Radiator/Cooling System equations

jcolbert666

I have been doing some work on the new Dallara DW-12 Indy car mod and somehow I found myself pulling my hair out most of the day yesterday trying to get the car's cooling system right. I could just take the lazy way out and rip off the cooling parameters from some other mod that already works but that's too easy.

I have searched high and low on the internet for the actual equations to determine the various engine cooling rates but haven't had any luck. I'm pretty sure that I am close but I haven't yet reached the promised land where all of my numbers jive. If anybody that knows could tell me what the correct equations are, I would really, really appreciate it.

The incorrect equations I have been using for full throttle are as follows:

Engine q = [(FuelConsumption * CombustionHeat) + EngineSpeedHeat] * RPM(rad/sec)


Oil-Water q = [OWHT1 + (OWHT2 * RPM(rad/sec))] * (OilTemp - WaterTemp)


Water-Air q = [WMC + {(RC1 + (RC2 * (Setting-1)) * Velocity(m/sec)}] * (WaterTemp - Constant(26?))


Where:
OWHT1 = OilWaterHeatTransfer1
OWHT2 = OilWaterHeatTransfer2

WMC = WaterMinimumCooling
RC1 = RadiatorCooling1
RC2 = RadiatorCooling2

My Oil-Water and Water-Air #'s are close in most situations but never quite equal. My Engine # is coming out a little bit less than the other two. As I said before, if anybody could help shed some light on what the equations actually are, I would really appreciate it.
 
Its one of the few areas where I just mess about a bit to be honest! Not as important as tires, suspension aero... Have you used kelvin for temperature? rFactor uses that internally which may or may not help you..
 
Thanks for the suggestion but it looks like the one big problem with my calculations was that I didn't take into account the increase in fuel consumption caused by boost. When I corrected for that, most of my numbers made sense. The only ones that don't seem to make sense now are my oil-water calculations when the oil temp is 95C or lower. I think I will leave that mystery for somebody else to decipher.
 
This may also not help, but I believe there is a temperature below which the water part of the cooling is turned off. Not sure if this is a fixed temp or a % of optimumoiltemp. When I did mess with the heating, I pressed control+T for some fast forward revving making sure the engine and water were hot first..
 
When I was working on that stuff, I also noticed something different is happening around 95*C (or, that could be around "OptimumOilTemp" which was set at that time to 95*C) but couldn't find out, what exactly was going on.
 
I was using this page to learn, and think I found something. Shouldn't

Water-Air q = [WMC + {(RC1 + (RC2 * (Setting-1)) * Velocity(m/sec)}] * (WaterTemp - Constant(26?))
Click to expand...

Actually be:

Water-Air q = [WMC + {(RC1 + (RC2 * (Setting-1)) * Velocity(m/sec)}] * (WaterTemp - AirTemp)
Click to expand...

?
 
You are correct, I probably should have labeled it "AirTemp" instead of "Constant".

If I'm not mistaken, in rFactor the AirTemp is fixed. What it is exactly I'm not sure. I did go back and look at my spreadsheet I put together and the outcome from a couple of different runs where everything completely stabilized and all of the runs gave me an "AirTemp" ranging from 25.89 to 25.91 so I'm going to go with 25.9 until I hear differently.

Water-Air q = [WMC + {(RC1 + (RC2 * (Setting-1)) * Velocity(m/sec)}] * (WaterTemp - 25.90)


In response to LesiU, I had my optimum oil temp set at around 105 or 110 for all of my cooling system test runs. Even so, 95C seemed to be the boundary temp, below which things behave differently.
 
jcolbert666 said:
If I'm not mistaken, in rFactor the AirTemp is fixed. What it is exactly I'm not sure. I did go back and look at my spreadsheet I put together and the outcome from a couple of different runs where everything completely stabilized and all of the runs gave me an "AirTemp" ranging from 25.89 to 25.91 so I'm going to go with 25.9 until I hear differently.
Click to expand...
Air temp does not change much during the day (but nights are colder than days), but it is definatelly not constant.

jcolbert666 said:
In response to LesiU, I had my optimum oil temp set at around 105 or 110 for all of my cooling system test runs. Even so, 95C seemed to be the boundary temp, below which things behave differently.
Click to expand...
OK, so it must be something else, maybe some sort of internal threshold or something like that, which affect general behavior.
 
I think the equations look more or less correct.

