[Closed] Would you buy a Diesel?

Funny thing is that the next gen petrols will mostly sound like diesels anyway (multistage direct injection and/or some sort of compression ignition) they'll also be laggy (need turbos on small engines to move heavy cars. Cars aren't going to get light any time soon.) they'll also tend to have lower maximum engine speeds thanks to all the stuff they need to make them powerful and less noisy.

Basically like a diesel.

They'll also have DMFs (many do already) and GPFs (instead of DPFs) and active exhausts and variable geometry turbos.

All things to go wrong.

Oh joy.

Tesla Model S has 900 litres of cargo space and 4wd!

Why do you need 500 miles of range? Do you often drive that far without a single break?

oldbloke

Looked at it originally. But I said realworld 40mpg. Combined official doesn't even get there!

A minor detail. It has a bigger boot than your stated requirement, you'll be a long time dead.

Think of it like this as an easy way to remember the difference: torque is the size of caravan you can tow, power is how quickly you can tow it

Not a very good explanation.

What you feel in the back of your chair is forward force. This comes from the torque at the wheel. That's it. Power is this force multiplied by how fast that wheel is turning.

Think back to your bike - if you are standing on the pedals really hard whilst applying the brakes, you are creating a lot of torque but no power at all. As you heave off the line you are putting in huge torque but not all that much power because you are not doing many rpm.

Now, in the context of motor vehicles, people quote engine torque and engine power, but these don't mean a lot because it's the wheels that make you go, and there's a gearbox in between. Because the car can move, torque is intrinsically linked with power. Torque will make the car move forward so the engine needs to keep applying torque as the wheel turns, which is generating power.

So torque is the instant push, and power is the sustained push. You cannot have one without the other.

As far as statistics go, the number quoted tells you the engine RPM that delivers peak torque, which affects how it feels when you drive. A diesel engine with more torque at say 2,000rpm will be generating more power at that same RPM. The BHP figure quoted is the maximum power, and this is higher for petrols simply because they can rev higher. Because we are talking about piston engines, we can say that in a diesel there is more force per bang; but a petrol engine can deliver more bangs per minute *at maximum*.

So if you drive around at high engine speeds, a petrol will feel nice and fast, but unless you are ragging your car all the time it won't. This is what people mean when they talk about 'torquey' engines - how much power there is at lower revs.

But we are just talking about engine speed here. It's important to remember that there is a gearbox in between the engine and the wheels and it's the wheel speed that is related to the car speed. So an engine with more torque at a lower engine speed can be made to feel the same as an engine with less torque but at a higher engine speed, by using a higher gear ratio. Therefore the only thing that actually matters is the shape of the torque curve.

If you had a diesel with a red line of 4krpm and a petrol with a red line of 6krpm, the torque curve was the same, max power was the same, and the diesel had higher gears, you'd get basically the same performance and they'd feel the same.

The fact they don't is that the torque curve is different. But not as different as they used to be in the days of PD engines.

Oh dear, looks like turny things 101 is needed again

I have a degree in Physics, but this is actually a-level stuff.

Yes if the economics worked in my favour.
My driving is rural and so are the fuel stations. Diesel every where, not always petrol. No urban driving so I reckon the pollution effects are less and I also believe that we should be hammering the leisure use of fossil fuels as a more effective way of saving the planet. Holiday flights and driving T5's to trail centres.
Where have the emotithingies gone?

@oldbloke - I agree electric isn't really there yet. Perhaps if we hadn't been dragged off down a decade long cul de sac by the fossil fuel diesel lobby and misguided govt policy the we might have been.

TBH its the OP's type of driving that really needs to be targeted first. Urban and suburban small cars doing short distances in populated area's and busy motorway traffic are killing people far faster and can be substituted by EV and petrol hybrids more easily than rural traffic.

molgrips

Not a very good explanation.

What you feel....
Think back to your bike.....
Now, in the context of motor vehicles.....
So torque is .....
As far as statistics go..

Did everyone else see this coming 😆

So if you drive around at high engine speeds, a petrol will feel nice and fast, but unless you are ragging your car all the time it won't. This is what people mean when they talk about 'torquey' engines - how much power there is at lower revs.

Are you considering all petrol engines there molgrips? Or are you just doing the usual thing of comparing a small normally aspirated petrol engine to turbo charged diesel?

