| 01-04-2008
Automatic transmissions manufactured by ZF are far and away the most popular type on large buses and coaches in UK and have long been so. There was a time when automatics gave significantly inferior fuel consumption compared to the same vehicle with manual transmission, but those days are long gone. With today’s sophisticated electronics, fuel consumption returns from automatics are very good. ZF have worked very hard in recent years to hone the software of the electronic control systems fro their Ecomat transmission to give smooth changing and improved fuel economy.
Now they have taken another massive step forward and introduced a new system which they claim gives infinite control of the gear selection process and demonstrably better fuel economy. In fact, they claim, that depending on the operational terrain, it will actually give between 2% and 10% better fuel consumption compared to the current Ecomat. What is more, they say it will never give less than a 2% improvement and the tougher the operating terrain the better the improvement will be.
The new system is called ZF TopoDyn and it is available now on all new six-speed Ecomat and Ecolife transmissions. As far as I know the only vehicle currently available in the UK with the new Ecolife box is the Volvo B9TL, although the Mercedes-Benz Tourismo is to be available with it as an option towards the end of this year, Ultimately Ecolife will probable take over from Ecomat but that is still some year away.
Back ground
Up until now the Ecomat has been supplied with a pre-set operating level. ZF have six levels ranging from Super Economy up to Power. These allow the specifiers to adopt a level they feel appropriate to the vehicle. Most OEMs select Super Economy for city buses and Power for coaches. It is possible to have the programme changed but this involves a specialist service facility. It is also possible to have the transmission set up with two different programmes with the change being made by the driver using a dash board switch. It is rarely offered because it still puts the responsibility on the driver and the operator has no control over which programme is being used.
The problem with the pre-set system is that it is in evitable that the vehicle will only be operating in the optimal setting part of the time. If you operate over a very flat route with out gradients or the need to pull out speedily into a moving traffic stream then Super Economy is probably OK, but if you are operating somewhere hilly, like Sheffield, things are very different. Here, although the city centre is quite flat, virtually all roads off that centre go up, so you would probably opt for more of a power setting to maintain good on-the-road performance. It doesn’t matter which programme you adopt, inevitably there will be times when the transmission needs to access one of the other bands. The problem with that is those bands it is not delivering maximum fuel economy.
In a set of tests carried out by ZF with an 18m artic not fitted with TopoDyn they were able to quantity fuel consumption for different situations. In a heavy urban situation with the transmission set in the power setting the vehicle consumed 79lit/100km and in the Super Economy mode 71lit/100km a variance of 8lit/100km. In an easy urban situation the figures were 68/67/65lit/100km, still a difference of 3lit/100km. The test were carried out across all levels of operation from peak times to non-peak times.
There is stand German test route used by all manufacturers. This is the 10km long Line 24 running between the Schlossplatz, Hauptbahnhof (railway station) and Schreiberstrasse in Stuttgart. Tested on this line, without TopoDyn and the Ecomat set to the Super Eco programme, the ZF technicians found that on no less than ten occasions on each trip the transmission had to go into other bands and was not therefore operating at optimum fuel efficiency.
The optimal engine speed range to achieve maximum fuel economy is between 1100 and 1300 rpm. Normally, to demand more power from the engine you increase the revs. What TopoDyn close is to use its ratios to give you the required extra performance without increasing the rev band significantly. Before you equate that with sluggish performance let me dispel that idea, it isn’t, in fact you cannot even detect that the transmission is changing to provide the extra performance. There is no need to kick down as it will respond instantly. Don’t worry you can still have the kick down facility but use of that too often will damage the fuel economy.
How does it work
So how does TopoDyn do it. First of all it does not need to be set to a predetermined fuel economy programe, it will automatically use whatever part of the band it needs to provide the performance required, coupled with maximum fuel economy. It does this by constantly computing the driving resistance be the vehicle going uphill, downhill, loaded or unloaded. The system always operates in the most cost efficient mode, yet is performance orientated. For example the system automatically maintains the engine revs in the downhill situation, so as to ensure full ratarder/intarder efficiency, but still protects the fuel economy.
The key to the system is the sensing of the resistance on the drive axle. This means that if you have a fully loaded bus on a hill it will automatically provide the right power to pull away but provide it in the most fuel efficient manner possible. It doesn’t actually know you are on a hill, it computes that from the resistance and automatically adjusts the transmission/engine correlation to allow the vehicle to pull away perfectly but always at its most fuel efficient.
I know it sounds far fetched, but believe me, it works.
