autos, cars, features, bmw, bmw 3 series, why diesel engines produce more torque than petrol engines

When you compare a diesel and petrol engine with identical displacements, the diesel version tends to produce more torque.

For example: The current BMW 3 Series range includes 2.0-litre turbo-diesel, and turbo-petrol options.

The diesel engine generates 140kW and 400Nm, while the petrol produces 135kW and 300Nm.

Below, we find out why this is the case.

Petrol vs Diesel

Petrol and diesel are both types of fuel derived from crude oil through fractional distillation at different temperatures.

The fuel types have different chemical compositions, though, with diesel generally having a ratio of 75% saturated hydrocarbons (primarily paraffins) and 25% aromatic hydrocarbons.

Petrol primarily consists of a mixture of paraffins, naphthenes, aromatics, and olefins – with the ratio of these elements varying on a sample-by-sample basis.

Petrol is more volatile and is generally less dense than diesel, due to this inconsistent ratio, as well as the individual additives that manufacturers put in their products.

It therefore contains less energy, leading to less efficient power delivery per volume of petrol when compared to diesel.

A petrol engine also works with a spark plug igniting the fuel in an engine cylinder, whereas diesel engines use heated air and pressure to ignite fuel and produce power.

autos, cars, features, bmw, bmw 3 series, why diesel engines produce more torque than petrol engines

Compression ratio and combustion speed

Another factor is the compression ratio of an engine.

This is the ratio between the total volume of the cylinder and the volume of the open chamber once a piston is fully extended inside the cylinder at its uppermost point – the top dead centre (TDC).

A petrol engine generally has a lower compression ratio due to the piston’s TDC being at a lower point to allow for a larger combustion chamber between the surface of the piston and top of the cylinder.

The combustion chamber is also larger than on diesel engines to avoid high temperatures from built-up pressure igniting the air/fuel mixture prematurely.

In petrol engines, a spark plug ignites the air/fuel mixture when the piston’s TDC is reached, with this explosion creating torque when pressure pushes the piston back down.

The explosion takes longer than in diesel engines, which leads to slower and weaker delivery of torque.

Diesel engines’ combustion chambers are smaller, due to the engine relying on the high heat of compressed air igniting the fuel when it is pumped into the cylinder as the piston hits the TDC.

While not exactly instant, this explosion happens much quicker and closer to the top of the cylinder, and due to the higher density of diesel, also delivers more instantaneous power – thus pushing the piston down at a faster, more powerful rate, as well as further.

This creates more torque.

autos, cars, features, bmw, bmw 3 series, why diesel engines produce more torque than petrol engines

Bore vs Stroke

Petrol and diesel engines also have different bores and strokes, which refers to the width and length of the cylinder.

The bore is the distance between the outermost edges of the chamber, whereas the stroke is the distance that the piston travels in the cylinder.

Petrol engines generally have a wider bore and shorter stroke than diesel engines and need to reach higher engine speeds (revolutions per minute) to match the equivalent output of a diesel motor.

As torque is the product of distance times force, both bore and stroke measurements have an effect on torque.

The difference in strokes generally has a higher impact than the differences in bore, however, as there’s usually a more significant deviation between the length of pistons than the width.

This means that the pistons in diesel engines travel further than petrol engines, thus producing more torque when the engines are operating at the same revolutions per minute (rpm).

While an engine using petrol and one using diesel might have the same maximum power output, the different bore and stroke will affect the levels of torque produced at various engine speeds.

autos, cars, features, bmw, bmw 3 series, why diesel engines produce more torque than petrol engines

Turbos

Additionally, diesel engines tend to be turbocharged and due to their higher operating temperatures, are generally made from stronger materials.

The engine also burns at a higher air to fuel ratio which makes turbocharging more efficient, as the turbo compresses more air while using less fuel when compared to an equivalent petrol engine.

The more air that is compressed, the higher the output will be.

Coupled with the stronger engine block and denser fuel type, meaning more energy per volume of fuel, a turbo is able to provide a much higher boost more efficiently in a diesel engine when compared to an equally-sized petrol engine running at the same rpm.