I was comparing NA petrol to TD yes, I didn't go on to talk about TP because it was a long post.

But the point I was trying to make was the relationship between power and toruqe in practical terms, and also that power *delivery* i.e. the torque curve are what's important, rather than the engine RPM at red line.

[i]Also I'm not convinced that small cap. turbo petrol engines will last the course - too highly stressed[/I]

I've run motorbikes past 50k, my Kawasaki was 130bhp from a 900cc and revved to 12000rpm - engine was solid.

Very rare for a 4 cylinder bike engine to fail (except not maintained etc).

I can't see why anyone doing less than 50 miles a day and considering a Mini wouldn't have an EV instead as long as they have off street parking.

The sooner they put an electric engine in these lifestyle type cars the better. Fiat 500 is another prime example - they even built an electric version for Europe for a couple of years......madness

molgrips

I was comparing NA petrol to TD yes, I didn't go on to talk about TP because it was a long post.

But the point I was trying to make was the relationship between power and toruqe in practical terms, and also that power *delivery* i.e. the torque curve are what's important, rather than the engine RPM at red line.

It's kind of moot though with low inertia turbos, twin sequential variable geometry turbos....electric superchagers compound charging turbos etc....there are now plenty of petrol cars with "diesel like" torque low in the rev range but they also have a fully usable, enjoyable rev range.

winston - Member
I can't see why anyone doing less than 50 miles a day and considering a Mini wouldn't have an EV instead as long as they have off street parking.

Maybe..

Just maybe people don't want an electric car.

bikebouy

Maybe..

Just maybe people don't want an electric car.

Fake news opec shill.

Find me a petrol estate with 4WD, good rear legroom behind a 6ft+ driver, >600L of boot space that is relatively quick yet does >40mpg in the real world.

[url= https://www.honestjohn.co.uk/realmpg/bmw/3-series-touring-f31-2012/320i-xdrive-automatic ]https://www.honestjohn.co.uk/realmpg/bmw/3-series-touring-f31-2012/320i-xdrive-automatic[/url]

You may want to look closely at the recent budget. I believe there was something hidden in there that indirectly affects diesels.

Went back and had a good read at [url= https://www.gov.uk/government/publications/spring-budget-2017-documents/spring-budget-2017 ].gov budget docs[/url] and this jumped out at me:

[b]6.3 Spending[/b]

[i]Air quality – The government is committed to improving air quality, and will consult on a detailed draft plan in the spring which will set out how the UK’s air quality goals will be achieved. Alongside this, the government will continue to explore the appropriate tax treatment for diesel vehicles, and will engage with stakeholders ahead of making any tax changes at Autumn Budget 2017.[/i]

I suspect that the other boot will drop at the autumn version. We are looking at an e-car by the year end to replace Mrs S diesel Note (a hateful piece of transport, but built to do the job it does really well).

What you feel in the back of your chair is forward force.

What you feel is acceleration, which is worked out by using time.
Cruising at a constant 94mph* on a motorway you won't feel anything in the back of your chair, yet I assure you there is a constant forward force.
I'm well aware of the existence of gearboxes, which is why I had already mentioned gearboxes. I fear not the gearbox. I actively enjoy the gearbox, especially slipping it into second at 50mph to commence an overtake and letting the revs build up to 9,000. 🙂
I appreciate that you do not share my love of the manual gearbox.
I also enjoy arguing the semantics of a poorly worded argument, as well as fine food, wine and music. 😀

*T'is the mildest of trolls, I can get away with that can't I? 🙂

^^^

Interesting that the x-drive auto manages 44.6 while the 2wd equivalent does 36.3.

Cruising at a constant 94mph*

I have a burning torch and a freshly sharpened pitchfork. The kettle is on, someone else bring the biscuits.

What you feel in the back of your chair is forward force. This comes from the torque at the wheel. That's it. Power is this force multiplied by how fast that wheel is turning.

And the torque at the wheels depends on the engine torque multiplied by the transmission gearing. Diesel cars are geared down less than petrol cars due to their lower working rpm, so although they make have more torque at the output shaft you don't necessarily get that at the wheels.

I'm concerned about the real world lifespan of the latest engines - they are getting more and more complicated.

"Maybe..

Just maybe people don't want an electric car. "

Oh dear....they are going to be very unhappy over the next decade then (assuming civilisation lasts that long!)

