Less engine, more gears
 

Yesterday while I was walking in the neighborhood with my dog, I spotted one of the first eco-cars I fell in love for. The Fiat Palio Weekend 6 marchas was available only in '99 and 2000, with a 61hp/60lb.ft. 1.0L engine backed by a 6-speed (6 marchas) manual transmission, while the previous base versions had a 75hp/90lb.ft. 1.5L and a 5-speed manual instead.

http://2.bp.blogspot.com/-TMY66R59hC.../Photo6081.jpg
http://2.bp.blogspot.com/-OwTZyrkvgb.../Photo6080.jpg
http://2.bp.blogspot.com/-5b9_DZZoc8.../photo6082.jpg

Altough at some point a significantly lower displacement won't actually help, the gears always play an important role for both performance and efficiency.

Higher gear count transmissions are definitely gaining popularity, in the near future chrysler will be using solely 8 and 9 speed transmissions. Aerodynamics is also a hugely important aspect, the public doesn't want to drive slower so the only way to get those high mpg numbers is small turbo engines, lots of gears and very aerodynamic bodies.

...gears are becoming like Archimedes' geometric approximations of a circle, just use enough small-length, straight, segments to approximate a smooth circle made of straight pieces...ie, use enough 'staight' gears to approximate a 'smoothly curving' power-vs.-load curve: a geared CVT.

My car has six forward gears too: 1-2-3-4-5 and Neutral! :rolleyes:

And two reverse? :rolleyes:

What do you gain with all those gears? If your deal is max acceleration rate, that is what you gain. If your deal is fe, you lose from all that shifting- a most inefficient process what with all that throttle blipping and halting forward motion- and you lose from a transmission that has more moving parts and I would imagine more internal friction.

In the '80s the eco-stick trans options were 4-speed instead of 5.

With my 5-speeds I'm always skip shifting, like 1-3-5. I would like to only have the 1-3-5 gears and throw 2-4 away and save the internal trans losses.

Like most things there are pros and cons.

• Pro: More gear ratio options allows a better ability to convert the real time road torque and RPM situation into a combination that is at more efficient point on a ICE's BSFC.
• Con: Manual transmissions has a loss of efficiency during the shifting period ... the more one has to shift the more shifting losses... more gears means more shifting over the same RPM and torque transition.
• Pro: Manual transmissions can be more energy efficient from input to output.
• Con: Finite Manual Transmissions have fewer gear options than other 'CVT' and the like ... ie they are less able to have the 'best' ICE gear ratio for all road torque and RPM conditions.

I have a interesting paper about the efficiencies of various transmissions.
Sadly it is not free... Link

But ... here are some teasers / interesting bits from the testing in it.

PumpCVT

Manual

Toroidal

BeltCVT

BallPump

FixedDisplacementPump

Automatic

I dunno. My bikes seem to do pretty well with 21/24 speeds - though I could always use a few more :-)

Right- and you go from 1st through each gear to 24th from a stop.

There was some guy on here that thought everything should have 18 or so speeds; maybe he likes to spend all his time shifting- I consider it a necessary evil.

If the vehicle is driven on relatively flat terrain, a manual transmission with four speeds is sufficient three was the norm for years. The problem is in most manual transmission the top gear does not get the rpms down low enough for best fuel economy. This seems to be the case whether equipped with a three, four or five speed. No personal experience with a six speed in a car. It’s as if the transmission is designed so under most driving condition you will not need to drop it down a gear. In the mountains it is nice to have multiple gear choices. In this case a 5 speed is better, especially if you have a low hp low torque car. Wouldn't it be nice if you had choices like the first four to be close ratio and fifth out in left field for economy.As gargantuan motors and the heard followers only want to sell the 20% of the vehicles that appeal to 80 % of the market. you are lucky to get what you want, to find it with a manual transmission a gem.

As for high gear count automatics just sounds more expensive to build and repair.

Six-speeds in the mass market of this country are similar--they shorten each gear so that the sixth is about the same revs/mile as an earlier five-speed.