OptimumOilTemp= does 2 things that I'm aware of.
It defines the starting oil temperature, which is simply this number OptimumOilTemp*0.5+14.5 degrees.
And you're exactly right that it controls when the thermostat opens, which is OptimumOilTemp-10 degrees

The thermostat disables the 2nd variable in the OilWaterHeatTransfer equation.
OilWaterHeatTransfer=(0.05, 4.0e-4) // heat transfer from oil to water (base, w/ engine speed)
 
Is it just me or has anyone else noticed you cannot have water temp higher than that of oil?

Seems like the progression of things in rf is:
Heat→OilTemp→WaterTemp→Radiator

Also shouldn't
Engine q = [(FuelConsumption * CombustionHeat) + EngineSpeedHeat] * RPM(rad/sec)
Click to expand...
be
Engine q = (FuelConsumption * CombustionHeat) + (EngineSpeedHeat * Engine speed [rad/sec])
Click to expand...
?
 
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The "FuelConsumption" is the rate of fuel consumption per RPM.
 
Ahh, I see. I was already figuring it as Fuel Consumption in Liters, and as a total heat added.
 
Sorry to resume this old post, but i really hope somebody can help to shed some light about an engine parameter that was mentioned here.

I did some test with a car, yesterday, and noticed that the oil temperature has an effect on engine performance.

In particular, in my case, when a steady oil temperature is reached in game, it looks like the engine looses some power, probably because this temperature is above the OptimumOilTemp.

Can anybody explain how this parameter and the actual in game oil temperature influence the final engine power? I have the feeling that deviating from OptimumOilTemp produce an engine power lost (above all if the oil temp in game is higher than OptimumOilTemp), but still don't know if this is described by an equation or if it has to do with the termostat effect described above.

Thanks a lot for your input!
 
I would say that the engine performance lost in that case, has to do with the LifetimeOilTemp= setting, but i have no clue how it gets calculated.
 
Hi redapg,

thanks for your input.

Does also LifetimeOilTemp have an influence on engine performance?
 
silente said:
Hi redapg,

thanks for your input.

Does also LifetimeOilTemp have an influence on engine performance?
Click to expand...

Life time oil temp is the variable that defines how oil temperature affects the wear/life of the engine.

If there is some parameter which relates performance wrt wear/life (there should be one but I dont know) it would indirectly affect performance.

For direct performance is the OptimumOilTemp settings. The other parameters that go with the temperature define how it affects being above or below that value. This way of setting things is quite common within vehicle characteristics (wear, grip, ...) for brakes for example.

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Euskotracks,

thanks for your reply.

Which other parameter (beside the OptimumOilTemp) you mean, having an effect on engine performance? And do you know exactly how engine performance are affected by OptimumOilTemp and whatever other parameter?

Thanks!
 
Engine performance should be influenced directly by the LifetimeOilTemp value.
As Euskotracks already wrote, does it have an influence on the wear of the engine.
And if your engine gets older/has a high wear in real life, you have a loss of performance/power.
So e.g. accelerating would be more bad, max power would be less....

And if you drive a longer time with a too high oiltemp, depending on the LifetimeOilTemp value, you will have a higher wear, like in real live.

It would be interesting to know the exact formula.
 
silente said:
Euskotracks,

thanks for your reply.

Which other parameter (beside the OptimumOilTemp) you mean, having an effect on engine performance? And do you know exactly how engine performance are affected by OptimumOilTemp and whatever other parameter?

Thanks!
Click to expand...
As I said, there should be one but I certainly don't know if it exists for sure.

I would expect to be easily found it it exists. It would be in the engine.ini file for sure. I am not in my PC to check.


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to be honest, the performance effect i noticed was there from the first to the last lap of a session and it showed no changes during the session itself.

It looked more like a pure performance/temperature related issue, as Euskotracks said, but i need to do more test to be sure.

But as i said, i had speed "A" as soon as i went out of the pit, then i always and pretty consistently had speed "B", with the oil temp pretty stable at a certain value and not changing significantly anymore.
 
Euskotracks,

here an example of engine.ini file for reference.

