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Discussion Starter #1
The New 2006 Civic has an EV-only mode.

How is that accomplished, and can the same technique be used on the insight?
 

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Essetially the electric mode deactivates the valves and turns the pistons into air spings. In this mode it takes very little energy to turn over the gasoline engine. Regeneration efficiency goes up and friction goes down to the point where most of the energy from the electric engine gets to the wheels. The practical application of this system required a whole lot of research, so we won't see it on the present Insight.
 

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No the Insight does not have it. Really it's pretty limited, but happens where it's probably the most beneficial. You have to be doing 10mph already at least and moving along at a constant speed and light throttle. They say it will work up to 35mph, but I've found it's really only good for 30mph on flat ground. Sometimes the car will willingly use it, sometimes you have to try and make it do it by letting off the gas until your in that "valves off" mode and just coasting then very slightly ease your foot back in to it at which point it will show between 1 and 4 bars of assist and the mpg gauge will be pegged at 100mpg. Any more than 4 bars of assist (keep in mind 1 bar on the civic is at least 2 on the Insight) and it kicks the engine back in.
 

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Discussion Starter #6
Rick said:
You have to be doing 10mph already at least and moving along at a constant speed and light throttle.
That seems a lot of engineering work/research plus mechanical complexity for minimal benefit (EV between 10 and 30).

So if I'm driving a New Civic Hybrid, I can't use electric-only starts like the Prius does?
 

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The Prius ability to crawl along in electric mode is a inherent function of Synergy drive, and not necessarily an advantage for the Prius overall.

What Synergy drive gains at a crawling pace it loses at highway speeds as it is more lossy than a conventional transmission. The Prius manages to eek out 1 or 2 percent greater overall gas mileage in real world conditions, and this is probably due to storing the engine coolant for preheating the engine.

Not only is the Prius a more expensive car to purchase, but it has other disadvantages in my opinion.

Synergy drive is inherently more complex technically, making it difficult to service if there is a problem, without specialized training.

The Synegy system is inherently more expensive, due to the requirement for two electric motors having a combined electrical power output about 3 times that of the IMA motor.

The Synergy batteries are of necessity more expensive and larger.

The ICE is smaller making it less powerful in mountainous driving or pulling a trailer. (OK I know you aren't supposed to pull a trailer) ;)

Unlike IMA assist, if the electronics fails for the Synergy drive system the gasoline motor stops.

Likely the next generation of Prius will outshine the Civic, but they are not there yet IMHO. The Prius advantage at that time may be due more to using silicon carbide switching transistors and lithium batteries than an inherent advantage of Synergy drive.

One might still prefer a Prius based on notability, brand loyalty, style, gadgetry, stowability, and ones personal taste in handling but I wouldn't make my choice on creepability unless I drove mainly in traffic.
 

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I was thinking today about what sort of mileage Honda might be able to get from the new small Insight replacement, considering ten years of experience with hybrid systems. One obvious answer is to use EV mode more aggressively. If so, then I have this question:

If you have an EV mode with a Honda hybrid drivetrain, and you wanted to be able to get started from rest, what sort of ratio would the CVT use?

If the CVT chooses a high ratio (like low gear in the manual), then the internal combustion engine is going to be turning fast, thus giving more friction. If the CVT chooses a low ratio, the ICE will be turning slowly (a lot more slowly), so you get less friction. But then the electric motor also turns slowly, and maybe it doesn't have enough torque to get the car moving.
 

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Dougie said:
If the CVT chooses a high ratio (like low gear in the manual), then the internal combustion engine is going to be turning fast, thus giving more friction. If the CVT chooses a low ratio, the ICE will be turning slowly (a lot more slowly), so you get less friction. But then the electric motor also turns slowly, and maybe it doesn't have enough torque to get the car moving.
ahhh...but the joy of electric motors! unlike ICE(who need to rev higher to get more torque)...electric motors generate all their available torque from 1rpm :D

and another downside to synergy drive...with the ability to drive from a stop with EV only, it has caused alot of shops to refuse to service hybrids under the pretense of: "if it will run without the engine on it will run without oil." obviously some idiot mechanic forgot the oil in a synergy hybrid, gave it back to the customer, and, most likely some very bad happened once they hit 25 or so mph!
 

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Regarding the shuting down of the ICE on the Honda civic, I wonder why they didn't consider a free wheel device between the engine and the electric motor instead of valve deactivation.

