Engine Displacement.

[Time Waster]

OK, it's obvious what it is but what are the implications of modern trends towards lower displacement?

I'm guessing they're improving air and fuel supply to get more power out of lower displacements. Even my old 2.0l diesel 01 plate astra was turbocharged but still needed the 2l displacement. So what exactly is causing the improvement/increase in power of lower displacement engines? Is this potentially a risk?

i've heard of the Ford ecobang engine for example. I've also just replaced engine on my 1.6 vivaro after turbo failed due to oil pump failure. Whilst 1.6 litres was OK in that 115ps van was the engine and turbo more stressed in use?

In my early car buying days you got 1l city cars, 1.6l small family cars or 2l for a bit more power in family cars or bigger family cars. Now I've seen large looking dacia dusters with 1.0 litre displacement. I think hyundai shortage are 1.2 l and others 1.4 l. What's the risks?

Benefits I'm guessing with lower displacement engines vs higher ones with same power is lower emissions. Is this same power output in smaller displacement engines not going to age them quicker.

PS I'm hoping the ev mob don't turn this into a thread about ev cars taking over. I'm asking specifically about ICE cars here.

 

[Drago]

Increasing volumetric efficiency via the use of forced induction is all.

No real risk. There have been some design bloopers (wet belts...) but those aside, everything else being equal, a small engine will have the same longevity as a large one. They're not like muscles or gearboxes, they can't be strained.

Of course, its all fiddling while Rome burns really.

 

[mustang1]

Does that "there's no replacement for displacement" thing still apply?

If we compare two engines, say a 2 litre 4cyl NA and a 1.0 3cyl turbo, and suppose they both produce similar hp and torque, I would argue the larger engine will be more "driveable".

 

[figbat]

Improving materials and manufacturing are allowing increased BMEP meaning you can get the same bang from a smaller unit with the turbocharger being a bigger part of the power generation. Improved electronic control also means they can run the engine in ways that would have been dangerous before, in terms of fuelling, ignition timing etc. There's also e-drive being added to the mix.

Some time ago I went to a presentation given by a turbocharger manufacturer who considered the engine as merely an external combustion chamber for the turbocharger, which did the work. Bigger and better turbo's are making up for reduced engine size.

 

[presta]

I would argue the larger engine will be more "driveable".

I've seen people complaining that the newer high efficiency engines are difficult and temperamental to drive. I got the impression that they have a very narrow power band that requires a lot of gearstick stirring, but I've never driven anything new so I've no personal experience.

 

[presta]

Does that "there's no replacement for displacement" thing still apply?

If we compare two engines, say a 2 litre 4cyl NA and a 1.0 3cyl turbo, and suppose they both produce similar hp and torque, I would argue the larger engine will be more "driveable".

The biggest I had was a V6 Cortina, and the engine in that was certainly nice and flexible.

 

[figbat]

I've seen people complaining that the newer high efficiency engines are difficult and temperamental to drive. I got the impression that they have a very narrow power band that requires a lot of gearstick stirring, but I've never driven anything new so I've no personal experience.

There's a large shift towards automated transmissions meaning the car can look after all that itself without a hapless driver getting in the way. Turbocharged cars do tend to have a lot of 'low-down' torque and a limited rev range compared to a nat-asp. Some find it effortless, others prefer the thrill of a 7,000+ rpm red line.

 

[raleighnut]

I've seen people complaining that the newer high efficiency engines are difficult and temperamental to drive. I got the impression that they have a very narrow power band that requires a lot of gearstick stirring, but I've never driven anything new so I've no personal experience.

Nah with VVT and electronic control over fuel and timing plus knock sensors and Lamda sensors (for combustion control) they're pretty flexible plus a smaller engine is a lot lighter (partially offset by the weight of safety gear)

 

[Regular.Cyclist]

I owned an imported 5.0 litre V8 Mustang for a few years. The car I have now has an engine 1/3 of the size, with a turbo. It's only a little down on power but has a very similar power to weight ratio. However that power is in a very narrow band compared to the Mustang.

 

[Jameshow]

The biggest I had was a V6 Cortina, and the engine in that was certainly nice and flexible.

I had it in a scimitar, on wet roads that was fun!

 

[Jameshow]

OK, it's obvious what it is but what are the implications of modern trends towards lower displacement?

I'm guessing they're improving air and fuel supply to get more power out of lower displacements. Even my old 2.0l diesel 01 plate astra was turbocharged but still needed the 2l displacement. So what exactly is causing the improvement/increase in power of lower displacement engines? Is this potentially a risk?

i've heard of the Ford ecobang engine for example. I've also just replaced engine on my 1.6 vivaro after turbo failed due to oil pump failure. Whilst 1.6 litres was OK in that 115ps van was the engine and turbo more stressed in use?

In my early car buying days you got 1l city cars, 1.6l small family cars or 2l for a bit more power in family cars or bigger family cars. Now I've seen large looking dacia dusters with 1.0 litre displacement. I think hyundai shortage are 1.2 l and others 1.4 l. What's the risks?

Benefits I'm guessing with lower displacement engines vs higher ones with same power is lower emissions. Is this same power output in smaller displacement engines not going to age them quicker.

PS I'm hoping the ev mob don't turn this into a thread about ev cars taking over. I'm asking specifically about ICE cars here.

My transit's a 2.2 TDI 125bhp. So is relatively unstressed compared to the 155 model. I think a 1.6 is a bit small for a mid sized van...

 

[BrumJim]

Correct as above.

Small engines with a turbo are more efficient (better fuel consumption) when the turbo isn't spinning, but the power of a much larger engine when it is. A larger engine will pull from lower revs, but will burn more fuel in normal driving.

Smaller engines will not only be more efficient at lower speeds, but since the engine is a significant proportion of the vehicle mass, and larger engines require more bonnet space, there is less to pull around too. The only trade off (now that reliability is better and engines have been optimised) is usable torque range, but since cars seem to have 5 or 6 speed gearboxes now, this is less of a problem.

 

[figbat]

...but since cars seem to have 5 or 6 speed gearboxes now, this is less of a problem.

Automatic gearboxes are routinely 7- or 8- speed these days, with some going up to 10-speed.

 

[Time Waster]

Does that "there's no replacement for displacement" thing still apply?

If we compare two engines, say a 2 litre 4cyl NA and a 1.0 3cyl turbo, and suppose they both produce similar hp and torque, I would argue the larger engine will be more "driveable".

AIUI from reading around the NA doesn't have turbo lag but the turbochargers these days are better with less lag. Then you've got superchargers too where the power to force the air in comes from the engine not the exhaust flow as in a turbo.

Then you have biturbos like on some vivaro vans. This has a convoluted flow where valves control which way air flows. IIRC it's like a big turbo but the second turbo fills in the gap reducing the turbo lag. So up to 1500revs the second turbo then that cuts out as the bigger main turbo kicks in. So turbo lag is virtually not there.

Whatever the case I've heard the tech has improved such that small engine with modem turbos are closer to larger NA cars indeed larger turbo cars from decade ago too. So to a point smaller engines might well be a good idea, I'm just not sure of the 1.0litre dacia duster SUVs. They seem too big to get away with a 1l displacement.

 

[tyred]

Bah! It's been all downhill since the straight 8 Bugatti.