Are my sums correct here

Cyrus

just on the whole diesel v petrol thing i decided to do a rough calc on what i would have saved if i bought a 530d instead of a 530i.

1 gallon = 4.546 litres

25mpg petrol = 5.5 mp/l

35mpg diesel = 7.7mp/l

10,000 miles in a year requires 1,818 litres of petrol

@ 1.15 per litre equals 2,090euro

10,000 miles per year requires 1,298 litres of diesel

@ 1.06 per litre equals 1,376 euro

saving is circa 700.

Is that correct? not really an issue for me as a) i wont do 10000 miles this year so the gap decreases and b) if i do much mileage its business and ill get 1.20 or so per mile.

Its not as big a gap as youd think tho and i certainly wouldnt trade the straight 6 petrol howl

Irish Wolf

Cyrus wrote:

just on the whole diesel v petrol thing i decided to do a rough calc on what i would have saved if i bought a 530d instead of a 530i.

1 gallon = 3.785 litres

25mpg petrol = 6.6 mp/l

35mpg diesel = 9.24 mp/l

10,000 miles in a year requires 1,515 litres of petrol

@ 1.15 per litre equals 1,742 euro

10,000 miles per year requires 1,082 litres of diesel

@ 1.06 per litre equals 1,146 euro

saving is circa 600.

Is that correct? not really an issue for me as a) i wont do 10000 miles this year so the gap decreases and b) if i do much mileage its business and ill get 1.20 or so per mile.

Its not as big a gap as youd think tho and i certainly wouldnt trade the straight 6 petrol howl

1gallon = 4.546l unless you live in the U.S.

Cyrus

fixed

prospect

Cyrus wrote:

fixed

Sounds about right, but my 2.0L car gets on average 46mpg, so 12.15 mp/l so that is 823litres at approx 1.06 is 872.38.
Also I do 30,000 miles per year, so that is €2617 for diesel.

If your 530i was to cover the same mileage than you are looking at €5226.

that is €2609 per year more than fuel. And if you are to keep a car for an average of 3 years, than the saving is going to be €7827. Plus a 3 year old 2.0l diesel car with 90K is going to fetch a few quid more, or be more saleable than a 3 year old 3.0L petrol with 90K.

So, if yo are doing low mileage, then the differenc is not huge, but if you are doing bigger mileage, then a circa 2.0L diesel makes FAR more sense.

Also, diesels are far better to drive.

Cyrus

prospect wrote:

Sounds about right, but my 2.0L car gets on average 46mpg, so 12.15 mp/l so that is 823litres at approx 1.06 is 872.38.
Also I do 30,000 miles per year, so that is €2617 for diesel.

If your 530i was to cover the same mileage than you are looking at €5226.

that is €2609 per year more than fuel. And if you are to keep a car for an average of 3 years, than the saving is going to be €7827. Plus a 3 year old 2.0l diesel car with 90K is going to fetch a few quid more, or be more saleable than a 3 year old 3.0L petrol with 90K.

So, if yo are doing low mileage, then the differenc is not huge, but if you are doing bigger mileage, then a circa 2.0L diesel makes FAR more sense.

Also, diesels are far better to drive.

far better to drive than what? and iwas comparing 3l diesel to 3l petrol

nastysimon

prospect wrote:

Sounds about right, but my 2.0L car gets on average 46mpg, so 12.15 mp/l so that is 823litres at approx 1.06 is 872.38.
Also I do 30,000 miles per year, so that is €2617 for diesel.

If your 530i was to cover the same mileage than you are looking at €5226.

that is €2609 per year more than fuel. And if you are to keep a car for an average of 3 years, than the saving is going to be €7827. Plus a 3 year old 2.0l diesel car with 90K is going to fetch a few quid more, or be more saleable than a 3 year old 3.0L petrol with 90K.

So, if yo are doing low mileage, then the differenc is not huge, but if you are doing bigger mileage, then a circa 2.0L diesel makes FAR more sense.

Also, diesels are far better to drive.

Your maths are correct but miss the point. Two supposedly equivalent cars, one petrol, the other diesel, cost not an awful lot different to run, unless you are doing huge mileage. BTW, I completely disagree with your last statement. Diesels sound worse, have worse throttle response and are generally heavier engines for the same power, their only real benefit is efficiency. There is a reason that there aren't any true sports cars with a diesel engines.

prospect

nastysimon wrote:

Your maths are correct but miss the point. Two supposedly equivalent cars, one petrol, the other diesel, cost not an awful lot different to run, unless you are doing huge mileage. BTW, I completely disagree with your last statement. Diesels sound worse, have worse throttle response and are generally heavier engines for the same power, their only real benefit is efficiency. There is a reason that there aren't any true sports cars with a diesel engines.

