Schitzo, RF900rkw.. Radiator Temp vs Pressure test info

[JimLev]

Oh, just so you don't feel left out (see post #9) Graham you also have my permission to read this post....but only once!

I couldn't get the KTMP above 105 C, it was 48 F outside when I started and 42 F when I finished.
I didn't bother running any tests with the 1.4 Bar cap. I'll leave the gauge connected and run the test again next summer. I've seen my KTMP as high as 110 C when the AC was on. Test results below pic. July 2013 UPDATE . A few days ago it was 99-100F here south of Boston. I went for a 30 mile drive. The AC was set to 68F on both sides, the KTMP got up to 106C. Not that it really matters but I was using the 2.0 bar cap. The cooling system pressure got up to 18PSI, which should cause a 1.2 bar cap to vent. The PDF has been updated.

[Spirit Force]

That is some nice info! So it would seem that the pressures don't get high during winter. I'll be waiting for the summer update. Great job!

[topaz540i]

i have never seen mine go past 106c

sometimes when i beat on it, the temp actually drops 1 or 2 as the coolant speeds up.

[Spirit Force]

i have never seen mine go past 106c

sometimes when i beat on it, the temp actually drops 1 or 2 as the coolant speeds up.

M62tu has electronically controlled thermostat. When you beat on it, DME will heat up the thermostat causing it to open up sooner.

[pshovest]

M52TU and M54 are similar. It's fascinating to watch KTMP, which normally runs at run at 94C, drop to 86C after WOT in top gear for 10-15 seconds.

M62tu has electronically controlled thermostat. When you beat on it, DME will heat up the thermostat causing it to open up sooner.

[topaz540i]

its because the water pump speed is directly related to engine speed via the belt. Beat on it too long im sure it will start to go back up

[pshovest]

Not on cars with MAP thermostat. DME senses high load, applies 12v to thermostat driving it open, boosting coolant flow. Higher coolant temp improves MPG, lower coolant temp lets engine make more power.

its because the water pump speed is directly related to engine speed via the belt. Beat on it too long im sure it will start to go back up

[topaz540i]

yea true it will use the thermostat to try and block the flow of water if the engine cools too much to keep it within a preprogrammed range.

[JimLev]

JimLev,

I really object to this. Addressing a thread towards certain members?

This forum is for everybody. You are attempting to make it elitist.

Moderator: Please edit the title of this thread, please.

I'm pissed.

GJH

LOL, think I addressed your concerns, see post #1

[webdesigner]

JimLev,

I really object to this. Addressing a thread towards certain members?

This forum is for everybody. You are attempting to make it elitist.

Moderator: Please edit the title of this thread, please.

I'm pissed.

GJH

Grow up, look at the treatment Raza got and he had the best E39 on the board

[JimLev]

Grow up, look at the treatment Raza got and he had the best E39 on the board

I'm sure he was just joking, as was my response back to him.

[Justin517]

Is this the coolant pressure in the block/heads? Or is it the pressure of the air in the expansion that that is being compressed by the expanding coolant? If there is a difference? I assume there is because air compresses, liquid doesn't?

Where did you attach the gauge to?

Nice too see the pressure so low. Going from 105 to the full 108 is the equivalent of going from 221f to 226f... I would doubt that last 5 degrees is responsible for 10+ more psi in the system, no?

[JimLev]

It's the pressure in the radiator.
The Zionsville radiator comes with a port that is 4" below the top of the radiator for the dual temp switch for the non-tu engine aux fans. The tu engines uses a sensor in the lower hose.
I removed the plug and plumbed the gauge into this port. There is coolant above this port. The system pressure should be similar anywhere in the system whether you are reading it in the top of the expansion tank (air) or at the bottom of the block, as it is a sealed system. It could be slightly higher at the output of the water pump, however that isn't easy to get at.

Edit....Graham you can read this one too....but only once!

[Justin517]

Cool, thanks for the info.

[16valex]

OK, I'm not suppose to be here but what the heck you can't hit me over the head so I don't care.

So, Jim. What are you trying to demonstrate here? Are you trying to say at 105C with 2.0 bar cap the Zionville radiator only push out 16.5 PSI?

This forum is for everybody. You are attempting to make it elitist.

+1000.

[topaz540i]

are all tests conducted at sea level? i heard jim was a "hill people".

[Schitzo]

Thanks for the numbers Jim. 16.5psi is much lower than I expected for peak pressure however, I doubt this is the max pressure the system sees. I will wait for your summer numbers.
I did find it interesting the initial 60C rise in temp resulted in a 7.5 psi increase in pressure and the last 5C change (from 100 to 105) also resulted in a 7.5psi increase ( I believe you were driving during the last 5C temp change)

[pshovest]

JimLev has put a lot of time and effort in proving that the 2.0 bar rating on radiator cap does not force cooling system to operate at 2.0 bar, as is widely believed, under all conditions.

