Ingenieur

Been watching it closely for while under varying condition, OA temps, etc
Steady state moderate load

Coolant/oil
194-195 F fluctuates, mostly 194 / 212 F exactly
In deg C 90 / 100
Tells me the coolant t-stat is 90 C and the oil is 100 C

2009 base car

Is this what others have observed?

BLKROKT

Yup. I'm usually at 194-197 and 215-220 while cruising. Water has been as low as 180deg and as high as 210deg, oil has been as high as 250deg.
Just ordered the 180deg thermostat from MHP - we'll see how that changes things, although there have been mixed results...

Ingenieur

I'm not sure lowering the operating temp for the coolant is good
The ecu is calibrated for this temp
In reality, probably no real difference

BLKROKT

Fans turn on earlier with my new files. Essentially turning on 'Desert Mode'.

The 'ECU calibration' for the stock thermostat is bull****. (no offense intended)

There's no downside to reducing coolant temp in these cars, even if it's only a minor difference. As soon as I find a source for phenolic intake manifold spacers those will go on as well. Any little bit helps IMO.

Ingenieur

What if the ecu does not give full advance until the coolant > 190 F ?
If they wanted a 180 F stat they would have done so
Bringing on the fans sooner does nothing
The stat regulates temp and will actually open more to maintain 90C
So they act in opposition
The fan 'cools' and the stat 'heats' lol

I wonder what the actual rating of the lower setpoint stat is
80, 85 C ?

Critter

Sorry guys, just not buying into the 180 stat, if the engineer has determined that a 190 stat is the operating range recommended, why drop it 10 degrees and this is just the temp at which it opens so in essence the engine is not up to operating temp, the ECU if adjusted for this drop it will cause the fan to start earlier to try to maintain. If there is a need to control engine temps in extreme temp then start with a larger radiator that has greater capacity. IMO any reduction will effect combustion temp also if the coolant can be controlled to the 180 stat. This is one case where increased capacity would win over lower temp control.

BLKROKT

Then why do we modify anything - if the car could be any better, MB would have done so from the factory right? LOL

Illegal Machine

This exactly for me. 2010 P30.

Ingenieur

Is thst a rhetorical question?

Engineers actual size things based on a bunch of varables and conditions we aren't privy to

If I size a CB setting on a 10 MVA 4160 vac wye system it was done for a reason(s)
Raising it because bigger (or lower) is better does not apply

Illegal Machine

Some of those conditions, though, are longevity and fuel economy, which most people modding don't care about. So his snark is relevant.

Though, the 180 tstat is an often debated mod on every vehicle platform. Some people thinks it keeps the car from pulling timing, some people think it's snake oil.

BLKROKT

Oh comeon, no snark there.

It was not rhetorical - I was asking you. Why put an exhaust on. Why use better oil or other fluids. Why install/change anything that isn't available from the MB parts catalog if they did such a good job from the factory. Is that your stance on this? If so that's fine, but it's not what I believe.

Ingenieur

A t-stat is a self regulating control loop
Sensing and control/actuation is usually expandable wax or something
And the output is a valve
The wax is calibrated to put the valve in the middle of the valve throw/travel at setpoint
90 C oem...this way you have +/- 50% of the valve range to keep temp setpoint

An 80C will be calibrated to be in the middle also
But the engine makes the same heat
So to keep 80C the stat must open more
So with normal load the 80 may be at 75% instead of 50%
Now if load goes to 90C the valve may go to 100%
If load goes to 100C you may not have capacity to deal with it
With the 90C you have 50% headroom or capacity left
100C load may take it to 75% so you still have headroom
This is an example of why changing may not be prudent
In addition to the ecu calibration

Folks can do what they like but engineers usually have a reason

Ingenieur

The delta between 80 and 90 in absolute or K is nadda as far as longevity
Lower would be better

But for emissions hotter is better, uses the fuel more efficiently and hence more power per unit of fuel

Niether will do much for charge temp

Without seeing AMG's docs, data and calcs it is hard to second guess their selection

Ingenieur

You better convince yourself you know why they did what they did
You need to be sure your solution is better
imho that is hard to do without all the data

BLKROKT

I don't think you're right here.

Let's say a 80C and 90C both open at 50% based on their respective temperatures, at that temperature. The thermostats are the same size, same flow, same everything except for the point at which they are open at 50%.

So they both have exactly the same overhead, except the 80C thermostat will be 100% open at say 100C versus the 90C being 100% open at 110C. Therefore they are both open 100% at 110C.

The reason for the 80C versus the 90C is that it is completely mechanical, and opens to that 50% 10C sooner. Thereby circulating coolant earlier, and overall stabilization of operating temp earlier. The ECU plays no part in this whatsoever, and does not need to be recalibrated in any way, with the exception of turning on the fans 10C earlier. In fact, you can turn on 'Desert Mode' in your car with the stock thermostat if you like, it will turn on the fans earlier to get more air forced through the radiator.

