What is the advantage of smaller engines?

[I-S]

Originally Posted by john.wigley

I prefer large, lazy engines and am prepared to pay any fuel penalty, especially as I now do a very small annual mileage. Larger engines are also less stressed and therefore more relaxing to drive than a 'buzz box'.

Not even necessarily a penalty - My husband and I rented a Chevrolet Impala in the USA one time - over 5m long (ie 7 series size), 3.6 V6 with over 300bhp, 6 speed auto gearbox. On a motorway trip we got 29mpg US, which is about 36mpg UK - seems pretty good for a big 300bhp saloon.

Similarly, our GS is a very "lazy" engine - 3.5 V6 but "only" 292bhp (low power density because of the atkinson cycle), but it matches our V70 D5 for fuel economy. The GS is FAR more relaxed than even the V70, as it can gear way down to about 1000rpm @ 100mph (not tried it - there's an autobahn video), and obviously a petrol 6 is distinctly smoother than a diesel 5.

Originally Posted by christheancient

Back in the past, I was an independent driving instructor and, because they were so 'popular' in the trade, I went for a Vauxhall Corset... sorry, Corsa... as well. And, being naive, I went for the 1-litre 3-cylinder jobby. Uncomfortable and needing to change down for slight inclines on motorways soon showed me the error of my ways!

That's the car I learned to drive in - S reg and T reg corsa 1.0.

I described it to my advanced driving examiner as "dangerously slow", a statement that he took issue with. I explained my view (and experience!) that driving up a hill on the A2 dual carriageway the vehicle was, regardless of gear, unable to maintain speed and dropped below 56mph. I had a foreign lorry bearing down on me - both unwilling to lose momentum on the hill but unable to go around me due to traffic doing 70 in the other lane - it certainly felt dangerous almost being pushed along by a 44t lorry.

[Whippy]

We are getting 52mpg out of 2ltr diesel and my 3ltr averaged 48 last year. Keep your little buzz box rubbish thanks.

[ThomasG]

Originally Posted by GMcL

The smaller the engine, the less volume, therefore less capacity for fuel to burn.

As you’ve found out the more weight the engine has to move (more passengers/luggage combo) the closer to the upper limit the smaller engine has to work to overcome the rolling friction. No surprises so far.

Did you know traveling on a level road, maintaining a constant speed, only needs around 20bhp so having an engine that can produce 300+bhp is a bit of a waste. The problem is getting to the rolling speed you also need to overcome the air drag. There is 4 times as much drag at 60mph as 30mph and that needs power = burn fuel to get there. Again, no surprises from Professor Physics.

Coming back to my opening sentence, we are in an age where air pollution is the main agenda and anything to reduce the volume of fuel burned must be good. The problem is we are tied into CO2 emissions which favour diesel BUT diesel is bad and petrol is viewed as less bad in terms of particle matter emissions but less good in terms of CO2. So, in my roundabout way, we arrive at if you must burn fuel burn it in a lower volume.

Back in the real world you have a fully loaded car weighing 1.5+ tonnes with all the safety equipment plus a 5-600kgs payload. You need to burn fuel to make power to make it move regardless of the swept volume of the engine burning the fuel.
A smaller volume cannot burn as much fuel therefore cannot make as much power taking longer to get to the required speed.

Reduce all speed limits to 30 mph and performance difference between a 5.0 V8 muscle car and a 900cc twin is less significant.

So that's why road traffic seems slower and slower tear by year...

[cheshired5]

Whilst the power output for the engine size is impressive along with the fuel economy, the one thing that you can't avoid is the lack of torque if you're going to be coming out of a diesel.
If you are going to be using the car on your own and with little luggage, the difference will be negligible but if you are loading up with passengers, luggage, towing or travel in hilly terrain you will be sorely disappointed.
It's interesting to see that VAG highlight the 200 Nm per litre headline figure which is of course very impressive and probably unequalled but as the engine is only 1 litre, the total torque is still only 200Nm which would be excellent on say a Fabia, Ibiza or Polo but is wholly unimpressive for a medium to large car.
For comparison, my ancient D5 is 340Nm which gives effortless driving in virtually all circumstances.
Me considering this 1.0 engine with just 58% of the torque of mine would be unacceptable.

