Why do modern small petrols feel like diesels?
Discussion
Recently I've had some trips for work where I've needed to get hire cars, usually some sort of base model crossover or small hatchback.
Invariably I've thought they made a mistake and gave me a diesel when it said petrol on the form. Lumpy feeling engine with a narrow powerband. Had a go in my parents' new A180 hybrid and that was much the same.
I initially thought it might be a direct injection thing but cars have been DI for years without feeling lumpy, and my 3cyl Fiesta ST was nowhere near as unrefined.
What is it about small engines in the last few years that has made them like this when it wasn't the case before? Have they had to retune engines for new emissions regs?
Invariably I've thought they made a mistake and gave me a diesel when it said petrol on the form. Lumpy feeling engine with a narrow powerband. Had a go in my parents' new A180 hybrid and that was much the same.
I initially thought it might be a direct injection thing but cars have been DI for years without feeling lumpy, and my 3cyl Fiesta ST was nowhere near as unrefined.
What is it about small engines in the last few years that has made them like this when it wasn't the case before? Have they had to retune engines for new emissions regs?
I've noticed this in the wife's Mini (1.2l turbo) - a lot of low/mid-range torque then it drops off rapidly after about 4000rpm. I suspect that the turbo fitted is quite small, much more suited to boosting at lower rpm's. It's a narrow powerband.
I actually quite like it, the car pulls well with no need to rev it out to make decent progress - ideal for a town car/ runabout.
I actually quite like it, the car pulls well with no need to rev it out to make decent progress - ideal for a town car/ runabout.
Will be its just that type of engine, most people dont want to rev a car out to get anywhere. I know people go on about N/A screamers but in reality, 95 percent of the time you dont want to be bouncing off the rev limiter, a good amount of low and mid range torque is ideal for most drivers and situations.
Plus, I think the mapping to meet emissions targets artificially can hobble how a car feels to drive.
Plus, I think the mapping to meet emissions targets artificially can hobble how a car feels to drive.
jhonn said:
I've noticed this in the wife's Mini (1.2l turbo) - a lot of low/mid-range torque then it drops off rapidly after about 4000rpm. I suspect that the turbo fitted is quite small, much more suited to boosting at lower rpm's. It's a narrow powerband.
I actually quite like it, the car pulls well with no need to rev it out to make decent progress - ideal for a town car/ runabout.
Try the 1.5 version and that really make you think for you have a quite diesel, pulls really nicely with 220nm at only 1250rpm, then fairly flat all the way up. Modern engines have the turbo in the output manifold reducing lag and as you say most like quite small, so spins up quickly. Define one of BMWs better enginesI actually quite like it, the car pulls well with no need to rev it out to make decent progress - ideal for a town car/ runabout.
Can't say I've noticed this with something super modern, but my mum had a Twingo GT from 2010 and that had a 1.2 turbo charged engine. To say it felt like a diesel would be harsh but as mentioned in another post, the power came in, in a chunk then tailed off like a diesel. But I assumed that was partly due to small engine and small turbo.
If you held it right, it was a nippy and fun little car, the engine suited it as they only weigh about a tonne.
I wonder if many smaller cars (likely turbo charged) aim for torque more than power, so may give that diesel feel.
If you held it right, it was a nippy and fun little car, the engine suited it as they only weigh about a tonne.
I wonder if many smaller cars (likely turbo charged) aim for torque more than power, so may give that diesel feel.
I have a vw with the 1.5tsi engine and it pulls like a small diesel but sounds fine. Peach of an engine - especially in eco mode when it shuts off 2 cylinders and you just can’t tell.
Having had diesels for 20 years, I honestly prefer it, not least because I mostly do short journeys these days.
Having had diesels for 20 years, I honestly prefer it, not least because I mostly do short journeys these days.
A lot of them are pretty nasty. Diesely rattle at low revs, torque chasm below 1k, sudden drop off at 4k and a flywheel from a truck.
Much prefer things likd the Fiat FIRE. Linear delivery without that hugely irrritating gutlessness either side of a tiny powerband.
Especially as a manual.
Much prefer things likd the Fiat FIRE. Linear delivery without that hugely irrritating gutlessness either side of a tiny powerband.
Especially as a manual.
