Top speed or acceleration?
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Hello there ! I've been hesitating whether to post this topic or not but i decided to post it anyway .
Question is , do you prefer top speed or high acceleration in city buses ? I prefer good acceleration over top speed.
Reason being that city buses are supposed to have many stop and gos , top speed isnt really a matter . Acceleration is far more important .
Thats my opinion . How about yours?
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In the city --> Good acceleration
On the expressway --> Top Speed -
Prefer ZZZZZ to XXXXXOriginally posted by Scania N113CRB luver:Hello there ! I've been hesitating whether to post this topic or not but i decided to post it anyway .
Question is , do you prefer top speed or high acceleration in city buses ? I prefer good acceleration over top speed. Reason being that city buses are supposed to have many stop and gos , top speed isnt really a matter . Acceleration is far more important .
Thats my opinion . How about yours?
Actually I prefer Top speed to acc. -
i prefer both lehz. how?
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There is a way of having both. ZF provides an ideal solution - the 6-speed automatic transmission. Not only can you have brisk acceleration due to a low diff ratio and close intermediate gears, but you can also have good top end speed at economical engine speeds with the double-overdrive gears (0.83:1, 0.59:1).
Regards,
Dave -
I remember theres a speed info from a bus manufacturer that its top speed with a 6-speed ZF 6HP502 is a whopping over 100km/h , more than Voith 4-speed , which is a max of 80+km/h . If im not wrong its either Volvo or Scania .Originally posted by Powered_By_CNG:There is a way of having both. ZF provides an ideal solution - the 6-speed automatic transmission. Not only can you have brisk acceleration due to a low diff ratio and close intermediate gears, but you can also have good top end speed at economical engine speeds with the double-overdrive gears (0.83:1, 0.59:1).
Regards,
Dave
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Yup . My above info is confirmed . According to Volvo's website , the Volvo B9L , with a ZF 6HP602 gearbox , has a top speed of 112-113km/h* , as compared with 94km/h* for a Voith 4-speed D864.5 .
*Speed depends on hub reduction ratio, which is of single hub , and tyres using size 295/80 R22.5" .
Hmmm... I noticed that bus manufacturers began fitting tyres of size 295/80 R22.5 as standard . They say it is now possible to fit larger tyres . What is the purpose of fitting large tyres on city buses?
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but LTA fits a speed limiter in heavy vehicles (our public buses included), which allows the bus to travel till 80km/h only. so wads the difference?? (am i correct??)Originally posted by Scania N113CRB luver:Yup . My above info is confirmed . According to Volvo's website , the Volvo B9L , with a ZF 6HP602 gearbox , has a top speed of 112-113km/h* , as compared with 94km/h* for a Voith 4-speed D864.5 .
*Speed depends on hub reduction ratio, which is of single hub , and tyres using size 295/80 R22.5" .
Hmmm... I noticed that bus manufacturers began fitting tyres of size 295/80 R22.5 as standard . They say it is now possible to fit larger tyres . What is the purpose of fitting large tyres on city buses? -
Not quite. Shouldn't it be [b]60/b] km/h?Originally posted by hiphop2009:but LTA fits a speed limiter in heavy vehicles (our public buses included), which allows the bus to travel till 80km/h only. so wads the difference?? (am i correct??) -
speed limitors don't affect the acceleration of vehicles just the max speedOriginally posted by hiphop2009:but LTA fits a speed limiter in heavy vehicles (our public buses included), which allows the bus to travel till 80km/h only. so wads the difference?? (am i correct??)
can imagine if the speed limiters were removed on the LO3x...within 10-20 seconds if BC good..can maximise the engine's potential and accelerate all the way...in no time pass 120kph -
lol like forum_dude say, chiong like ferrari? (WTF)Originally posted by SBS9888Y:speed limitors don't affect the acceleration of vehicles just the max speed
can imagine if the speed limiters were removed on the LO3x...within 10-20 seconds if BC good..can maximise the engine's potential and accelerate all the way...in no time pass 120kph 
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Then what about those PA registered coaches used for going Genting/KL? Also fitted with speed limiter??Originally posted by hiphop2009:but LTA fits a speed limiter in heavy vehicles (our public buses included), which allows the bus to travel till 80km/h only. so wads the difference?? (am i correct??) -
Speed limiter is just the devices attached via the meter cables,The nasty ones should be the fuel pump that any thing you do also the limit top speed.
For ideal SG Citybuses
Good/Powerful acceleration for better pick up & mid speed.
Top end 65-70 kmh are more than enough.
There's a huge different between 60 & 65kmh -
It is mandatory by law that all buses have a maximum speed of 60kph. But tolerance will be given as long as the speed is between 55kph to 64kph. Anything above that is against the law. Both the BC and the workshop will get it if the bus is caught outside speeding.
For your info, WOCC & EOCC is capable of catching the speeds of the buses. So if someone is speeding, the tabulated datas will show.
In Singapore, buses top speed is uesless because of the 60kph limitation. Even if the bus can hit above 100kph will also be useless.
Our speedlimiters are from Siemens VDO.
Top speeds are also determined by the gearbox gear ratios. However to all trained automotive professionals, we all know that if you want to have more top speed, you have to sacrifice acceleration. Different gearboxes with different gear ratios satisfy different type of needs. So there is no particular brand of gearbox which will be confirmed better in top speed or acceleration. It is only by the design of the gearbox operational control, material, user that determines the superiority of the gearbox life & performance. -
Drive F1 car, can have both
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To add to what MS has said above, the engine and the transmission can have an enormous impact on the acceleration and speed behaviour of a bus.
Basically, if you go from a 5-speed ZF transmission to a 6-speed ZF transmission without changing the diff ratio or engine, you will gain top-end speed. The same occurs if you change the diff ratio to a high ratio.
The 6-speed ZF transmission has thus enabled operators to use smaller engines (downsizing) to produce the same result. Instead of 12-litre engines, 9-litre engines can be used with a 6-speed transmission and lower diff ratio to provide similar acceleration and top-end speed characteristics of previous buses. Also note that engine development has meant that new smaller engines actually have much higher power and torque output of similar engines from, say, 10 years ago.
If 60km/h is the absolute maximum speed allowed in Singapore, a 5-speed ZF transmission would be the best choice, matched with a very low diff ratio that allows cruising at 60km/h well within "green zone" engine speeds for the lowest fuel consumption figures.
Regards,
Dave[/b]