Idling in N vs D observations

[stimpsonjcat]

Originally Posted by Nevyn

You IDLE at LIGHTS???

"Even I get boarded sometimes."

[user removed]

I tossed my two autos, with instant fuel mileage bar graphs, in neutral and the Altima maxes the bar at 60 MPG at 16 MPH. The Insight maxes the bar at 150 MPG at 16 MPH. Both were coasting in neutral.

Works out to about .25 GPH for the Altima and .11 GPH for the Insight. Those are consumption when coasting with engine on in neutral. The Insight was rather harsh when you went back into gear and required some rev matching. The Altima was completely different. It seems like it does not engage the torque converter until you give it some gas, you can shift into gear at any speed (have done it up to 80 MPH) and the revs stay very low until you give it some gas, probably no torque converter lockup. The car does lock up the converter very quickly normally at about 12 MPH.

regards
Mech

[stimpsonjcat]

As a follow-up...the Versa definitely uses less fuel in N.

I installed a UG in my F-150, and it actually uses MORE fuel in N.

Just goes to show you need the gauges!

[HighMPG]

I always use N at stops since basically a less loaded engine looses less energy even at idle. Also when I am coasting to a stop or when having to use the brakes it may take 2% less force on the pedal to stop and even more at lower speeds. coast longer from higher speeds with less engine braking.

[bwilson4web]

Originally Posted by stimpsonjcat

. . .
I installed a UG in my F-150, and it actually uses MORE fuel in N.

It sounds like the F-150 does not back-off the idle rpm when shifted into "N" but expects the transmission drag to slow the engine down. Is there a change in the rpm when you shift to "N"?

What about "P"?

Bob Wilson

[stimpsonjcat]

Originally Posted by bwilson4web

It sounds like the F-150 does not back-off the idle rpm when shifted into "N" but expects the transmission drag to slow the engine down. Is there a change in the rpm when you shift to "N"?

What about "P"?

Bob Wilson

Did not try P...I'll try it next time I drive the truck.

Yes, I think I remember the RPM increasing in N.

[gone-ot]

...and, here's how GM implements DFCO in the Cruze (both man & auto):

GM News - United States - News

[tjts1]

This depends more on what stall speed torque converter you have than RPM.

[gone-ot]

...it's an engine function, not a transmission function...at least on the Cruze.

[tjts1]

Originally Posted by Old Tele man

...it's an engine function, not a transmission function...at least on the Cruze.

The lower the stall speed the more power it will take to maintain a given RPM at idle with the car standing still. Most newer automatic transmissions with a lock up torque converter will have a higher stall speed which would be impractical for daily driving without the lockup tq. With a low stall speed tq there are situations in D where allowing the the car crawl forward will actually consume less fuel per minute than standing still. With a high stall speed TQ you could idle in N, D, D at 1200rpm and the fuel consumption will hardly change.