-soD

No, if I'm riding on flat pavement. But it's not at all unusual for me to start out riding on a level stretch, climb a few miles of paved road at 6% grade, then go off on a mountain trail. On a ride like that, I do use the majority of the gears. (Of course there's some overlap between the front 3 gears, and the rear 7-8.)

FTM, my pickup has 10 speeds, when you combine the 5 speed transmission with high & low range in the transfer case. And I do use that low range on roads where 1st gear in high range would stall out.

I see CVTs and DCTs being the transmissions of tomorrow. A traditional automatic is being phased out, although you go to the dealership and the sheeple don't know what anything is so they label everything as an automatic transmission. CVT has continual power to the road, but has higher torque loses. (Which is why it is so hard to put them into trucks) The DCT, dual clutch transmission, is essentially twin manual transmissions that are shifted by the computer so that the lack of power during a shift is kept to a bare minimum. As the odd number gear transmission begins to let go, the even number gear transmission begins to grab. Pretty slick, there are 6speeds like this and luxury 8speeds, with 10 and 12 easily foreseeable. A traditional automatic transmission is just a mess of moving parts (read failure points) adding more to this mass, just doesn't seem wise. Although, when my father found out that my girlfriend, now wife, was driving a manual tranny; he knew we would probably get married. I love manual transmissions. And I have owned several 6 speeds; I agree that most are true 6 speeds, and what would be best for FE is an overdrive 6 speed tranny.

The additional gear ratios of the CVTs can be an asset for the ICE ... which is very susceptible to non-ideal RPM and Torque combinations ... but the CVT transmission itself is significantly less efficient than the Manuals transmission.

I agree in the near term I expect more CVTs ... but as Main Drive Electric motors grow in size and Market % ... I wonder if that will continue to hold long term?? ... Electric motors are not as vulnerable to efficiency losses as ICEs are , from fewer ideal gear ratio options... as that starts to play a more dominate roll , we may start to see fewer manual gear ratios ... maybe a DCT style you mention.

I usually only use 1st or 2nd and 5th, no need for any of the other gears except when
1. Pulling
2. going up hills.

My insight I find myself using more gears, cobalt though is stuck in 5th 99% of the time.

I am guessing frank that if you have a motor that is underpowered enough you could actually "need" the gears or if you overgeared where 5th was unusable a good chunk of the time like my suburban or my subaru 360 that doesn't have enough power to skip any gear without coming to a stop.

I rhink that is what cripple_rooster was getting at in the OP and I think that is indeed the future with regards to better FE. The tranny may be more likely to fail with more parts, but that is offset by smaller and less cylinder-ed engines. And with the reviews (read as Consumer Reports) coming back that small engines with turbos isn't really working, more gears is would be the next logical step.

On shifting speed, if time spent shifting is of concern:

1. Simply loading the alternator can help slow the engine between gears during upshift.

2. for faster results, It could be a well calculated pre-ignition too.

How much power/energy to slow a 4cyl for upshifts within one engine revolution? Does it justify regen starting and stopping?

Though clutch is nice since it transfers much of the energy from the higher rpm engine rotating mass, that would be the comparison, lower rotating mass=better, or use hydraulic motor/generator for the starter (and stopper) if you are stuck with a flywheel, maybe :)

The folks might remember that, in Europe due to smaller engines which were more usual for a long time, a higher count of gears was usual there, and in Brazil due to fuel costs we tend to follow the European school more often. The case of the Fiat Palio Weekend was a specific one, since it had an engine even smaller than the base offering in the Euro-spec version (a 67hp 1.2L 8-valve gasser), while the Brazilian domestic versions had the 1.5L as the base engine before the introduction of the 1.0L engine.

The two exceptions given are the reason for 5(or 6 or 7+) gears & there are other reasons, too.

I loved my CVT which transferred power to the ground continuously & I did get better mpg than the 5 speed manuals delivered. It made stop & go commuting, bearable & even elegant without shift shock. Yes, travel from 1 to 15 mph can be...... OK, if you can't go 60mph. Also my car, which didn't have an efficient body or engine, had the ability to get 32-33mpg traveling over 4000 & 5000 foot mountain passes & was due to CVT's ability to set the exact right geariing for ALL slopes & configurations.