RPMTorque=( 0.0, -17.7, 0.0)
RPMTorque=( 500.0, -33.0, 255.6)
RPMTorque=( 1000.0, -47.5, 432.4)
RPMTorque=( 1500.0, -65.8, 564.8)
RPMTorque=( 2000.0, -78.7, 598.2)
RPMTorque=( 2500.0, -89.6, 604.7)
RPMTorque=( 3000.0, -98.7, 600.8)
RPMTorque=( 3500.0, -111.5, 605.9)
RPMTorque=( 4000.0, -116.5, 640.7)
RPMTorque=( 4500.0, -133.5, 662.5)
RPMTorque=( 5000.0, -144.5, 663.8)
RPMTorque=( 5500.0, -153.5, 670.2)
RPMTorque=( 6000.0, -166.4, 671.5)
RPMTorque=( 6500.0, -179.2, 673.1)
RPMTorque=( 7000.0, -186.5, 660.3)
RPMTorque=( 7500.0, -192.0, 617.1)
RPMTorque=( 8000.0, -208.4, 570.6)
RPMTorque=( 8500.0, -215.4, 526.9)
RPMTorque=( 9000.0, -225.5, 470.7)
RPMTorque=( 9500.0, -234.0, 414.5)
RPMTorque=( 10000.0, -244.0, 65.5)
FuelConsumption=6.3e-05 // affected by throttle position and engine speed
FuelEstimate=1.1711 // fudge factor for differences between vehicle types (used for lap estimates and AI pit scheduling)
EngineInertia=0.1061 // rotational inertia of engine components
IdleThrottle=0.2 // throttle multiplier to help maintain idle speed
IdleRPMLogic=(1200, 1500) // attempt to maintain idle speed between these RPMs
LaunchEfficiency=0 // efficiency (0.0-1.0) of launch control, or 0.0 if N/A
LaunchRPMLogic=(4200, 5200) // holds RPM in this range before launch (used for AI even if launch control is N/A!)
RevLimitRange=(5700, 100, 29)
RevLimitSetting=18
RevLimitLogic=0 // RPM range around current setting where rev limiter operates
RevLimitAvailable=1 // whether to use a rev limit (if 0, you still must have a "rev limit", just make it 40000 or so, and make sure to change [CONTROLS]->UpshiftAlgorithm to fix shifting points)
EngineBrakingMapRange=(0, 2.400e-04, 6) // input throttle is ranged from minimum to 100%, with the minimum = setting * step * RPM,
EngineBrakingMapSetting=2 // the default is 1 * 0.000133 * 15000 RPM = 2% applied throttle at zero input throttle
EngineBoostRange=(0.01000, 1, 3)
EngineBoostSetting=0
BoostEffects=(250.0, 0.00, 0.0) // RPM increase per setting, fuel increase (1%) per setting, engine wear rate (101.5%) per setting
BoostTorque=0.0000 // 0.4% less torque per setting (applies to all RPMs)
BoostPower=0.00000 // % more horsepower per setting // % more horsepower per setting
OptimumOilTemp=96 // degrees Celsius at which engine operates optimally
CombustionHeat=28 // degrees Celsius added per liter of fuel burned
EngineSpeedHeat=1.470e-03 // heat added linearly with engine speed
OilMinimumCooling=8.000e-03 // heat dissipated without radiator
OilWaterHeatTransfer=(4.000e-01, 8.000e-05) // heat transfer from oil to water (base, w/ engine speed)
WaterMinimumCooling=3.750e-03 // heat dissipated without radiator
RadiatorCooling=(1.800e-04, 0.400e-04) // cooling rate with velocity (base, per setting)
LifetimeEngineRPM=(7500, 500) // (base engine speed for lifetime, range where lifetime is halved)
LifetimeOilTemp=(105.0, 2.5) // (base oil temp for lifetime, range where lifetime is halved)
LifetimeAvg=6689.072 // average lifetime in seconds
LifetimeVar=0 // lifetime random variance
EngineEmission=(0, 0.4500, -0.65) // where flames and smoke are emitted (relative to ref frame at rear axle)
EngineSound=(0, 0.3000, 0.0) // where engine sound is played (relative to ref frame at rear axle)
SpeedLimiter=1 // whether there is a pitlane speed limiter
OnboardStarter=1 // whether vehicle restarts when stalled
StarterTiming=(0.70, 0.0000, 0.7000) // average and variable cranking time, then time to blend with starting sound


Would be cool to know your opinion about the "other" parameter.

Thanks!
 
Could you give these information?:
- What did you set as max RPM in the setups menu?
- What was the value of the Oil Temperature that you had while driving?

And did you see that?:
RevLimitRange=(5700, 100, 29)
RevLimitSetting=18
and
LifetimeEngineRPM=(7500, 500)

When you set the max possible RPM in game, you get 8500 RPM which will cause an elevated engine wear if you use it too often, because of the LifetimeEngineRPM= setting.
 
This is only an engine file from enduracers, not mine.

