[Eastwood]

Hi everyone. In the quest for higher mileage (winter is almost over! :yahoo, I've just recently come upon the pulse and glide technique. I have a 1.4L Turbo. Here's my question:

Am I going to hurt my engine by switching from drive to neutral and back to drive while the car is moving?

I've tried it a few times and I haven't been aware of any strange sounds and it doesn't feel/sound like the car is working at all to re-engage the engine after being in neutral at any speed I've tried 0 - 65. Just curious if I'm missing anything.

Also, as far as safety and reverse are concerned, you cannot move the shifter into reverse unless you push the button on the shifter. You can switch from drive to neutral and the "manual" mode without using the button.

And yes, please use the pulse and glide technique responsibly so as to not annoy your fellow drivers on the road and to make sure you can safely accelerate/brake/maneuver as needed.

 

[Sunline Fan]

I've heard this isn't a good idea with the automatic.

Putting it in neutral won't allow you to utilize the DFCO mode (Deceleration fuel cut off). Granted you could roll farther in neutral than with the engine slowing you down.

 

[jblackburn]

I wouldn't...unless you are rolling to a complete stop (in which case the transmission drops into neutral in the Cruze anyway). Dropping the transmission back into "drive" where it has to match the RPM the tires are spinning back to the engine will wear out the clutches.

Same concept as a teenager flooring the gas in neutral and slamming it into drive...though much less abusive.

 

[obermd]

Put your car into manual mode and do the P&G there. Full automatic decelerates too fast to get an effective glide. Leaving the car in gear will allow you to take advantage of DFCO where you'll be gliding along without using any fuel. (The CDT also implements DFCO.) You want to start your glides at a minimum of 1700 RPM to give the ECU a chance to detect the glide and enter DFCO. This takes about 4 seconds with the LT and LTZ automatics.

One place I have found P&G to be really effective is in rush hour where you accelerate and then decelerate. As long as you can avoid using your brakes you can take advantage of P&G techniques.

 

[Eastwood]

Thanks for all the great info, everyone! Especially the whys of all of it. And for the acronym expansions. There are so many acronyms used here that things can be a little hard to follow occasionally Much appreciated!

I'll start gliding in manual from now on.

 

[sx sonic]

Does anyone have confirmation of when and what criteria the automatic will go into DFCO? For instance on the manuals there is a threshold RPM, on mine it won't kick on unless RPMs are above 1,500RPM and once in DFCO it stays active until 1k RPM, 6th gear is sometimes slow to kick into fuel cut.

BTW Eastwood, cheers on working towards hypermiling! it can become an addicting game for awhile, just remember to always be considerate of other drivers, which is sounds like you will be.

 

[obermd]

For the Lordstown Cruze (gas and diesel) DFCO will start anytime you let off the throttle (or the cruise control lets off the throttle) and the engine speed remains above 1500 RPM for x seconds. In the manuals, x is roughly 2. In the automatics x is roughly 4. As far as I can tell the car will enter DFCO at any engine speed from 1500 RPM to the red line. DFCO will turn off when the throttle is engaged (pedal or cruise), the clutch is pushed in, or the engine speed drops below 1300 RPM. The automatic transmission will remain in DFCO during downshifts. The manuals will go right back into DFCO about a second after you let the clutch out as long as you have not touched the throttle and the end of shift engine speed is above 1500 RPM (after the ~1 second delay).

If you have been hard on the throttle it takes longer for the car to enter DFCO. How much longer I don't know. You can see DFCO engage by switching your car to metric and watching for 0.0 L/100KM. If you're paying attention you will also feel the car enter and exit DFCO as very small power surges. On cruise control the car can enter and exit DFCO about once a second, which has resulted in some people complaining they feel their car is surging when descending long moderate hills.

DFCO works in all forward gears. I have managed to get my ECO MT to register 0L/100KM in all six forward gears. I haven't checked in reverse. Also DFCO will not operate when the engine is still in open loop mode during initial warm up. This is one of the reasons winter fuel economy takes a nose dive.