Ingenieur

You are correct but so am I
Both 50% at their rating
Same flow too or close
But the engine is producing the same heat
So to reject more heat it needs more flow
Q = k x flow x delta temp
But if the engine is producing the same Q but must cool more, ie reject more heat, flow must increase since the drop across the radiator is the same for a given speed and oa temp

If the 80 is 100% at 100C
And the 90 is 100% at 110C
So the 90 is only 75% at 100C
So as load increases >100C the 80 will not be able to reject the heat and the system is out of control and can't keep up
The 90 can open more since it is only at 75% so it may keep up

For a given load the engine produces the same heat with either stat
To cool more (80 vs 90 or 10 deg) it must reject more
Since the radiator delta is constant more flow is required
The stat must open more

BLKROKT

Nope. The 80C thermostat 100% open at 100C means the 90C is only open say 75% at 100C. Which one is flowing more at this moment? The 80C. By being more open, it is circulating more coolant, thus keeping the temperature cooler or at least slowing down the heat increase. The 90C is only open 75%, so the car is more likely to keep heating up at its current rate.

At 110C, the 80C is still open 100% while the 90C is now finally open 100%. Which one is flowing more at this moment? Both are the same.

The 80C thermostat starts stabilizing temperature earlier, because it is flowing more at that particular moment in time. Even at our max temp of 110C for this example, the 80C and 90C are flowing the same. There is a ceiling as far as how much either can open. The 80C thermostat will always outflow a 90C at ANY given temperature, because there is no situation where the 90C thermostat could possibly be open more.

BLKROKT

To add to the above, think of it this way. At any given temperature, the 80C thermostat will be more % open than the 90C thermostat. It's mechanical - that's just how it works.

So by the time the 80C thermostat maxes out opening at 100% at say 100C, that is the maximum possible cooling condition (flow). For either thermostat - they are both mechanically exactly the same, with the same opening and max flow rate, with only the spring changed. If the 90C thermostat is only 75% open at that 100C, then it is not in the maximum cooling (flow) state. At 110C, the 80C thermostat will have already been in maximum cooling state (flow) for the past 10deg, while the 90C is just getting there. The 80C will be slowing the rate of heat increase sooner than the 90C under every condition.

At 120C they are also both in maximum cooling state (flow), but since the 80C thermostat had already been in that state for a longer period of time, it is likely that the rate of heat increase has slowed much more than with the 90C thermostat.

The 90C thermostat in its maximum flow (cooling) state, is still only open as much as the 80C. It cannot open to flow more than the maximum for the 90C - it can't go to 110%, or increase the diameter of the inlet/outlet.

bhamg

IIRC some of the guys from the Middle East tried the 180d tstat and found that it did not work at all. Let us know what happens...

BLKROKT

Yeah I've heard of the mixed results. I've put lower temp thermostats in many many cars. Sometimes they make a difference and sometimes the results are inconclusive. It's worth the shot for me.

Ingenieur

The engine is producing the same heat with both
One is just controlling to a lower setpoint
The 80 is flowing more to the radiator as you said
The 90 is bypassing more
The 80 will reach its limit sooner saturating/overloading/overwhelming the system

Critter

Guys, the stat is there for fast warm ups opening at 180 or 190 depending on which you run and to reduce the flow to allow the radiator to effectively remove heat from the coolant. If you want remove the guts from a stat and run it in your car, the temp will effectively be controlled by the radiator and fans and will take a long time to warm up to operating range and the temp will fluctuate depending on city stop and go or highway.
Now running without a stat allows the coolant to race around and through the rad uncontrolled except by engine revs, this car will over heat because the coolant flow is greater than the rad can dissipate heat.
A mod would be a larger capacity rad not reduced stat temp.
The opening for a 180 stat is no larger or smaller than a 190 so flow would be the same through both.

BLKROKT

Right. The car will reach its max temp regardless of the temp thermostat eventually. The idea behind the lower opening temp is to slow the rate of increase, that's all.

Ingenieur

As you said
100C load, ie, a load that would stabilize at 100C with full flow to radiator

80 is 100%
90 is at 75%
If the load increases the 80 can't respond, the 90 can
Although flow may be ~ the same at 50% it changes with position
Due to seat are, oriface, whatever, the constant is Cv and varies with stroke
Flow = Cv x sqrt(press drop across valve)

We can debate this all day
I know how a thermostatically controlled valve works
They aren't only used in cars

There is a book by Fisher: Control Valve Handbook
Pretty much the reference standard

Not saying maximum cooling capacity changes ( although it may ) but that the throttling or range of control does

Critter

Using your logic " The idea behind the lower opening temp is to slow the rate of increase, that's all". Then why not run a 160 stat?
As stated prev, the stat (190) is to provide fast warm up so the emission control systems can be brought on line. This is why a fault will occur if the ECU has seen a longer than normal time for warmup, usually seen when stat fails, open or extreme cold as we see here. Besides all benefit is lost with the 180 as the oil temp takes longer to reach operating temp and any benefit with the 180 is lost. Larger rad(thickness) will give you what you wish to achieve.