[quote=mamskas;246393]To begin, Toyota does not recommend neutral coasting. That written, I tried it today and met with good success./quote]

Pulse and Glide originated with the hypermilers trying to get more mpg out of their conventional cars, and primarily in competitions, not routine day to day driving.

You may be interested in a graduate student paper on the subject. Link is here:

Acceleration and Coast Strategy

It is kind of hard to read, and I need to give it a second try. However my first effort came to the conclusion pulse and glide improved mileage about 90% in conventional vehicles an 0-10% in hybrids. Unfortunately many think what works in a conventional vehicle also works in a hybrid. Not always true.

In reality a hybrid already does the pulse and glide strategy but in a bit different way. It loads up the engine to make it more efficient and stores excess in the battery. Then during "glide" it either assists the ICE with electric power, or runs on electric power alone. That is why there is no huge (if any) benefit in using it in a hybrid.

The real coast of a hybrid is an issue discussed in the paper. The problem is that there is no real coast with the e-CVT that Toyota uses. Even in neutral the engine spins if you are going over a certain speed. All Neutral does is cut the electrical connections to the electric motor generators. That of course wastes energy, as there is friction in the ICE even if no fuel is going to it. A conventional engine can stop the ICE by use of a clutch or a real neutral in a manual transmission.

I think in the end the most effective coast in a hybrid may be the "manual neutral". When you are slowing down watch the very left gauge. When the needle goes down from the zero position you are charging the battery. It happens when you take your foot off the "gas", even without touching the brake. A manual neutral position leaves the selector in Drive, but you feather the gas to keep the indicator right at the zero position. This lets the ICE stop if you are going slow enough, and also prevents any drag from the generators. I think it is as close as you can to simulating a real neutral.

All this said, I think the practice is unsafe and unpractical. I would never do it other than to have fun in an area out of the traffic.

 

Thanks Ron for the link. I looked it over and read a few parts of it and did examine most of the graphs which were very interesting. They came up with 40 mph being about maximum efficiency for the engine. With my TCH I see that 40 and 45 mph work about the same instant mpg using the cruise at both speeds.

P&G or pulse and glide is something that won't work with the hybrid. I tired it a few times in the '07 TCH I use to have and the acceleration back up to speed erased any gliding (coasting) I did.

Why pulse and glide in a hybrid, that's what a hybrid does at a steady speed. The engine propels the car along at a constant speed, shuts off then the traction battery takes over till it gets low, a short recharge then the cycle starts over again.

Sorry, I see you said about the same thing in your post before mine.

I learned the coasting technique back when I was in my late 20's. I didn't exactly pulse and glide, but instead did my coast with the engine idling to improve my mpg. I figure driving downhill was lots better with the engine idling in neural than with the engine up at 3000 rpm (higher engine friction) while driving along at 60 mph. my cars back then were usually manual shift.

I have never owned a car that coast as far or as easy as the '07 TCH and now the '12 TCH. I have various places I can coast a good ways. One is on the 4-lane divided highway to our turnoff. Another is down in front of a very long park from 35 mph to a red light. Another in town is from 40 mph down to a red light stop. I do put the selector back in drive to do a full but slow stop when or if needed.

My favorite is a small level bridge 1/2 mile before our turnoff from the 4 lane highway to the 2 mile country road to our house. Driving along at 40 I pull the cruise lever about 200 feet before the bridge. I see the EV light come on (engine stopped, I could see the rpm drop to zero on the scan gauge) as the car is now in the EV mode. I move the lever to neutral by the end of the short bridge and can now coast 2727 feet to our turnoff which is almost 100 feet over 1/2 mile. This is dead stick, no battery power or engine is used here while I do that coasting. I say that, and at night I do have the headlights on and the heater running on low fan speed.

I may be wrong but to me the engine is not connected due to the small clutch between the power split device and the engine when I coast in neutral. It's shows as blue in the graph shown in the link you included. If it is connected when I coast in neutral it's the least friction I have ever seen in my life and how to they remove all the compression when coasting. I do now about the fuel shut-off when coasting in drive to save fuel.

I say again, I never seen a car coast like the TCH which reminds me more of coasting on a bicycle when I was a teenager.

I can tell in the TCH when coasting down from some experimenting at 60 mph in neutral with the EV light on. Once the car slows down to 40 mph it seems to coast along much easier and goes farther around 40 to 30 mph. Below that I usually go back to drive to apply the brakes if needed.

The times I coast has helped me maintain some mpg here during the cold weather.
I have dropped about 11 mpg from my 60 mpg record tank down to 49 mpg at less than a half tank to go. No doubt the mpg may go lower as the temps here is 35 degrees for the high today. We hit 5 degrees here this morning at 5 am.

 

To the best of my knowledge there is no clutch in the TCH (or the Prius). What they do have is a torsional shock absorber. It has some springs and looks a bit like a clutch, but does not function as a clutch. All it does is absorb some of the pulses of the pistons firing to make for a smoother drive.

 

Your right, during the first few minutes of this you tube video, explains it in detail. I had seen a similar PSD video a while back and the word clutch stuck in my mine.

