SMRT trials MAN double-decker bus

last SG · 2014-09-28T10:05:57+00:00

Now we knew why SMRT only orders 101 Alexander Dennis Enviro 500.I guaranteed this will be a sucessful trial and probably they will order at least 150 units...

SexyMichael SG

Why? Do you understand that the 10.5-litre engine provides amazing driveability and represents as near as makes no difference to no fuel consumption penalty compared to the 6.9-litre engine?

A larger engine working less hard lasts longer too!

i'll challenge your premise on fuel consumption penalty concerning the D08 and D20 engines. fuel consumption is measured on a g/kWh against rpm scale, which comes with the caveat that the actual consuption is highly dependent on the amount of power output by the engine at the particular rpm. All other factors equal (as unrealistic as it is but for the purpose of this discussion), if a D08 and D20 have the same fuel consumption at say 1500rpm, with the D20 producing 320hp and D08 producing 290hp, wont the D20 still consume more fuel?

i appreciate your knowledge and passion on these issues, but there has to be reasons why many PTOs are moving to smaller engines despite the benefits offered by bigger engines.

SexyMichael SG

I would choose the A95 DD over B9TL anytime,2nd choice will be the Enviro 500.The only thing i dont like A22 is their bodywork plus that hybrid copycat lion hair..Im not suprised if Daimler also began to custom made DD to SBST based on the new 10700cc 350hp Citaro engine

the germans, or evobus specifically, dont do businesses where markets are fragmented and where orders come in on a cyclical basis. the RHD DD market, for most purposes, is fragmented enough to the point that the germans have pretty much stopped doing that business (on that note, A39 production has stopped early this year).

the MAN A95, for most purposes, is nothing short of unsustainable should there be a lack of "sustained persuasion by concerned parties" to the PTO and other companies involved :) it is nothing short of wading into a market with really big names, thinking that small name with a not-as-well-received prior product would get some attention and hopefully elevate to big name status :D on that note as well, similar persuasion makes procurement easier, and novelty wears out much faster too.

Powered_By_CNG SG

i appreciate your knowledge and passion on these issues, but there has to be reasons why many PTOs are moving to smaller engines despite the benefits offered by bigger engines.

You are assuming that the engines are compared under full load. In practice, most of a city bus engine's life is spent either at idle or under low load. Furthermore, simple physics suggests that a certain amount of energy is required to perform a certain amount of work so you cannot assume that a larger displacement engine automatically consumes more fuel than an engine with a smaller displacement.

The downsizing of engines is due to stringent emissions requirements. A smaller engine working harder running at full load more of the time will produce lower emissions because exhaust aftertreatment systems are more efficient at higher temperatures.

SexyMichael SG

thanks for the clarification. comparing say, half-load and full-load, how much of a power discount am i looking at?

similarly, how highly would you rate mercedes's latest generation of engines (the OM936(h)/LA and OM470LA) against the older generation Euro V engines (namely the OM457hLA and OM906hLA)? being a stickler for flat torque curves i am infatuated withe the OM457hLA rated at 299ps/1250Nm, but the OM906hLA and more recent Euro VI engines seem to have lost that.

Powered_By_CNG SG

thanks for the clarification. comparing say, half-load and full-load, how much of a power discount am i looking at?

1. Well it depends on the % of load you place on the engine, naturally!

2. Naturally the 936 will not have the same off-the-line performance that the 457 has in spades despite having similar peak power and torque values in base form (299hp and 1200Nm or 1250Nm respectively). In saying that though, the 936 is a significantly stronger engine than the 906 that it replaces so now there is less of a case to use the larger engine on a standard city bus unless absolutely necessary. The OM 470 would without a doubt be an amazing performer with the same 'high torque at low engine speeds' characteristics of the old 457 but with even stronger mid-range torque.

My contacts in Germany are returning excellent consumption figures with Citaros using the 936 at 299 PS with ZF EcoLife gearbox, just above 30L/100km measured at the pump on urban duties which is actually quite a bit better than the figures returned with the 936 at 286 PS and ZF EcoLife gearbox on previous Citaros and with better performance to boot.

SexyMichael SG

1. Well it depends on the % of load you place on the engine, naturally!

sounds like evobus got their e6 engines right :)

while i understand your strong preference for the ZF Ecolife, how would you rate the suitability of the Voith DIWA for double decker applications (with a MAN engine of course)?

Powered_By_CNG SG

sounds like evobus got their e6 engines right :)

while i understand your strong preference for the ZF Ecolife, how would you rate the suitability of the Voith DIWA for double decker applications (with a MAN engine of course)?

The Voith DIWA.5 matches very well with the MAN D20 engine.

carbikebus SG

SBST prefer Voith more than SMRT,Honestly i find most SBST B9TL voith poor on acceleration.

