Volvo B10BLE (CNG)

Powered_By_CNG SG

Alright, just to share my knowledge.

Voith DIWA transmissions are designed very differently to ZF-Ecomat transmissions. Especially of interest is the design of the torque converter.

The Voith transmission (at least on paper) seems to have a lower first gear ratio compared to the ZF (5.05:1 for a Voith D864.3), however, because of the design of the Voith torque converter, this is the ratio for the entire 1st gear because the Voith does not have seperate unlocked and lock-up stages. In contrast, the first gear ratio given by ZF for their Ecomat transmissions is 3.43:1, but this ratio is achieved during the "lock-up" stage - in the hydraulic stage, that ratio is lowered to nearly 6:1, giving impressive initial transmission power. This is why you will experience better initial acceleration with a ZF transmission.

In practice, buses with Voith transmissions generally have lower final drive ratios to compensate for the (lack of) acceleration. ZF transmissions can use a slightly higher final drive ratio yet achieve the same acceleration as the Voith, while achieving the same top-end speed (comparing a Voith D864.3 and ZF 5HP 500). The new 6-speed ZF transmissions give a whole new meaning to the word "flexibility" - 0.59:1 in 6th gear means that an extremely low final drive can be used, providing outstanding acceleration AND top speed while improving economy. To prove my point, compare the performance betwen a Mercedes-Benz O 405 with a Voith and then a ZF.

And talking about economy, the ZF transmission has more intermediate gears, meaning that there is always a correct gear for each situation. Compare that with the Voith that easily pushes engine revs on new buses to near 2000 rpm and you will be able to see a visible difference. What the ZF transmission lacks in durability it more than makes up in fuel efficiency and engine protection.

Regards,
Dave

SBS9818A SG

He's contributed far more than you ever have, Alan.

MS SG

hi dave... wrong infos.

Gear Ratios
Gear ratio is the ratio between n revolutions made by the driven gear is to the n revolutions made by drive gear.

eg. Gear Ratio for Voith is 6.1 for 1st gear, Gear ratio for ZF is 3.43 for 1st gear

Meaning that for every revolution the driven gear makes in the Voith gearbox for first gear, the driven gear makes 6.1 revolutions.

For every revolution the driven gear makes in the ZF gearbox for 1st gear, the drive gear rotates 3.43 revolutions.

The bigger the gear ratio the more powerful and slower it is.

However the lower the gear ratio the faster the bus will be. Therefore anything lower than 1 is an even more deeper exploitation of the engine power to bring about greater speeds.

Let me illustrate:
If I have a higher gear ratio, the bus moves towards a concrete wall and try to ram the wall down. The bus will not ram it down via impact. But via slow unstoppable strength. It will only give up until the bus cracks or the wall collasps.

But if the gear ratio is low, the bus initially builds up speed with a lower gear until a desired speed to accomodate the lower gear ratio but higher speed, the bus is trying to bring down the wall via impact. But if that impact fails & the bus is still intact, for the bus to try a second time is impossible because it will need to start from 1st gear and build up the speed again until it reaches a higher gear with lower gear ratio.

Torque converter
only comes in use in first gear. Torque converter helps to multiply the torque in order to help to start move the heavy bus.

Lock Up
will only come after the torque converter seizes to work when 2nd gear comes in. In order to cancel the powerful torque and start moving with lesser torque but more speed.

Gearbox brains
The gearbox has 2 'brains'. One is the ECU while the other is the valve body run by solenoids which receives signal from the ECU to decide which clutch to lock.

ZF 4HP
A B C D E F solenoids
H solenoid is the lock up.

Reverse gear = C + F
Neutral = no solenoid activated
1st gear = A + F (no H because under the influence of torque converter)
2nd gear = A + E + H
3rd gear = A + D + H
4th gear = A + B + H

In other words, if solenoid 'A' is not working, the bus can only reverse gear. Or if the pins and connections between the ECU to the solenoid 'A' is short or open, the bus can only reverse gear. And don't laugh. It happened before and the bus was at 4th floor. So have a guess how did we get the bus to the first floor workshop? It was a Leyland 3 axle superbus.

