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markmurfie
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Nope. Cylinder head temp is exactly that. Engine coolant temp is the needle gauge in the lower left if your dash board. They have a direct relationship with each other but you will notice cylinder head temp reaches tempature before that needle gauge. Things like after market thermostats will affect both.
Higgs Boson
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I am thinking coolant temp is inferred based on the cylinder head temp on these cars. There is no engine coolant temp sensor.....so yes, the ecm calculations are based on CHT.
markmurfie
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They must have coolant temp sensors. There's "actual coolant temperature" vs "engine coolant temperature". They infer engine coolant temps from cylinder head temps and coolant temps in the radiator. This information would surprise me more than finding out there's no map sensor.
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Higgs Boson
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Check your tune, first tab/page. Is Engine Coolant Temp Enabled or Disabled?
You can't go by PIDs.
markmurfie
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Exactly there's no engine coolant tempature sensor. There is an actual coolant temp sensor. Which would be radiator coolant temp.Chevy just puts the temp sensor right in a water jacket of the engine. Why ford likes to do math and complicate this I don't know. Precision and accuracy of heat transfers I can only guess.
I actually caused a condition in my engine that when I was rolling down a hill my cylinder head temps would drop below 160*. I thought it was really cool until I read about different ways pre ignition is determined. Very unsafe.
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Rhinogt
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And they aren't directly related in terms of temp difference. I've seen in different logs where they differ as little as 2 degrees and by as much as 20 degrees. But it is not linear in any way on my car. So I don't see how it could be inferred from one to the other mathematically. I may be wrong of course but I just don't see the pattern.
markmurfie
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Yes not directly related in terms of temp difference. But in terms of btu produced by the engine and btu reduced by the radiator.
Example if temps at the cylinder head reduce but the radiator temp didn't show it doing it they can say that heat was absorbed in the engine. If your piston absorbs to much heat you will end up with a hole in it.
Example if temps at the cylinder head reduce but the radiator temp didn't show it doing it they can say that heat was absorbed in the engine. If your piston absorbs to much heat you will end up with a hole in it.
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It's not linear just means the equation isn't addition or subtraction. There's a curve (but I don't know what it is).
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Rhinogt
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Ok so basically there is another variable in the equation. The ECU sees CHT AND coolant temp from radiator and infers it from there. I can see that. I just couldn't see how it would infer it strictly from CHT.
And when I said "not linear", I mean't that as the Temps go up the differences get bigger and smaller. Say from 100-120 it might be 2 degrees. Then from 120-150 10 degrees. 150-170 5 degrees.
And when I said "not linear", I mean't that as the Temps go up the differences get bigger and smaller. Say from 100-120 it might be 2 degrees. Then from 120-150 10 degrees. 150-170 5 degrees.
markmurfie
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That's why I'm saying there is a coolant temp sensor. not on the engine but it has to be there somewhere in the rest of the radiator system. The only other way would for Ford to know how much heat the entire engine and radiator radiates precisely. Then from that do the calculations.
Rhinogt
Well-Known Member
Yea I think so. But I'm not going to dig through the entire engine bay looking for a sensor to prove it, LOL. I'm not going to argue with the experts, I was just pointing out that I can't see how a computer could mathematically correlate the two directly.
markmurfie
Well-Known Member
Oh. Well x amount of fuel and air will produce x amount of BTUs. From there you would need to know the water/coolant ratio with the radiator volume and you could get the maximum BTUs it could remove and still maintain x temperature. The water/coolant ratio is why you need the temp sensor. Of course exhaust egt and natural engine radiation factors in making it not direct.
Every path from point a to b to me is linear. I guess a direct temperature relationship may not be the best way to describe it. Lines can have curves cross over themselfs go one direction then another or just be straight. The BTUs produced and BTUs radiated is or should be a direct relationship other wise the engine is soaking them up and that's not a good thing after a certain point..
Every path from point a to b to me is linear. I guess a direct temperature relationship may not be the best way to describe it. Lines can have curves cross over themselfs go one direction then another or just be straight. The BTUs produced and BTUs radiated is or should be a direct relationship other wise the engine is soaking them up and that's not a good thing after a certain point..
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