Transmission Activity

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Gordon McGrew wrote:


if it doesn't, then there's something wrong. how old is it?

that's what the lockup clutch in the torque converter is for.

you'd hate cvt. there's no "relationship" between revs and engine speed at all.

you're looking at fuel economy, right?

ok, yes, but we're talking about different things. torque converters can increase torque output from a little to a lot in a very limited rev range. ratio change is something different and that's what the gears are for.

see above.

civic hx was significantly more fuel efficient than the stick.

don't know. given "consumer demand", i expect so.

i've never heard of problems with the civic hx.
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On Mon, 08 Jan 2007 21:25:13 -0800, jim beam

It is a '94 with a 5-speed manual transmission. What kind of MT cars have you driven that shift themselves???

But it isn't engaged all the time. When it disengages, that is when it "slips" and I do not find that satisfying as a driver. Like I said a the outside, it is a preference for MT. I like to drive cars and the MT is more enjoyable than the ATs I have driven. I don't like it shifting when I don't want it to and I don't like the slippy feel of the torque converter. The fact that the MT is usually faster and more fuel efficient is a bonus.

I think you are probably right. That is why I mentioned the fact that the CVT isn't very popular in the US (if anywhere) and I think it is because lots of people hate it. Why else would Honda sell a 7-speed CVT?
OTOH, it probably appeals to - or at least doesn't repulse - the hybrid buyer because it befits the unconventional nature of the car. I realize there are technical benefits to the combination of hybrid and CVT, but I am saying that the unconventional nature of the CVT is less of a negative when you are already committed to buying an unconventional vehicle. If you are attracted to the hybrid because it is unconventional, the CVT is a plus.

Fuel economy was significantly better for the MTs but the biggest difference was acceleration. The MTs blew the doors off the ATs. In terms of 0 - 60 time differences, the Yaris AT was the best - "only" 2.1 seconds slower than the MT version. Even the slowest MT car, the Kia Rio was faster than the Versa CVT. The fastest AT car, the Yaris, was 1.4 seconds slower than the Versa CVT.

You understand that the ATs torque output at a certain rpm (i.e. power transmitted) is higher when the torque multiplication is active. There are only two way this can happen. The first is to increase the efficiency of the transmission. I think we can dismiss that. The other way is to increase the power input. The only way to do that is to increase the throttle opening or increase the rpm. The throttle opening is determined by your foot (and it wouldn't be much of a trick for the torque multiplier to be just an extra jerk on the throttle and it wouldn't do much good if the throttle were already wide open.) However, rpm is largely controlled by the transmission. The transmission allows the engine to run a little faster and therefore produce more power which is transmitted to the wheels. This is what I meant by a mini downshift.

I gather that was the CVT-equipped model. They don't sell it anymore. I guess people hated it more than high fuel costs.

Like I said, they hate it just like you think I would. (Actually I would love to try one, I do think it is a neat idea and it would be fun for a while at least. Only after the novelty wore off could I tell you if I like it or hate it. I actually suspect that I would like it more than a conventional AT.)
Here is an interesting review I found. (It indicates that the Versa CVT does not have "gears," so the fact that it was slower and less fuel efficient than the "clunky" MT is significant.) I made one editorial comment in brackets.
--quote-- But the CVT is the one that shines. Its proprietary design, benefiting from Nissan's global cooperation with French carmaker Renault, is uncanny in the way it maintains optimal engine rpm within the most fuel-efficient torque range. It senses, for example, when the Versa is proceeding downhill and glides effortlessly into a lower gear range to slow the car with engine braking. [What if you don't want engine braking? It is wasting kinetic energy = fuel. What it needs in a powerful computer with optical sensors to look ahead, evaluate the situation and decide whether engine braking is advantageous.] Conversely, under pedal-to-the-floor acceleration, the CVT instantly launches the engine to its max-torque rpm, then keeps it there unchanged until a desired highway speed is reached.
This goes against every traditional sensation of driving, wherein gear changes trigger a momentary drop in rpm as the higher gear ratio is engaged. There's a lot of mechanical inefficiency in that traditional gear-change syncopation; and Versa's CVT eliminates it. When first experiencing the CVT's behavior, it feels wrong, sounds noisy. In truth, however, it's mostly the lack of noticeable gear changes that's merely thwarting a driver's subconscious expectation of rising-falling rpms as gears change. --end quote--
http://www.carlist.com/newcars/2007/ncr1116.html

Neither have I, but then there aren't a lot out there.
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Gordon McGrew wrote:

i misunderstood you.
originally, you said "If I want to downshift, I can do that." well, you can on an auto. on my car, the shifter is in the same place as a stick would be too. and the auto replicates engine braking when you need it - just like you'd do yourself. really, it's a good system.

