Turbocharger Simulator
How a Turbo Works in 2D, 3D & Cutaway — Boost • Turbo Lag • Compressor Map • Fuel Efficiency
Display Controls
⚙ Turbo size, intercooler, blow-off valve, engine and air
Turbo size scales both wheels together: the diameters by the factor, the turbine nozzle area by its square and the rotor inertia by its fifth power, so a bigger turbo flows more at high speed but spools more slowly. The compressor is checked against its own map: it surges at too little flow for its pressure ratio and chokes at the right of the map. The controller caps the shaft at 97 % of the speed where the compressor tip Mach number reaches 1.45.
Σ Live equations — values substituted from the current operating point
📋 Station table — pressure and temperature from the air filter to the tailpipe
⚙ Shaft power balance — turbine, compressor and bearings
💡 What-if coach — insights from the current operating point
1 Overview
The Turbocharger Simulator runs a four-stroke engine on a dynamometer with a turbocharger feeding it. Air comes in through the filter, is compressed by the centrifugal compressor, cooled in the intercooler, passes the throttle and fills the cylinder. The exhaust then drives the radial turbine, which turns the compressor through the shaft, while the wastegate or the variable-geometry vanes hold the boost. Every number on the page comes from one model of the whole system.
There are three views. 2D cuts the whole system open, with the wheels turning in their housings, the flow coloured by temperature, gauges, the wheel end views and the velocity triangle at the compressor tip, beside five diagrams. 3D shows the turbocharger on its engine; you can turn it, cut it open and click any part. Cutaway is an isometric drawing of the turbocharger on a stand with a quarter cut away; hover a part in its key to find it.
2 Running the Engine
- Pedal — the throttle on a petrol engine, the fuel quantity on a diesel (a diesel has no throttle; less fuel means a leaner mixture). Engine speed is held by the dynamometer, from idle to the rev limit.
- Floor it snaps the pedal to 100 % and the Spool diagram records the boost, torque and shaft speed as the turbo winds up: that delay is turbo lag. Lift off snaps it shut at full boost: with the blow-off valve fitted it opens and vents the charge; without it the compressor is pushed across the surge line.
- Boost set point is what the wastegate or VGT controller holds. Turbine control (above the canvas) chooses Wastegate, VGT or None; with None the turbo floats free and overboosts at high speed.
- Turbocharged / Naturally aspirated removes the turbocharger, so you can compare the same engine with and without it.
- The advanced panel holds the turbo size, the intercooler effectiveness, the intercooler and blow-off valve switches, the compression ratio, the fuel octane, the altitude and the air temperature.
- Units — SI (bar, kW, N·m, °C, kg/s, g/kWh) or Imperial (psi, hp, lbf·ft, °F, lb/min, lb/hp·h). Shaft speed stays in rpm.
3 The Five Diagrams
- Compressor map — pressure ratio against corrected mass flow, shaded by efficiency, with speed lines, the surge and choke lines, the full-load operating line and a trail of the live operating point.
- Spool — boost, torque and shaft speed against time over the last eight seconds, with the naturally aspirated torque for reference.
- Curves — full-load torque and power against engine speed, turbocharged and naturally aspirated.
- Energy — where the fuel energy goes: brake work, friction, pumping, coolant and exhaust, and how much of the exhaust the turbine recovers to drive the compressor.
- Efficiency — the downsizing comparison: fuel consumption of this turbo engine against a naturally aspirated engine large enough to make the same peak power, at the same road power.
2D, 3D and Cutaway, at the left of the strip above the canvas, switch views. The page always opens on the 2D section; a link ending ?view=2d, ?view=3d or ?view=anat opens that view.
4 Calculations, Learning Panels and Export
The calculator icon works the operating point step by step: compressor work and outlet temperature, the intercooler, the air the cylinders take, the fuel, the exhaust temperature, the turbine, the shaft balance and the engine output. The learning panels show the live equations, a station table from the air filter to the tailpipe, the shaft power balance and a what-if coach. CSV exports the operating point, the full-load curve and the spool history; PNG exports the view. Right-click the canvas for more.
