One of the many reasons why a lot of drivers choose a diesel engine over a gasoline-powered one is that the former can generate more power because of the much higher compression and the slower burning diesel combustion event, which provides more torque.
Aside from that, diesel engines are more fuel-efficient and require less maintenance compared to petrol engines.
Diesel engines are indeed mean machines, but could they possibly get meaner?
Yes, they can with the help of a turbocharger.
While a lot of diesel engines come with turbochargers nowadays, there are still a handful of them that are naturally aspirated. Naturally aspirated diesel engines create low pressure as the pistons travel down on their intake strokes with the intake valves open, and the naturally higher pressure in the ambient air rushes through the manifold to fill the combustion chamber. The diesel fuel is injected during the compression stroke.
In its most basic function, a turbocharger is a forced induction upgrade that pumps additional air into the combustion chamber so that the engine can generate more power and burn fuel efficiently.
If you’ve been driving a diesel engine without a turbocharger and you think that it’s powerful enough on its own, imagine what a turbocharged diesel engine can do for you.
Depending on your engine and the kind of turbocharger you’re planning to get, you can get up to 30% more horsepower than a naturally aspirated engine.
Turbochargers generally work the same way regardless of whether they’re in a diesel or gasoline engine. The slight difference is that a turbocharged diesel engine uses the compressed air before fuel injection.
A turbocharger basically adds compressed air into the combustion chambers to produce more power, and it does that with the help of a turbine wheel that pumps exhaust gas back into the intake system. So how does it compress the air?
There is a turbine in the exhaust that is driven by the exhaust flow, and it drives a shaft that has an impeller in the intake stream. The faster the exhaust flows, the more positive pressure is created in the intake. This is a controlled boost to prevent the engine from destroying itself and there are bypass valves that prevent overboost as the pressure increases in the intake manifold.
An air charge cooler is a heat exchanger that cools the air, which is heated as it is compressed by the turbocharger. Flowing through the charge air cooler (intercooler) is the compressed air, and passing through the fins outside the charge air cooler is ambient air. Cool air has more O2 molecules per cubic inch than hot air, so the air that is forced into the cylinders is compressed first and then cooled.
A diesel engine turbocharger (or turbodiesel) operates in four key phases.
Exhaust gas exits in irregular pulses during combustion. The exhaust flows past the turbine, driving that wheel and the shaft, which drives the wheel that is in the intake stream, forcing the air into the intake. The process is self-feeding so that it has to be controlled by a moveable wastegate (bypassing the turbine wheel) to prevent it from destroying the engine.
As exhaust gases come into contact with the turbine blades, these blades rotate the turbine shaft at approximately 150,000 rpm or more. Variable geometry turbochargers used on Duramax and Power Stroke diesels can regulate the flow past the impeller so that the turbocharger can respond more quickly.
The exhaust gases leave the turbo housing and pass through the catalytic converter.
The turbocharger’s turbine drives the air compressor where air is compressed to anywhere between 19 and 30 psi above atmospheric pressure, through the charge air cooler (intercooler) and into the intake plenum, where it enters the combustion chamber as the intake valves allow.
A variable geometry turbocharger is a type of turbocharger commonly found in diesel engines. This type of turbocharger doesn’t rely on engine speed and has no need for a wastegate unlike other turbochargers.
Instead, a variable turbocharger has adjustable vanes mounted to a unison ring. As the unison ring rotates, the vanes change their angle.
Every time the vanes are opened, flow is minimized at the turbine and exhaust back pressure at low engine speeds. By increasing exhaust gas velocity, turbine speed increases as well.
The electronic control module (ECM) is responsible for turbine activity, particularly the turbocharger vane position actuation.
The ECM provides a signal to the valve solenoid, as well as a low-side reference. Then, a pulse-width-modulated signal from the ECM moves the valve to the desired position.
In a nutshell, a turbo diesel engine lets you enjoy the following advantages:
It’s no secret that diesel engines are much more fuel-efficient than gasoline engines, with some diesels letting drivers save money at the pump by as much as 33% over gasoline-powered vehicles.
With a turbocharger, you can expect that number to go even higher.
Increased torque output is arguably one of the driving forces behind diesel owners installing turbochargers.
With more air entering the cylinders, air density and pressure increase at the same time, leading to more fuel injection, torque, and power.
With a turbocharger, you can expect a significant boost in horsepower, improved altitude compensation, and more power per unit weight than a naturally aspirated engine.
A turbocharged diesel engine is also known to have better towing capabilities than a regular diesel engine, making it ideal for tractor use and other off-highway vehicles.
A turbocharged engine is essentially more environment-friendly than a naturally aspirated one, mainly because it reduces exhaust emissions by directing them back to the engine.
As fun as it is to drive a turbocharged diesel engine, doing so might come with a few challenges, including the following:
One downside to having a turbocharger is that it can cause the engine to vibrate excessively due to the power being generated.
This might not be a big deal for some drivers, but others consider excessive vibration as a dent in their vehicle’s overall ride comfort.
Turbo lag is what happens when an engine takes time to release a full burst of torque. The delay typically occurs when the engine is operating at a low RPM in low-load cruising mode.
In many instances, a turbocharger is installed as an aftermarket upgrade, making it another item to add to your maintenance list.
Always remember that a well-maintained engine is key to your vehicle’s longevity and optimal performance.
If you’re planning to install a turbocharger to go along with your diesel engine, keep in mind that it’ll need as much care and maintenance as other critical components. Only then will you be able to enjoy all the benefits of having one.
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