Engine braking : IDFSO ?

[David_fr]

Hi !

not sure my english will be enough good to explain you what I would like talking about...
Let's try.

There is something I absolutely hate on my truck.
When I drive in town or on low speed roads every times I remove my foot from accelerator pedal, the engine is braking too strongly so when I put my foot back on the pedal it's not smooth. Engine is coming back from braking to accelerate "roughly" .

After a research it seems that this is how work the IDFSO system ( Interactive Deceleration Fuel Shutoff ).
IDFSO locks the torque converter and shuts off fuel to the engine when your foot is off the gas.

I can feel that more when I drive with MDS off ( select gear 8 with wheel command )

are you disturbed by this phenomenon too ?

What do you suggest ?
Do you think that buy a unlocked ECU with a Tune will disable this IDFSO ?

Thanks .
David.

 

[kurek]

I don't have an answer to your question but your English is fine and the question is easy to understand.

My truck has the older 6 speed transmission and the effect of engine braking is much stronger with Tow/Haul enabled, but as you say at low speeds the effort of spinning the engine without fuel is enough to feel. It's a little bit annoying, not extremely annoying.

For the 8 speed transmission I have read there are 40 different shifting behavior patterns the controller can choose from. It is supposed to adapt over time so if you live in a city but visit mountains for a weekend it doesn't switch you to a mountain appropriate pattern but if you move to a new home in the mountains it will eventually change. There should be a fast learn mode that can be enabled by the Ram dealer or possibly with AlfaOBD (maybe somebody knows?) which may allow you to change the behavior of the transmission a little.

I know about this because I had a misbehaving Jeep before buying my Ram and the dealer tried this fast learn mode & instructed me to "drive the #### out of it" to encourage the transmission to pick a more sensitive shift pattern.

Sorry I cannot be of more help but I hope you can solve or improve this to your satisfaction.

 

[David_fr]

Many thanks for your answer.

Even if you didn't gave me a fast and magic solution, for sure your answer is helpful and give me the way

This transmission is amazing most of the time, the only issue is at low speed and smooth driving.
The worst time is on slight descent when the engine is braking but I want to keep a constant speed.
Passing from a braking torque to a engine torque give a "surge" ( not sure this word is good in this case )

I'll read and learn about this "adaptive mode" and see how I can take benefit of this.

Many thanks .
David

 

[Barney556180]

This seems to be typical of how manufacturers are squeezing more MPG.
Our XT5 also does this, as well as several other late model vehicles I’ve driven.

 

[Tach_tech]

Decel fuel cut off has been around for just about as long as electronic fuel injection has been around. It can be annoying but it does save fuel and is needed for manufactures to meet economy requirements.

As for the transmission learning, the 8 speed is constantly adapting to your driving style. The adaptives can be reset so it will start over but depending on which 8 speed you have, the 845RE or 8HP70, the quick learn is very different.

The 845RE can be done with a scan tool and under 5 minutes. However the 8HP70 does not have a quick learn and uses a drive learn process, which involves monitoring the adaptives and driving in a certain manner that allows it to learn. You pretty much need to drive like an old lady and do multiple decelerations in order to get all the clutches to learn. It usually takes about 1-2hrs of driving to do it properly, and that’s if you have flat roads with little traffic on them.

 

[Rado]

Can the 845RE do the Drive Learn mode or only by scan tool ?
Thanks

 

[Tach_tech]

Can the 845RE do the Drive Learn mode or only by scan tool ?
Thanks

Both have the ability to do the drive learn. That’s the adaptive learning that constantly changes based on how you drive and as the transmission ages. The 845 just also has a quick learn which speeds this process up. It was added by FCA since FCA has a little more control over manufacturing/programming the 845 than the 8hp.

 

[David_fr]

...The adaptives can be reset so it will start over but depending on which 8 speed you have, the 845RE or 8HP70, the quick learn is very different....

I didn't know there are two different 8 speed transmission. Thanks.

A VIN decode confirm that I've got the 8HP70 :
DFK 8-Spd Auto 8HP70 Trans (Buy-US)


EDIT : it seems that the 845RE is a Chrysler version of the 8HP45.
It comes in V6 3.6 RAM ( and EcoDiesel ? ), all 8 speed Hemi have the 8HP70.

David.