Rough V12?

[hedges88]

Went on a Volvo coach to the seaside yesterday, beautiful new machine and It was very impressive, nice I-shift gearbox too. I sat right at the back over the engine, and it was as rough as a badgers bottom. It actually felt like a massive 4 cylinder owing to the lumpiness and vibration.

To my horror the driver told me it was a V12. I thought they were supposed to be a smooth as an engine can get, in perfect primary and secondary balance?

Does the length of the crank and cam cause that level of vibration in such a large engine? (13-16 litre)

[jamieduff1981]

V12s run great at much larger sizes. The RR Griffon was 37litres.

It's possible to get the crankshaft design completely wrong but that's almost more effort than getting it right.

It may be (likely) that the driver was mistaken.

[hedges88]

jamieduff1981 said:

V12s run great at much larger sizes. The RR Griffon was 37litres.

It's possible to get the crankshaft design completely wrong but that's almost more effort than getting it right.

It may be (likely) that the driver was mistaken.

I though about that, if he was mistaken then it would of at least had to have been a straight 6 which would probably be just as smooth

Unless it's a 5 cylinder they are popular for commercial applications. I've never found them to be rough though, but at large sizes I guess they could be

[leafspring]

Unless it's ECU was tuned for economy and it had shut down some of its cylinders.

[dowahdiddyman]

Think you will find the driver was talking bull. Cannot see there being a V12 diesel engine in a coach, if so i`m sure it would have been on a truck as well and the biggest is a 750hp and that ain`t a V12.

[s p a c e m a n]

B12 Is a model of Volvo bus/coach

[jamesson]

Never in a million years will it be a V12. Straight six is far more likely.

[Magictrousers]

As a Volvo, a straight 6 is a given.

[Rammy76]

Magictrousers said:

As a Volvo, a straight 6 is a given.

Still shouldn't be as rough as the OP says though? Issue with engine mounts or any numerous other things could cause it.

[anonymous-user]

Biggest problem is "cabin boom" and shake. This where the critical frequency of response of the cabin structure is excited by the engine frequency. You could have the smoothest engine in the world, and the cabin would still shake at that speed.

[Stamford]

s p a c e m a n said:

B12 Is a model of Volvo bus/coach

<bus nerd>

Yup, in Volvo B = Bus, 12 = 12l Engine capacity, then M=Mid Engine or R=Rear Engine.

So for example, the B9R is the new(ish) weight-optimised smaller 9l engine, rear engine bus chassis.

Rear engine tends to be used more on Intercity or Airport routes because having the engine at the back leaves plenty of room a for large passenger luggage space under the main seating area.

</bus nerd>

[iva cosworth]

I doubted this coach had a V12 but didn't want to wade in before those

with knowledge had had their say...

[Raize]

Don't the coaches have flat-sixes rather than inline sixes for packaging reasons?

[jamesson]

No, they're inline sixes.

[Mr2Mike]

Raize said:

Don't the coaches have flat-sixes rather than inline sixes for packaging reasons?

I believe many of them have in-line sixes mounted horizontally, but don't know of any horizontally opposed sixes.

[folos]

I've driven an n/a V12 15,000cc mercedes coach - it was rough as fk (company swapped it short term with a cowboy independent for a double decker) - however it sounded monstrous and was good for setting car alarms off :-)

Coach in the OP is probably a B12, 12000cc (straight 6 ?). They idle rough anyway but alot of them get ragged rotten on national express clocking up interstellar mileage. Most probably leased so will have had minimum maintenance and servicing.

Nice coaches but nothing comes close to the wonderful manual B10M imo :-)



clocking up

[Benbay001]

v12 diesel in a coach? yeh fking right!

you still get some six cylinder 40ton HGVs ASAIK

Even the biggest HGV engines the 700hp ones are only v8s.

Bare in mind a coach weights about 12 ton.
Driver is either mis informed or a liar.

[folos]

Benbay001 said:

v12 diesel in a coach? yeh fking right!

you still get some six cylinder 40ton HGVs ASAIK

Even the biggest HGV engines the 700hp ones are only v8s.

Bare in mind a coach weights about 12 ton.
Driver is either mis informed or a liar.

Nope, mercedes 0303s had 15l V12s, can't remember the exact reg of the one I posted about but this is one of the same batch:

Vehicle enquiry

The vehicle details for G892 VNA are:

Site Last Updated: 17/07/2013

The enquiry is complete.

Date of Liability 18 01 2002
Date of First Registration 25 05 1990
Year of Manufacture 1990
Cylinder Capacity (cc) 15078cc
CO2
Emissions Not Available
Fuel Type HEAVY OIL
Export Marker N
Vehicle Status Unlicensed
Vehicle Colour ORANGE Vehicle
Type Approval Not Availabl

Edited by folos on Sunday 4th August 17:46

[Benbay001]

folos said:

Nope, mercedes 0303s had 15l V12s, can't remember the exact reg of the one I posted about but this is one of the same batch:

Vehicle enquiry

Site Last Updated: 17/07/2013

The enquiry is complete.

Date of Liability 18 01 2002
Date of First Registration 25 05 1990
Year of Manufacture 1990
Cylinder Capacity (cc) 15078cc
CO2
Emissions Not Available Fuel Type HEAVY OIL Export Marker N Vehicle Status Unlicensed Vehicle Colour ORANGE Vehicle Type Approval Not Availabl

Crikey!
I knew some of the big military trucks had v12s.

[Magictrousers]

Merc were relatively late to turbocharging, they went for bigger naturally aspirated engines.

At one point, they had V6's, V8's, V10's and V12's.