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Is there any good reason why buses & any other large diesel do not have there exhaust fumes emitting from high level as opposed to their current method of coming out at ground level. When i'm in a town centre sometimes surrounded by buses the amount of exhaust fumes i inhale can't be doing me or any one else any good. Surely if the fumes were emitted from the top of the vehicle (particularly double decker buses) it would give the fumes time to dissipate before getting down to pedestrian level.
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Diesel exhaust is so well filtered these days that it is cleaner than the air going in the engines intake.
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Are you saying that diesel exhaust fumes are non-toxic?
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>>Diesel exhaust is so well filtered these days that it is cleaner than the air going in the engines intake
Rubbish. Complete codswallop.
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>> Diesel exhaust is so well filtered these days that it is cleaner than the air
>> going in the engines intake.
>>
Except for the fine particulates and the soot and the dirty smoke when they accelerate..
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Some of the London buses have very clean exhaust. But they may be running on LPG or something like that.
I recognised diesel exhaust as toxic cycling uphill in Plymouth behind a bus accelerating slowly away from a bus stop, in the earlyish fifties. Very nasty and toxic indeed to my clean little 14-year-old's lungs, panting a bit with effort. Didn't make that mistake again. Still remember the moment, and the place.
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:-)))))))))))
Last edited by: Old Navy on Mon 12 Aug 13 at 18:34
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Stagecoach Manchester run a fleet of mostly Trident 2s and Enviro 400s. The problem is a lot of their old Enviros (2006 plates) have dirty injectors so they belch out thick smoke. When I had my office I used to have to drive down one of the busiest bus routes in Europe, and the amount of thick black smoke I saw belching out of the old Trident 2 magic buses were unreal but being a massive company they seem to get away with it.
I am sure their buses are very well maintained on paper, but in practice dirty injectors on buses seems very common.
Most the newer buses are now hybrids and they do seem to be a lot cleaner but time will tell.
Last edited by: RattleandSmoke on Mon 12 Aug 13 at 18:44
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About 50 years ago a pal of mine used to sell Redex-type stuff for diesels to local authorities and bus companies, on the basis that it saved them money by improving fuel economy. Presumably it did if they kept buying it.
Maybe that was to do with keeping the injectors clean. Certainly I could stop my diesel Scorpio smoking with a big dose of Millers.
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>> :-)))))))))))
Higher St. Budeaux ON, about three quarters of the way up the hill, well past the State Cinema and the cycle speedway track on the tough kids' recreation ground...
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>> >> :-)))))))))))
>>
I was only having a giggle at the responses to my post.
Last edited by: Old Navy on Mon 12 Aug 13 at 19:38
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>> I was only having a giggle at the responses to my post.
You were in the wind up merchant navy ON.
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Sorry. I thought you were being sentimental about one of the navy towns.
Of course I know your natural habitat once let out would have been the grotty end of Union Street ON... I meant no disrespect...
:o}
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The grotty end of Union Street was high class compared to many recreational areas I have frequented. :-)
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>> The grotty end of Union Street was high class compared to many recreational areas I have frequented. :-)
Heh heh... me too I am happy to say... purely as a trained observer of course...
Last edited by: Armel Coussine on Mon 12 Aug 13 at 20:12
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>> Diesel exhaust is so well filtered these days that it is cleaner than the air
>> going in the engines intake.
>>
Really? Try breathing it.
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Reason for not fitting a roof level exhaust, as on trains, can only be cost.
In 13yrs of cycling in London I've seen the last smoky buses disappear and the first generation of low emission types succeeded by a second. While the 'cleaner than intake' message my be hyperbole modern exhausts, eg the 'BorisMaster', produce no visible trace.
Last edited by: Bromptonaut on Tue 13 Aug 13 at 11:19
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>> Reason for not fitting a roof level exhaust, as on trains, can only be cost.
>>
Not really, its the engineering.. Where would you take a bus exhaust up to roof level, without it being dangerous to people, or prone to damage? If you take up inside you could be setting everyone up to be poisoned if it leaked.
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>> > If you take up
>> inside you could be setting everyone up to be poisoned if it leaked.
>>
>>
>>
No, it would be cleaner than the air inside.
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>> Not really, its the engineering.. Where would you take a bus exhaust up to roof
>> level, without it being dangerous to people, or prone to damage? If you take up
>> inside you could be setting everyone up to be poisoned if it leaked.
So the engineering is too costly?
Exhausts have gone up the outside, an occasionally inside, of DMU's at least since the fifties. Trains however are much more structurally robust than buses.
Another problem though would be that roof top bus exhausts would be nicely at first flootr window level.
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Space is at a much bigger premium than on trains too. The exhaust would have to be enclosed as it would be too dangerous on the outside or inside as pointed out. This would require the bus to be a few inches longer and that space is better spent on offering more seats or a better seat pitch to improve comfort.
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It would be helpful if more of them would at least direct the exhaust downwards, towards the road. Crawling in traffic the other day in the MX5 with the roof down, a coach was alongside with the exhaust spewing out of the side nearly at face level; and it wasn't clean either, absolutely filthy.
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I noticed some buses here are diesel electric are they any cleaner?
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Most new buses here now have that, they are simply hybrids. A diesel engine charging a battery which then powers the electric motors. In very slow moving traffic often the engines are shut off completely which is strange but they certainly are cleaner in that respect. Alexander Dennis claim their hybrids are 30% cleaner.
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>> Exhausts have gone up the outside, an occasionally inside, of DMU's at least since the
>> fifties
Trains run on rails, passengers run on platforms, its easy to keep the two apart. Not so on buses.