For Voith I need to use a lot of pictures to explain as the Voith gearbox is more complicated with different brake stages and retarders being catered for in Voith gearbox.

However, up till now I have never needed to activate the whole workshop to push any Voith gearbox buses before while I've already pushed many Leylands already. And damn... if the engine is not working, we cannot build up the air to release the brakes then we'll be in deep shit. The superior designs of the Voith gearboxes helps to extend the lifespan of the gearbox which led to lower maintenance costs on Voith Transmission. I designed the repair kit for both the ZF and Voith gearboxes for use in workshop that's why I am so sure that Voith gearboxes have a cheaper package yet longer lasting lifespan due to it's design. I have the Tansmission Technology modular training notes. If you're interested I can lend out for photocopy. It's not any confidential info also. Known by many people in this industry.

Oops... did I accidentally reveal the answer on how I got the Leyland down from 4th floor?

SBS9806J SG

Is this a CNG thread or a gears thread?

Scania N113CRB luver SG

Originally posted by MS:

hi dave... wrong infos.

[b]Gear Ratios
Gear ratio is the ratio between n revolutions made by the driven gear is to the n revolutions made by drive gear.

eg. Gear Ratio for Voith is 6.1 for 1st gear, Gear ratio for ZF is 3.43 for 1st gear

Meaning that for every revolution the driven gear makes in the Voith gearbox for first gear, the driven gear makes 6.1 revolutions.

For every revolution the driven gear makes in the ZF gearbox for 1st gear, the drive gear rotates 3.43 revolutions.

The bigger the gear ratio the more powerful and slower it is.

However the lower the gear ratio the faster the bus will be. Therefore anything lower than 1 is an even more deeper exploitation of the engine power to bring about greater speeds.

Let me illustrate:
If I have a higher gear ratio, the bus moves towards a concrete wall and try to ram the wall down. The bus will not ram it down via impact. But via slow unstoppable strength. It will only give up until the bus cracks or the wall collasps.

But if the gear ratio is low, the bus initially builds up speed with a lower gear until a desired speed to accomodate the lower gear ratio but higher speed, the bus is trying to bring down the wall via impact. But if that impact fails & the bus is still intact, for the bus to try a second time is impossible because it will need to start from 1st gear and build up the speed again until it reaches a higher gear with lower gear ratio.

Torque converter
only comes in use in first gear. Torque converter helps to multiply the torque in order to help to start move the heavy bus.

Lock Up
will only come after the torque converter seizes to work when 2nd gear comes in. In order to cancel the powerful torque and start moving with lesser torque but more speed.

Gearbox brains
The gearbox has 2 'brains'. One is the ECU while the other is the valve body run by solenoids which receives signal from the ECU to decide which clutch to lock.

ZF 4HP
A B C D E F solenoids
H solenoid is the lock up.

Reverse gear = C + F
Neutral = no solenoid activated
1st gear = A + F (no H because under the influence of torque converter)
2nd gear = A + E + H
3rd gear = A + D + H
4th gear = A + B + H

In other words, if solenoid 'A' is not working, the bus can only reverse gear. Or if the pins and connections between the ECU to the solenoid 'A' is short or open, the bus can only reverse gear. And don't laugh. It happened before and the bus was at 4th floor. So have a guess how did we get the bus to the first floor workshop? It was a Leyland 3 axle superbus.

For Voith I need to use a lot of pictures to explain as the Voith gearbox is more complicated with different brake stages and retarders being catered for in Voith gearbox.

However, up till now I have never needed to activate the whole workshop to push any Voith gearbox buses before while I've already pushed many Leylands already. And damn... if the engine is not working, we cannot build up the air to release the brakes then we'll be in deep shit. The superior designs of the Voith gearboxes helps to extend the lifespan of the gearbox which led to lower maintenance costs on Voith Transmission. I designed the repair kit for both the ZF and Voith gearboxes for use in workshop that's why I am so sure that Voith gearboxes have a cheaper package yet longer lasting lifespan due to it's design. I have the Tansmission Technology modular training notes. If you're interested I can lend out for photocopy. It's not any confidential info also. Known by many people in this industry.