you'd hate cvt. as i said before, there's zero relation between engine speed and vehicle speed - if you drive on engine revs, and it sounds like you do, you'll be suffering total loss of feedback.

check the modern civics in that department.

because they rely on dealer feedback, and dealers are morons? cvt was pretty popular in europe iirc. volvo sold them as well as daf, and they did quite well.

nah, it's a pure engineering logic decision. cvt allows extremely good engine efficiency. if you don't want that, you don't want a hybrid.

dude, compare like with like - not different car to different car if you're trying to compare trnasmissions, i.e. yaris with cvt, yaris with stick, etc. yaris stick to versa cvt doesn't work.

no, it depends on input/output speed differential. within certain rev ranges, torque transmission is very high, even with a rev differential. if it gets outside of that band, it drops right off.

that's the lockup clutch releasing.

my money's on dealer prejudice, not consumer. by the same token, the hatchback has been all but dropped in the u.s. afaikt, that's more to do with vehicles with the same utility selling for $30k rather than $15k for a hatch, not consumer demand. try buying a used hatchback civic here in the bay area - good luck! people just keep them - they never sell.

not correct. when engine braking, fuel delivery is completely stopped.

why? i don't want my car making /that/ kind of decision. seriously, auto engine braking only happens when you're foot braking - just like on a stick. you can't criticize what you've not used dude.

/all/ the 96-2000 hx autos are cvt.
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On Wed, 10 Jan 2007 20:43:45 -0800, jim beam

The AT Civic gets slightly better highway mileage than the MT - I am guessing it may have a higher final ratio. The Accord 4 and V6 and the Fit all get better mileage with the MT. I don't have any test results, but I bet the MTs are universally faster (see below.)

Why is that in the past tense? We agree they are more efficient than conventional ATs and if they were popular, why didn't they drive conventional ATs off the market? Reliability could have been an issue but shouldn't be now (as long as you stay away form GM.)

Exactly right. The converse of that statement is that, if you want increased efficiency, you will tolerate or even embrace the CVT. And if you like the hybrid because it is odd or technologically advanced, then you will love the CVT.

It doesn't matter whether you compare like to like or unlike to like. All of the MTs are faster than all of the ATs and the CVT. Let me tabulate it for you:
            0-60        45-65    1/4 mi
Fit AT     12.4        8.4        19.0 Fit MT      9.9        6.5        17.4
Versa CVT     10.1        6.4        17.8 Versa MT           9.5        5.9        17.2
Rio AT        12.8        8.1        19.3 Rio MT        10.0        7.1        17.5
Accent AT        12.5        7.7        19.1 Accent MT         9.5        6.5        17.2
Yaris AT        11.4        6.9        18.6 Yaris MT         9.3        6.0        17.3
As I said, "The MTs blew the doors off the ATs."

http://en.wikipedia.org/wiki/Torque_converter#Efficiency_and_Torque_Multiplication
--quotes-- [my comments in brackets]
Unlike a fluid coupling, however, a torque converter is able to multiply torque when there is a substantial difference between input and output rotational speed, thus providing the equivalent of a reduction gear. [IOW, a mini-downshift, a slightly lower gear that allows the engine to run faster and produce more power.]
The principal difference is that whereas a fluid coupling is a two element drive that is incapable of multiplying torque [IOW, it has a 1:1 ratio of input to output] , a torque converter has at least one extra element - the stator - which alters the drive's characteristics during periods of high slippage, producing an increase in output torque. [IOW, it allows the engine to run faster and produce more power, just like a lower gear.]
The Buick Dynaflow automatic transmission was a non-shifting design and, under normal conditions, relied solely upon the converter to multiply torque. [IOW, there was no gear transmission, all ratio change was due to slippage of the TC - an early CVT!] The Dynaflow used a five element converter to produce the wide range of torque multiplication [i.e. wide range of drive ratios] needed to propel a heavy vehicle.
* Acceleration. The load is accelerating but there still is a relatively large difference between pump and turbine speed. [i.e. low gear] ...The amount of multiplication will depend upon the actual difference between pump and turbine speed, [i.e. the effective drive ratio] as well as various other design factors. [efficiency]
* Coupling. The turbine has reached approximately 90 percent of the speed of the pump. Torque multiplication has ceased [i.e. gear ratio is slightly less than 1:1 but the slight power increase from higher engine rpm is lost to inefficiency] and the torque converter is behaving in a manner similar to a fluid coupling. In modern automotive applications, it is usually at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.
--end quotes--
When they say "torque multiplication" what they really mean is a drive ratio less than 1:1. IOW, every transmission is a torque multiplier, at least in the lower gears.

