Pulse and Glide with an auto
 

I just started trying out "the pulse and glide" with my car. I go up to 50 or 55 and then put the car into neutral (no shuting off the engine) drift down to 35(so I can still keep the car in final gear) . Do a small rev match and put the car in Drive. I don't think I am going o kill my tranny by doing this...right? So does this have a mpg gain or is it more troble then its worth.

It's a good question.

I once did a little experiment and calculated that using P&G between 70 and 90 km/h, leaving the engine running through the glides netted a theoretical gain of about 8% in my car (5-speed) over steady-speed FE at 80 km/h.

https://metrompg.com/posts/pulse-and-glide.htm

It's theoretical because: I didn't average the comparisons over a set distance, I was just looking at instantaneous readings (subject to more error).

So I'd take that with a BIG grain of salt.

If I had to bet, I'd wager it's pretty close to being a wash, since the automatic isn't as efficient in the pulse as a manual.

Edit: only way to know for sure is to do a little experiment. Where's your MID? :)

I am looking for a car first. I will get a computer for that one. ok.

Right! Forgot about the car search.

I tried this with mine but can't locate the data for it :confused: I abandoned it pretty quickly after a couple of runs because the FE was about 3% lower. I think with an auto the only way to be succesfull with P&G is engne off. Although METRO saw a gain with his 5 speed. Sounds like we need someone else to test it:) YMMV.

I never tried P&G before because I thought it was too much work.

So, metro do you kill your engine when you P&G?

I would say killing the engine on auto with P&G is way too much trouble (no bump starting).

YMMV=Your mileage may vary (I had to use wikipedia)

Oh yeah, I kill the engine all the time.

I've got a momentary kill switch attached to the shifter, because I make it one movement: ease off gas, push/pull the shifter into neutral (no load, so no clutch used). I let the engine drop to idle, pause another second or 2 (to let some more hot coolant flow away from the hot areas), then hold the switch with my thumb until the motor stops.

You're right: having to key off & key start definitely adds to the work.

But it's like anything else. After you do it enough, it becomes automatic and you don't really think about it while doing it.

I know that when coasting down from 65mph, leaving the car in gear results in twice as much energy lost compared to putting it in N. And as long as the rpm is under say, 1.2-1.5k, the engine will idle even if it's in gear, so given a choice between having the more drag on the car, with the engine idling in both situations, then it seems like coasting in N could increase mileage by a fraction of what the transmission losses are. Also, for an auto, I don't have to rev match, since it does that stuff itself, like shifting into a gear higher than dropping down into the gear it's supposed to be in so there's not as much of a shudder. But your tranny may be different so YMMV.

Actually, depending on what year your Saturn is, you may be able to coast in N w/ the engine off w/o messing up the bearings in the auto tranny. I'd suggest contacting Saturn and asking if you can tow your model in N.

I already know its ok to coast w/ the engine off on my car(I think i read it on this site somewere), and i do coast down hills almost daily.

I think this is a last ditch effort to get good mpg before I get a different car.

I'd bet you can pull 40+mpg out of it np compared to just cruising at ~50mph, but then again, i don't know your route, so you may have already hit the upper limit in terms of that and the average speed you want to travel at.