Citroen Berlingo Multispace - Should there be any lurch on automatic gear shifts?

BOWFER

lordmountararat said:

Torque converters are probably set to go the way of the dinosaurs, so enjoy them while you can.

Yes, I expect you're right, but what a shame. I hate these automated manual 'automatics'  with a passion; torque converters are just so much smoother, reliable and predictable. Fuel consumption is marginally worse, true, but that is a small price to pay, imho.

I agree, if you want an auto you surely want it to be smooth - which these gearboxes often aren't.
But we're stuck with them now, people like to think they're playing F1 by using paddles etc.
And don't even start me on them all trying to place umpteen gears in them (7/8/9 speeds).
You only need that many gears when the engine's powerband is narrow, it simply doesn't apply to road engines.
It's just stupid sales oneupmanship or fashion.
Guy in the street has a BMW M-something with the 8-speed gearbox and it sounds ludicrous,.
It's honestly changed gear about 4 or 5 times by the time he's done 50 yards and 30mph.

knightstyle

The latest Smart for2 has a great smooth auto box, unlike the earlier ones. We also have a Cmax with 6 speed powershift and it is trouble free and very very smooth and yes I have the oil in it changed regularly, that is why it is trouble free.

Goudy

Sports cars will tend to be developed to keep the engine in it's power band as much as possible, the more gears the more it can hold on to peak power for longer, though they might have a fairly long final ratio to make cruising more comfortable.

Most everyday cars will be developed to hold the engine in a state of efficiency and comfort, having more gears enables the engine to operate in this state for longer.

But cars with 6, 7 or 8 gears isn't a new fashion or fad.

In 1948 you could buy a Standard Vanguard with a Laycock Overdrive system which effectively added a couple of extra gears, one with a final drive < 1:1. (hence the name Overdrive, one revolution of the engine turned the gearbox output shaft more than one revolution)

Overdrives were all the rage in the 60's,70's and into the 80's, so we've come back around to the idea of more gears are better because of the push to make cars more efficient, plus Dual Clutch systems are fairly easy and cheap to add to, adding an extra cog to each shaft that is already there negates the need for extra shafts and selectors a normal gearbox would require or a seperate Overdrive unit altogether.

Most of these automated manual gearboxes require a bit of anticipation, if you note the rpm when the car normally changes up and easy off the accelerator a little when it's about to change, it can smooth out the normally jerky changes a little.

When I bought my latest car I tested out all the competition and settled on the Clio TCe 130 with the EDC7 (Dual Clutch) gearbox. It was far smoother and much more responsive than the VW DSG, Fords TC and hollowing CVT's from the Japanese.

It's almost impossible to provoke a jerk from it unless you hammer the kickdown to drop 2 gears, it's quick witted and responsive from the off even when the auto handbrake is set and Renault now come with 5 years warranty, so they are really backing their products these days.

BOWFER

Goudy said:

Sports cars will tend to be developed to keep the engine in it's power band as much as possible, the more gears the more it can hold on to peak power for longer, though they might have a fairly long final ratio to make cruising more comfortable.

That's my point, cars don't have power bands.
Try riding a 2-stroke motorbike with a power band of 1500rpm, nothing below and nothing above.
That's when you need multiple gears, not a car that may make peak torque from 1800rpm and rev to 5500rpm.

Ditzy_Mitzy

BOWFER said:

Goudy said:

Sports cars will tend to be developed to keep the engine in it's power band as much as possible, the more gears the more it can hold on to peak power for longer, though they might have a fairly long final ratio to make cruising more comfortable.

That's my point, cars don't have power bands.
Try riding a 2-stroke motorbike with a power band of 1500rpm, nothing below and nothing above.
That's when you need multiple gears, not a car that may make peak torque from 1800rpm and rev to 5500rpm.

It has more to do with emissions testing than anything else.  Very few cars 'need' more than five forward gears: three underdrive, direct, and one overdrive ratio.  Some function perfectly happily with four speeds.  That was the way until about 2010, when emissions testing got really silly. 
A computer is used to measure what comes out of the exhaust pipe at various speeds, whilst the car runs on rollers.  For each speed: 30 mph, 40 mph, 50 mph etc. there is a corresponding minimum emissions revolution count for the engine; say 1,800 RPM for 30 mph (all figures made up).  The way to keep revs within the minimum emissions range for a variety of speeds is to have lots of gears.  Essentially one takes a car engine, which is designed to run at different speeds in few gears, and makes it more like a lorry engine, which runs at almost constant revs and uses many gears to generate the necessary variety of vehicle speeds.  It's all completely artificial contrivance and a lose lose.  Cars get hampered with all sorts of expensive, complicated and environmentally damaging rubbish whilst real world emissions have gone up!  

