whats the ideal P&G cycle? best % FE increase?
 

Having finally gotten over the mental phobia of doing things different, and giving P&G a shot on a recent trip to find an eye widening improvement in fuel usage, i'm starting to get enthusiastic about this...

Assuming a person has rural roads where there's little traffic so you can get away with it, whats the theoretical ideal... get up to the max speed possible then extend the coast as long as possible? Or because of higher speed drag (it doesnt take long to coast down from 75 to 65mph, it takes forever for me to coast from 50 down to 40mph) is it diminshing returns, at least without aero modifications, to go faster than a certain amount? Where even though your starting up sooner, and not coasting as long, you still get better total mileage?


Whats a rule of thumb for the kind of fuel efficiency improvement you can experience? Lets say i'm comparing 55mph steady state to a P&G cycle which will average that same speed, should I have an improvement of 10%? 30%? Is there some handy dandy figure, like try to coast for 30 seconds, or 60 seconds, or at what shorter length of coast is P&G relatively pointless to even do..?


At some level of minor fuel efficiency improvement i'm guessing the additional wear that must happen to either starter or clutch (depending how I restart the engine) kills it, I don't think I would P&G for another 4mpg I mean... do people usually restart with the starter, or clutch, and is there any trick or benefit doing it one way vs the other? I used the clutch to restart but I became uncomfortable with the jerk back up worried I might be injuring something so it was a one time P&G experiment.

I do not have any idea on numbers. I thought of pulse and glide ten or more years ago--I thought of it as "Leapfrogging," but I stopped when I did not notice any better fuel economy, but I did not have instrumentation.

The first time that I tried it with my Ultragauge I did not see an improvement, but I was one mile higher, whatever difference that makes. After that road trip, my average MPG was coming down, so I pulsed-and-glided again, which seemed to help. I was accelerating from fifty to sixty and then coasting down, but I noticed that my instant MPG increased as I continued accelerating. It seems to peak about seventeen or eighteen at 70 MPH, although I wonder how much quicker I decelerate from higher speeds.

My last tank was 27 MPG in a Subaru Forester rated 18/24. The EPA says "20 combined," so I think that I have improved thirty-five percent, and I do not know what I have changed besides higher pulses.

I don't P&G much at all anymore but when I did I went from 55 or 60 down to 25, of course in light or no rural traffic. You'd sure think the big big HUGE gain would come from that extended time of the glide part that is under, say, 50 mph, because the aero loading is so much less per mile traveled. W
Also with peak and min speeds at that wide a spread, a huge percentage of the time was spent with the engine OFF.

I brought my stopwatch when I went to see my mother. I would accelerate to seventy, time from when I shifted to neutral to when I hit sixty, coat to fifty, accelerate to seventy again, and then time it from sixty to fifty. After doing this many times I came to these conclusions:

1. The highway is not level, just level on average.
2. My speedometer needs to be lubricated. I do not think that it was smooth enough to be accurate.

I would have needed to do a huge amount of time trials in order to average out inclination variance, but overall, I could not determine that I coasted longer from sixty to fifty than from seventy to sixty. However, I would travel eighteen percent further in the same amount of time.

I'm a bit new to the P&G method, but had outstanding performance with it this past weekend on the highway. Traffic was stop and go for about 5 miles, up and down hills. Seldom got up to 20-30 mph. I can usually get 43-47 mpg on the interstate driving 70 mph, but I got 50 mpg in the rush hour traffic. I would have expected to get around 30-40 mpg in that situation.

I did not cause any issues for anybody behind me, and may have helped smooth the flow with my gradual slow downs.

I don't bother with shutting off the engine. I tried it on one hill one time, then did a bump start, which cost me 3 mph (maybe better technique could reduce that). I don't want to use the starter excessively either.

I started adding a bit of pulse and glide to my regular commute and I am seeing a difference.

I don't P&G on anything up hill. Not much on level roads either. Mostly do it when there is a slight down slope that is not enough to simply cost.

A must is a gauge to show your instant and average mpg at the same time. I like my Scangauge II, I also monitor my speed and Throttle Position Sensor (TPS) at the same time. It's easier to have everything in one place, and not have to look down at the speedometer.

P&G is proven to work very well at lower speeds, pay off drops as speed increases. The length of the pulse or of the glide will vary depending on the given conditions. I prefer to not go to extremes with it to avoid issues with other drivers. The pulse should usually be fairly strong, but I think it varies from one engine to an other. Some are going to be most efficient at near full throttle, but other cars perform really well at low rpm and light throttle.

My P&G cycle needs very aggressive accelerations. If i just keep that, then it wont matter that much how long i EOC.
I occasionally forget to accelerate aggressively, and the P&G actually decreases FE.
My car is made for accelerations :D

you need a bsfc chart to determine the best pg practice.