TornadoRed, you're spreading a lot of partially informed knowledge around of not much benefit, especially in the 3rd and 4th paragraphs of post 87.
TR said:
Aditionally, if the fuel temperatures are already ~110° when you start your trip, you would have to travel several hours before the fuel temp would climb much higher. The best you can hope for with a fuel cooler would be to keep the fuel from getting much hotter than 110°. But the air temps would affect performance no matter how far or how long you drive. And the air temps would limit the effectiveness of a fuel cooler, too.
Thus, it would seem to me that a fuel cooler can have only limited effectiveness, even in the most extreme conditions. And even less effectiveness in more temperate climate zones. The only exception would be if you plan to drive several hours at a stretch, during which time the hot fuel being returned to the tank could raise the temperatures there by many degrees.
There's so much confounded anti-logic here, it's hard to know where to stab this dragon of goofiness.
TR said:
Aditionally, if the fuel temperatures are already ~110° when you start your trip, you would have to travel several hours before the fuel temp would climb much higher.
No, the hotter the ambient temps are to begin with, the faster your fuel will heat up, and it will sustain higher steady-state temps as well.
TR said:
The best you can hope for with a fuel cooler would be to keep the fuel from getting much hotter than 110°.
Yup, but so what. That's a BENEFIT, duh. Your intercooler suffers from the same thermodynamic limitation, but I don't see you poo-pooing intercoolers.
TR said:
But the air temps would affect performance no matter how far or how long you drive. And the air temps would limit the effectiveness of a fuel cooler, too.
Thus, it would seem to me that a fuel cooler can have only limited effectiveness, even in the most extreme conditions.
This is the first part that's made any sense at all. But you're just stating the obvious, that hot air is hot. If you changed the word "even" above to "especially" then it would ring more true.
TR said:
And even less effectiveness in more temperate climate zones.
Wrong. It's much more effective in temperate climates, because of the temperature differences you hinted at before. Have you been drinking?
TR said:
The only exception would be if you plan to drive several hours at a stretch, during which time the hot fuel being returned to the tank could raise the temperatures there by many degrees.
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Fuel temperatures do matter, as do IAT's. And you're making wild inferences about asphalt temps heating air approaching 160f? Where do you get this stuff from? Have you ever recorded intake air temps that high? I really doubt it. Show me the numbers.
I recorded some data on a dynometer with my old 2002 Tdi
You can estimate a linear rate of temperature rise of 3 degrees celcius per minute--look at the plots. Fuel temperatures obviously rise rapidly under even mild load, and we were just testing it on the dynometer at 60 mph, constant speeds! Your last inferred claim that fuel does not raise in temps much or very fast is dead wrong.
I've logged fuel temps of 73C (My Tdi did not have fuel cooler). That's hot. Real hot. Too hot to touch.
You can see that as fuel temps rose in each run, fuel consumption dropped in a pretty strongly related inverse correlation--Ernie Rogers has discussed the physics behind it here in other threads before.
But another thing to strongly consider is that hotter fuel has worse lubrication properties, and since fuel system components depend heavily on that, you don't want to compromise it, so fuel cooling does matter.
Opinions are great. But qualified ones are even better.