Oops... did I accidentally reveal the answer on how I got the Leyland down from 4th floor?[/b]

No you didn't reveal it. Laughing But u hint it larh......

Btw i agree with dave. ZF allows better fuel efficiency and engine protection. Cause diesel engines actually weren't designed for high rpm working jobs( what i meant high rpm is reacher near the max engine rpm), which explains why ships and diesel generation uses lower rpm diesel engines. Maybe im wrong about this, i dont know, i dont wish to start a debate again. Smile

But dont worry about ZF faults. ZF is coming up with the new ZF Ecolife series. Hopefully the new gearbox doesn't have the solenoid design bugs. Yea, i stongly agree with what MS said, if solenoid A is spoilt, the bus can only move in reverse. This is extremely troublesome (imagine moving a DD in reverse down a 4 storey building like what MS has said. OPPS! I revealed the ans. Embarassed ).

Actually, i still prefer ZF. Remember about what dave said about engine protection, about engine being runned at high rpm near its max working range? If Voith makes engine overhauling more frequent due to more engine strains, now you have to cover more engine costs as well. But if driving a bus in reverse because the solenoid is spoilt and the bus cnt move in forward gears and that damages the engine even more, i have nth else more to say. Smile
And also, dave also mentioned that due to ZF having correct gears for each situation, the engine will have less strains and thus engine breakdowns will be less frequent, just like riding a 18-speed MTB and a 24-speed MTB. Obviously the one with the 24-speed will go up the hill much more easily than the 18-speed, and you wont get tired that easily as well. Wink

btw why is it that Voith-ed Habits have that "roaring" sound when speeding? ZF-ed Habits dont have leh.

Ok larh, stop arguing and debate whos right and who's not. We both have our interest in certain things and we have to respect that. No point arguing and end up getting unhappy with each other. Mr. Green So lets peace and stop here ok?

Ok larhs, we like heck care bout TS question liao. Talk about CNG bus become gearbox debation. Laughing

SBS1985C SG

Although this info in off topic. I do not mind as its a very INFOMATIVE Post instead of those +1s.

(This post can be in fact also be called +1).

so +1 Laughing

manjieass SG

+1 Laughing

Powered_By_CNG SG

@MS: A "lock-up" torque converter is in fact a hydraulic clutch that links the bus engine with the transmission input shaft. Also, lower (higher number) final drive ratio gives more responsive acceleration but less top speed, and a higher (lower number) final drive ratio gives less responsive acceleration but more top speed. Same applies for gear ratios for transmissions because both ratios are directly linked.

Alright, back to my specialty now, CNG-powered bus engines. Singapore has only experimented with one type of CNG engine and that is the Volvo GH10B with open-loop lean-burn combustion and central gas injection via four injection valves. Such a system provides adequate performance but suffers greatly if there is too much variation in fuel quality. The latest CNG engines offer either closed-loop stoichiometric or closed-loop lean-burn combustion and provides resistance to such variations, and are also able to adjust the air/fuel mixture in real-time to allow for such things as temperature and pressure changes, ignition condition, and other manufacturing tolerances. The new generation also provides signifcantly improved power and torque outputs as well as improved responsiveness. The latest Volvo CNG engine is the G9A which features a maximum rating of 300 PS/1400 Nm, closed-loop stoichiometric combustion with exhaust gas recirculation and a three-way catalytic converter to meet Euro 5+/EEV emissions specifications.

Regards,
Dave

MS SG

... ... Question

Initially there was also a thread in businfohub which led into gearbox. I have previously indicated that there're many wrong infos about gearbox being spreaded around. That is why I initiated explanations.

But if you all insisted on your own theories I have nothing else to say.

I have the official SBST transmission module theory textbook my explanations are taken from the textbook and hands on training. Also on the ground 1st hand experience.

But if you still feel that it is not enough to convince that some of your theories are actually very wrong. I have explained once and that's quite sufficient. Then I have no choice. No pt arguing further also.

MS SG

eh... no. it's pushed down manually. its too dangerous to reverse drive down.

^tamago^ SG

That's because I see no point contributing, Darryl. You will only see recognition from your own people and help yourselves. Laughing

I am in fact glad that I've learnt my lesson and not step into your pithole again.