Right, there is no torque multiplication in the TC unless it is slipping.

I personally like hatchbacks and I know they have a following. I too am surprised and disappointed that they have all but disappeared. I don't know I am ready to sign on to the conspiracy theory though. If there were a strong market, Someone like Mazda or Nissan would jump to serve it to increase their sales. apparently there isn't enough demand to justify the high expense of two body styles and the sedan is more popular.
I suppose I could blame the shortage of MTs on greedy dealers and manufacturers who want to force me to buy a more expensive AT. However, I am more inclined to blame Starbucks.

But kinetic energy is being lost. Doesn't matter if the car has to be brought to a stop anyway, but if the driving situation requires little or no compression braking and the computer orders a lot, the car will slow unnecessarily and fuel will be consumed bringing it back up to speed.
I use compression braking a lot. Sometimes I use a little, sometimes I use a lot. Sometimes I coast with the clutch disengaged for maximum distance. A transmission that always applies medium compression braking is not as going to achieve the same thing.

But you are satisfied with it making the decision mindlessly. I agree I do not want the car making that decision. I want to make it myself and shift the transmission accordingly. My brain is the powerful computer and my eyes are the optical sensors.

Not true. I use compression braking all the time with my foot off the brake. Descending grades would be a prime example except that I live in Chicago and there are no hills. Instead, I am the only guy in crawling rush hour traffic not flashing his brake lights every 20 feet. It is way more fun than an AT if you play the game.

I am only pointing out that this feature has a down side. It might not bother 95% of drivers, but it would bother me.

Yes, but how many is that? If they had sold that many, it would still be on the market. Don't get me wrong, I don't think they are any less reliable than a conventional Civic AT, but I don't think there are enough out there to really know for sure. They certainly aren't terrible like the GM CVT.
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Gordon McGrew wrote: <snip>

that's unsafe btw.

no i'm not. i am satisfied from extensive experience over many years in all conditions and many many miles, clearly based on extensive research on driver usage and testing of driveability, that programmed engine braking algorithms used in electronically controlled automatics are highly proficient and effective. as you would know if you'd driven one.

i don't want it making an independent decision. they're programed to make *dependent* decisions based on how the driver is asking the vehicle to behave. which is what you want.

you can - use the shift lever.

but the two are apparently unable to work together to get the ass on into a dealer to test out the new fangled machine the mouth is criticizing.

no, it's true. autos engine brake, just like a stick. and you can engine brake without the foot brake too. we've discussed that repeatedly.

see above.

but your assessment of the whole situation is flawed - it's assumption and speculation /not/ based on either experience or sufficient knowledge. modern autos shift to engine brake. they do it flawlessly and just as a normal driver would shift a stick. and the degree of braking depends on how hard the driver's braking - /that/ is /more/ sophisticated than the average stick driver.
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On Sat, 13 Jan 2007 09:34:29 -0800, jim beam

Why?
It can have all the algorithms it wants but it doesn't know whether the hill is long or short. It doesn't know whether, at the bottom of the hill, there will be the beginning of a steep ascent or a freight train crossing. It just goes for some predetermined drive ratio, oblivious to what is outside the window. I chose the level of compression braking based on information the computer just doesn't have.

No, I want to tell it what to do. I don't want it to infer what I might want the transmission to do based on what I am doing with the throttle and brake. At least a conventional AT gives you some direct control over this. I would like to believe that the CVT does also, but I don't really know. It should assume that I want minimal compression braking unless I specifically signal otherwise. If it wants to assume I want more compression braking if I am at least moderately on the service brake, that is OK. But if I take my foot off the brake, it should resume minimum compression.

Not clear on how you control the CVT, but the article implied that it automatically went to some medium level of compression braking. It wasn't clear that you could over-ride this and force less or more compression braking.

That's just it. I don't test drive cars unless I am considering buying one. If I get the opportunity, I would gladly take it. But I don't think I would ever consider buying one if an MT were an option.

But you said it happens *only* when you are foot braking. I thought you were referring to the CVT. I know how a conventional AT works.