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One of our local bus company's buses has a substantial bumper on the front which bears the message "He who dares loses". I've never got close enough to see whether the bus has a smoky exhaust or not.
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Most buses have their engines at the back so it can't be too difficult or expensive to run the exhaust up the back of the bodywork and encase it in cosmetic paneling so it looks disguised. Regarding the comment about first-floor residents, the hot gases rise anyway so they will get their share wherever the exhaust is located. I hate cycling in cities, older vans seem to be quite bad as well, it surely can't be difficult to sort this problem out.
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What kind of volume of exhaust gasses are produced per something or other relevant, such as a mile? What if they were collected in a balloon and taken back to base to be disposed of by safe'n'clean magic in some way.
How big would the balloon have to be for a bus journey I wonder?
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Have you never tied a condom over a car's exhaust?
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No! I have stuck a condom over most things (including my mates head) but never an exhaust.
What happens?
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>> No! I have stuck a condom over most things (including my mates head) but never
>> an exhaust.
>>
>> What happens?
If you get a good seal around the exhaust pipe, it inflates to an enormous size before exploding with a very satisfactory bang. On one occasion the flapping ends produced a lovely raspberry.
Especially effective next to the 'just married' sign.
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Burning 1 litre of diesel produces about 2.7kg of CO2. So that's 3 x the weight of fuel burnt for a start.
The density of CO2 at standard temperature and pressure is about 2kg per cubic metre.
So if a bus did say 150 miles a day at 10mpg, that's 15 gallons, or 68 litres of fuel, 184 kg or 92 cubic metres of co2, = big balloon.
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Thanks for the sums. Not impossible then. Length of a bus, let's say 15 metres. So 92/15, need a balloon on top of the bus that's 6 metres high?
What if we then cool the gas inside?
Edit and it could be swapped or emptied more than once every 150 miles.
Last edited by: Crankcase on Tue 13 Aug 13 at 20:55
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It's purely cost.
The customers, i.e., the bus companies aren't asking for high level exhausts
There's no legal requirement to fit a high level exhaust.
So, the exhaust needs to comply only with the requrements of getting the exhaust gases away from the vehicle, complying with noise requirements, and supporting the vehicle's compliance with emissions legislation.
So, with an engine under the bus, or at the back, hanging the exhaust from existing framework represents the most cost effective way to support it along it's shortest route.
Anything extra costs more.
The only reason high evel exhausts are sometimes seen on trucks is when it's to satisfy the owner driver's ego - they are rarely specified on "normal" fleets.
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>> It's purely cost.
>>
>> The customers, i.e., the bus companies aren't asking for high level exhausts
And I contend there is also a risk and safety issue at work. High level exhausts only exist where public access is limited. Between coaches, behind tractor unit for example.
Plus it makes accident damage more expensive to fix, it hinders access for cleaning, (especially in automated washes)
There are loads of practical reasons why high level exhausts are not specified.
Last edited by: Zero on Tue 13 Aug 13 at 21:32
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>>where public access is limited.
If you did put the high level exhaust outside the vehicle, you would also have to fit a guard to prevent burns. Cost.
>>Plus it makes accident damage more expensive to fix, it hinders access for cleaning, (especially in automated washes)
Cost.
>>There are loads of practical reasons why high level exhausts are not specified.
Which all boil down to cost.
Last edited by: Number_Cruncher on Tue 13 Aug 13 at 21:35
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Well obviously you wouldn't spend more money to create problems that need money to rectify.
Its not just cost - its sensible design and engineering.
like
"we wont fit a high level exhaust because there is no requirement or benefit in doing so"
Last edited by: Zero on Tue 13 Aug 13 at 21:41
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>>its sensible design and engineering.
Which on any vehicle used in the furtherance of a business is driven to exclusion of virtually all other considerations by .....
COST!
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>> >>its sensible design and engineering.
>>
>> Which on any vehicle used in the furtherance of a business is driven to exclusion
>> of virtually all other considerations by .....
>>
>> COST!
Second only to compliance. And there's no regulatory requirement for high level exhausts.
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>> you would also have to fit a guard to prevent burns.
Indeed. I once leaned nonchalantly on the welded-on exhaust extension that ran up one rear corner of an early Range Rover adapted for desert rallying. Painful, and a bit embarrassing.
Of course with a bus, the exhaust could run inside the bus and be integrated into the heating system.
Last edited by: Armel Coussine on Tue 13 Aug 13 at 21:39
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What about the water that collects inside the exhaust as a result of combustion?
You'd have to arrange a drain tap unless you could ensure the gas flow would be sufficient to blow it out, otherwise the pool at the bottom of the vertical stack may possibly sucked back into the combustion chamber.
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>> What about the water that collects inside the exhaust
>>
It doesn't seem to be a problem with lorry exhausts. You don't see them spouting water like whales, unlike modern cars which seem to emit considerable gushes of water, perhaps when cold.
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>> >> What about the water that collects inside the exhaust
>> >>
>>
>> It doesn't seem to be a problem with lorry exhausts. You don't see them spouting
>> water like whales, unlike modern cars which seem to emit considerable gushes of water, perhaps
>> when cold.
>>
tinyurl.com/pvxnz43
"For every 1kg of diesel fuel burnt, there is about 1.1kg of water (as vapour/steam) .......... produced." I imagine it's about the same for petrol.
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>> What about the water that collects inside the exhaust as a result of combustion?
There'd be a small quantity of condensate at start up but hot combustion gas would soon evaporate it. Rainwater ingress is stopped by either a flap or by turning pipe through 90degrees at upper end.
As others observe lorries (and trains) work like that.
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Diesel exhausts on Buses. - Number_Cruncher
