Quote:
Originally Posted by Gary@simod.net
Absolutely not how it works. the oem thermostat like ALL BMW oil thermostats only open 30-40% been like this forever oil temp has nothing to do with the thermostat opening. BMW ALSO puts a restrictor in the return line to help keep the oil in the actual cooler longer you can see it on a stock 135 it is a metal band in the middle ish of the line that band holds the restrictor in place... we remove those to..
We pull them out of all E36 and 46 M cars that run the OEM oil filter housing thermostat unit especially S54 cars which are heat monsters on track... Some of them we end up running two oil coolers on just to keep temps down for racing.
ALL aftermarket thermostats run 100% flow rate when opened up.
I have to go pick the car up when I have it I will post pictures of the street car set up we use and later the track/race set up. We also NEVER leave the opening without a screen or mesh grill on them. on track or even street you can easily get a puncture on the cooler due to how low they are.
I think we have pictures of the street set up on our Facebook page under SIMOD, Christiansburg Va.
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I am not sure what you mean by "it doesn't work like that." It works exactly like that. Thermostat spring expands from heat which then in turn pushes a piston down and unblocks the orifice for oil to pass through to the oil cooler lines. Factory thermostat has holes in it so you always have a small amount of flow through the oil cooler even when the oil is cold.
You're partially correct that the stock thermostat does apparently block the oil cooler feed passage by a hair even when it's 100% open. However, it's maybe a 10% overlap at most. There is probably 0 real world difference in flow between a stock thermostat once and something like the BMS oil thermostat delete which is shorter and doesn't block the passage at all. Saying the stock thermostat only opens 30-40% is just plain hyperbole. Maybe you're experience on other BMW's varies?
Here is a picture of a thermostat when fully open:
As for your comments about their being a restrictor in-line on the return line, I can't speak to that. BMW would do it for a reason if it's there. Does the oil going through the cooler return to the pan? I'll check tonight or tomorrow. I was under the impression that cooled oil feeds the engine. No real reason to have a restrictor in that case. I would imagine the necking down of the oil return line isn't actually a restriction at all since again the oil feed/return hole in the oil filter housing itself is probably the main restriction dictating flow. The line switch to a metal line to keep it rigid as it travels over the pulleys...
Where on the line is this restrictor you make reference to? I am not seeing what you are.
