Flamin' fuel costs.

[Spiny Norman]

I heard* that it goes to the Army to use in tanks as their engines can run on anything vaguely flammable.

*so it's probably bollox....

[Cavcraft]

Big firms like the AA and iirc Halfords have a misfueling service thing. They can’t just throw it away, surely?

 

A company I used to work for specialised in the collection/removal of mixed fuels. We'd collect from garages/workshops/recovery companies etc, and it eventually got blended into Cemfuel.

[M'coli]

I reckon in 20-30 years time the 'average' Joe on 'average' wages in the UK won't be able to afford to drive at all.

I believe this is quite likely, but I do believe that the 'average' Joe on 'average' wages will still be able to commute to work, just not in a car.

 

Think back 40, 50, 60 or so years and the average man at the time didn't have a car, he had a motorbike - hence the proliferation of 3-wheelers at the end of the 50s as a way of accomodating the burgeouning family on a motorbike license.

 

I think motorbikes will return as the mingebag transport of necessity, because ordinary punters will still need to travel to their jobs. It may be a 200cc diesel-electric hybrid that does about 200mpg, but it may yet come to pass.

[Albert Ross]

I still fancy a Royal Enfield DIesel.

[Station]

Its the nature of our jobs. Kinda comes with the territory. Luckily her commute is all on dual carriageways so its only 90 mins each way. My journeys are all over the place, but mainly out of hours, so the roads are quiet.

 

We tend to spend around £200 a week each, on fuel alone. Brakes & tyres every few weeks too!

 

I do 140 miles on Sunday night, and do the same on Friday night. I spend a week down there just working and have a couple of days to fit everything in on the weekend. 'Working away' sucks massively and I 'A1' your missus doing the commute to stay at home than spend five days in the least pleasant city I've ever seen (Coventry) and having to cram every single thing I've wanted to do in about 36 hours on the weekend.

[oman5]

I do roughly 30 miles a day commuting, luckily the firm I work for let us do longer shifts so we only work 4 days out of 7. I reckon the Torslanda would be too thirsty otherwise.

 

I agree, it will come to the point where the average person won't be able to afford to run a car. It will be interesting to see what possible solution there is to this.

I'm going to go and buy a big american V8 car while theres still fuel to run it.

[Pillock]

My commute varies massively - this week I've got two days of 70 mile round trip, and then one day of a 260 mile trip. Last week was 1000 miles all in. I get my mileage costs back but it's flat rate at 12p per mile so the more the fuel costs, the grumpier I get - on a long motorway journey I just about break even at £1.40 a litre or so.

 

I do think the government will do next to nothing to fix this, and let us find other forms of transport - as has been mentioned, not many years ago it was all about motorbikes, an actual car was a luxury yet these days you get kids finishing college, buying their first car, and whinging about fuel costs - why do you need a car? The further the fuel cost misery goes, the more likely we are to find an alternative (because those fuel blockades were a success, right?) and the problem will go away. The government hopes.

[jonny69]

Using petrol/diesel directly into an engine is far more efficient than burning fuel to make electricity, then distributing it (with all the associated costs to provide infrastructure) , not including all the processess and inefficiencies involved in making batteries etc.

That's actually not correct. In normal use, an internal combustion engine (ICE) converts a maximum of 15-20% of the energy in its fuel into motion and the rest is lost as heat. Electricity generation and distribution loses about 60% of the original energy in coal/oil/gas/nuke by the time it gets to your house. An electric motor system is over 90% efficient at converting electricity into motion, so the whole system is way more efficient than any ICE system can be, even if you add more inefficiency into the equation. And that doesn't take into account any energy lost in the refining or distribution of liquid fuels.

 

I saw it quoted once that an ICE could convert 30% of the energy in fuel to motion, but I have no idea what conditions they managed that. A realistic figure is much closer to 15%.

[Mr_Bo11ox]

I'm fairly certain a half-decent diesel engine is a lot more thermally efficient than 15%, OK its still not mega but over 40% is not impossible.