Powered_By_CNG SG

MS, you're probably not understanding what I was trying to explain above. Look at Voith's specifications. They claim they can replace the first two gears (including torque converter lock-ups) of a "standard" (read: ZF) transmission with a longer first gear. The first gear of a Voith D864.3 is a constant 5.05:1.

Also note the huge difference between the first and second gear ratios of a Voith transmission. First gear on a D864.3 is 5.05:1, compared with 1.36:1 in second. This in in my opinion too big a difference and a cause of inefficiencies.

A bus with a Voith transmission will almost always have less acceleration than an equivalent bus with a ZF transmission. Examples I have in mind are the M.A.N. SL 202 buses in Sydney and Adelaide (Australia) and Mercedes-Benz O 405/O 405 NHs. The SL 202s fitted with Voiths also seem to have consistantly more worn out engines. The Mercedes-Benz O 405 NHs clearly demonstrate the differences - the Voith units fitted with a higher 5.4:1 diff to compensate for the lack of accelerating power (compared with 4.8:1 for the ZF units) - the only way to make the Voith units perform the same as the ZF units.

Regards,
Dave[/b]

^tamago^ SG

sian, one from SBST, one from Australia. >__<

MS SG

Originally posted by Powered_By_CNG:
[b]MS, you're probably not understanding what I was trying to explain above. Look at Voith's specifications. They claim they can replace the first two gears (including torque converter lock-ups) of a "standard" (read: ZF) transmission with a longer first gear. The first gear of a Voith D864.3 is a constant 5.05:1.

Also note the huge difference between the first and second gear ratios of a Voith transmission. First gear on a D864.3 is 5.05:1, compared with 1.36:1 in second. This in in my opinion too big a difference and a cause of inefficiencies.

A bus with a Voith transmission will almost always have less acceleration than an equivalent bus with a ZF transmission. Examples I have in mind are the M.A.N. SL 202 buses in Sydney and Adelaide (Australia) and Mercedes-Benz O 405/O 405 NHs. The SL 202s fitted with Voiths also seem to have consistantly more worn out engines. The Mercedes-Benz O 405 NHs clearly demonstrate the differences - the Voith units fitted with a higher 5.4:1 diff to compensate for the lack of accelerating power (compared with 4.8:1 for the ZF units) - the only way to make the Voith units perform the same as the ZF units.

Regards,
Dave[/b][/b]

Hi Dave,

I have previously explained in BIF the reason why ZF is unable to last as long as Voith. It is due to the valve body design. I have also enclosed a picture of it. With a massive fleet, the difference in maintenance cost will be very visible. This is undisputed and you have no case against this fact.

Having a powerful first gear at about gear ratio of 6, helps to move the vehicle more effectively especially when with load. Because the bus travels with passenger load most of the time.

I have previously said that ZF has a flater gear ratio. But it does not offer the kind of boost required for ferrying the mass of the people. Even though the 2nd gear of the Voith gearbox is looks weak. But think back on practical means. With a weaker first gear ratio, the driver will have to accelerate more in order to achieve the correct speed to activate the solenoid to start to shift to 2nd gear. Voith on the other hand has a shorter first gear which 2nd gear kicks in quicker than ZF. The momentum of the vehicle has already reach the optimum and thus cruising off is no issue at all. Therefore if 2 same engines are used. Before the ZF can catch up at the 2nd gear, the Voith has already moved off and the 2nd gear with a lower gear ratio number meaning as you can understand higher speed, ZF will have to accelerate more to catch up. Not talking about the load yet.

In order for you to understand, you need to use a ZF mobidig and Voith gearbox tester, plug into the ECU of the bus and get someone to drive normally while you monitor the gear changes and brake stages then you will be able to understand. It is very hard for me to explain via words.

