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Stupid motoring point dept

Community Veteran
Posts: 7,154
Thanks: 54
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Registered: 30-08-2007

Stupid motoring point dept

The coach/bus I usually drive. is capable of propelling 72 passengers at any speed limit under the governed 56mph it is saddled with. Its engine is a 6.5 ltr turbo diesel coupled to a 3 speed automatic gearbox, with a power output (when new) of around 250ish bhp.
A Ferrari F430 is a two seater with an engine that develops something around 350bhp but still subject to national speed limits in this and most European countries (yes I know there are track days, but these account for a relatively small amount of time in the life of a road based car)
So should Ferrari stop making supercars and start building bus engines instead? 
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46 REPLIES
Community Veteran
Posts: 1,850
Registered: 11-08-2007

Re: Stupid motoring point dept

what would be the point if they will be restricted to 56mph?  prolly not even its optimum cruising speed.
Community Veteran
Posts: 3,364
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Registered: 06-04-2007

Re: Stupid motoring point dept

What is Petelw trying to say?
The engine and gearbox on the bus will be optimised to produce torque not power, the rpm at which max power is produced is not the same as when max torque is produced.
This is illustrated by my Polo 1.6l 75bhp having a race with my friends Celica 1.8l VVT 190bhp, at some slower speeds my car out accelerates his, so on country roads I have no trouble keeping up with him. The Polo has lots of torque. Smiley
SW.
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3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
madjbright
Grafter
Posts: 184
Registered: 09-06-2007

Re: Stupid motoring point dept

Quote from: godsell4
This is illustrated by my Polo 1.6l 75bhp having a race with my friends Celica 1.8l VVT 190bhp

I hope that you do not do this on public roads!!
Lurker
Grafter
Posts: 1,867
Registered: 23-10-2008

Re: Stupid motoring point dept

Quote from: Petlew
speed limit under the governed 56mph it is saddled with

Do you know why your bus company insists upon a 56mph limiter being fitted? I didn't think you went abroad!
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Stupid motoring point dept

you dont have to go abroad, the speed limiters are also a British requirement see http://www.dft.gov.uk/pgr/roadsafety/speedmanagement/vanspeedlimits
Lurker
Grafter
Posts: 1,867
Registered: 23-10-2008

Re: Stupid motoring point dept

Two points Pierre - firstly, the article you linked to makes no mention of PCVs, its an article discussing the use of limiters on Vans/Trucks.
Secondly, the point is nothing really to do with the fitment of speed limiters per se, its a question of why 56mph.
None of the speed limits in the UK are 56mph, for *any* vehicle.
scootie
Grafter
Posts: 4,799
Registered: 03-11-2007

Re: Stupid motoring point dept

The way bus drivers drive here in the country side i am glad they are limited. going back 15 years it was more pratical to have the bus stops in the fields as this is where most buses ended up.
Community Veteran
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Re: Stupid motoring point dept


Am I the only person to have been overtaken on a Motorway by a National Express coach? I am sure I was doing 65/70 mph at the time!  Undecided
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3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
Lurker
Grafter
Posts: 1,867
Registered: 23-10-2008

Re: Stupid motoring point dept

Quite possible - the national speed limit for buses on motorways is 70.
(60mph on other dual carriageways, and 50mph on national speed limit single carriageways.)
Community Veteran
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Registered: 05-04-2007

Re: Stupid motoring point dept

Quote from: godsell4
Am I the only person to have been overtaken on a Motorway by a National Express coach? I am sure I was doing 65/70 mph at the time!  Undecided

Nope some of them do go a bit mad .. I've been overtaken by them and they must have been going over 70.
Lurker
Grafter
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Registered: 23-10-2008

Re: Stupid motoring point dept

Quote from: Alex
I've been overtaken by them and they must have been going over 70.

Worth noting that their speedo's have to be extremely accurate as its part of the Tacho - whereas the speedo in your car is allowed to be 10% out.
So when your speedo indicates you are doing 70, you could in reality only be travelling at 63mph.
Its common practice for car manufacturers to err on the side of caution, and generally aim to have speedo's reading a speed around 5% higher than the actual speed you are travelling at.
Around town, this means that you will probably be doing 28.5mph in a 30 zone, and 38mph when your speedo says 40.
The equivalent works out at 66.5mph when your speedo shows 70mph.
Again, assuming that you tyres have *exactly* the same circumference as the ones that the car was specified to use - clearly, as the tyres wear down, one revolution will carry you a slightly shorter distance.
This inaccuracy will also have a greater effect the faster you are travelling.
Not at all impossible for you to be travelling at an indicated 70, and the bus to be travelling at an actual 70 - with the bus travelling significantly faster than you are.
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Stupid motoring point dept

Allright I am getting old and forgot the Passenger vehicle speed limits, But when I last worked part of my Job function was to check speedometer accuracy so I do know how to do that.
Below is my current vehicle when new
Community Veteran
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Registered: 06-04-2007

Re: Stupid motoring point dept

Quote from: James_G
... whereas the speedo in your car is allowed to be 10% out.

understood and taken that into account!
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https://portal.plus.net/my.html?action=data_transfer_speed
Community Veteran
Posts: 3,486
Registered: 02-10-2008

Re: Stupid motoring point dept

I once worked on a project where the police lent us a traffic car for a few weeks  !!! - and I had to have a driving test with their chief driving instructor  Grin
Great fun, but we were strictly briefed not to drive at the limit, be it 50, 60 or 70 - but about 5mph slower - so that people could overtake us.
But they have special speedometers - with a tighter specification .
It's amazing how well most people drive when one of those cars is about .
Oh and no blue lights or two tone horns except in specially controlled circumstances.