Pulse & Glide vs Cruise Control - a study

You may want to check some of the data but this is my best guess at plotting it:

Make sure your data shows: min<average<max -> MPG. For plotting, use the average mph and the Y-axis should be MPG and on the right, the min and max mph.

This data is consistent with what I'm seeing:


Good job!

Bob Wilson

 

great I have been using the CC per recomendations by another member here, I guess I'm going to keep on doing it

P&g works better at slower speeds tho

 

Good testing Doc. I need to do something like this myself.

The thing about P&G is it is very skill and technique dependent. We should be wary of claiming a definite results without further testing. Because of the skill and technique variables, I don't think we have a valid result yet. Cruise Contral on the other hand, takes the human element out of the equation. There may be differences car to car, but at least the human variances are negligible.

If we had someone like DiamonLarry run P&G over the same route, we may get quite a different result. He and others are pulling out some astonishing numbers

I know JimboK was thinking of coming up with a set of parametes and having several people replicate the exact detailed set of circumstances to validate the results. I don't know what happened to that idea.

If we get a group of people all trying the same parameters, I would like to participate.

 

It's still very much alive. I've just been waiting for a weekend day off with decent weather. It seems like it's been cool or rainy every day off since spring began.

My goal is not only to compare P&G to steady-state, but also to compare two different P&G methods with one another. Finally, I want to compare various P&G acceleration rates with one another.

For the benefit of Willie and other interested parties, here's some background. Bob Wilson and I first started talking about comparison testing last spring in this thread and on GreenHybrid. You'll see in the GH thread that I had a number of practical problems that cropped up during my testing. By the time I finally got into a rhythm, so to speak, I had to unexpectedly replace my tires, pretty much rendering invalid any comparisons of subsequent results to those already obtained. Between that, hot weather (I didn't want to run the AC for the tests); a house hunt, purchase, and move in the fall; and winter, I suspended testing. I'm now ready to begin anew.

The test course and its traffic were part of my problem. (It is linked in either thread if you want to see it.) I think I found a new one a few weeks ago. It's 45 MPH, but traffic seems very light on weekends; it's in the area of some industry stuck in the middle of an otherwise rural area. And it's 4 lanes virtually the whole distance. Net elevation change and the difference between high and low points are probably pretty comparable to the old route, but overall it is flatter, with the changes less frequent and more gradual. From end to end it is 3 miles, so I figure to use about 2.5 of it for actual testing -- about the same as the old course. I will run up and back 3 times for each method tested, recording the MPG after each one-way leg. I will average the 6 numbers for the final result.

As you can see from his test protocol, Bob compared P&G at a range of 25-43 MPH with CC at an equivalent average speed. His P&G technique is different than most of ours (to save space here, I'll just refer you to the links for a description). At a minimum, I want to repeat his test and then compare both results to a more conventional P&G. I want to do the same at other speeds and ranges between 25 & 40 MPH.

As you can imagine, this will be time consuming. So I envision multiple phases of testing spanning multiple days. What I describe above will be phase 1 and will be to determine the best overall method. If P&G proves superior, phase 2 will be conventional P&G in the following ranges:

• 15-25 MPH
• 15-30 MPH
• 15-35 MPH
• 20-30 MPH
• 20-35 MPH

From those results I will pick the top two or three speed ranges, and then during phase 3 will use those to compare various acceleration rates as defined by ICE speed -- say, 1400, 1800, & 2200. Not sure yet which rates I'll use.

We have to be careful to account for confounding variables. Weather in particular can be problematic. First, I want to test on a day with little or wind. It might seem that with an up and back test route, the wind's effect would balance out. But it doesn't. A tailwind coming from your 6 o'clock gives the best push, as you would expect. But wind coming from about 33 degrees off your front is worse than a dead-on headwind. And 90 degree cross winds from either direction hurt fuel economy. We have to control or adjust for temperature changes throughout the day and from one day to the next. Etc., etc. So to make adjustments for variables, I will use Wayne Brown's Prius MPG Simulator. I will have my laptop computer with mobile broadband on board to regularly check temperature and wind conditions throughout the test, and use simulator results to adjust for changes.

Evan mentions state of charge. Bob also mentions its potential effect in his PC post. He didn't control for it in his tests, but he suggests force charging to a defined level before each test to eliminate yet another confounder. I might do this before the steady-state cruise control segments. CC routinely has the car running on battery power alone, and the beginning of one test segment could show a substantially different SOC than the next. I could also do it at the beginning of each overall P&G test, though I don't think it will be necessary for each individual segment -- a properly executed P&G is designed to keep you out of the battery, of course. I can use CAN-View to precisely monitor SOC, and I can either force charge or run a short segment of EV to nudge it up or down to the desired level.

Willie, I agree with Evan about reporting your methodology in as much detail as possible. In my high-speed fuel economy study, I reported methodology and results in a format consistent with what I am accustomed to in medical journals (as you are too, I'm sure). Whether it fits the format of a technical paper like the engineering guys might author, I don't know. It works for me, and it documents the scientific method applied to the topic of interest.