Statistically proven that ZF costs a lot more in maintaining the gearboxes as it breaks down more than the Voith. I'm sorry as the actual details are truely classified. I need to protect both the interests of my gearbox suppliers financially. Mainly due to the valve body design. The so called ZF ecomat transmission is unable to overcome the shortcoming of the valve body design to achieve the cost savings demands of the company. Voith on the other hand due to a superior design is able to. The valve body you see in BIH I'll post it here again.

http://i115.photobucket.com/albums/n298/arakyo/valvebody.jpg

This valve body being the 2nd brain of the gearbox is the executor part while the ECU is the planner part. A very critical portion of the gearbox installed underneath the gearbox assy. It is totally submerged into hot ATF while operating. Hence exposed to the conditions in the gearbox. Notice that they are merely electrical items. How long do you think it can last against the valve body of the Voith transmission which is installed externally? Stats have already shown all these years.

If I do not have ground experience, then I will be thinking like you. I see that you learnt most of your knowledge via reading. Get into some real action and maintain a fleet. Understand the perspective with a macro view and start maintaining the gearbox both technically hands on and follow up statiscally. Then it will be beneficial to your knowledge. The textbook only helps to explain theoretically on the issue on their own point of view. Actual situation requires a hands on experience coupled with theory knowledge in order to find out the truth on which gearbox actually reaps in more savings and give enough power. Also you need to differentiate between lock up and torque converter clearly as they are totally different items which have different uses. Otherwise you're confusing the readers here.

MS SG

Don't worry. This is a healthy discussion. No hard feelings at all.
Its not a matter of where we come from but what we do.

I'm not against using ZF or against supporting ZF but I just want to bring out the facts between the myths between these two gearboxes. The origin of the notes I got are from the manufacturers themselves so it is the most accurate.

But I can reveal that ZF lasts about 3 years. Some even gone in less than 2 years.

But Voith with the same maintainance team can last 5 years. There're some even 7 years. That's why the great difference prompted a lot of issues.

Scania N113CRB luver SG

Wah. U know so much man! I really envy you! I know nuts, and ended up spouting nonsense here. Embarassed

But erh, you mentioned that Voith gearboxes lasts longer and ZF has a shorter lifespan. In ZF, this is compensated by having a longer engine lifespan. In short Voith has a longer lifespan, but the engine it is coupled to has a shorter lifespan. In ZF, it has a shorter lifespan, but engine lifespan is longer. Therefore which ever gearboxes u use, its going to be the same. Both requires major overhaul if something breaks down. In Voith, engine requires more overhauling. In ZF, gearbox requires more overhauling. Therefore, whether if its ZF or Voith, the maintainance cost is going to be about the same, unless engine overhauling is more expensive or vice versa, as said by MS, who said that ZFs cost more to operate.

Btw, MS, did the cost of maintaining of the gearboxes that u mentioned earlier on cover the cost of overhauling of the engines due to extensive wear? Question

stooper SG

OMG! How many people did you need? 20? Shocked Shocked

Don't Voith buses hold the first gear until very high and then shift later?

Just anotehr question, not tryign to argue but if it's statsically proven that ZF are lousier and cost more to maintain, why are SBST still buying buses with ZFs, like most of the B9s?

MS SG

haha.. the whole workshop. Whatever men we can activate. Some may end up looking but there are always opporunities. One takes a break the the other comes and push.

As for why still buy ZF? haha. I also want to know. But many people in the workshop feels that's a wrong decision made. I can only reveal that many purchasing are done by people who have no technical knowledge or little knowledge. This is the furthest I can reveal. The actual purchasing agenda is classified.

Those info which I revealed abt ZF and Voith are merely open info which anyone in the world can come to know. But still if I have a choice, I'd prefer to have only Mercedes Benz.

carbikebus SG

Hey i've asked some HGDEP tech why Tridents never use ZF their replies are as same as you,Quite "Leceh" to maintain.You'll West side all "Pakat" huh?

Scania N113CRB luver SG

Hi guys!

Heres two videos, one for ZF lovers, one for Voith lovers. You can clearly tell that A Voith makes the engine runs at a higher RPM as compared with ZF.

http://www.youtube.com/watch?v=u-19lrIdZdo For ZF lovers (PS: Gearbox locks-up at second gear. Actually this bus sounds like the box bendy instead of a rigid!)

http://www.youtube.com/watch?v=nqnJzYjCm2Y For Voith lovers (For Voith lovers, you defintely love this! Its whistle sound is DAMN loud!)

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