Hi all,

Have you noticed that the car feels like it's coasting when you depress the throttle at 30mph and 40mph? The rpm stays around 1000 rpm, but it feels like the car is coasting in neutral. This can also be induced by SS shifting to higher gears.

Recently I start manually coasting the car by shifting into N to try improving the fuel economy. I notice that even when the gear is in N, the engine still holds at 1000rpm as long as the car is moving. As the speed reduces, it slowly drops to 900-800rpm, and then finally down to idle 700rpm when the car completely stops.

I used to think the coasting was achieved by the ECU shutting off the injection (that's the explanation what I found on the web.) But now having observed similar behaviour from the car when coasting, I am thinking it's not what happens.

So... does anyone know what is actually happening? Thanks for any input.

 

I don't know what's happening on yours because I never shift to N for improving fuel economy.
I'd rather get 1mpg less than replacing my tranny.

 

Shifting into N does little to nothing to save your overall fuel economy and it's very bad for your transmission.

 

You're not going to see any improvements in fuel economy by shifting to Neutral while coasting. In fact you may end up damaging your tranny by doing that especially shifting into D while car is in motion

 

Thanks for the warning... you guys are probably right about the minimal gain (if any), I guess I do it just because I used to do so when driving manual.

I do it only when situation permits though, e.g. I know the traffic light won't turn green for a while.

 

While it is tempting to use N for coasting, there is a generally accepted theory that coasting in N will reduce the fluid flow in the transmission and create hot spots that can cause a complete failure of the transmission. It might be more than a theory -- I don't know. I do know that at least one person has attributed his transmission failure to this practice.

 

On a Manual Transmission vehicle, its perfectly acceptable to coast in neutral but in a AT, it can be detramental. Besides ecu doesn't deliver little to no fuel when there is no load on the engine.