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I'm a mechanical engineering student and work part time doing CAD for an engineering and manufacturing company.
:hi:

I must say, I can't argue with a single thing you've said thus far :( Especially your bit on cavitation.


P.S. Long time, no see :eeps:
 

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I thought you weren't talking to me. :p

Yeah, it's been a while. We need another bbq or something once Kalim gets back.
Lol the last I saw you was when we did my wheel bearings and brake swap. You're just not in NGC anymore and I don't like OT :rofl:

:werd:

More back on topic before they delete out posts :eeps:....did you ever prototype or draw up an ET after BFest using the dimensions off that blown one I left you? There's so many things wrong with lowering the system pressure and so much misinformation in this thread :b:
 

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Lol the last I saw you was when we did my wheel bearings and brake swap. You're just not in NGC anymore and I don't like OT :rofl:

:werd:

More back on topic before they delete out posts :eeps:....did you ever prototype or draw up an ET after BFest using the dimensions off that blown one I left you? There's so many things wrong with lowering the system pressure and so much misinformation in this thread :b:
lol, I sawed your expansion tank in half, and it's mind boggling at how complicated it is. I'll show you next time we meet. The expansion tank has more secondary functions, parts, and passageways inside it than makes sense.
 

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lol, I sawed your expansion tank in half, and it's mind boggling at how complicated it is. I'll show you next time we meet. The expansion tank has more secondary functions, parts, and passageways inside it than makes sense.
could you pls post the picture for all to experience/examine. :hi:
 

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Stop responding like a dick head. The point I was trying to make is the high humidity in the volume you're considering affects the applicability of the Ideal Gas Law.
The law is applicable to air. It is a tool for estimation in this context. It is perfectly valid for these speculations which are imprecise at best. If we are using speculated minimum and maximum temperatures +/- 15 C then there's no reason to go looking into steam tables and consider quality and all that nonsense. We are looking for ballpark figures perhaps even just the order of magnitude.

Just FYI you can estimate an engine cycle with the ideal gas law (even though it's a fuel air cycle) to within +/- 10-15%. It's more than acceptable here.
 

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Stop responding like a dick head. The point I was trying to make is the high humidity in the volume you're considering affects the applicability of the Ideal Gas Law.
100% humidity, which is the max that you can have, is defined as a maximum of 4% H2O molecules in the air. Hence the air is still a pretty good approximation to an ideal gas.

Your point is pointless. Get a clue before acting like you have any.
 

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The law is applicable to air. It is a tool for estimation in this context. It is perfectly valid for these speculations which are imprecise at best. If we are using speculated minimum and maximum temperatures +/- 15 C then there's no reason to go looking into steam tables and consider quality and all that nonsense. We are looking for ballpark figures perhaps even just the order of magnitude.

Just FYI you can estimate an engine cycle with the ideal gas law (even though it's a fuel air cycle) to within +/- 10-15%. It's more than acceptable here.
I know it's valid for air, I was just questioning its applicability for this scenario. Thank you for clearing it up.

That I knew - we use it regularly in engine applications for the purposes of estimation.


Your point is pointless. Get a clue before acting like you have any.
:rolleyes: $20 says you don't behave like this in real life
 

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:rolleyes: $20 says you don't behave like this in real life
No I don't, then again, I don't have too people around me with half-assed knowledge.

Glad that the situation is clear for you now though. If you read the entire thread before posting, you'd have known sooner. It's been discussed before.
 

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I thought you weren't talking to me. :p

Yeah, it's been a while. We need another bbq or something once Kalim gets back.
BBQ soon so you two can brohug it out. :rofl:
 

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Hello everyone,

We've done extensive testing on this subject, and wanted to share some of the results. For testing, we used a 1997 E39 at idle in a garage. The main radiator fan was removed, and the auxiliary fan blocked off in order to force the system into higher temperatures and pressures. We first tried with only the main fan removed, but the auxiliary fan was successful in preventing the temperature from rising above 103 degrees C. It would turn on at 103 C and lower the system temperature to 95 C at which point the fan shut off again. We monitored coolant temperature both through the on-board diagnostics and through external software. Each test began with everything at ambient temperature. The expansion tank was tapped and a low-pressure gauge installed to monitor the pressure in the expansion tank.

Results:

We saw a maximum temperature of 126 degrees C (~260 F) before ending the test. We were unable to increase the temperature above this due to the efficiency of the system even without airflow. Keep in mind that a 50/50 mix of coolant will boil at approximately 135 C (275 F), so we were very close. Pressure at this temperature (126 C) was 20.5 PSI. The temp gauge needle was in the red zone well before this and the coolant temp warning light was on. Pressure never increased above 15 PSI before a temperature of 120 degrees C. We ran the test several times and achieved virtually identical results each time. We also tested the system with purposefully low coolant to see how that would affect the results. At a given coolant temperature, the pressure is lower in a system with low coolant.

During normal operating conditions, the system never operates anywhere near 2 bar. Assuming normal operating temps of 105 C (a bit on the high end), the system won't see pressures above 10 PSI.
 

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Hello everyone,

We've done extensive testing on this subject, and wanted to share some of the results. For testing, we used a 1997 E39 at idle in a garage. The main radiator fan was removed, and the auxiliary fan blocked off in order to force the system into higher temperatures and pressures. We first tried with only the main fan removed, but the auxiliary fan was successful in preventing the temperature from rising above 103 degrees C. It would turn on at 103 C and lower the system temperature to 95 C at which point the fan shut off again. We monitored coolant temperature both through the on-board diagnostics and through external software. Each test began with everything at ambient temperature. The expansion tank was tapped and a low-pressure gauge installed to monitor the pressure in the expansion tank.

Results:

We saw a maximum temperature of 126 degrees C (~260 F) before ending the test. We were unable to increase the temperature above this due to the efficiency of the system even without airflow. Keep in mind that a 50/50 mix of coolant will boil at approximately 135 C (275 F), so we were very close. Pressure at this temperature (126 C) was 20.5 PSI. The temp gauge needle was in the red zone well before this and the coolant temp warning light was on. Pressure never increased above 15 PSI before a temperature of 120 degrees C. We ran the test several times and achieved virtually identical results each time. We also tested the system with purposefully low coolant to see how that would affect the results. At a given coolant temperature, the pressure is lower in a system with low coolant.

During normal operating conditions, the system never operates anywhere near 2 bar. Assuming normal operating temps of 105 C (a bit on the high end), the system won't see pressures above 10 PSI.
Those are the two key things. That shows that filling your ET to "minimum" will be safest for durability.
 

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So based on real world testing, the system never reaches 2 bar. I'm now starting to believe the 2-bar cap might be for emissions purposes or something like that. Government forcing manufacturers to limit the amount of coolant that can possibly be vented to the atmosphere.
 

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Good info kmulder!

Seems mostly like BMW just opted to have the expansion tank cap act more like an emergency vent valve, and also probably taking into account people using just plain water and at high altitude which lowers everything slightly. It would be nice to know when problems of boiling actually start but that would probably be pretty hard to test.


Those are the two key things. That shows that filling your ET to "minimum" will be safest for durability.
And also filling to the minimum will be the most dangerous for risking boiling and warping in an overheating situation.

So based on real world testing, the system never reaches 2 bar. I'm now starting to believe the 2-bar cap might be for emissions purposes or something like that. Government forcing manufacturers to limit the amount of coolant that can possibly be vented to the atmosphere.
I don't think any government cares about evaporated water.
 
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