Use of "N" for coasting

"The modern cone system was developed by Porsche and introduced in the 1952 Porsche 356; cone synchronizers were called "Porsche-type" for many years after this. In the early 1950s only the second-third shift was synchromesh in most cars, requiring only a single synchro and a simple linkage; drivers' manuals in cars suggested that if the driver needed to shift from second to first, it was best to come to a complete stop then shift into first and start up again. With continuing sophistication of mechanical development, however, full synchromesh transmissions with three speeds, then four speeds, and then five speeds, became universal by the 1980s"

Albins off Road Gears :: Synchromesh and Dog Engagement Gearsets... What are the differences? :: Transaxle :: Transfer Gears :: Gear Design :: Performance Gears :: Gearsets :: Dog Gears :: Performance Transaxle :: Sequential Transaxle

So yes, many laws were written before the 1980s.

I learned on a 1962 Ford 'three on the tree', so I had synchros between second and third, but learned never to shift to first or reverse unless stopped.

 

My first car was a 1949 Ford with a three speed, with very effective synchromesh on 2nd and 3rd which was ancient history by 1949. It was absolutely no problem shifting into 2nd or 3rd at speed to restart an the engine when I had shut it off.

Double clutching into 1st took some practice but wasn't all that difficult, I did it a lot.

Here's how synchronizers were done when Ferdinand was still goose stepping for Hitler.
Ford Top Loader Three Speed Transmission Synchronizers

Ferdinands VW didn't have any synchromesh until 1951.

 

To avoid legal and technical problems but still allowing the Prius to glide in neutral,
What Toyota should do is:

As Bob and Tom's discussion suggested, they should simply set a high limit to the speed of MG1, at which point the ICE will spin up. Simply re-engage "D" automatically putting MG1 into regen when MG1 reaches this highest rev limit. Furthermore, they should also reprogram it to re-engage "D" automatically whenever the brake or gas paddle is tapped. This way at no time the car is "out of control" or without access to power. There are rare cases that you do want to further speed up the car even though it is gliding faster and faster downhill, for example, just to avoid being rear-ended by another out-of-control suddenly-accelerating Toyota from your back.

Maybe they should even rename "N" to "C" for coast or "G" for glide.

I believe these are very simple programming changes without incurring any extra material cost except for the time of the programmer, which is pocket change for Toyota.

 

I'm also wondering, if Toyota warns that "N" shouldn't be engaged while the car is moving, why did they even provide this "N" at all. If the car is stopped, it's pretty much automatically put to neutral so that no matter if the ICE is firing/spinning (as in warming up) or not, the car won't move.

There doesn't seem to be a need to have the car put to Neutral manually if neutral while moving is not allowed, both technically and legally.

 

I was under the impression that N was a requirement. If not legally, at least by industry standard.

Tom

 

It is a legal requirement
http://edocket.access.gpo.gov/cfr_2002/octqtr/pdf/49cfr571.102.pdf

 

Seems like Toyota should think ouside the box of "industry standard", 'cause the Prius is not a car anywhere near "industry standard". It is industry leading, if I may.

If it's a legal requirement, then this "law" is rediculous and obselete. You are not allowed to put your car to neutral while moving, and yet you are required to provide a neutral gear position even though you don't need it.

Let's start a revolution...nah...a petition...nah...TOYOTA, JUST DO SOMETHING

 

Ok, I just thought of a better solution. When my son drove the Prius he complaint that the brake is too responsive compared to his own conventional car that he jerks the Prius a lot while trying to just slow it down a bit, not wanting it to full stop.

This got me thinking: You know the ECO & PWR buttons are really remapping the response rate of the gas pedal? Why not do the same to the brake pedal (only for the electric regen part, leave the mechanical part as is), so that the user can remap the brake pedal to different response rate to their likings.

Furthermore, the difficulty of making it neutral glide in "D" is that when you take your foot off the gas pedal (or cancel cruise control) without touching the brake pedal, the Prius automatically trickle-regen the battery to similate an engine drag. If the amount of similated engine drag is configurable to ZERO, the problem is solved.

You'd have the gear always in "D", no need to put it to "N" at all, thus meeting legal requirements. You'd have automatic "neutral gliding" first, then trickle-regen when you tap the brake slightly, more regen if depressed more, then mechanical brake applies when floored.