Well,

Missed what poit exactly, my whole equation was based on doing 30,000 miles, so that was the very point. Summed up by my second last line???

RE: Diesel driving. it is personal preference, isn't it.

I prefer diesel, thats why I said it, and your argument of 'sounds worse' 'throttle response' is the same dated, misinformed rubbish i hear being spouted by some incoherent auld fellas in my local on a friday night. I am sure you prefer the drive of a petrol, but at least drive a modern diesel before coming out with that kind of drivel.

As for a true diesel sports car, http://en.wikipedia.org/wiki/Audi_R10 , where have you been?

unkel

Cyrus wrote:

Its not as big a gap as youd think

Indeed. In your case you'd need to do big miles to recoup the higher second hand price of the 530d had you bought one of them

Big engined petrol cars are bargains in Ireland

Wossack

prospect wrote:

Well,

Missed what poit exactly, my whole equation was based on doing 30,000 miles, so that was the very point. Summed up by my second last line???

RE: Diesel driving. it is personal preference, isn't it.

I prefer diesel, thats why I said it, and your argument of 'sounds worse' 'throttle response' is the same dated, misinformed rubbish i hear being spouted by some incoherent auld fellas in my local on a friday night. I am sure you prefer the drive of a petrol, but at least drive a modern diesel before coming out with that kind of drivel.

As for a true diesel sports car, http://en.wikipedia.org/wiki/Audi_R10 , where have you been?

So what makes diesels far better to drive then petrol?

C_Breeze

Wossack wrote:

So what makes diesels far better to drive then petrol?

a thing called torque

prospect

Wossack wrote:

So what makes diesels far better to drive then petrol?

Holey Moley,

Are you trying to make a perfectly stright forward point more confusing?

Try reading this bit again:

prospect wrote:

RE: Diesel driving. it is personal preference, isn't it.

I prefer diesel, thats why I said it,

Fey!

As well as a higher purchase price, you also have higher maintainence costs. I think that the break even for petrol/diesel is usually aroud 17,000 miles.

That said, the 530 diesel is supposedly quicker than the 530 petrol, can be chipped, and has more torque, as well as using less of a cheaper fuel.

Finally, as a friend of mine says, if you can't afford to run it, don't buy the car.

Wossack

prospect wrote:

Holey Moley,

Are you trying to make a perfectly stright forward point more confusing?

Try reading this bit again:

try not to jump down my throat - your first point stated it as fact, not as opinion. Your second post made that clear, but not the basis of your opinion.

Thats all my question was about, what do you prefer about diesels? Sorry if it was construed as hostile

prospect

Wossack wrote:

try not to jump down my throat - your first point stated it as fact, not as opinion. Your second post made that clear, but not the basis of your opinion.

Thats all my question was about, what do you prefer about diesels? Sorry if it was construed as hostile

At the time you posted, you had read both my posts, and therefore knew that I was expressing my opinion only.

You then asked:

Wossack wrote:

So what makes diesels far better to drive then petrol?

which is a different question than:

Wossack wrote:

what do you prefer about diesels?

so to answer your question,

I prefer the "extra torques" as per Mr Clarksons dictionary of motoring. I prefer the power delivery in the mid range. I prefer the less effor required in the gears if you want a lazy drive. I prefer the economy. I prefer paying less at the pumps. I prefer almost everything about them. I really see very few advantages a modern petrol car has over a modern diesel, except when you go into supercar territory, and even then, they are not much use in our country.

Cyrus

prospect wrote:

At the time you posted, you had read both my posts, and therefore knew that I was expressing my opinion only.

You then asked:

which is a different question than:


so to answer your question,

I prefer the "extra torques" as per Mr Clarksons dictionary of motoring. I prefer the power delivery in the mid range. I prefer the less effor required in the gears if you want a lazy drive. I prefer the economy. I prefer paying less at the pumps. I prefer almost everything about them. I really see very few advantages a modern petrol car has over a modern diesel, except when you go into supercar territory, and even then, they are not much use in our country.

well the only part of that argument that relates to driving is the torque, which plenty of petrol engines have in abundance esp any turbo ones as extra torque is normally due to the turbo not the fuel

Eoin

I won't say that my diesel engine doesn't sound quite rough, but it certainly isn't bad to drive. Personally I like the pick-up at low revs, and I don't find it slow to react; there is very little lag at all.

