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Popelka
Member Since: 31 May 2008
Location: Praha (Prague)
Posts: 2430
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I keep reading about how efficient the new diesel is in regards to heat and then I read about FBH being used so my question is to those that can explain .
what/why is it so efficient that you then have to have the FBH, whats the saving CO2/ MPG or what?
and then the biggy is compared to petrol what is the most efficient temperature for a diesel car as it works by compression does the outside temp effect the efficiency and how ???? Experience is a difficult teacher, because she gives the test first and then the lesson afterwards!!!!
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 6th Nov 2009 4:44 pm |
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SJR
Member Since: 09 Aug 2006
Location: East Manchester
Posts: 4030
  
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Popelka wrote:
what/why is it so efficient that you then have to have the FBH, whats the saving CO2/ MPG or what?
All engines take time to get to the optimum operating temperature, the FBH merely gives it a boost to get there a bit sooner, with the benefit that the cabin heating works much sooner than it would if no FBH was fitted. Not sure the FBH is linked to efficiency directly  I believe that every human has a finite number of heart-beats. I don't intend to waste any of mine running around doing exercises.
Buzz Aldrin (1930 -
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| 6th Nov 2009 5:11 pm |
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wvlenthe
Member Since: 07 Jan 2009
Location: Arnhem
Posts: 1967
 
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I'm not an engine expert but...
Since diesel is ignited by compression, the outside temperature is only indirectly a factor. Physics say that the temperature of the air/diesel mixture will rise always the same way. But this demands a certain start temperature of the mixture. So the air and fuel temperature are factors influenced by outside temperature but the actual combustion proces not really.
This is BTW the one of the reasons that in northern countries fuel tanks are warmed (exhaust through the fuel tank!!!) and radiators are shielded from direct airflow. The other reason is that the fuel and coolant will just freeze 
The reasons to warm up your engine are several:
- warming up the oil makes it work better. Like all fluids, it will be less fluent at lower temperatures. This effect is diminished by the synthetic oils these days
- engine parts may vary in size as a result of temperature. Every material has an extension factor under the influence of temperature. If different materials are used for (examples!) pistons, block and springs, you can imagine what happens when temperature varies.
regards,
Wiljo D3 V8 HSE Auto in Zermatt silver - driveway version gone but not forgotten, only the living room cupboard version remains
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| 6th Nov 2009 6:52 pm |
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TSR2
Member Since: 22 Jul 2008
Location: North Lincolnshire
Posts: 1104
 
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Guys,
Excuse my ignorance but in laymans terms isn't it just that the much different dieseling system gives off much less heat than the petrol engine. By giving off less heat more of the energy is converted to more useful mechanical energy to drive the car..hence higher efficiency. 
Or am I just doing my usual impersonation of Homer Simpson. Doh! 
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| 6th Nov 2009 7:11 pm |
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wvlenthe
Member Since: 07 Jan 2009
Location: Arnhem
Posts: 1967
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TSR2 wrote:Or am I just doing my usual impersonation of Homer Simpson. Doh!
Dunno about Homer. Popelka is effectively asking 4 questions. You're answering one of them
Wiljo D3 V8 HSE Auto in Zermatt silver - driveway version gone but not forgotten, only the living room cupboard version remains
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| 6th Nov 2009 7:24 pm |
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TSR2
Member Since: 22 Jul 2008
Location: North Lincolnshire
Posts: 1104
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Popelka,
Apologies, if the engine is running more efficiently giving off less wasted energy as heat then you either get cold or you need to supplement the heating with the FBH. I guess it's just a fact of life with the diesel engine but the FBH doesn't show on any CO2 figures quoted does it? as it is a heater not an engine. Bit of a fiddle maybe but everyone is only getting excited over engine CO2 figures.
The effect of temperature on the diesel engines are much less because of the much higher compression ratios.
http://en.wikipedia.org/wiki/Diesel_engine
Homer!
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| 6th Nov 2009 7:53 pm |
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dick dastardly
Member Since: 29 May 2007
Location: wiggleigh bottom
Posts: 1112
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intercooler cools input air for combustion, reduces air volume so you can cram more air in an burn more completely. Also heat from combustion can then produce more pressure = more torque/mechanical efficiency. Less waste heat around plus cold input air means extra heat to warm up engine in cold conditions is needed.
Engine should give more torque in the cold (once transmission has warmed up) There's one wheel on my wagon, but i'm still rollin' along, it's the cherokee, they're after me, but I'm singing a happy song
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| 6th Nov 2009 9:05 pm |
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Popelka
Member Since: 31 May 2008
Location: Praha (Prague)
Posts: 2430
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wvlenthe wrote:The reasons to warm up your engine are several:
TSR2 wrote:By giving off less heat more of the energy is converted to more useful mechanical energy to drive the car..hence higher efficiency
dick dastardly wrote:Less waste heat around plus cold input air means extra heat to warm up engine in cold conditions is needed.
Gents,
thanks for clearing that up especially the TSR2 wrote:the FBH doesn't show on any CO2 figures quoted does it? as it is a heater not an engine. Bit of a fiddle maybe
and I guess it's not used in the fuel usage calculations either?
Chris Experience is a difficult teacher, because she gives the test first and then the lesson afterwards!!!!
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| 8th Nov 2009 12:53 am |
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Winger
Site Moderator
Member Since: 15 Feb 2005
Location: UK
Posts: 3428
 
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Popelka wrote:I guess it's not used in the fuel usage calculations either?
It certainly makes a difference to fuel consumption, that's for sure.
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| 8th Nov 2009 9:07 am |
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wvlenthe
Member Since: 07 Jan 2009
Location: Arnhem
Posts: 1967
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Popelka wrote:I guess it's not used in the fuel usage calculations either?
Chris
I suppose not in the onboard computer which is off anyhow. Come to think of it; it uses fuel gauge I think and therefore it may include it somewhere. I can imagine that the FBH uses so little fuel that you won't really notice.
If you calculate usage by means of spreadsheet then obviously its used.
Wiljo D3 V8 HSE Auto in Zermatt silver - driveway version gone but not forgotten, only the living room cupboard version remains
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| 8th Nov 2009 12:50 pm |
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