I guess people wanted to hang on to their horse and cart too.

Or, rather, you are over optimistic that people will want one.

Assuming the world lasts that long, obvz, goes without saying etc.etc.etc.

sbob - Member

Never understood why some people are so averse to using the range of an engine

I use 100% of the range of my diesel, it can drive around at idle and it makes power to the soft limiter... tbh I think you're just making a bit of a wrong assumption, it's not about being averse- it's about using the car's capability and characteristics.

Also, arguing about power vs torque is completely stupid, each is a function of the other, you can't have only one. What you really mean is delivery- power/torque curves. Some people like fat, some people like pointy, but neither's better or worse.

Honestly people are bad at thinking about these things. We don't feel power, we barely distinguish acceleration, a loud exhaust makes people feel faster than a hot cam even if it doesn't add a single bhp... And a fat consistent power curve can feel slower than a car that makes the exact same peak power but with a hole in the middle. And most of all we confuse best with what we like.

I remember getting my bike dyno'd one time, and there was a feller with a GSXR absolutely doing his nut because they'd "ruined it", it was gutless after the tune. So they got the charts out and it had about 10bhp more at peak, and more everywhere else... But before the tune, it had a really shit lean midrange and was bogging down. What the rider felt as power, was actually just the recovery from the flat spot.

What you feel is acceleration, which is worked out by using time.

No, you feel force. That force results in acceleration.

I actively enjoy the gearbox, especially slipping it into second at 50mph to commence an overtake and letting the revs build up to 9,000

And I enjoy letting the revs build up to 4,000.

My point is there's not much difference in two cars with the same power. It's only distribution.

Having driven two small cars back to back, one NA petrol and one TD with the same power, the TD felt far far quicker and was far more fun. You didn't have to 'work the gears' as much.

there are now plenty of petrol cars with "diesel like" torque low in the rev range

This is true.

but they also have a fully usable, enjoyable rev range

There are also plenty of diesels with fully usable enjoyable rev range.

@bikebouy

In general many people want what they are told they need and the more clued up want what they need. Nobody wanted a diesel Mini.....but the advertising spoke highly of it and for those not so easily convinced the goverment sponsored hard sell came next which made most people an offer they couldn't refuse.

Why do you think an electric mini will be any different?

be like fred
[img] [/img]

Northwind - Member

I use 100% of the range of my diesel, it can drive around at idle and it makes power to the soft limiter... tbh I think you're just making a bit of a wrong assumption, it's not about being averse- it's about using the car's capability and characteristics.

I was thinking more of petrol. Been a passenger in plenty of petrol engined cars that will barely ever see the upper half of the rev range, so the car's capabilities (high revs) and characteristics (max power at high revs) are certainly not being used. No assumption, just an observation.
🙂

Find me a petrol estate with 4WD, good rear legroom behind a 6ft+ driver, >600L of boot space that is relatively quick yet does >40mpg in the real world.

If you add "ideally have a manual gearbox", the choice becomes practically zero. Hence my next purchase dilemma

[s]Civic tourer? >600L boot, and the 1.8 gets just over 40mpg real world. When a tourer version of the 2017 1.5 comes out, that might/should improve on that. [/s]

Not 4wd. Missed that bit.

No, you feel force. That force results in acceleration.

So you can't feel acceleration? 😕

sbob - Member

I also enjoy arguing the semantics

Which is good, because we both know that force is derived from acceleration.

You didn't have to 'work the gears' as much.

This is the crux, I enjoy changing gear more than you (although my last three cars were autos 😆 ).

So you can't feel acceleration?

No, you feel forces. That's what feel means.

Which is good, because we both know that force is derived from acceleration.

No, other way round. Acceleration happens because there's a force. Newton's first law.

This is the crux

It is, yes.

Although you can still work the gears if there's a wider torque curve, be that in turbo petrol or turbo diesel.

Van - there's barely any choice. Well, there is a petrol vw 2l tsi with 204ps/350Nm, that sounds fine, but it's as rare as hen's teeth in the uk.

A manual, petrol LWB Kombi (or panel van) would be ideal for me.

So you can't feel acceleration?

Actually let me rephrase my answer.

You feel a force differential. There's a force on your back but not your front, which causes a pressure increase on the skin on your back and also inside your body.