I justed wanted you guys to point out where the problem could cone from and which parameters euskotraks meant.

is there a way to delete all wear effects anyway? And also any engine damage? This way we could test eliminating these parameters from the list...

Thanks!
 
There's no parameter to set the performance loss due to oil temp, and to be honest apart from obvious power loss when overheating I didn't think oiltemp affected power at all. But I also didn't do any testing specifically for it.

*And sorry, to answer your last question, if you change the second value in the two Lifetime parameters (oil and rpm) to very large values (or possibly 0... I can't remember if that cancels it) it will stop engine wear being related to your current RPM and oil temp. Personally I don't think engine wear % has any effect on power, except when it's actually starting to fail (sometimes you get some warning, with smoke... other times it just dies)
 
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Guys,

thanks a lot for your replies.

Any chance any of you could help me to understand what exactly the second parameter of the LifetimeEngineRPM and the LifetimeOilTemp means and does?

I will try as soon as possible to test with their first parameter set very high, so to limit its influence to the minimum. Don't know if it could be set to 0, maybe will try this as well. At least we can understand if, even with their influence reduced to the minimum, we still have a power effect depending on temperature. In that case, i don't know which other parameter could be used to reduced oil temp effect on power, in a similar way to tire pressure for tire grip, for example.
 
Oppositely to what I would expect, Optimum oil temp doesnt have other parameters to adjust so I guess the effect in perfomance is hardcoded within the game. Oherwise the optimum temperature term would be misleading.

I cannot understand why optimum oil temperature doesn't have modifiers to define what happens when you are above or below temperature as for example brakes.

I cannot find either any parameter that relates wear with performance. If such effect is simulated it appears to be hard coded as well.

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I didn't find any sign that there is power loss due to engine oil temperature. I have made tests with very cold and very hot engine, and changing optimum temperature to extreme values. Engine wear can make influence, but on the conditions you are exposing i guess you should see your engine explode not much time after the loss of power.
We would need to check your engine files and the way you are using your engine when driving, but we also would need to check how the car is performing on other areas: aerodynamics, tyres... If you are losing speed early after leaving pits perhaps there is an issue related to tyre pressures and temperatures, aerodynamics, ride heights.. are you sure they are performing right? Could you show us a telemetry where we can see what happens to main car elements on both 'speed A' and 'speed B'
 
Raintyre said:
I didn't find any sign that there is power loss due to engine oil temperature. I have made tests with very cold and very hot engine, and changing optimum temperature to extreme values. Engine wear can make influence, but on the conditions you are exposing i guess you should see your engine explode not much time after the loss of power.
We would need to check your engine files and the way you are using your engine when driving, but we also would need to check how the car is performing on other areas: aerodynamics, tyres... If you are losing speed early after leaving pits perhaps there is an issue related to tyre pressures and temperatures, aerodynamics, ride heights.. are you sure they are performing right? Could you show us a telemetry where we can see what happens to main car elements on both 'speed A' and 'speed B'
Click to expand...
Well. It seems pretty much clear that OptimumOilTemp does nothing then.
Your tests are quite conclusive.

The only parameter that can be changed then is engine lifetime which is affected by both oil temperature and RPM.

As an anecdote my first car died after an engine heating which broke the seal that prevents water being mixed with the oil. However, I drove it for about a month by refilling the water tank every day. When it got hot about 100-110 degrees it literally had no power and I had to full throttle so that it would move in a traffic jam where it ocurred.

It is quite strange that something apparently not difficult to measure like temperature effect on delivered torque is not implemented by ISI.

For the other not addressed aspect, F1 teams could provide typical figures for engine wear effect on torque.

It is typical that for high % of throttle venues like Spa or Monza, teams put a new engine to be competitive leaving the older units for less requiring tracks as Hungary, Monaco....

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He he, nice anecdote!

I forgot to answer this:
>>>>>>>Any chance any of you could help me to understand what exactly the second parameter of the LifetimeEngineRPM and the LifetimeOilTemp means and does?

The theory says that 2nd parameter is the offset from 1st parameter where "life is halved". You could also say "where wear is multiplied x 2". For example:


LifetimeOilTemp=(110, 3)

at 110º >> wear caused by oil temp: 'normal'
at 113º >> wear caused by oil temp: normal * 2
at 116º >> wear caused by oil temp: normal * 4
at 119º >> wear caused by oil temp: normal * 8
.....

This would be only the wear added due to oil temperature.
Both 'LifetimeEngineRPM' and 'LifetimeOilTemp' are involved in engine life calculations.