I can see why people wouldn't like one, but I have a feeling that a lot of perceptions are based on their experience with much older engines.

When you look at the old BMW 320cd, new 335d, Alfa GT (and Brera I think), Octavia RS TDI cars coming out, you can see that diesel is becoming a viable fuel for sporty cars, not just long distance cars.

unkel wrote:

Indeed. In your case you'd need to do big miles to recoup the higher second hand price of the 530d had you bought one of them

Big engined petrol cars are bargains in Ireland

The 530D is more likely to get a better resale price than the 530 as you have alluded to, so he probably wouldn't have to do huge mileage.

unkel

eoin_s wrote:

The 530D is more likely to get a better resale price than the 530 as you have alluded to, so he probably wouldn't have to do huge mileage.

Good point. I suppose it depends on the age of the car in how far that is true. New they cost the same, so it makes much more sense to buy the diesel (which nearly all 530 buyers do these days). Lower depreciation and lower fuel costs

From my point of view as a last owner (well, not last owner but the one that's going to depreciate the car until it's not worth much really), it's higher depreciation (as the higher purchasing price will depreciate to zero) and lower fuel costs

You really have to put serious effort to get anything like the manufacture say.

My bmw with a 6cyl 2.5l gets as low as 21 mpg on my daily drive to work if I drive normaly. 6 miles main road then as much as 10min stop start driving that gets me the remaining mile.

Keeping it in a lower rev range, A/C etc off, no bursts of strong acceleration can yield 27+ on the same trip.

MercMad

That said, the 530 diesel is supposedly quicker than the 530 petrol, can be chipped, and has more torque, as well as using less of a cheaper fuel.

...........didn't TopGear disprove that myth quite conclusively !!

Either way.............if it were me and I was doing anything over 10,000 I would buy the 530D over the 530i, or the E320Cdi over the E350, puelry for the turbo torque !

However I would never, repeat NEVER buy a 4 cylinder diesel car, they just sound cack !!

I find the above Merc & BMW 6 cylinder diesels sound quite nice actually, and for me that is a big consideration when selecting a car to drive ! Its called enjoyment !

Cyrus

the 194 bhp of the 530d loses out to the 231 bhp of the 530i in nearly every instance.

proof here:

http://www.fastsaloons.com/


wouldnt fancy replacing a turbo on the 530i either!

nastysimon

prospect wrote:

Well,
Missed what poit exactly, my whole equation was based on doing 30,000 miles, so that was the very point. Summed up by my second last line???

The point was that unless you are doing the miles, it doesn't make sense. Comparing your much less powerful 2.0 diesel with his 3.0 petrol makes no sense, it is not a fair comparison.

RE: Diesel driving. it is personal preference, isn't it.

Perhaps, though those cars which are most about driving are very rarely diesel. Similarly, those cars which are driven by those least worried about fuel consumption are also rarely diesel. I have driven a few modern diesels, some of which are considered class leaders, but the truth was that they lacked the driving satisfaction of their petrol brothers. The fuel economy was important for the owner, but were it not, the petrol would have been the prefered choice.

I prefer diesel, thats why I said it, and your argument of 'sounds worse' 'throttle response' is the same dated, misinformed rubbish i hear being spouted by some incoherent auld fellas in my local on a friday night. I am sure you prefer the drive of a petrol, but at least drive a modern diesel before coming out with that kind of drivel.

As I said, I have. If diesels sounded better, wouldn't those very people who go most for driving pleasure build diesel cars; the sports car manufacturers. The throttle response of a well sorted petrol engine is better than that of a well sorted diesel. That is not to say that the pick-up of a diesel at low revs is not as good or better than a petrol, just that the time to respond to one pressing the throttle is slightly worse (unfortunately, most petrol engines are getting worse at this, so soon you're opinion might actually be correct for the average). BTW, if it is drivel, please point to a learned source that says so. Otherwise, my experience backs up my assertion, so I'm not going to change my opinion just because you decide to resort to calling it drivel.

As for a true diesel sports car, http://en.wikipedia.org/wiki/Audi_R10 , where have you been?

