Diesel v petrol fuel economy
#11
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
"Chris Bartram" <news@delete.me.piglet-net.net> wrote in message
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
#12
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
"Chris Bartram" <news@delete.me.piglet-net.net> wrote in message
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
#13
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
"Chris Bartram" <news@delete.me.piglet-net.net> wrote in message
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
news:81Pcf.5207$Lw5.4701@text.news.blueyonder.co.u k...
> Noisy bacon wrote:
> > On the subject of fuel economy I wonder if anybody on the ng can answer
this
> > question. Do diesels give more mpg because there's simply more energy
per
> > unit volume in diesel fuel compared with petrol, or is a diesel engine
> > intrinsically more efficient at turning hydrocarbons into kinetic energy
(or
> > perhaps I should phrase it "less inefficient")?
> >
> Well, there was a rumour that at the time of it's launch, the VW-Audi PD
> 130 TDi was the most thermally efficient production car engine
> available, if that's any help. I've read somewhere that it's acpable of
> transferring 43% of the fuel energy into power, so "less inefficient"
> may apply here, but that's much more efficient than, for example, an
> ordinary lightbulb.
Sounds like someone's dream - the mere age of the fuel would make several
percent difference in conversion efficiency, let alone the fact that they're
using the same thermodynamic cycle as everyone else!
It's been a couple of decades since College, but 43% sounds like the Carnot
Cycle (i.e. theoretically perfect), rather than something produced by a
typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
um ;o)
Standing-by to be corrected...
H1K
#14
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
Hairy One Kenobi wrote:
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
#15
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
Hairy One Kenobi wrote:
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
#16
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
Hairy One Kenobi wrote:
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
#17
Guest
Posts: n/a
Re: Diesel v petrol fuel economy
Hairy One Kenobi wrote:
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%
>>Well, there was a rumour that at the time of it's launch, the VW-Audi PD
>>130 TDi was the most thermally efficient production car engine
>>available, 43% of the fuel energy into power
>
> Sounds like someone's dream - the mere age of the fuel would make several
> percent difference in conversion efficiency, let alone the fact that they're
> using the same thermodynamic cycle as everyone else!
>
> It's been a couple of decades since College, but 43% sounds like the Carnot
> Cycle (i.e. theoretically perfect), rather than something produced by a
> typical petrol engine. The hs tables are undoubtedly in the loft, but, well,
> um ;o)
>
> Standing-by to be corrected...
>
> H1K
Hmmm. A diesel-cycle, with an expansion ratio of 5, a CR of 19 and
using eta=1.4 gives a theoretical efficiency of 57%, even ignoring the
increased effective CR due to the turbo.
IIRC modern low NOx diesels have flame temperatures of under 2000K, and
exhaust temperatures of around 500K, so the equivalent Carnot cycle
efficiency would be around 75%