Example:
LifetimeEngineRPM=(7500, 200)
LifetimeOilTemp=(120, 4)
LifetimeAvg=3600
LifetimeVar=0

If engine RPM are 7500 and oil temp is 120 then engine life is 3600 seconds.
If engine RPM are 7700 and oil temp is 124 then engine life is 1800 seconds.

Of course rpm and oil temp are not constant during driving, but those are true references you can have in mind. Keeping rpm under 7500 and oil temp under 120 your engine should live at least 3600 seconds.
Probably there are also other minor factors involved in engine life calculation, and 'LifetimeVar' adds a variation range when it is > 0.
 
Raintyre said:
If engine RPM are 7700 and oil temp is 124 then engine life is 1800 seconds.
Click to expand...

Minor correction, I think you mean 900 seconds as both factors have increased by 2.

In practice it's difficult to predict the overall expected lifetime if you start playing with these values, but you can use accelerated wear and representative driving to get a good gauge. (10x timescale, timescaled failures, failure after 8 laps ~= actual failure after 80 laps. But have to be wary of warmup periods and effects of pitstop overheating etc)


Regarding engine wear -> performance, I don't recall any league members mentioning power loss at the 'power tracks' (monza, spa, ...) through years of running mods that often had complete engine failures (therefore a good percentage of engine wear) for some drivers. So from a purely anecdotal standpoint I find it unlikely. But it's true I haven't tested for it specifically.
 
I just can report my own experiences, what comes from some years ago to be honest, but i think i remember right.
It was a league race with an Audi R8 LeMans Mod and i noticed that the longer i was driving, the acceleration was decreasing more and more.
Other members noticed the same and some of them used the XD Tool, where the engine health was displayed.
And they told me, that the health and power loss happened in a same curve.
And changing the lifetime-, max. RPM and temperature values, changed that behaviour.

But because different settings correspond with each other and it also depends on your driving behaviour, it's hard to make a senseful statement without knowing the formulas, with that they are calculated and without knowing the way how it is programmed to bring all together.
 
>>>>Minor correction, I think you mean 900 seconds as both factors have increased by 2.

No Lazza, i think it is like this because each parameter contributes with half of wear (and that makes it more difficult to explain, by the way!)

This is a explanation by Bristow/ISI/... (http://ausfactor.com/rfc/rfactor_Engine.htm):

LifetimeEngineRPM=(17730.0,344.0) // (base engine speed for lifetime, range where lifetime is halved)
LifetimeOilTemp=(125.4,2.90) // (base oil temp for lifetime, range where lifetime is halved)
LifetimeAvg=8105 // average lifetime in seconds
LifetimeVar=2940 // lifetime random variance
This section calculates the engine life dependant on rpm, oil temperature relative to optimum, and statistical treatment of average life. The following is from ISI, courtesy of Maxsilver. I have edited the original to fit with the numbers in this file -

"The LifetimeAvg and LifetimeVar are ... the mean and one standard deviation of a normal distribution.

The lifetime of the engine is continually reduced based on the current RPM and temperature. If you were able to drive around perfectly maintaining an RPM of 17730.0 and oil temp of 125.4 deg C, the lifetime would reduce by 1 every second. So on average, you'd have 8105 seconds before your engine exploded.

Now obviously you can't maintain that exact RPM & temp, so the lifetime reduction happens faster if you're above the RPM & temp and slower if you're below. It's an exponential curve - at 17730.0 + 344.0 RPM and 125.4 + 2.90 deg C, the lifetime reduces by 2 every second. At 17730.0 + (2 * 344) and 125.4 + ( 2 * 2.90) deg C, the lifetime reduces by 4 every second, etc. The RPM and temperature each contribute half to the calculated lifetime reduction."


Engine wear can reduce engine power, there is no doubt, but i think it is not a strict rule. I would say there is some randomness, so sometimes you blow the engine suddenly and sometimes the engine lose performance step by step. I am not sure whether loss of power comes before life arrives 0 or after....
 
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Raintyre said:
>>>>Minor correction, I think you mean 900 seconds as both factors have increased by 2.

No Lazza, i think it is like this because each parameter contributes with half of wear (and that makes it more difficult to explain, by the way!)
Click to expand...

Yeah, I think you're right... after I posted I recalled the 50/50 split and realised I was probably wrong :)
 
For completeness of this thread:
oilTemp does indeed affect engine performance! With some cars more, some less. Was the case at least since rF1.
What coding this behaviour depends on, seems still unknown?
 
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