If the ICE were turning slower than the IMA or was stopped the IMA would drive the car and when powered up and matching the rpm of the IMA the ICE would drive the car too higher speeds.

In other words the IMA would be the primary mover for starting and low speed EV drive with the ICE coming up to rpm for faster driving. Imagine the drive of a bicycle with the pedals being the ICE and an electric motor driving the front wheel,you start off not pedaling but the electric motor moves the bike up to speed
then you start pedaling and when the pedal speed matches the EV wheel speed the free wheel locks in and you add to the speed by pedaling harder and faster.

No clutch would be required and shifts on a
manual would be accomplished by steering wheel paddles with electric activation of ratio change controlled through a CPU.
PS an electric motor developes its max torque from zero RPM not 1RPM.
DGate
 

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Dgate said:
Regarding the shuting down of the ICE on the Honda civic, I wonder why they didn't consider a free wheel device between the engine and the electric motor instead of valve deactivation.

No clutch would be required and shifts on a
manual would be accomplished by steering wheel paddles with electric activation of ratio change controlled through a CPU.
PS an electric motor developes its max torque from zero RPM not 1RPM.
DGate
What type of free wheel device that disconnects the EM and ICE and not have a clutch were you thinking of?
 

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IamIan.......I'm not sure a particular device exists that could make for easy installation but Honda could certainly engineer one. There have been several instances of free wheel on cars in the past,in the thirties,in the fifties and seventies. The Saab two stroke,the German DKW and some Citroen 2CVs had free wheel.
Previously when used on cars just by letting off on the throttle the link between the ICE and gearbox was broken so gear changes can be made without a clutch.All these cars had a clutch to facilitate starting and stopping.
This would not be necessary on my proposal since the ICE would be in autostop and the car would initially pull off on the electric motor and could be driven this way up to its controlled max before the ICE came in.
By doing this the present clutch would be redundant.
Free wheel devices can take several routes in the design detail but are simple and maintenance free.All bikes have one.
Sorry to ramble on but feel this would be a more elegant and efficient solution to achieving the same results on the Civics.
Also maybe if it could engineered into an after market kit the Insight could be updated to become a PHEV.
The main glitch is starting the ICE since the IMA is no longer linked to it in the direction of needed rotation,but this too could be overcome.
DGate
 

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Dgate said:
IamIan.......I'm not sure a particular device exists that could make for easy installation but Honda could certainly engineer one.
DGate
I have pdf copy of a technical paper I enjoyed reading from the University Of Michigan that had some graduate students do a project where they studied the effects of adding a 2nd clutch to the Honda Insight between the IMA motor and the ICE... the computer models they did showed some nice improvements... ~7.2% improved emissions and ~22% improved MPG / FE over a standard drive cycle.

But rarely does the things you see Universities doing ever reach the consumer level.

Although this would have been simple enough to put in by Honda from the beginning... it is very difficult for most people to be able to alter a Insight after-market to do this... although I admit I have thought about how nice it would be from time to time.
 

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What is the title of the paper you are speaking of, I would like to read it. I did a quick search on google scholar and didn't find anything obvious.
 

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IIRC it was also completely done in simulation. No physical devices were constructed. A _ carefully_ crafted simulation will yield good real world numbers. But doesn't address the engineering challanges in making something work.

Sorry But I don't have the link anymore, maybe Ian does. :)

HTH! :)
 

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Here is a copy of the 6 page paper I uploaded to my web site.

As it was said... it was a computer simulation.
I contacted the University of Michigan where it was done at after I had first read the paper years ago.
It was a M.S. in Engineering project for the 4 authors listed.
It was the 'final' for the class that they were in... If I recall correctly it was worth something like ~20% of the total grade for the class.
The faculty adviser ( I don't recall his name off hand ) for the project talked to me for about an hour on the phone about it.
The students had all moved on after they completed their Master's programs, so none of them were available to comment.

Originally they had intended to build a prototype to test the computer modeling ... but they did not get the grant to fund that part of the project.... and then they moved on to other Automotive engineering projects like HEVs, PHEVs, BEVs, Fuel Cell Vehicles... and given the small production volume of the Insight-I the Faculty adviser thought it was unlikely that they would later return to this project again.

I had hoped they would give me a copy of some of the data and such, but no such luck.

Still... I like the idea... it is elegant and it makes use of existing equipment already in the OEM stock car... while the limits of the 10kW IMA motor would be significant , it would still be nice to be able to be in 5th gear burning no gas at 50+MPH or driving around parking lots and such... or traffic... Especially for the PHEV Insights that have additional grid charged battery packs.