We have the 1.5 triple in the F40 118i and it does feel a little diesely in its power delivery but in a good way, very well tuned for mere road use and very quiet unlike diesel 4 pot. Power band no where near as narrow as a modern 4 pot diesel. Picks up earlier and doesn't run out until much higher in the rev range. Obviously not a high rev screamer for perfect tool for the application while returning 40mpg long term average.
Which make/model of car are you referring to and what era of diesel car are you referencing? My recent experience of small capacity Ford and VAG petrol engine characteristics is nothing but positive. On the flip side, I’ve not driven a diesel for yonks but when I last had one (BMW) I thought it felt surprisingly petrol-like.
Some marques have always had rough/unrefined engines but overall I think things have come a LONG way from the horrific 1.4CVH of my first car!
Some marques have always had rough/unrefined engines but overall I think things have come a LONG way from the horrific 1.4CVH of my first car!
tallpaul26 said:
Which make/model of car are you referring to and what era of diesel car are you referencing? My recent experience of small capacity Ford and VAG petrol engine characteristics is nothing but positive. On the flip side, I ve not driven a diesel for yonks but when I last had one (BMW) I thought it felt surprisingly petrol-like.
Some marques have always had rough/unrefined engines but overall I think things have come a LONG way from the horrific 1.4CVH of my first car!
Hopefully not wet belts. VAG diesel have always been great, if not as clean as they should.Some marques have always had rough/unrefined engines but overall I think things have come a LONG way from the horrific 1.4CVH of my first car!
AC43 said:
A lot of them are pretty nasty. Diesely rattle at low revs, torque chasm below 1k, sudden drop off at 4k and a flywheel from a truck.
Much prefer things likd the Fiat FIRE. Linear delivery without that hugely irrritating gutlessness either side of a tiny powerband.
Especially as a manual.
But aren't they generally gutless everywhere ?Much prefer things likd the Fiat FIRE. Linear delivery without that hugely irrritating gutlessness either side of a tiny powerband.
Especially as a manual.
I know they did some more powerful variants but most were in the 45 to 75 bhp range, I suspect that may be a bit of nostalgia and cars were a bit lighter back then.
I think I would take a small turbo triple, we had a Fiesta 1.0 Ecoboost, I know they have their issues but they have a nice lump of low down torque, feels more like a proper car than a weedy supermini, tried the same car with an N/A version of the same engine, felt broken.
I remember old superminis on the motorway, was out of their depth where these modern small turbos have enough get up and go to mix it in lane 3, used to jump between than and a Citroen C1, night and day difference.
And anyway, whats wrong with how a diesel feels ? Been my sons 1.6 diesel Golf DSG this weekend, its actually quite decent and does 50 odd mpg, not fast but the DSG masks the narrow powerband to an extent. Would take a diesel over a small petrol by and large, wish it was the 2.0 version, they are great.
They sound diesel-y not just because of the higher fuel pressure and injector noise but also because many run a stratified charge at low loads so you get more cylinder to cylinder variation at idle, when running they inject fuel late in the compression stroke and in multiple short bursts and at higher compression ratios so you get faster pressure rises and "sharper" combustion events vs port injection, which means more knock-like sounds at low speed like a diesel. Add in the super light construction of modern engines and you've got nasty sounding engines.
They drive like diesels because they ARE like diesels, relying heavily on boost to make power and the turbos are sized to bring that boost in early. People like it, you get 80% of what the engine has to give for 20% effort and unless you really go for it the car feels far more powerful than it is. Just like turbodiesels they're only disappointing when you put the the other 80% and find out that the car only has another 20% to give
As mentioned the 1.5 turbo 3 pot in a Mini is like the best diesel you've ever used, feels like a monster until you realise how quickly it runs out of puff.
They drive like diesels because they ARE like diesels, relying heavily on boost to make power and the turbos are sized to bring that boost in early. People like it, you get 80% of what the engine has to give for 20% effort and unless you really go for it the car feels far more powerful than it is. Just like turbodiesels they're only disappointing when you put the the other 80% and find out that the car only has another 20% to give
As mentioned the 1.5 turbo 3 pot in a Mini is like the best diesel you've ever used, feels like a monster until you realise how quickly it runs out of puff.
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