This video is easier to understand than the one I remember seeing a year ago.

If you watch the start of this video it's hard to not watch it all which is very informative. Click the small square in the lower right of the video for full-screen.

 

Thank you for the link to the video. I've watched it once and saved it for future reference. It clearly shows the flywheel damper device, which is not a clutch.

The video does raise some questions that I have never fully answered. In the video the demonstrator seems to lump the Camry 2007-11 transaxle which I believe is model number P311, in with the Camry 2012, which I believe is P314. To date I have not been able to find any specific detail on how the P314 differs. The sales promotional material says that bearing friction has been reduced, and efficiency improved. But how?

The Green Car Congress 2012 Camry review indicates much more extensive changes. A quote:

"The 2012 Camry Hybrid features an all new hybrid transaxle. Like all Toyota hybrid transaxles, it is a series-parallel design with two motors: MG1, which primarily acts as an engine starter, a generator, and a motor to modulate the gearing ratio of the engine; and MG2, which primarily functions as the vehicle's traction motor, as well as a generator during regenerative braking. Both motors are driven by three-phase current up to 650V AC. In the new transaxle, which has less electrical and mechanical losses than its predecessor, peak MG1 speed remains high at 13,000 RPM. However, peak MG2 speed is 4,500 rpm, down from about 14,000 RPM in the first-generation Camry. This reverses a trend in Toyota transaxles toward higher peak motor speeds."

This would indicate that the P314 transaxle has eliminated the second planetary gear reduction set. In other words it is more similar to the original Prius design except that it uses a gear as the final drive instead of a chain. That is a very major design change, and if correct the P314 is very different than the P311 design. That said, I have not been able to confirm from any independent source that the Green Car Congress information is correct. No Toyota site that I have found gives that kind of detail.

There are parts of a paper on the P314 that I have found on the internet that gives some details of the changes in the P314. There is no hint of any motor speed changes, or of elimination of the second planetary gear reduction. In fact I think I can still see it in the complex drawing they have provided.

It is clear one of the changes was a reduction in weight primarily of the casing. And, noise increase as a result was a concern. With the criticisms one sees from time to time about the whine of the 2012 TCH, perhaps they were not as successful in containing noise in the new lightweight casing, as they are claiming.

I am starting to think unless there is another successor to the P314 that we don't know about the Green Congress report is flat out wrong about the details of the 2012 TCH transaxle.

 

Best I can tell is the 2011 TCH was 187 total hp, 147 hp for the engine that leaves 40 hp for the EV mode.

The 2012 TCH is 200 total hp, 156 hp for the engine which leaves 44 hp for the EV mode.

Ron, your way ahead of me on digging into the PSD and MG1 & MG2 details.

Best I could do is to came up with this simple theory.

So even though they slows MG2 down from 14K to 4500 rpm they still pick up 4 more hp for the EV mode. The loss of 9500 rpm would be lots less friction on the gears and possible slightly larger bearings, plus the new larger MG2 design puts out 4 more hp.

I could be wrong, the 4 more hp could be part from MG1. I read MG1 is used mostly as a generator including to back the car up in reverse and as the engine starter.

I read on your link how toyota upped the '12 TCH method of insulation big time around the dash are. This could be to help isolate engine noise, but could also be trying to muffle the slightly louder wine from MG2 during braking.

Here are some '12 TCH insulation details from the side you provided.

A dash outer silencer uses an air layer between the dash panel and sound absorbing felt. An inner silencing layer uses soft and hard felts to block a wide range of low-to-high frequencies. Damping-coating thickness and application areas have been optimized for reduced floor-panel vibration and noise penetration through the floor, and a new type of carpet helps eliminates noise. Silencer panels installed in the rear-wheel housings, and new sound-absorbing materials added to the trunk’s interior side trim further reduce road noise from the tires and wheel housings.

 

It's ok haroldo, I enjoy reading your comments, even the ones about me. lol

You must be thinking of all 4-lane divided highways at a 70 mph speed limit. This one is also 70 toward El Paso. I only drive the posted 55 mph headed north on the 4-lane divided highway the 8 miles to Alamogordo, NM. I drive 40 mph to town which is 15 mph below the speed limit.

In town the 4-lane main drag is posted at 45 mph. I drive 40 mph though that area. Next to a mile long park the speed drops to 40, I do 37 mph though that area. The heavier business area of town the limit drops to 35 and I usually drive at 30 unless someone in a hurry is pushing me, then I speed up to the 35 speed limit.

Driving like this gives me those 54, 57 and 60 mpg readings at the end of each tank of gas. I could not begin to do this in any large city like where you live.

I do flash once any car or truck I see approaching from the rear 300 feet or more behind me so they can easily pass. Driving at 40 mph I enjoy not hearing any wind noise that's very apparent to me at speeds of 60 mph.

The other day I mentioned my age to my wife and she said, I was a year older than what I thought I was. That usually would not bother me, but when your already a old man, go figure.

 

Better watch that flashing Jimmy, you can get arrested for that unless you move to San Francisco......

 

That's a good one! lol

 

I've done the same thing. Here is a pic of the speedo at ~52 mph in EV mode.