When you are free falling, you feel nothing because the force acts on all parts of your body simultaneously so there's no force differential. You feel nothing but you are still accelerating rapidly.

a11y - I saw 1 advertised when I last looked. It was a kombi not a caravelle. 4motion too. Maybe a special order/import then?

These topics do go off on tangents don't they.

Anyway, aren't you actually feeling electromagnetic repulsion of quarks?

Not sure how touch nerves work. Not a biologist 🙂

You are also using your inner ear to sense force, which your brain interprets as acceleration.

The problem isn't what type of fuel, its just the sheer volume of cars going into city centres.

I ride my bike into Birmingham everyday and see huuuuuge long lines are of cars, sat in traffic slowly belching out fumes, and in about 3 miles from Great Barr to the flyovers I very rarely see more than one person per car.

Most people say that they reason they don't use public transport is because its not convenient but then park a mile or more from the city centre where the cheap parking is. It's just daft.

They should congestion charge most of the cities, between 8 & 10am so as not to finally kill off the high st, but stop people driving in every day. Most of the people that I work with in Brum live nearer to the town than I do too.

Good public transport investment. It's pretty clear this is what we need.

Insanity to procrastinate on this, imo.

TBH round Birmingham PT is pretty good, just need to get more people on it.

Carrot hasn't worked - Stick time.

TBH round Birmingham PT is pretty good, just need to get more people on it.

Carrot hasn't worked - Stick time.

I can see Birmingham starting to congestion charge soon. It's a big enough city that people will still go there and with the metro, major rail links, an airport and enough buses to annoy any patient motorist everyone will find a way.

Being local the biggest issue I see with the PT is the security, especially on buses. There has been an increase in stabbings and fighting on the top decks. They need to scrap double deckers and increase the number of single decker buses.

[i]I ride my bike into Birmingham everyday and see huuuuuge long lines are of cars, sat in traffic slowly belching out fumes, and in about 3 miles from Great Barr to the flyovers I very rarely see more than one person per car. [/I]

But those folk could've come 40 miles already, not everyone wants to move when the job moves and/or you have to find another job.

Half the people that work in Birmingham think that Cannock is in another country.

Fair enough if there's no choice (although I've heard some train stations even have car parks now), but I see most of those cars still with frost on the windows in the winter.

if they come up with a hybrid truck that do 400 plus miles on one charge/tank, whilst towing a couple of tonnes or having about a tonne of kit in the rear of it then I'd happily give it a go. As it is diesel is what I've got to use for work. Can't use public transport as it doesn't go where we need and you cant haul kit so basically I'm a fully bunny killing, lung destroying planet mangler and there is bugger I can do about it. 😕

so basically I'm a fully bunny killing, lung destroying planet mangler and there is bugger I can do about it.

Don't worry about it - the comments clearly aren't aimed at you. There will always be exceptions, at least for the forseeable future.

Definitely a hybrid.

I'd love full 'leccy but I'm not they quite have the range yet, nor that the infrastructure is in place yet?

I have a large car, powered by a Euro 6, diesel engine.
While it would make less sense to power that car with a petrol engine, I would have liked the choice. The OEM which produces my car for sale in other markets, offers my car with a petrol engine, not available in the UK.

If by some horrific accident of fate,I "needed" to drive a small car.
Yes, with latest petrol developments, I believe that after the appropriate vacinations, I could, drive a small petrol powered car.
Although I suspect it would be some sort living hell.
**shudders**

So, if I'm buying a large, heavy car, it would be the cleanest diesel.
smaller car would not be diesel.

Oh and the villification of private diesels cars is unsurprisingly over looking the older Euro engined commercial vehicles.
The current fleet of black cabs in my city emit such a dense, toxic fune, that I'd suggest haters start there!

I just picked up a Nissan Leaf. I commute 10 miles each way, and use the car to run the kids around. It's perfect. I commuted on bike for years, but got hit/knocked off too many times that I have lost my nerve on the roads. This feels like a good compromise,

When we change the family car next year, I'll go for the biggest hybrid I can find - the Mitsubishi Outlander looks ok, just need something that we can drive off a charge for day to day (my wife uses the big car to get to work and back), but with the range that a tank of fuel will give us for holidays.

The moment an electric car is made with a 400 mile range is made, I will never visit a pump again. It can't come soon enough.

Carrot hasn't worked

Jasper hasn't for a while but his daughter is/was in the archers as Hayley.