Keyword: Why diesel engines produce more torque than petrol engines

CAR'S NEWS RELATED

2023 Kia Sportage, Toyota BZ4X headlines this week's new car reviews

The 2023 model year ramps up with Toyota’s first dedicated electric vehicle and Kia’s first hybrid iteration of its bestselling Kia Sportage. Here’s what else moved us this week.  The Sportage sizes up for 2023, with sharper, more futuristic styling, a hybrid model, and new rugged X-Pro trims. It ...

View more: 2023 Kia Sportage, Toyota BZ4X headlines this week's new car reviews

This 2022 Kia SUV Comes In Dead Last in Rankings

The 2022 Kia Sorento is one of Kia’s popular SUVs. It’s a three-row midsize SUV with plenty of room and a stylish exterior. Yet things with the Kia Sorento are not all great. Consumer Reports reviews of the 2022 Kia Sorento have it in last place of all midsize three-row ...

View more: This 2022 Kia SUV Comes In Dead Last in Rankings

Spain: Plug-In Car Sales Maintain 10% Share

The Tesla Model 3 appears to be the most popular BEV model in early 2022. New passenger car registrations in Spain decreased in April by 14% year-over-year 70,393, after a 31% decrease in March, resulting in 61,225 sold that month. A similar situation is noted also in other European markets ...

View more: Spain: Plug-In Car Sales Maintain 10% Share

Florida Man WaterskiIs Barefoot Behind a Formula One Car on Its Way to the Miami Grand Prix

The team at Red Bull Racing sure has fun in their Formula One cars for the “Road Trips” video series. Episodes range from Max Verstappen ice racing on spiked tires to Daniel Ricciardo blasting across the USA at top speed. For the first-ever Miami Grand Prix, Red Bull driver Sergio ...

View more: Florida Man WaterskiIs Barefoot Behind a Formula One Car on Its Way to the Miami Grand Prix

Hot Tires Alert: The Jeep Wrangler 392 Is Getting a Burnout Mode

Some people like to make an entrance, but with the Jeep Wrangler Rubicon 392, you can create one heck of an exit. Word on the street is that the 2022 Jeep Wrangler 392 and the Ram 1500 TRX could be getting a 4LO burnout mode.  The Jeep Wrangler 392 gets ...

View more: Hot Tires Alert: The Jeep Wrangler 392 Is Getting a Burnout Mode

Happy Mother's Day: One Thing Is For Sure, Elon Musk Loves His Mom

Musk told reporters at the recent Met Gala that he only attended because his mom wanted to go, so, of course, he took her. This article comes to us courtesy of EVANNEX, which makes and sells aftermarket Tesla accessories. The opinions expressed therein are not necessarily our own at InsideEVs, nor ...

View more: Happy Mother's Day: One Thing Is For Sure, Elon Musk Loves His Mom

Tata Nexon EV Ready To Launch On May 11

Tata Motors is all set to announce the long-range Nexon EV prices on May 11, 2022. According to sources, the long-range Nexon EV will get a 30 percent larger battery than the current model and will have a claimed range of around 400km. It will also have some new ...

View more: Tata Nexon EV Ready To Launch On May 11

Peugeot Sport’s 9X8 hypercar won’t be in Le Mans race, to debut later in 2022 WEC season

Last year, when Peugeot Sport announced its new program to develop the 9X8 hypercar for endurance racing, it expected to join the World Endurance Championship in 2022. However, the team decided to forego the first two rounds, at Sebring and this weekend at Spa-Francorchamps, and was planning to debut ...

View more: Peugeot Sport’s 9X8 hypercar won’t be in Le Mans race, to debut later in 2022 WEC season

Only 1 Dodge Model Is Recommended by Consumer Reports

Do You Need an OBD2 Scanner?

Tesla Model 3 Performance Puts Up A Great Fight Against Lamborghini Urus

Why ‘really tough’ Miami strategy will have F1 teams thinking

Howell Is Elite At Rocket Raceway Park

2022 Maruti Suzuki XL6 with a wide-body kit: What it’ll look like

Rosario Highlights NOW600 Winners At Port City

Cummins Wins POWRi At Macon Speedway

Anderson Wins Again In Salt Lake City; Craig 250SX Champion

Laney Wins, Claims California Clash Title

Twitter to have “extreme” work ethic expectations for its employees, says Musk

Toyota Land Cruiser 300 Looks Menacing With Carbon Fiber Body Kits

OTHER CAR NEWS

;
Breaking thailand news, thai news, thailand news Verified News Story Network