I did a small test tonight to see what effects P&G and B&G would have on FE.
Disclaimer: I only did each test once, and it was a small 3.8 mile round trip.
Results: B&G was actually worse than P&G, which was not expected. I think because this is a typical backroad setting, the burn and glide method was not as good as it could be due to curves and elevation changes. I would expect that on flat highway B&G would be better, but perhaps at lower speeds it is not as effective. Best glide was the best for FE, but also took the longest. This was similar to the P&G run, but acceleration was careful with the terrain instead of strictly based on accelerating when speed got to 35MPH. The brakes were only used at the halfway point where I turned around, and at the very end, but all instances were similarly light.
EDIT: Road description: This stretch of road has 2 curves which are hard to go around above 40mph. Elevation of inclines does not change more than 10-15ft, and gently rolls up and down, with only one small section which I would say is steeper. It is generally a road that speeds above 45mph would be unsafe, except for one stretch of about half a mile.
I plan to test this route often and see if I can increase the average MPG to produce new best runs.
B&G was actually worse than P&G, which was not expected.
It's what I would have expected! 2 issues: losses from friction (e.g. engine & transaxle) increase with the square of RPM. Also 4000 RPM min. is almost certain to be well beyond the most efficient engine RPM range (BFSC zone) for acceleration.
I'm not sure I get the difference between "best glide" and P&G. Can you explain it differently?
Hmm I'll try agian
The pulse and glide run went like this: accelerate with rpms around 2000 until the speed reaches 45mph, then glide in N until speed reaches 35mph. Sometimes this would mean accelerating up a slight incline for 10 seconds, or sometimes it would be downhill for 5, since I was only shifting when the specific speed was reached. The "best glide" run was more complicated. I would accelerate in areas that were more or less flat, trying to avoid acceleration on inclines when possible. I think it came out better because I could speed up before an incline, glide up it while loosing speed, then resume acceleration to keep the speed above 35 at all times, but under 45 at all times. I hope that's a little more clear.
I'm adding a description of the road to the original post.
Purpose of the test:
The focus of this test is log runs on a specific route that I can attempt maximum fuel economy. I plan on adding to this data each time that I make this trip.
There is a correlation between average speed and fuel economy. The highest averages yield better fuel economy, which I think is because the engine is running more efficiently at higher speeds. For slower runs, the acceleration was low, while the two fastest runs had shifted into a higher gear which is why the mileage increased. Run 4 was from the previous day, in very wet roads. Runs 5-9 were on a less wet road. Run 7 was an interesting one, because I was stuck behind a truck on the 2nd half of the run, but afforded more gliding around 20-25mph.
Ideas on improvement:
1) I still have not perfected the speeds at which to roll exactly to the starting point and halfway point. If I make sure to stop the acceleration at the right point, I could effectively roll until the speed is almost zero to these points.
2) If I pay careful attention to the exact speeds that I am able to shift up, I could find a sweet spot for speed. For example: If it shifts to 3rd gear at 35mph, but I'm driving 40mph in a higher engine speed, more energy is lost.
3) I need to make each acceleration have more benefit. At the slower speed runs, the accelerations were very low and less effective than on the higher speed runs where the engine speed was 300-500rpm faster.
4) I think the average speed could rise a little more to benefit fuel economy, but due to the curves of the road it probably cannot increase to more than around 40mph.
I have noticed that at the half-tank mark, I'm 15-20 miles ahead of where I usually hit it, and I've been riding it pretty hard this week (bad idea with the state of my clutch, but the damn thing needs to rev to make any power!). What I can't speak for, though, is that I did also have to re-install my intake manifold last weekend, and had some vacuum leak problems. I don't know if the better economy, therefore, is because I licked a chronic problem I didn't know I had, or if this car possibly responds to burn better than pulse...
'67 Mustang - out of commission after an accident
'00 Echo - DD
'11 Kia Rio - Wife's DD
'09 Harley Nightster - 48mpg and 1/4 miles in the 12's