At the end of the day, it's down to what you want, need or expect.

[Whippy]

Originally Posted by cheshired5

Whilst the power output for the engine size is impressive along with the fuel economy, the one thing that you can't avoid is the lack of torque if you're going to be coming out of a diesel.
If you are going to be using the car on your own and with little luggage, the difference will be negligible but if you are loading up with passengers, luggage, towing or travel in hilly terrain you will be sorely disappointed.
It's interesting to see that VAG highlight the 200 Nm per litre headline figure which is of course very impressive and probably unequalled but as the engine is only 1 litre, the total torque is still only 200Nm which would be excellent on say a Fabia, Ibiza or Polo but is wholly unimpressive for a medium to large car.
For comparison, my ancient D5 is 340Nm which gives effortless driving in virtually all circumstances.
Me considering this 1.0 engine with just 58% of the torque of mine would be unacceptable.

At the end of the day, it's down to what you want, need or expect.

Or 'Horsepower for show, torque for go"

[GMcL]

Originally Posted by cheshired5

Whilst the power output for the engine size is impressive along with the fuel economy, the one thing that you can't avoid is the lack of torque if you're going to be coming out of a diesel.

For comparison, my ancient D5 is 340Nm which gives effortless driving in virtually all circumstances.

Modern petrol engines are overcoming this with direct injection which is why EU VI NOX emissions for petrol are not much better than diesel, 0.6 vs 0.8.

I have a 2011 S60 D3 with stage 1 remap which produces 470Nm. I also have a 2017 Focus RS 2.3 petrol that produces 470Nm overboost without remap.

[biggbn]

Turbo engines tend to overcome torque deficits. I love a big engine, effortless, turbine like power, the Lexus v8 in my old ls400 being a great example, it too would comfortably top 30mpg on runs. But there are other plus points of small engined. As Colin Chapman once remarked, to make a car faster, add less weight. This anomalous term highlights many advantages, less weight means lighter more balanced handling can be achieved using less tyre, less rolling resistance, more frugal, more fun. I honestly felt in my test drive the wee basic mini diesel was nearest thing in feel to a mk1 or mk2 golf gti I has driven in ages, upright screen, great geaechange, light, chuckable feeling handling...although it must weigh about 200k more than either golf mentioned, such us progress?

But, progress? We go on about how big cars can be frugal, and Eben big petrol ones can, I have run loads...but nowadays torquey high tech petrol tiny tots are quick, light, fun and can get 50 plus mpg...diesels have moved on even more so, some returning freakishly high mpg. So yes, it is progress, but maybe not in the way some like. But remember, many people firmly believed the internal combustion engine would never catch on....

[Markos01]

Originally Posted by T5R92011

An interesting comparison could be the V60 Polestar.

The earlier models had a 3.0-litre inline 6 with 350bhp and 6 speed auto.

The later models had a 2.0-litre inline 4 with 367bhp and 8 speed auto.


Which would you rather have?

Good question. We all love more power, but overall I love more cylinders than less, so without test-driving the two I'd have the 6 cylinder as I'd hope it to be aurally better and have a smoother delivery.

[green van man]

I've done the small capacity screamers, 875 imp, was a fun car, BUT high maintenance, and because you were always down the gears and up the rev range not very frugal. We had a 1 in 4 Hill that needed 6k rpm in 1st gear to do 20 mph up.
Had to tow a trailer when going on holiday as no room for 2 adults 2 children and luggage.

Graduated from tent to caravan and 2l now a minimum in my view, 2.5 being far better.

My D5 xc70 does more to the gallon than my imp ever did, I accept it is not the same technology but the principle is still the same, low torque lots of work, high torque lazy motoring.

Paul.

[Whippy]

Spent a while in the SW of the "Good Old" USofA a few years ago, drove around in an F150 pick up, V8 petrol heaven!