Originally Posted by 08FEH

With the 2009, you are now stuck at 2000 rpms, even with the slightest of pedal pressure

anybody have anything to add??

Originally Posted by 08FEH

If you read what you quoted from my other post, I didn't type that you couldn't increase mpgs with less pressure, I typed that the rpms were stuck @ 2k.

I agree that ANY vehicle can increase mpg significantly with lighter pedal pressure. You won't be able to match the mpg in the 2k rpm mode with the regular (lower) rpm however...

Originally Posted by 08FEH

Steve,

I have been fooling around to find out why the 09 does this. I can tell you that it is costing about 4mpg on the highway for sure. Around the city could be even more detrimental.

Here are some things I have discovered on MY 09feh:

It has to be over 91 degrees outside temp.
When it is behaving this way, the only way to get the rpms to drop back to normal is to shut the a/c button off.

"..shut the A/C button off..."

Does this disable the A/C compressor entirely or does it still run at low volume, lower engine RPM, only to keep the batteries cooled..??

When the A/C is on, there is no throttle position other than idle that will allow the engine to drop below 2000 rpm.
The amount of charge in the battery (using the primitive nav gauge) does not make a difference.

The amount of charge, SOC, wouldn't be of interest insofar as the need to cool the batteries, that would be primarily a function of the discharge or recharge rate plus some extra cooldown period after.


Sorry, the above statement is probably wrong. Even the shelf like of some batteries will be reduced if stored at higher temperatures. Your hybrid batteries may need to be cooled FULL TIME, "in service time", if the incoming FRESH airflow is above some design temperature.

The inside adjustable temp does not matter, regardless if it's set to 60 or 90.

Yes, if the A/C is enabled for cabin cooling, or by default wintertime dehumidifcation purposes, the cabin temperature setting would have virtually no effect since the temperature of air outlet flow to the cabin is a function of the reheat/remix blend door/vane position.

Manual inside fan settings, auto temp, recirc, econ buttons have no effect on the behavior.
It never does the high rpm until after at least 20 minutes of driving.

Once it starts with the behavior it does not stop unless you shut off the a/c
A caviat to this is, at certain times I can see the truck TRY to come out of this mode and the rpms will drop to 1300 or so, but one or two seconds later and it's right back up to 2000 rpm.

Today when I got home from an irritating 2000 rpm drive, I got under the truck and one of the a/c lines running to the rear battery was cold.

On a side note, it makes me wonder why the A/C lines running to the rear aren't insulated in any way....

And the answer was..??

Our 2008 FEH NEVER did this. The beauty of that truck was, as long as the engine was running, the a/c was nice and cold, even at lower rpms.
With the 2009, you are now stuck at 2000 rpms, even with the slightest of pedal pressure, even at 41mph and that sucks.

There are many many reasons I wish I had just kept the 2008, this is just one.


Sean

that's all I have for now, anybody have anything to add??

Originally Posted by wwest

So the batteries must be cooled using FRESH airflow that comes into the system at ~95F.

Originally Posted by stevedebi

I STILL haven't gotten any feedback from 2009 FEH owners. Have you ever seen this "high RPM" behavior? The outside temp needs to be above about 97 F.

Originally Posted by wwest

While the Cabin A/C efficiency can be improved via recirculation of previously cooled airflow I doubt that the battery compartment could use that technique. So the batteries must be cooled using FRESH airflow that comes into the system at ~95F.