[dollywobbler]

I'm fairly certain a half-decent diesel engine is a lot more thermally efficient than 15%, OK its still not mega but over 40% is not impossible.

 

This. It's a very valid point, but I'm pretty sure the figure is 20% petrol and at least 30% for diesel - and that's based on knowledge that's several years out of date now. Engines have got a fair bit more efficient since.

[Des]

I'm wondering now if engines have become any more efficient of late, remember when Leyland or Austin or whatever their name was were doing the lean burn thing, and producing results, didn't seem to go anywhere. Was that because exhaust emissions became more of a priority leading to everything getting catted, and aren't cats merely a band aid fix? Maybe if priorities were switched to burning the fuel inside the engine then eventually cats wouldn't even be needed, and we'd all be getting 100 MPG from big low revving motors that can pull 70MPH at tickover and never wear out.

[Lacquer Peel]

http://autoexpress.co.uk/car-news/59840 ... -confirmed

 

Here's a car for you Des. 70 MPG, 200 MPH, 980 RPM at 70 MPH!

[willswitchengage]

Sorry for tangent, but these graphs, Brake Specific Fuel Consumption maps, are useful for undertsanding "real world" fuel consumption:

 

 

This one's for your boggo 1.9 TDI. On the y axis is load factor and the x axis engine speed, therefore modelling the two main dimensions to determine engine conditions (how far your foot is put dow, and how fast it's spinning, respectively). The minimum (better) value of 197g/KWh corresponds to about 40% efficient, but the maximum of 500g/KWh corresponds to about 15%. However, in real-life driving conditions your probably not going to stray far out of the 250g/KWh value of that graph. For diesels, BSFC is generally very consistent wherever your foot is.

 

Jonny69 is generally right except that efficiency is electricity generation is growing far quicker than that of the ICE engine, modern cogeneration (gas and steam turbines combined) offer between 60-80% and transmission losses offer little more than a 5% reduction.

[Pillock]

I have no idea what that graph means. I thought I was a reasonably intelligent person but it's got me flummoxed and now I feel stupid.

Does it answer the age old question of whether "labouring" an engine at low revs (so getting into top gear and damn well staying there whatever) is worse than changing gear more often, using higher revs, but a more appropriate gear? It looks like it should answer that, but equally it could be showing me the best cuts of meat to take from a horse.

[gtd2000]

Jonny69 is generally right except that efficiency is electricity generation is growing far quicker than that of the ICE engine, modern cogeneration (gas and steam turbines combined) offer between 60-80% and transmission losses offer little more than a 5% reduction.

 

Is this efficiency still applicable once you introduce charging systems and batteries though?

[Tayne]

willswitchengage said:

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[willswitchengage]

Does the y axis show pressure on the throttle in bar?

 

Brake mean effective pressure - the average pressure applied on the engine's cylinder in the expansion stroke. It's proportional to torque.

 

And what are the blue lines about?

 

Powah = torque x angular velocity (engine speed), hence why the lines are strait as it's a linear relationship. Think of the y axis as throttle... that makes it far easier. For instance, looking at the "100hp" line, the engine does this at all point at that line, 4500rpm at 8 bar (50% load factor) and 2750rpm and 16bar (100% load factor).

 

Surely if the engine's is spinning at 3000rpm and I'm only using 10bhp then I'm going down a massive hill with almost no throttle and thus should be closer to 197g/kwh (whatever the fuck that means) than 500g/kwh?

 

g/Kwh is a convenient measure of fuel efficiency. 197g/KWh means you've used 197 grams of fuel to produce one KWh of energy. Diesel's heating value is about 12KWh/Kg, or inverted, 83g/Kwh, or about 40% of 197 (maths in action!).

 

In that particular example you've just given of a car going downhill in a low gear with no throttle. What happens here? The car doesn't accelerate.The engine requires so much power to tick over at that high rpm that that's where your retarding/engine braking effect comes from.