For most of the time, I've been in Ireland. Even I, who it seems spouts drivel, knows that it's not a sports car, it's a race car. I hope you too can tell the difference. The ACO have a set of rules for the 24 hours of Le Mans which stipulates the restrictor sizes for various engines. The larger the restrictor the more power the car can make. Diesel engines are allowed to have larger restrictors than petrol engines, so the rules favour them.

nastysimon

nastysimon wrote:

For most of the time, I've been in Ireland. Even I, who it seems spouts drivel, knows that it's not a sports car, it's a race car. I hope you too can tell the difference. The ACO have a set of rules for the 24 hours of Le Mans which stipulates the restrictor sizes for various engines. The larger the restrictor the more power the car can make. Diesel engines are allowed to have larger restrictors than petrol engines, so the rules favour them.

Are ya sure? Restrictions in WRC effectivly mean a cap on BHP. According to an article I read through turbo charging and magic I don't quite understand they can hugely increase torque.

Maybe the same restrictors favour the torquey diesel engine. More energy per unit less air required ect ect.

nastysimon

ronoc wrote:

Are ya sure? Restrictions in WRC effectivly mean a cap on BHP. According to an article I read through turbo charging and magic I don't quite understand they can hugely increase torque.

Maybe the same restrictors favour the torquey diesel engine. More energy per unit less air required ect ect.

Yes, I'm certain. For a supercharged (including turbo-supercharged) diesel engine, you can have one 55.9mm restrictor or two 39.9mm ones. For a supercharged petrol engine you can have one 45.3mm or two 32.4mm restrictors with more than 2 valves per cylinder, or one 46.8mm or two 33.4mm ones with 2 valves per cylinder. Thus a petrol engine with a turbo could produce 50% more bhp with the restrictor that a diesel has rather than the standard petrol multivalve one. That sounds like a big advantage to me.
What happens is that the restictor allows air through it at the speed of sound, which means that there is an absolute limit to how much air one can get through the restrictor, resulting in an absolute power limit. With turbos and very large normally aspirated engines, one can get this maximum power for a very large part of the rev range, ultimately giving lots of low down torque (bhp=revs x torque). This ideally suits diesels as they opperate in that rev band, but if diesels had the same restrictors as petrol engines, they would not be competitive.

For reference:
http://www.lemans.org/sport/sport/reglements/ressources/auto_2007/regl_2007_prototype_ACO_fr_gb.pdf

Sandwich

nastysimon wrote:

ultimately giving lots of low down torque (bhp=revs x torque).

Can someone here please explain in laymans language why 'torque' matters. It seems to in most discussions, so I guess it does, but have never understood why it is quoted.

bhp=revs x torque, so is bhp not the best indicator of a car's pullingpower/acceleration capability(or bhp/weight of car).
Everything else being equal, will the higher bhp car not beat the lower bhp car for pulling power. Even if it has lower max torque, does that just not mean that it will be turning at a higher rpm, than the one with more torque? i.e. does the matching of gear ratios to a given engine not take account of the different torque/speed characteristics of the engine, and still leave bhp to the wheels the important measure.

Appologies to the cognoscenti if I'm missing the blindingly obvious.

maidhc

Sandwich wrote:

Can someone here please explain in laymans language why 'torque' matters. It seems to in most discussions, so I guess it does, but have never understood why it is quoted.

A car with higher torque will deliver its power from the sheer force of the engine as distinct from the speed at which the crank is turning. So while a diesel may be able to overtake safely in 4th at 1500rpm, a petrol of similar bhp is likely to need second an 2x/3x the RPM.

A diesel is a lazier car to drive, but gives the impression of having more power as there is far more grunt available in the higher gears. In everyday driving (e.g. going up hills, overtaking on the N7 and so forth) there is less of a need to stir the box, and IMO driving is a more relaxed affair.

Its horses for courses though. I much rather the engine in my bosses MB s600, than my focus diesel, but I get about 40MPG more than he! But he can afford it, and I still get to drive it sometimes!

Sandwich

Thanks maidhc. So is torque a misleading figure to be getting excited about (except for those too lazy to change gear).

The other car might have more torque, but as long as you are prepared to revyourengine/changedown, if you have more power, you have the quicker car ?

maidhc

Sandwich wrote:

Thanks maidhc. So is torque a misleading figure to be getting excited about (except for those too lazy to change gear).