However, CVT's extreme unwarranteed repair cost caused me to trade my car before such an event occurred. Wanting my accustomed manual transmission again, I could never find it on the dealer's lot & got an extremely fine deal on a 6 speed automatic Elantra. Bolstered by the 100,000 mile warranty, I expect no out-of-pocket transmission repairs for a decade & possibly long after that! Plus, the Elantra, bad-mouthed for poor mpg by lead-footers, is delivering 39mpg average. Under the conditions, I don't think a manual could have rendered higher mpg than the auto.

The auto tranny is a pleasant experience, tho not the wonder of the CVT.

My sister and I made a trip to California and back in her husband's new Elantra. I had thought that it was a beautiful car and was surprised that they bought it new for $16,000. We got at least 36 MPG the entire trip, "driving the speed limit." It turns out that is Sister for 4 MPH over, so 79 in a 75.

Only by excellent luck was I able to buy my auto Elantra with lots of nice options for $15,500, but I did. Elantra is supremely beautiful, but of exceedingly low 131 lbs-ft of torque. Recently, a highway trip & return with travels into a town & a smaller city w/two major cool-downs, but freeway travel limited to GPS:62mph(mostly) to GPS:66-69mph(occasionally), netted a trip computer reading of 43.8 mpg. Your extra speed travels at 79 mph netting 36mpg, shows how the Elantra small torque will kill mpg, despite Elantra being fairly aerodynamic(no mods).

My brother-in-law complains that the car lacks power for hills, but my sister says that he must not know how to downshift.

Sure, had I driven by myself, I would have wanted to drive fifty-five, but we needed to drop our lives, hurry out there, help the family, rush back, and try to catch up. Even though one nephew had the iPad and the other had an iPhone, hardly anybody likes traveling.

Yes, Elantra must be downshifted for hills & as much as 2 or 3 gears. Things can be done to hold higher mpg, often concerning those hills. Without knowledge, hills will take huge chunks of mpg away from drivers. Actually, the extra speeds (& speed) can be used as an ally to keep mpg up, but again, it takes fore-thought & knowledge.

Ah, Arizona is wonderful to travel in. Too bad the family was rushed not to enjoy travel, landscapes & viewing new territory.

My Prizm can climb a 5% grade past 2000 ft with 100 degree ambients in 5th gear. I am not amused.

I like auxiliary transmissions, personally. In a 5&4 setup, you get something like 20 nominal ranges, but there are overlaps, and if you know your input/output ratios and what the engine /wants/ versus what you want, you can do some funny things with it... for instance, in one of the old trucks we had, you might split between 3/2 and 3/3 by shifting to 2/5 or 1/5. It takes a bit of practice and understanding of the ratios to do things like that, though.

I really love multi-speed transmissions. The loss in forward momentum can be solved with dual clutch gearboxes though. Ask VW about that.

I don't like how small the ratio between my top gear and 1st gear is, it is only 4.34 on a 5 speed, I have plenty of power in 5th gear to the point that I think toyota should have made 4th as tall as 5th and made 5th taller.

...back-in-the-day, most generic 3-speed automatics had axle-ratio gears of 2.73 or there abouts (seldom higher than 3.18); most non-muscle models used 3.23 or maybe 3.55 ratios; and, muscle models used 3.91-4.10 ratios.