Problem solved. TOYOTA, ARE YOU READING THIS?

 

Yes, wouldn't it be great if the Prius were sold with an optional "programming package" that gave us the ability to modify various system parameters.

Of course, that will never happen because most consumers are afraid of things that they might have to think about, and most manufacturers are afraid of giving consumers any control over the products they buy (fear of possible liability issues).

 

As pointed out earlier, many state prohibitions against moving in Neutral apply only downhill, not on level or uphill sections.

Also, you missed the massive Runaway Acceleration discussions months ago. Shifting to Neutral is a standard universal response to a runaway engine from whatever cause, even in a Prius. The warning in the manual concerns potential transmission damage, but there are certain situations were sacrificing the transmission is a good choice when human life in endangered.

 

I was only posting in jest. If Toyota really removes the "N" I'm sure a lot of people will be kicking and screaming.

I didn't miss that massive runaway acceleration discussions although I didn't join in. During that time I was researching what car to buy to replace my 15 year old Civic, and Prius was number 4 in my list, after Honda Insight, Mercedes B-200, and Chrysler Town & Country. The Prius beat them all INSPITE OF the massive negative publicity of those stupid runaway episodes by Mr. Sikes and Mr. Wozniak.

Am I brave, or am I BRAVE?

 

They could charge an extra 2 grand for this "programming package" to fund the legal expenses and/or possible liability responsibilities.

 

How is the Prius meeting S3.1.3?

 

Actuallly Ken@Japan, good Prius friend Hobbit, and those with the DashDAQ are well equipped to do similar measurements.

My Auto Enginuity works with my wife's ZVW30 so I'll gather some data for this model and the NHW11 for "N" hill descents. I'll be looking at rpm and fuel consumption (both MAF and ICE rpm-injector timing) as a function of hill descending speed. This is just another part of mapping the vehicle performance profile.

I can not guarantee the equivalent data for pedal 'feathering.' I want to capture MG1 metrics (MG1 rpm and torque) to understand the total energy flow. Without understanding what it takes to 'spin' the ICE, we would be ignorant of an undefined power flow. Right now, Auto Enginuity has some problems with MG1 metrics although I can use my Graham miniscanner for the NHW11.

Either approach works, I tend to use "N" only on shallow grades during warm-up simply because it doesn't require instrumentation and has a measurable effect. I don't like high-speed "N" because without instrumentation, we're 'tickling the tiger'. Still, I don't begrudge others willing to experiment with their $25,000 car. <grins>

Bob Wilson

 

I have never managed to put the Prius in a driving mode (D or R) while it was not started. The Prius always starts in Park mode which seems ok with 3.1.3.

 

Reading this thread one question comes to my mind.

When the Engine is free-wheeling, that is rotating just to keep MG1 speed in check, are exhaust valves kept open? If this can be done at least losses in compressing air and letting it out can be prevented. Only the frictional losses will remain.

I feel losses in compression (which are really what are mainly used in Engine brakes 'B') are much more than frictional losses.

I know keeping the exhaust valves open all time would mess up with valve timing. But I do not feel that is very hard to achieve in today's technology. My feeling is, if exhaust valves are kept open when engine is freewheeling, it could easily contribute couple of MPG.

 

Good question, I hadn't thought of that one.

Buried in this document
http://edocket.access.gpo.gov/2003/pdf/03-12051.pdf
lies your answer.

A part of the article before the Toyota/Honda approval is interesting. Some aftermarket, company with a hair brained scheme for automatic stop-restart was denied approval because it wasn't safe, so NHSTA was on the ball.

 

MG1 clearly is 'the starter' in a Prius and it clearly is 'operative' when in R and D.

Luckily XS650 knows our answer. They do NOT meet the letter of S3.1.3, but the NHSTA has ruled that they meet the intent.

 

Keeping the valves open increases losses. With the valves closed you only have frictional losses from the engine components. With the valves open you also have pumping losses from forcing air through the engine.

Compression does not in and of itself increase losses. The energy used to compress the gas during the compression stroke is returned during the expansion stroke. It's a net zero operation.

Presumably compression may increase the drag from the piston rings, but pumping losses are much worse.

Tom