Which one more heavier?
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U mean the OM447-series the pistons have a short stroke? Cause i remember engines with longer strokes have higher torque, engines with shorter stroke have higher RPM. Is that true?
You're right in saying that an engine with a longer piston stroke will have more torque and run at lower speeds. The OM 447-series engines have a bore diameter of 128mm and a piston stroke length of 155mm compared to 122mm x 140mm on a Volvo 9.6-litre engine - hence the difference in piston displacement and therefore power/torque.
Btw ya, the OM447 has low down torque, cant remember with version, the engine only has 900Nm, quite low for a 12litre engine , as compared with 1700Nm for the new 12litre D12E engine from Volvo.
You cannot compare engines from different generations. The OM 447 hA engine was developed and marketted for Euro 1. The engine was turbocharged (without intercooling) and developed what was then a very high maximum torque output of 900 Nm @ 1000 to 1700 rpm. What was more impressive about this engine was the fact that it reached 90% of it's maximum torque at a mere 800 rpm - more than what can be said about the new Volvo D12/DH12-series engines as well as the comparitively sluggish Volvo engines of the time.
The OM 447 hA engine was eventually replaced by the OM 447 hLA turbocharged intercooled engine, although both were sold side-by-side until the Euro 2 regulations came into force in Europe. This engine produced an incredible 1100 Nm @ 1000 to 1400 rpm of maximum torque and 1050 Nm @ 800 rpm - that's more than 95% of peak torque at that engine speed, even though the power curve was almost identical to the OM 447 hA.
Regards,
Dave -
Even if you totally ignore the technical specifications of the merc o4o5 and the b10m, you can simply tell by the experience of riding in these two buses that the merc bus has more torque low-down..There's this feeling of you yourself being pinned to the seatback harder in the merc bus than in the b10m..
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Try taking the Second batch Habits with ZF gearboxes and those Volgren artics. Altho not SDs, but they can surely pin you harder onto the seats.Originally posted by alleggerita:There's this feeling of you yourself being pinned to the seatback harder in the merc bus than in the b10m.. 
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Haha..but anyways, there's always this hissing sound of escaping air in a Merc O405..and i always thought it's the sound of the wastegate of the turbocharger..like what u hear from a Subaru Impreze WRX or Mitsubishi Evo..lolx..but now people also say it's from the suspension or gearbox..So WHAT actually causes the sound of escaping air? Suspension, turbocharger, or the gearbox? Lolx..
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Most likely is the suspension. Older MB buses are most well known for their hissing suspension. Took a MB coach at Genting and its suspension sound was like someone breathing loudly angrily.Originally posted by alleggerita:Haha..but anyways, there's always this hissing sound of escaping air in a Merc O405..and i always thought it's the sound of the wastegate of the turbocharger..like what u hear from a Subaru Impreze WRX or Mitsubishi Evo..lolx..but now people also say it's from the suspension or gearbox..So WHAT actually causes the sound of escaping air? Suspension, turbocharger, or the gearbox? Lolx..
But if you hear a "psst psst psst....tsui" sound then i guess it maybe from the gearbox, the sound of retarder i guess? LO3x, VO3x and most other ZF buses produces this sound, if you notice carefully. I dont know what causes it, but i think its the retarder sound i guess?