ZF carried out tests in four different German cities: Stuggart, Dresden, Trier and Portugal. The vehicles operated the same routes every day and operated for the full day span so experiencing different loadings. In all cases there was at least a 2% saving in fuel and in some instances as much as 10%. The average across all five cities was 5%. Across all the tests the TopoDyn fitted vehicles were consistently better on fuel economy than non-TopoDyn fitted vechicles.
Now ZFhave primarily developed TopoDyn for city buses because that is where most Ecomats and Ecolifes are used, but here I think the UK coach operator has a big advantage. In the UK we are big users of the Ecomat in coaches and have been so many years. That is not the situation in Europe where there is still a preference for using six-speed manuals(Europe isn’t always right). In fact, the UK is one of the largest markets in Europe for the Ecomat. It is used in coaches for the UK produced by most leading manufacturers including: Volvo, Scania, MAN, VDL, EvoBus, Irisbus-Iveco, ADL and even integral manufacturers like Temsa and VanHool. Currently these will have the Econmat set to the power setting but that means they are not operating at their most fuel efficient fro much of the time. With TopoDyn fitted they will be, and that should mean real benefits in fuel economy for coach operators. The Government shows on sign of giving us BSOG on coaching activities, but this promises some of the saving the industry has been asking for, and on every mile the vehicle covers, without the paperwork.
The benefits of TopoDyn can be summarized as:
Optimum fuel consumption, because more power is only called fro when it is really necessary;
Noise levels will be lower, due to the engine speed rating is lowered;
Excellent dynamics, because there is no gear hunting thanks to the gradient adapted shift programme;
Increased flexibility, because the vehicle is always traveling with the optimum shift programme;
Maxmum braking performance during downhill travel, because of the performance optimized shift pattern, which means no additional fuel consumption;
Influence of the driver is eliminated, because the topography not the driver determines the shift pattern.
Trying TopoDyn out
Now you know me. I don’t take manufacturers claims at face value, I have to try it myself. ZF provided us with a test vehicle to see and try the system in practice. The vehicle was MAN Lion’s City service bus. It had the MAN A21 understructure (available in the UK in combination with the Wright Meridian body) with a MAN D2066 LUH engine rated at 350bhp matched to a six-speed Ecomat4 6HP604C automatic transmission with TopoDyn.
In the trial we were able to watch on a computer screen as the system selected the various power bands and at the same time we could see graphs of the engine revolutions, the fuel consumption and the gradient profile. During the tests it was remarkable how flat both the engine revolution and fuel consumption graphs stayed. We experienced the vechicle operating on ZF’s test track including re-starts on a 15% hill. On the hill it naturally needed full power to move off but, interestingly, it stopped demanding full power much earlier that you would have expected and yet there was no loss of performance. Similarly, dropping down the other side of the hill, it provided full engine revolutions need ed by retarder but the fuel consumption graph stayed flat.
Next we took the vehicle out around the town of Friedrichshafen. Being on the shore of Lake Constance the town’s roads are pretty flat and the vehicle operated in the super eco band fro most of the time. We then headed out into the rising land on the outskirts of the town. It was fascinating watching the system selecting the optimum programme fro the differing road situations.
Actually, driving the vehicle was quite surreal. You barely noticed the ratio changes, in fact there were times when it changed and the only way you knew it had changed was because the computer screen showed you it had. Of course in a normal situation you won’t have that data available, all you will have is an indication of which gear the transmission is in. What was really surreal was pushing the vehicle along in sixth when you would expected it to be using the power band, it wasn’t. In fact, for most of the time, even though you were traveling at speed, it was only using the lower end of the programme.
Cost
Now this is the real surprise. TopoDyn isn’t especially expensive. ZF say that it costs about Euros500 to equip the gearbox with TopoDyn.
If you have a vehicle on order for delivery in 2008 with Ecomat transmission then you should insist that it has TopoDyn fitted. It is only a software programming issue so it takes no time at all to do it.
It is also possible to retrofit TopoDyn. If you have a vehicle which has an Ecomat transmission built in the last two years, then it can probably be upgraded. Your dealer will have to arrange this by checking with ZF that the transmission is upgradeable.
If you have a vehicle on order with the Ecolife box, no worries, that already comes with TopoDyn installed.
Conclusion
TopoDyn is impressive and, once again, ZF have raised the bar. Anything, which saves raised the bar. Anything, which saves fuel but does not compromise the vehicle’s performance has to be seriously considered.
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