While I have not given up on this idea... It is way down on my list of modifications... especially because of the work and cost needed for such an after market modification... it might have cost Honda another $100 to engineer and include it from the beginning ... but to do it now after the fact is a much bigger fish to fry.
 

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IamIan..
This would not be necessary on my proposal since the ICE would be in autostop and the car would initially pull off on the electric motor and could be driven this way up to its controlled max before the ICE came in.
By doing this the present clutch would be redundant.
There's probably a few reasons why Honda didn't do a free-wheel system...

The first is that the original IMA motor was a lot thicker and that's one of the reasons they made the I1 ICE a 3 cylinder rather than a 4 cylinder, as the space given up by the extra cylinder was used by the IMA motor. The later IMA motors were thinner so the Civic and I2 have 4 cylinder ICEs again.

The second is that the IMA motor is used to start the ICE so a free-wheel device won't work (it can't apply reverse torque to start the ICE because it's free-wheeling). You'd need a secondary clutch or some kind of hydraulic lockup to allow the IMA to drive the ICE to start it and then the lockup would have to disengage to allow the ICE to run in free-wheel mode. The extra clutch and control system would have made the I1 even more expensive to make than it already was (and Honda lost money on every I1 they sold as it was).

The IMA was bolted on to the flywheel as a heat sink. Separating it would have meant dealing with the heat build-up in the IMA separately.

Lastly, I'm not sure how much power / shock a free-wheel drive can take. On a bicycle the driven gear is only receiving 60-100W of power at maybe 60 RPM with the driven gear doing about the same. So the potential engagement RPM differential is very low at the point where the free-wheel gear "bites". On a Civic the engagement differential potential is going to be high with the ICE having to get from idle (700 RPM) to maybe 3,000 RPM and match the speed in such a way that the rate of RPM change near the point of engagement isn't too high. If the rate of RPM change is high (the ICE is revving up too fast to match the driven gear speed) you might hit the engagement point hard and cause the car to jerk, or worse, strip the teeth on the free-wheel gear. The ICE is going to be practically unloaded all the way up to the engagement RPMs and then suddenly heavily loaded. This would mean the ECU will have a hard time getting the fueling right at the transition from no load to high load at the same RPMs.

When I had a manual geared car, I used to free-wheel sometimes on long highway hills but it's tricky to balance the throttle to bring the ICE up to the driven gear speed (or as close to it as you can manage) before letting the clutch out. You only need a little bit of throttle to make the engine race but as you let out the clutch and the engine takes up the load you have to apply a lot more throttle suddenly. Get it wrong and the car slows or surges suddenly and in both cases you burn up the clutch a bit. Mind you, lots of people drive like that all the time - Lifting off the throttle too soon when pulling in the clutch and forgetting to press the throttle before letting out the clutch during gear changes (giving that "face in the dash" gear change smoothness).

Bicycle free-wheel gears also make a ticking noise when free-wheeling which is the escapement lever clicking over the teeth backwards. This is fine in a gear only working at 60 RPM but will wear out one working at 3000 RPM. Not to mention the ticking noise becoming an annoying whine. No doubt there are other types of uni-directional drives that could be used but the cost and engineering problems should not be underestimated.

Compared to all that, devising a control mechanism to just shut the ICE valves, kill fuel delivery and use low friction cylinder linings and so on (which benefit ICE efficiency as well) are probably the best compromise between cost, complexity, and payback.

As a side note, people have been saying the Insight does not have this EV mode (with the valve-shutting). The I2 does do this and you can see on the drive information display as you are driving whether the system is in ICE, ICE+IMA or IMA mode so that you can modulate your right foot to produce the conditions that will allow you to "select" a drive mode.
 

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No the Insight does not have it. Really it's pretty limited, but happens where it's probably the most beneficial. You have to be doing 10mph already at least and moving along at a constant speed and light throttle. They say it will work up to 35mph, but I've found it's really only good for 30mph on flat ground. Sometimes the car will willingly use it, sometimes you have to try and make it do it by letting off the gas until your in that "valves off" mode and just coasting then very slightly ease your foot back in to it at which point it will show between 1 and 4 bars of assist and the mpg gauge will be pegged at 100mpg. Any more than 4 bars of assist (keep in mind 1 bar on the civic is at least 2 on the Insight) and it kicks the engine back in.
 
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