Auto in N question - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

Doofus McFancypants · 08-20-2008, 07:46 AM

Hey All.
Just a quick update. I have not had a lot of time to play with wife's car - was in a conferance all last week in Upstate NY.

But i have managed to do a little with it. No SC info - only car's Tach.
@ startup (cold) the RPM hover above 1000 for a while then settle under 1K
@ startup (hot) the RPM touch above 1000 then quickly drop under 1k

driving at speed - Shift to N - the RPM do drop very slowly but will fall back to under 1K if long enough coast ( still at speed)
Neutral coast to a light - the RPM seems to drop faster then just a long N coast.

Conclusions - the engine does seem to be watching the transmissions RPM and keeping things close. As i noted before the engine does not have a Fuel Cut off - so for me it seems that coasting in N is the best way to go ( about the same MPG from SC - but longer coasts)

Thanks for the input - If / when i get the SG in her car - i can update with GPH info as well.

Steve

IndyIan · 08-20-2008, 08:42 AM

My Neon idles slightly higher coasting in neutral but not very much, 900-1000rpm vs. 600-800 rpm idling. It does coast alot farther in neutral than drive and uses less fuel doing so. Even coasting to a stop it uses less fuel coasting in neutral than drive.
How does the PT cruiser like shifting back to drive? Hopefully slips into top gear without a fuss.
Ian

Doofus McFancypants · 08-20-2008, 08:48 AM

The times i have shifted back - never an issue - no noise - not "bumbs" no blips - "Smooth as Silk" - which also makes me believe the engine is "following" the transmission RPM to some digree.

I am going to post this on a PT Cruiser forum to make sure thers are doing this as well.

Steve

mush3gan · 08-20-2008, 03:10 PM

does lower RPM equate to higher MPG?

when i'm driving on the road and shift to N, my RPM drops
but if i'm idling at a stop and shift to N, my RPM goes up

kaveman12 · 08-20-2008, 03:21 PM

Quote:

Originally Posted by mush3gan

does lower RPM equate to higher MPG?

Not always. Many cars cutoff the injectors when coasting and allow the wheels to turn the engine at say 2000 RPM while using no fuel, but if at the same speed you shift to neutral and disconnect the wheels from the motor you still have to use fuel to keep the engine running at about 750 RPM. In this case you are actually using more fuel at a lower RPM.

Thats a special case though, in most instances lower RPM=higher MPG