Learned something about my car's reluctant DFCO behavior

[theholycow]

I've previously observed that my VW is often reluctant to DFCO except under certain perfect conditions. I recently observed something: When it would normally not DFCO, such as after a downshift, it will DFCO if I brake moderately (not merely enough to trigger the brake lights) first. I guess it's kinda like when you eat something to show your dog that it's ok to eat.

I think that's actually the engine braking protection that's engineered into my car. It has a feature that's supposed to prevent engine braking induced skids, where it will feed a little gas to prevent engine braking.

[kamesama980]

makes sense. don't you love overcomputerized junk that tries to think for you?

[theholycow]

Actually, I was wrong...it's some other stupid bit of overcomputerized junk trying to think for me. Here's the feature I thought it was:
http://www.vw.com/rabbit/highlights/...braking-assist

Engine Braking Assist

Sometimes when you downshift too hard, the reduced gear ratio and engine compression can cause skidding. Not with the intelligence of VW at the wheel. Using the wheel speed sensors, the system monitors the drive wheels for slippage and modulates engine braking torque to prevent skidding.

If that's accurate, then EBA is not to blame for rev hang and also not to blame for the DFCO behavior.

[Geonerd]

If it's variable engine braking, it's VERY poorly implemented.

The idea is fine, and might even be helpful in the wet or out on a racetrack. You'd think that any engine braking program would be driven by wheel rotation data. Only when the rear wheels are starting to slip would the ECU kick in a bit of gas.