 

This hopefully makes lots of sense, I probably couldn't change a headlight bulb.

[Tayne]

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[Mr_Bo11ox]

The dark blue line on your graph Tayne is much the same as the black 'outer' line on will's graph. They are saying much the same thing about the engine's peak output at any particular speed . However Will's graph also gives us a 'map' describing what happens at part throttle in terms of fuel efficiency.

 

Will's graph does not have a power curve on it, although you can tell from it (by looking at the direction that the blue lines go in as they increase) that peak power is going to be just over 4000rpm, which coincides with your graph. So the two graphs are describing two very similar engines (yours has a bit more grunt than will's going off the peak torque numbers)

[willswitchengage]

+1

[Lankytim]

Well, I have decided to save on fuel by running the SAAB Mon-Wed and on Thu-Fri I'm using the wifes Astra as she works part time. Not sure how much of a difference that will make but you never know. However all of this has been negated this week as I've been on training courses and faffing all over the place resulting in ECONOMY FAIL.

[Tayne]

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[Tayne]

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[Mr_Bo11ox]

The loading factor on that graph is the green BMEP scale. BMEP is the average cylinder pressure during a power stroke, and it varies with how hard you are pressing the acccelerator as this varies how much fuel goes in therefor how big an explosion you get. The graph could equally have 'throttle openeing' or 'load factor' or 'torque' or whatever up the side and it would look the same.

 

This engine is not producing 100bhp between 2750 and 4500, i'm not sure there that came from but its wrong. It can produce (upwards of) 80 bhp from 2750 to 4500.

 

The isobars tell up how much fuel is needed to get a kwh of useful work out of the engine at any point in its operating range. Theyre a result of loads of factors but the main ones are:

 

lower engine speed = less frictional losses > the engine is less efficient the more you cane it at high revs.

greater throttle opening > more efficient as you are getting more work out per firing event.

 

Therefore the engine is most efficient in the lower part of its speed range at maximum throttle openings.

[reanimation-films]

Interesting thread.

The tax gets amplified the more it costs that's a bit of an issue. It is getting to the point where trips have to be justified especially the longer ones, saying that its still cheaper than 2 people/family on public transport, well it is if you're already running a car and I'm not giving them/one up just yet, oh... no!

 

Well since the Xantia broke in the chill snap and Christmas blues boiler breakage hell we've commuted soley in the Mondeo 2.0Si Wow worked it out and its between 23 and 25MPG! More on a run but it currently has a fault that hates motorways!

Its done well and got us back down to earth and I cant wait to recomission the clattery Xantia! Might just be hell and £££ fixing it sure I'll get the economy back at well over 40MPG...

[willswitchengage]

From personal experience, I don't get along with the statement from Will'sWitchExchange that engine can give 100bhp from 2750-4500rpm.

Can it?

 

Oops sorry yes that was an error, I forgot about the limiting thick black line. 100+bhp is possible between its blue line and the black boundary curve.

 

Driving at "peak torque" etc and in the engine's "sweet spot" is (I assume they can be used interchangeably, with no patronising intended, a load of rubbish if you want to have an economy run. You want to drive at either peak power, or peak economy. Peak torque is more theoretical and only interesting to the engineer as its location is defined as where the in-cylinder pressures during the expansion stroke are greatest. Torque = stroke x force on piston, and force on piston = BMEP (in cylinder pressure) x area of piston. Peak torque in gasoline engines is generally at a higher RPM than in diesels as their spark-ignited nature means that flame speed plays an important role in determining combustion performance, flame speed being optimal at medium-high RPMs. Conversely, in all engines performance and efficiency are adversely affected at low RPMs as combustion heat conducts through the cylinder walls quicker than it can be converted to work on the piston.

 

Apologies again if this is still woefully confusing, let me know if you're still stuck on anything and I'll try and answer any questions.

 

Will'sWitchExchange

 

NB has anybody ever heard of these guys? They're a boy band from the U S and A:

 

[Tayne]

Mr_Bo11ox said:

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