The other car might have more torque, but as long as you are prepared to revyourengine/changedown, if you have more power, you have the quicker car ?

Pretty much my understanding of it anyway. Mind you the power may be at 8000rpm, and thus less "available" than it may be in a diesel.

Interestingly the yanks were big into slow revving petrols with loads of torque and a couple of gears before the automatic became popular.

nastysimon

Sandwich wrote:

Can someone here please explain in laymans language why 'torque' matters. It seems to in most discussions, so I guess it does, but have never understood why it is quoted.

bhp=revs x torque, so is bhp not the best indicator of a car's pullingpower/acceleration capability(or bhp/weight of car).
Everything else being equal, will the higher bhp car not beat the lower bhp car for pulling power. Even if it has lower max torque, does that just not mean that it will be turning at a higher rpm, than the one with more torque? i.e. does the matching of gear ratios to a given engine not take account of the different torque/speed characteristics of the engine, and still leave bhp to the wheels the important measure.

Appologies to the cognoscenti if I'm missing the blindingly obvious.

I'm afraid that I've yet to come across a very simple explanation.
The first thing you have to realise is that an engine produces different amounts of torque (and therefore power) throughout its rev range. This means that a car which does 200bhp, maximum, may only do 50bhp at 2000rpm, but 200 at 8000rpm (that is actually a case where it produces the same amount of torque at both). Diesel cars generally don't rev to high revs, they can't. Most cars produce maximum power near to their maximum revs. So a diesel which produces 200bhp at 4000rpm will be producing twice the torque of the petrol engines which needs to get to 8000rpm. Thus, the aforementioned 200bhp diesel at 4000rpm will be able to accelerate as hard as the aforementioned 200bhp petrol at 8000rpm as power determines one's ability to accelerate.
This of course assumes the same power for both, which is rarely the case. So long as your power is through a useable power band, more power will be quicker when driving hard (as in racing).
Since diesels use a lower rev range than petrols, they have to produce more torque to get the same amount of power. One of the advantages of this is that in a diesel you often drive closer to maximum power and well into the useful power band. In a petrol, you are more likely to be driving well below the maximum power for most driving, in fact you may be well outside the useful power band for quick driving in a petrol, often requiring you to drop a gear to accelerate as hard as the guy in his diesel. That said, to go from gentle cruising to accelerating really hard in either will require that you drop one or more gears, at which point the petrol's ability to rev higher and, most likely, greater power will make it the quicker.
Therefore, diesels give a more relaxed drive and better economy. A petrol is better for spirited driving, has better acustics (less clatter, more aurally pleasent when driven hard), more power and a considerably lighter engine. For really relaxed driving where economy is no object, huge petrol engines are best of all as they are more refined, give smoother power delivery and will pull hard from the off.

mukki

this is my take on petrol vs diesel, might be completey wrong but it makes sense to me


diesel
because of the high compression ratio (+ turbo + faster speed means less time to leak by the cylinder rings) they will blow the head gasket if the ecu doesn't reduce the ammount of fuel injected as the speed increase. because of this they have huge torque from 1200-2500, this gives you an illusion that the diesel car is stronger then a similar bhp petrol,

petrol
because the same air leaking past the cylinder rings leaves less oxygen to burn fuel the ecu cuts back fuel to save the enviroment, at higher speed there is less time for leakage, so the ecu can add more fuel (compression ratio is small in petrols so head gasket is safe upto about 7,000 then its time for the ecu to cut back)

diesel are for economy or heavy loads !
petrol for speed and power (although pretty economical if ya have 6 gears)

prospect

mukki wrote:

petrol for speed and power (although pretty economical if ya have 6 gears)

Don't agree.

In everyday driving on nearly all roads in this country, in nearly all conditions, including 'spirited' driving on country roads, most 1.9Turbo Diesels will be a far better solution than an equivalent 2.0 Petrol, in terms of ease of driving and suitable amounts of available power when it is required.

If you are on a race track in a sports/race car (essentially the same thing pedantic pat), then a petrol may be a better option.
That said, I personally drove 2 Alfa 156's in mondello at a promotional event. One was a 1.8Petrol the other a 1.9Turbo Diesel. From my personal experience (not age old hear-say) of comparing these two cars, the diesel was far better and faster on the track, fact. It didn't seem faster, or give a false impression of power, it quite simply was the better engine on the day.

Cyrus

but the 1.9jtd is much more powerful engine than the 1.8ts? its not a fair comparison