 

Doc Willie has contacted me about present the info at Hybridfest. I think this would be a good topic for the Sunday morning member-only technical sessions on at the hotel. Especially if others have info to present as well.
What do others think?

 

When I performed my P&G experiments, the initial ones used cruise control to handle the acceleration and "N" to handle the glide. I did everything I could to minimize human variables.

My only other suggestion is to run the car for at least 30 minutes at speeds above 42 mph. This ensures the engine, transaxle and tires are uniformly warmed up and the battery should be pretty much at 60%. Also, I use randomly chosen runs with a spreadsheet random number generator. Then I run multiple tests recording the results.

I've posted my results before (use search function) but the synopsis:

• P&G (as I've described) requires a significant dV >= 15 mph at speeds under 42 mph
• P&G around the maximum range speed, 18-20 mph, is measurably worse than steady speed of 18-20 mph

There may be other techniques than accelerate under cruise control and glide using "N". But I haven't found any that are documented as independent of the individual driver. Until I have a programmable throttle driven by Graham scanner values, I won't have a way to test these other approaches.

Bob Wilson

 

OK... Jumping on board here.

I usually don't do a 15 mph dV. My largest dV is about 22 kph. Dropping below 30 kph gets the gearing a bit to low for my likes (I know eCVT). In competition, I believe I slacked my window to a bottom out at 25 kph, but I probably unconsciously wiggled it back up to 30 kph pulse entry.

My smallest dV is usually around 4 kph. As mentioned before pulse RPM, IGN, and TPS should all be noted. dSoC is also critical.

As a side note I've emailed Texas World Speedway to see about securing some track time. I know they rent it out to speed freaks who want to zip around at 120 without fear of a ticket.

11011011

 

I thought the range in speeds was a bit wide also. P&G is best for rolling hills, from what I've read, CC better for the flats. I want to do some tests at some point based on terrain, when I get the chance (and nice warm weather so I know I'll actually glide).

 

TWS is interested if anyone wants to fly down to Texas. They haven't quoted rates yet. They are still just interested in finding out more about what our needs are. I have a MMH and a Prius. I can probably muster up a TCH and possibly an Insight if we wanted a broader testing. I could talk to some of the local dealers if anyone has some other models they think might be interesting.

I'll report back with the rates. Pointless unless the rates are reasonable.

TWS: Texas World Speedway

11011011

 

I have been playing around with deltas of ~5 mph or so and they seem to work best so far. Like Jim, I'm having trouble finding good weather on days that I'm off work. Most of the roads around my area have a stop sign every mile with a few areas of 2-5 miles between stops. On the 1-mile stretches, I usually pulse to 35-40 mph(sometimes maybe only 30) and can glide to the next stop. The only time I like to go below 30 mph is when I know a stop is coming up. As for what little experimentation I've done with cc, I can't even come close to the FE numbers I get with P&G even on the flats. I just got back from my mom's(5.1 miles) and was able to pull into my driveway with 124 mpg showing on my SG2 by P&G'ing to a high of 40 mph and gliding to as low as 30 unless I was coming to a stop sign. A week ago this Friday, I had 132 mpg on a 5.2 mile trip from my Church to home. SoC was at 6 bars from beginning to end. Also, my SG2 is currently reporting my tank at 75.8 after 449.1 miles. Just in case you're wondering about the SG's calibration, my last fill showed at 5.85 gallons and the pump showed 5.9 gallons. Sorry for the rambling.:redface:

 

Dan and Larry: What are your typical acceleration rates as measured by RPM?

 

I will have to start keeping a closer eye on the rpm's but, it seems to me that 1700 rpm's is on the high side. Probably closer to the 1500 range. I'll watch it tomorrow.

 

That's more of a battery maintenance question than a P&G question. If I'm planning an EV stretch in the next 5 miles I pulse slow (1400 RPM). If I need to bleed off some charge I'll EV. I will also use low speed pulses to heat up the engine if needed. On a deserted road I will usually pulse in the high 14k to low 16k range. Most of the time I'm chasing IGN. I always want to pulse with IGN at either 14 or 15 except in the cases noted above. Sometimes IGN will stick at 17 and you have to lure it down by dropping RPM way low (high 13k).

In the end the RPM comes into the strategy part of the drive. Just depends on what I'm gonna need in the next 10 miles. When I did my HF run I had it pegged at 1600 RPM. I'd consider 1590 to 1610 optimal assuming a 30 kph to 54 kph window. To me it's pointless to go over 54 kph if your playing for high score.

11011011

 

I really like the idea! Anyone wanna' volunteer to plan this?
I have two hotel conference rooms (1 larger, one smaller) rented for Sunday morning from 8-noon and I'll take care of getting them set up.

I just need someone to "take the bull by the horns" and line up the willing participants for the panel, as well as a moderator (in case things get too unruly. )

PM me email, or give me a call.

 

Doc Willie is still offering to do his presentation.
Does anyone else want to get in on being a part of a panel discussion on this Sunday morning at the hotel?
PM me ASAP if you are.