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The data doesn't lie. OhSix's fluid is going through the OTW exchanger first, OTA second. Bobcat20's is the other way around.
One is tempted to wonder whether Honda changed the order in which the ATF hits the coolers between '06 and '14. The way your ATF is routed, OhSix, will shed more heat; better for high load conditions. The way bobcat20's ATF is routed will lead to warmer ATF during warm-up (and likely warmer ATF during most of the drive cycles that most of the trucks are expected to be used for), and so better performance during EPA fuel economy testing procedures. It will also dump a bit less heat under high load conditions.
Cooler ATF is not better when there's no limit to how cool "cooler" is. It _is_ better to have sufficiently cool ATF, than to have too-hot ATF.
Thanks for the continued data and updates, OhSix!
One is tempted to wonder whether Honda changed the order in which the ATF hits the coolers between '06 and '14. The way your ATF is routed, OhSix, will shed more heat; better for high load conditions. The way bobcat20's ATF is routed will lead to warmer ATF during warm-up (and likely warmer ATF during most of the drive cycles that most of the trucks are expected to be used for), and so better performance during EPA fuel economy testing procedures. It will also dump a bit less heat under high load conditions.
Cooler ATF is not better when there's no limit to how cool "cooler" is. It _is_ better to have sufficiently cool ATF, than to have too-hot ATF.
Thanks for the continued data and updates, OhSix!
Yep, I see there's no disagreement after all, though my own recollection had it backwards, too.
Good summary, OhSix!
The OTW exchanger most definitely IS a pre-heater! That the OTA cooler eliminates some of that heat is true, yet consider: The OTA cooler will, in most climates, cool the fluid the majority of the time. The OTW exchanger raises the start temp from which that cooling begins. So, OTW is still a very effective pre-heater.
It would be ideal if the OTA cooler had a thermostat that allowed the fluid to bypass it until it reached a sufficiently high temp so as to 'need' the auxiliary cooling it affords. However, that adds cost and complexity that is likely not deemed necessary or useful for this kind of application.
And you're absolutely right that the pre-heating is for mpg/CAFE reasons. Too, Honda places a lot of emphasis, including marketing efforts, on a certain ideology that is to do with not just efficiency, but relatively low usage or consumption of 'stuff' (fuel, oil, maintenance items, and so forth). There are many, MANY SAE papers and other technical publications dealing with ways to eke out _very_ small increases in mpg. GM has been doing it on a large scale for perhaps the longest time of the majors in North America.
Again, very well done, and thanks!
The OTW exchanger most definitely IS a pre-heater! That the OTA cooler eliminates some of that heat is true, yet consider: The OTA cooler will, in most climates, cool the fluid the majority of the time. The OTW exchanger raises the start temp from which that cooling begins. So, OTW is still a very effective pre-heater.
It would be ideal if the OTA cooler had a thermostat that allowed the fluid to bypass it until it reached a sufficiently high temp so as to 'need' the auxiliary cooling it affords. However, that adds cost and complexity that is likely not deemed necessary or useful for this kind of application.
And you're absolutely right that the pre-heating is for mpg/CAFE reasons. Too, Honda places a lot of emphasis, including marketing efforts, on a certain ideology that is to do with not just efficiency, but relatively low usage or consumption of 'stuff' (fuel, oil, maintenance items, and so forth). There are many, MANY SAE papers and other technical publications dealing with ways to eke out _very_ small increases in mpg. GM has been doing it on a large scale for perhaps the longest time of the majors in North America.
Again, very well done, and thanks!
I ran a super-informal 'test' this week. I use a ScanGauge to monitor ATF temp (and other things) as reported to/by the ECU. Yesterday I watched as ATF temp camp slowly up to 100F and then held there for nearly all of my ~38 mile freeway commute. Then I zip-tied a piece of cardboard in front of the OTA exchanger, and watched ATF temp this AM. Outside temps were the same each AM (~38F at my house), as determined by the reported Intake Air Temp. ATF temp was the same to a max of 2 degrees F higher. I'd need to watch quite a bit more, of course, but I was surprised at just how little difference blocking the OTA had on bulk ATF temp.
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