SexyMichael SG

The Voith DIWA.5 matches very well with the MAN D20 engine.

interesting to hear that, was expecting you to mention the Ecolife over the DIWA.

that mentioned, is the D20's lack of low-end torque an issue when it comes to drivability? based off observations, the local A22s dont seem to suffer that issue whilst the A24 demonstrator and to some extent the A95 show it.

also, would you propose a 6.2:1 rear axle ratio for future A95s?

TIB429E SG

SBST prefer Voith more than SMRT,Honestly i find most SBST B9TL voith poor on acceleration.

I remebered I came across a video showcasing that ZF Ecolife is much durable than Voith or something ? Is it true??

23ispolo SG

I remebered I came across a video showcasing that ZF Ecolife is much durable than Voith or something ? Is it true??

Well, here is a comparision video I found where ZF Ecolife is compared with Voith:

https://www.youtube.com/watch?v=4Z1vrmoYxeg

It says that ZF is quieter... But I believe ZF has more advantages than Voith.

PoweredByCNG SG

interesting to hear that, was expecting you to mention the Ecolife over the DIWA.

also, would you propose a 6.2:1 rear axle ratio for future A95s?

Out of all the products, the MAN D20 engine is by far the best match for the Voith gearbosx that I have come across. Impeccably smooth changes up and down and great power delivery.

The D20 engine, which not having the same % of peak torque below 1000rpm as the Mercedes-Benz OM 457 or OM 470, is definitely no slouch. The slow initial takeaway that you are experiencing is a product of the gearbox electronically limiting the starting torque to improve ride quality and to reduce fuel consumption and output emissions. All modern gearboxes apply significant torque restriction in the lower gears, especially considering the peak torque output of today's engines.

SexyMichael SG

Out of all the products, the MAN D20 engine is by far the best match for the Voith gearbosx that I have come across. Impeccably smooth changes up and down and great power delivery.

thanks for the clarifications.

onto transmissions and torque limitation, i understand that MAN and possibly Evobus have torque limiting features in their citybuses (ASR for MAN iirc) that prevent wheel skidding and hence ensure safety. however, this torque limiting aside, can I assume that a 360ps/1800Nm engine mated to a gearbox with 1600Nm max input torque will only have 1600Nm of effective torque (assuming no torque restriction by the gearbox is in place)?

i'm floating this question because MAN offers their NGxx3 articulated buses with the Ecolife 6AP2000B and DIWA 864.5 transmssions as options; suppose the above scenario does apply, what implications are there on the driveline and more specifically engine power/torque output?

On a secondary note, what are possible reasons for MAN mating the 6AP2000B with the D2066 LUH32 engine?

PoweredByCNG SG

thanks for the clarifications.

On a secondary note, what are possible reasons for MAN mating the 6AP2000B with the D2066 LUH32 engine?

Stability control is not the only reason why torque is restricted in lower gears. Even the heaviest city bus under the most strenuous conditions would never require the full services of an engine with 1800 Nm of peak torque. The Voith D864.5 can take an input torque of up to 1700 Nm but there's a good chance that the usable torque is 'capped' at a set value (e.g. up to 1500 Nm). The use of an engine in a higher state of tune would allow an even larger 'window' where actual peak torque is available. Because modern buses have systems communicating via CAN bus, it is possible for the gearbox, whose job it is to send power to the driving axle(s), to send a signal to the main 'brain' of the bus requesting limited torque. This is achieved either via electronic wastegate (to limit exhaust gases flowing through the turbocharger(s)) or via control of fuel injection.

carbikebus SG

Im in love with this decker,Hopefully SMRT will order more with tree guard of course

SexyMichael SG

what about the converse, where the transmission has a max torque input significantly higher than the engine's max torque?

Bus Stopping SG

I think what he means is the configuration of MAN D2066 LUH32 (with a max torque of 1600Nm) mated to the gearbox ZF Ecolife 6AP2000B (with input torque of 2000Nm) which is strange.

Any ideas of why would this configuration be used instead of using the 6AP1700B which has a much closer input torque range?

Powered_By_CNG SG

I think what he means is the configuration of MAN D2066 LUH32 (with a max torque of 1600Nm) mated to the gearbox ZF Ecolife 6AP2000B (with input torque of 2000Nm) which is strange.

Any ideas of why would this configuration be used instead of using the 6AP1700B which has a much closer input torque range?

There's absolutely no problems with using a gearbox that has a higher torque input maximum. If anything, the gearbox will last longer this way as it is put under less stress than it was intended for.

iveco SG

Very good

I feel sorry that SBST's progress efforts still remain comparatively stagnant.

Hope they wake up and order more KUDs.

iveco SG

What's with bus manufacturers preferring Voith's 4-speed over the 5-speed? Voith's website says it produces 5-speed transmissions too. The Transperth B7Rs and the SBS WEGs use the 4-speed, but I think the 5-speed may be better. In fact, I would like them mated with the KUB engine.

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