Cooling system pressure depends on 1) coolant temperature, and 2) the amount of air in exp tank. Coolant temp impacts coolant vapor pressure and air in exp tank gets compressed as coolant heats and expands, and heated, raising pressure.

With 50/50 AF & water, if we could vent the air from exp tank after engine is at temp, pressures would likely be under 5 psi.

.......... What are you trying to demonstrate here? Are you trying to say at 105C with 2.0 bar cap the Zionville radiator only push out 16.5 PSI?........

[TriniSpeC]

Jim is flossing that dinan CAI in the picture.

[JimLev]

So, Jim. What are you trying to demonstrate here? Are you trying to say at 105C with 2.0 bar cap the Zionville radiator only push out 16.5 PSI?

Alex,
Schitzo, RF900rkw and I were having a discussion about the different caps in another post, sort of hijacked one of Dunne's post. I had mentioned that I was going to do some testing to see what the pressure was in our cooling systems.

are all tests conducted at sea level? i heard jim was a "hill people".

Thought you were from the hills? LOL, Hillsborough NJ where the heck in that?
I'm maybe 75' above sea level.

Jim is flossing that dinan CAI in the picture.

You know it, CF always looks nice, it weights less too.

Thanks for the numbers Jim. 16.5psi is much lower than I expected for peak pressure however, I doubt this is the max pressure the system sees. I will wait for your summer numbers.
I did find it interesting the initial 60C rise in temp resulted in a 7.5 psi increase in pressure and the last 5C change (from 100 to 105) also resulted in a 7.5psi increase ( I believe you were driving during the last 5C temp change)

Nice graph, I was thinking about doing it but didn't have time.
I was flogging it at the end to try and get the temp up, in the summer the KTMP usually is 106-108.
I expect the pressure to climb more, I'd like to get the temp up to 110-112 just to satisfy my curiosity.

With 50/50 AF & water, if we could vent the air from exp tank after engine is at temp, pressures would likely be under 5 psi.

As long as the temp is below 100 C we could release the pressure without the coolant boiling. I'll give it a try, maybe if the pressure goes higher than 20 PSI the 1.4 bar cap might vent and lower the pressure, however that would lower the boiling point. A 60/40 mix (or higher) would bump it up somewhat.

[240sxguy]

This is nice information and it's interesting to see the graph. Thanks for taking the time to test.

[rf900rkw]

Damn, late to my own party.....

Where jim tapped in is probably the lowest pressure in the system, the pump suction side of the radiator. But since this is the same place that the header tank feeds, it's same pressur ethe cap will see and totally relevant

And Schitzo's graph tells the sorty of what happens when temps are pushed over 100C. A little more temp means you have to cover for a potential of a large pressure rise.

[JimLev]

When I pulled into the garage and shut the engine off I expected that some heat soak might raise the pressure. That didn't happen, it stayed at 16.5 and after a few minutes it started to slowly fall.
I was thinking about connecting the gauge to the rear crossover manifold on the back of the heads. I'm pretty sure there is a plug back there too.

[pshovest]

50/50 AF & water shouldn't boil at 105C, but it's close. According to graph on page 11, at 105C, 50/50 AF & water has vapor pressure of ~700 mm Hg absolute, less then 760mm atm pressure. The Antoine eqn on same page will calculate vapor pressure more precisely.

http://www.meglobal.biz/media/produc...Global_MEG.pdf

It be great to see the effect after venting exp tank. All you need to do is crack cap and bleed off pressure. Even if it flashes a little, there's no real consequence. It would give us another trick to reduce cooling system pressure when we know system is or will be under stress. Unfortunately after engine cools down, vac relief in cap will open and let air back in.

...........As long as the temp is below 100 C we could release the pressure without the coolant boiling. I'll give it a try, maybe if the pressure goes higher than 20 PSI the 1.4 bar cap might vent and lower the pressure, however that would lower the boiling point. A 60/40 mix (or higher) would bump it up somewhat.

[mattmartindrift]

its because the water pump speed is directly related to engine speed via the belt. Beat on it too long im sure it will start to go back up

yes, water pump speed is related; but, that isn't exactly a good thing - the WP was designed for average use and may decrease in efficiency at sustained high RPM.


also, I've done track days - sustained 4k-6k rpms, and the temp stays around 97ºC when commuting, I average between 107º and 114ºC.