Learned something about my car's reluctant DFCO behavior - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Go Back   Fuelly Forums > Fuel Talk > Hypermiling
Search Today's Posts Mark Forums Read Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 07-29-2009, 02:40 PM   #1
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
Learned something about my car's reluctant DFCO behavior

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.
__________________

__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 08-03-2009, 08:01 AM   #2
Registered Member
 
kamesama980's Avatar
 
Join Date: Nov 2007
Posts: 742
Country: United States
Location: Columbus, IN, USA
Send a message via AIM to kamesama980 Send a message via Yahoo to kamesama980
makes sense. don't you love overcomputerized junk that tries to think for you?
__________________

__________________
-Russell
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
kamesama980 is offline   Reply With Quote
Old 08-03-2009, 08:20 AM   #3
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to 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
Quote:
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.
__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 08-03-2009, 10:50 AM   #4
Member
 
Geonerd's Avatar
 
Join Date: Aug 2009
Posts: 47
Country: United States
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.
Geonerd is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fuelly Android App - eehokie Fuelly Web Support and Community News 2 07-14-2010 09:59 PM
Combined totals of all my vehicles? nizationpcs Fuelly Web Support and Community News 0 03-30-2009 07:41 AM
considering rear turbulence management Philip1 Aerodynamics 35 10-10-2008 08:45 AM
New here GasSavers_landon Introduce Yourself - New member Welcome 10 11-08-2007 07:05 AM
Maximum tire pressure holypaulie General Fuel Topics 13 10-02-2007 08:25 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 09:06 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.