Goudy

Engines aren't as efficient or produce the same power right across the rev range, just look at any dyno graph for any engine, it will have an operational rpm range and somewhere in that it will produce it's optimal power, but I suspect that you know that from your comments on NA petrol engines in another post.

So an engine rated at 120hp and 150nm of torque will not produce 120hp and 150nm of torque from 1 rpm all the way to the redline, there is a point between the two where it's "best" power is produced.

The longer you can keep the engine operatering at this optimum point the better, which is why most engines are attached to gearboxes and gearboxes with more gears tend to keep the engine in the range for longer.

This optimum is sometimes known as a "Power Band", (though I did not refer it as such myself), the phrase can relate to all engines.

https://en.wikipedia.org/wiki/Power_band

All 2 stroke engines and gas turbine engines tend to have a very narrow, pronounced optimum, these petrol, gas and diesel ones all have a very different point in there rpm range where optimum power is produced, which is why the term "power band" is closely associated with them as the "art" over the years is to try and operate them within this narrow point as much as possible, but it it not solely a 2 stroke thing.

If you worked with diesel marine engines, you would more than likely refer to their "Power Bands" to be at a very low rpm range, particularly a 2 stroke diesel or in F1 it being at very high in the rpm range.

BOWFER

These are all very good points, but I'll never be convinced there's not a huge element of sales oneupmanship when it comes to multiple gear gearboxes.
It reminds me of the seemingly never ending race to add blades to razors.
"the latest and ultimate three blade razor"
"here's our new four blade razor!!"
Repeat ad nauseum.

Goudy

It's all just life, we want progess and barriers appear, we negoticate them and something else gets in the way.

All those years ago, back in the day of the Standard Vanguard, roads got better and better and cars went faster and faster. No one's ears could really stand up to 40mph at 6000rpm for very long, so the engineers made Overdrive units which added a couple of ratios.

Cost and manufacturing weren't really a problem as motoring was considered for the well heeled, you wanted comfortable cruising, you paid for it.

Evertually everyone wanted a slice of motoring, so manufacturers looked for cheaper and cheaper ways to make cars and along came FWD, transverse engines and transaxles, now Overdrives wouldn't fit, so they got stuck with oddly ratiod 4 speeds until there was an oil shortage, fuel prices rocketed and a 5th gear started to appear.

This lasted well for a while, but now we have emissions to worry about and gearboxes came under reveiw again. 6 gear manuals started to now appear, in design terms this wasn't a massive leap, just another ratio added to a shaft, operated by the same selector fork that all fitted roughly inside the same size case. 

Now "normal" automatics were an emissions nightmare, after all the torque convertor is basically designed to slip the majority of the time, which wastes fuel and increases emissions a lot.

Designers turned their attention to the Auto and came up with various solutions, one of which the dual clutch was really easy to add more gears to as it didn't need extra shafts and selector forks, just slightly longer ones with an extra cog on them.

So we're now back with all the gears of the Vanguard and what they all bring, with cheaper manufactured FWD's and decreasing emissions as the engines can run in for longer in an efficient window.

Some of these new auto gearboxes are actually more efficient and produce less emissions than the manual alternative.

Fiat's hateful Dualogic in the 1.2L 500 produces 105g/km compared to 110g/km for the manual and does around 20 more miles per tank. The DSG version of the latest Polo is only a few grams more than the manual.

You don't have to go back too far and these types of cars would never have been offered in auto (and if they did they were truly F'ing awful, I'm old enough to remember the DAF 33) and the ones that did had a massive gap in economy and emissions between manual and auto.

peter3hg

lordmountararat said:

Torque converters are probably set to go the way of the dinosaurs, so enjoy them while you can.

Yes, I expect you're right, but what a shame. I hate these automated manual 'automatics'  with a passion; torque converters are just so much smoother, reliable and predictable. Fuel consumption is marginally worse, true, but that is a small price to pay, imho.

In some areas the market is moving towards torque converters and away from DSG type 'boxes.
BMW is an example of this where the latest M3 & M4 use the excellent ZF 8HP torque converter box whereas the last generation used a dual clutch gearbox.

The rise of DSG caused the torque converter manufacturers to up their game, so they are now almost as fast changing as dual clutch, almost as efficient as a manual (thanks to the increased number of ratios and better lock-up clutches) but still with the smoothness inherent in the design.

The big advantage dual clutch gearboxes have is that they are much more compact so small and medium sized front wheel drive based cars will generally continue to use them over torque converters.

GoldenArbs

Thanks for all the comments, lots to learn here. To address my original query - yes it looks like it's working properly and it's just one of those things to get used to as I really like the rest of the car.

I suppose all these gearboxes will be a thing of the past with the emergence of the EV