some plastic parts in the cooling system, make the engine bay a bit tightly packed because you sucked up a bit more space for better suspension geometry and still wanted to squeeze a big overhead cam V8 between the shock towers and poof, you get a lot of cooked plastic. Now add that plastic needing to handle 29 psi instead of the less than 20 common to a lot of cars and suddenly it makes sense why the stuff doesn't last as long as it should. Same story with why these engines cook the valve cover gaskets to death frequently too. Doesn't seem to cause any real engine durability issues, mind you. And BMW did it for exactly the reason you mentioned: better gas mileage.
Yep, the oil cooler thermostat on my 135 doesn't even open until 235° or 250° in the name of efficiency.
Alfaromeoguy said:
Evens coolent is zero pressure.
The water pump will make pressure. Without pressure, there is no movement of fluid.