It may or may not be more sophisticated than the *average* stick driver but it is no way more sophisticated than what *I* do. I can't decide what gear to be in without assessing the situation outside the windshield. No matter how powerful the computer and elegant the software, it is a blind driver. I use engine braking instead of the service brake. To have it mindlessly aping what I do with the service brake is hardly sophisticated.
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It doesn't allow engine braking for one thing and it's illegal for another.
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On 1/14/2007 4:23 AM Brian Smith spake these words of knowledge:

FWIW, neither of those responses have anything to do with safety, although I suppose you could make a tenuous case for the first, given some not-obvious assumptions about manufacturer's intent to provide and buyer's intent to use engine braking.
RFT!!! Dave Kelsen
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a troublesome servant and a fearful master. Never for a moment should
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For one thing, the fact that coasting doesn't allow for engine braking is a safety issue. For the second, the fact that it is illegal makes it a valid point.
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On Sun, 14 Jan 2007 15:07:02 GMT, "Brian Smith"

Saying that coasting is unsafe because it doesn't allow engine braking is like saying that not pushing on the brake pedal is unsafe because it doesn't allow frictional braking. Engine braking is available if I want it, just like frictional braking. When and where each is used is a decision to be made by the driver based on the situation. For example, coasting on glare ice is a lot safer than compression braking, especially on a rear wheel drive car. Even more so with the advent of ABS.
As for laws against coasting; they may vary from state to state. Here is one form Maine:
An operator, when traveling on a downgrade, may not coast with the gears of the vehicle in neutral. [1993, c. 683, Pt. A, 2 (new); Pt. B, 5 (aff).]
Now notice that it specifies coasting *on a downgrade* *in neutral*. Coasting on level ground or coasting down a hill with the clutch disengaged but the transmission in gear is legal. I would agree that this is generally a bad idea and certainly bad if you are riding the foot brake. However, if you are coasting down the hill with the clutch in, not using the foot brake, and you are satisfied that your speed is not excessive, what is the problem?
The only purpose of such a law is to give them another charge to throw as some idiot who causes a wreck because he doesn't know how to control his vehicle. Can you imagine being pulled over because you were coasting down a hill?
And just to be sure we are perfectly clear on this point, I use more compression braking and less frictional braking than about 95% of drivers in the same situation. But I don't use any braking where it is not needed.
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Gordon McGrew wrote: <snip> you just want to express your opinion, not discuss merits of either system. that's fine if the opinion is informed, but since you have no experience and apparently don't wish to pay any attention to fact, then your opinion isn't opinion, it's mere prejudice.
i'm sorry i wasted my time.
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On Sun, 14 Jan 2007 08:17:02 -0800, jim beam

I stand by my original position; if it doesn't know what is happening on the road ahead, it cannot possibly make the best decision regarding operation of the transmission.
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Gordon McGrew wrote:

jeepers, engage brain before opening mouth will ya? if it had that kind of autonomy, it wouldn't even need a steering wheel!!! way you talk, having 1930's style manual ignition timing controls in the middle of the steering wheel are the way to go too.
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On Sun, 14 Jan 2007 10:54:37 -0800, jim beam

I don't expect anywhere near that level of autonomy in the foreseeable future. Nor am I looking for it. I like to drive the car.

I am hardly a Luddite. I like technology when it is well applied. My first Honda had a manual choke. It was fun, but I never hesitated to exchange it for an automatic choke and later FI. These systems manage the engine so that it gives me what I want as a driver; smooth, predictable throttle response. That increases my control over the power.
I remember being in 3rd grade (1964) and reading how in the future (by the year 2000?) you would just hop in the back seat of the car and tell it where you wanted to go. I hope they have that perfected by the time I am too old to drive. Until then, I have no use for it. And as long as I am driving, there are certain things I want to control. If new technology increases my control, I am all for it. If it makes driving easier while decreasing driver control, I have no interest in it and I resent having to pay for it. That is how I feel about every AT I have ever driven. I is the fundamental way in which they work which I object to. Refining that operation does not address my primary objection.
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On Fri, 05 Jan 2007 19:35:03 -0600, Gordon McGrew wrote:

I would agree that they do not belong on any sports car, but IMO, the only time I really WANT an Auto is for heavy city traffic.
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On Sat, 6 Jan 2007 05:31:46 +0000 (UTC), Joe LaVigne

It depends on your attitude. For me, the only joy in "stop and go" traffic is seeing how far I can go without touching the clutch or the brake. When traffic is heavy but moving, I like the control that I get from an MT.
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jim beam wrote:

Yeah, my friend's Prelude of mid -80s did same thing.
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Your tranny is fine.
The extremely sophisticated electronics installed these days have considerable control over shift behavior. In addition, the transmission will actually "learn" your driving style and adjust its behavior for that.
Some people find newer transmissions' behavior disconcerting when compared to older designs.
The very best thing you can do for your transmission is to change the fluid precisely according to the maintenance schedule, and to ONLY ever use Honda genuine ATF-Z1 fluid. If you want to change the fluid MORE often, that's even better.
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Thanls for all of the responses. I figured it was a function of these intelligent transmissions. Of course, I could read the manual but every time I think about it, the car isn't actually here....!
Dan D '07 Odyssey EX Central NJ USA
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Take the Manual in the house, then when you're in the reading room, you can find out all about the vehicle.
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