Fiat Siena, with the same driveline.
http://2.bp.blogspot.com/-4mFjhBCCEX.../Photo8485.jpg
http://2.bp.blogspot.com/-qBG2oRuojp...to8487_001.jpg
http://1.bp.blogspot.com/-z09v1qajNq...to8488_001.jpg
http://3.bp.blogspot.com/-OordI05QcC.../Photo8489.jpg

This long 6 year inactive thread considered the pros & cons of extra geared transmissions. In general, I agree with Frank Lee, whether transmissions are automatic, CVT, DCT, or manual. Since this thread's last post, the disastrous CVT, DCT, & 9 & 10 speed automatic repair follies for so many customers, have blasted to bits the desire to save gasoline money, while giving ten(20?) times more money to transmission mechanics. What.... only Toyota probably "succeeded" with their high MPG auto transmissions. Other brands?
At their best, these automatic transmissions MAY have gotten similar MPG to manual transmissions, but only if drivers used automatic transmissions in ways most auto transmission drivers would not.
I have had a CVT transmission in the past, & presently we have two Elantras, one 6-speed manual, & one 6-speed automatic. I used the CVT to deliver the same & better MPG than other alternative 5-speed manual transmission drivers for the brand. As to our Elantras, I have worked hard to get good MPG from both, which are similar. Under certain conditions tho, the manual gains more MPG than the automatic.
Anyhow, 3 of our 4 cars have manual transmissions (oh, yeah....4, 5 & two 6-speeds).

Skip gears. Means car improperly-loaded. A situation which shouldnt happen but rarely is considered the norm.

And what benefits accrue on skip-shifting?

I'm not going to load the car with ballast just so it's loaded "properly". Yes, it is overpowered. I've long thought of disabling two of the four cylinders, or repowering with a smaller engine. But it runs good, reliably, and reasonably efficient so there we are.

The act of shifting is in itself inefficient. Skip-shifting gets me in top gear quicker. Fewer clutch activations. Fewer quick throttle-offs. Fewer throttle-ons when accelerating.

I recently had a talk with a Bolivian tourist who owned a F-150 with the 3.5L EcoBoost and the 10-speed transmission. He was very satisfied with the truck. DCTs on the other hand might be quite a PITA on harsh operating conditions.

One vote fer 10-speed transmissions. Do I hear a bid a 2? Do I hear 2? Sold american!

Jawohl! Fer sure.
The great increase in transmission gears started with small 65HP economy cars of the latter 70's & 80's, so they had a chance to keep up with "real" cars. Those with 5-speed manual trannies, I viewed with much envy. But that didn't keep me from skipping gears with my 4-speed manual. I love turning my manual transmission into half an auto tranny by skipping gears in a 5-speed. With little traffic & accommodating terrain, my 6-speed manual Elantra gets the 1-3-6 or 2-4-6 shuffle. Its BETTER than half an auto tranny.

Even before WWII, American cars often had fewer gears than some of their European counterparts. Sure there were some exceptions such as the Ford Prefect which retained the 3-speed while the competition was already switching to 4-speeds.


Skip-shifting, or no shifting at all depending on how accomodating the terrain would be, is another long-time American tradition. No wonder engines such as Chrysler's flathead-six had a long life in the market, since they already got their peak torque just a little above idle.

Reasonable and efficient. Agreed. MPG is only a marker and far from the important ones.

And I’m well aware of skip-shifting. Even though it goes against best chances of long term reliability.

So the question for any of us is power-to-weight. So far as I can tell, everything out there is overpowered. Even when loaded.

As long as traffic and terrain conditions are safe for skip-shifting, I see no point for it to decrease long-term reliability.

I’m not 100% sure but it seems that skip shifting can lead to premature gear synchronizer wear... I’ve always skip shifted my car and now for the past 5-6K I’ve had to be cautious on any shift into third gear to avoid a crunch...

I see no point to it at all. A moments emotional gain against long term health. My pickup has a transmission from a medium duty truck. Slow isn’t the word. The operators is clear in advocating every gear, every time. I get (or used to get) arguments from other owners about skip-shifting. They’re the ones now buying new clutches and re-man transmissions, or have spent it forward to the next owner.

Gee, I can float the gears in this truck, if I so choose. Again, why?

It’s part of owning it. Shifting is a rhythm. Part of being smooth in every eventuality.

I hadn’t thought of the skip shifting causing premature clutch wear too, but that seems even more likely than the synchro wear and I’m fairly certain that my bad 3rd synchro is related to going 1-3-5 the first 25k I had the car before the problem surfaced