View Single Post
Old 10-28-2013, 12:50 AM   #9 (permalink)
t vago
MPGuino Supporter
 
t vago's Avatar
 
Join Date: Oct 2010
Location: Cedar Rapids, IA
Posts: 1,766

The Karen-Mobile - '05 Dodge Magnum SXT
Team Dodge
90 day: 26.72 mpg (US)

Fiat Dakota - '00 Dodge Dakota SLT RWD Quad Cab
90 day: 16.67 mpg (US)

The Red Sled - '01 Dodge Durango SLT 4WD
90 day: 16.96 mpg (US)
Thanks: 799
Thanked 681 Times in 437 Posts
Quote:
Originally Posted by UltArc View Post
What about if it is in Drive, like the OP is doing it?
The answer depends on three things - selected transmission gear, the stall rating of the torque converter, and the vehicle speed. If all three are such that the transmission can still turn the engine over, even if it's turned off, then the engine turning will then drive the transmission oil pump. As long as the transmission oil pump continues to be driven, then it is still circulating fluid throughout the transmission.

I see this happen fairly regularly with the Karen-mobile, in fact. Whenever it enters DFCO (normally in D at speeds above 50 MPH and with no pressure on the gas pedal), the engine computer will cut power to the injectors, and the engine will still turn over, due to the fact that the drive wheels are now driving the engine through the transmission. Below about 50 MPH, though, the engine computer will "start" the engine again by re-energizing and driving the injectors as before. I suspect that if this did not happen, the engine would probably come to a stop at some point not far below 50 MPH, as transmission oil pressure would drop to a point where it could not hold its selected gear any longer, thus disconnecting the drive wheels from the engine.
__________________
The Fiat Dakota


The Karen-mobile


The Red Sled
  Reply With Quote
The Following User Says Thank You to t vago For This Useful Post:
101Volts (10-28-2013)