5 Explore, Practice and Quiz
Explore has eighteen cards in four groups: How it works, Inside the turbo, Thermodynamics, and Efficiency & control. Practice draws from twelve problem types (compressor outlet temperature and power, turbine power, pressure ratio from a boost gauge, engine air flow, tip speed, intercooler outlet temperature and density gain, brake power from BMEP, efficiency from BSFC, spool time and blade speed ratio), each with a worked solution. The Quiz asks six questions drawn from a pool of twenty-two.
6 What the Model Assumes
The compressor does Euler work Δh = ψU² with a backswept work coefficient ψ = 0.86 − 1.55φ, where φ is the flow coefficient, and an efficiency that peaks at 76 % and falls towards surge, choke and high tip Mach number. The turbine is a nozzle of fixed effective area (or a variable one for a VGT) in parallel with the wastegate, with efficiency 72 % × (2X − X²) on the blade speed ratio. The engine is a speed-density four-stroke with a fuel-air Otto efficiency, Heywood’s friction correlation and the Douaud–Eyzat knock delay; petrol runs at λ = 1 and is enriched when the exhaust passes 950 °C, diesel runs no richer than λ = 1.4. Pressures in the manifolds follow the shaft at once (no plenum filling), so the lag comes from the rotor alone. The presets are typical engines of each kind, not any maker’s data.
How a Turbocharger Works — Turbocharger Simulator
A turbocharger is an air pump driven by the engine’s own exhaust. A turbine wheel in the exhaust stream and a compressor wheel in the intake stream sit on the two ends of one shaft. The hot gas leaving the cylinders spins the turbine; the compressor, spinning with it at 100 000 to 250 000 rpm, pushes air into the intake manifold above atmospheric pressure. A cylinder full of air at 2 bar absolute holds about twice the mass of air it would at 1 bar, so it can burn about twice the fuel and the same engine makes nearly twice the torque.
Turbocharger Parts
- Compressor wheel and housing — an aluminium centrifugal impeller with full and splitter blades; air enters along the axis, leaves the tip at high speed and is slowed in the diffuser and volute so its speed becomes pressure.
- Turbine wheel and housing — a radial-inflow wheel cast in a nickel superalloy and welded to the shaft; the scroll housing (its size is the A/R ratio) speeds the gas onto the wheel tips.
- Centre housing and rotating assembly (CHRA) — the shaft running in two floating journal bearings and a thrust bearing, fed with engine oil, sealed by piston rings, often water-cooled.
- Wastegate or variable vanes — a bypass valve with its actuator, or a ring of pivoting vanes, that controls how much of the exhaust energy reaches the wheel.
- Intercooler and blow-off valve — the charge-air cooler after the compressor, and the valve that vents the boost when the throttle closes.
The Power Balance and the Compressor Map
The compressor does work on the air in proportion to the square of its tip speed (Euler’s equation, Δh = ψU²); the turbine extracts work from the exhaust in proportion to its isentropic enthalpy drop and its efficiency. Because both wheels share one shaft, the turbo settles at the speed where turbine power equals compressor power plus bearing friction. Engineers check a match on the compressor map: the engine’s operating line must stay right of the surge line, where flow reverses, left of choke, and pass through the best-efficiency islands. In the simulator’s 1.4 L petrol engine at 4 800 rpm and full load the compressor runs at a pressure ratio of about 2.0 at 176 000 rpm, with the wastegate about 40 % open.
Turbo Lag
Floor the pedal at low engine speed and the boost takes about a second to arrive. The rotor has to be accelerated by the surplus of turbine power over compressor power: J·ω·dω/dt = WT − WC. Since the rotor inertia grows with the fifth power of its size, a large turbo that flows freely at high speed spools much more slowly than a small one. Variable-geometry turbines, twin-scroll housings, ball bearings and electric assistance are all ways of beating lag.
How a Turbocharger Improves Fuel Efficiency
A turbo does not make energy: the turbine work comes from exhaust enthalpy that a naturally aspirated engine throws away, at the cost of some back pressure. The large fuel saving comes from downsizing. A small turbocharged engine can match the peak power of a much larger naturally aspirated one, but in everyday driving it works nearer its full load, with the throttle more open (less pumping loss) and with less friction to drag round. The simulator’s Efficiency diagram compares the two at the same road power; at light load the downsized turbo engine uses about 10–30 % less fuel. On a diesel, which has no throttle and no knock limit, the turbo also lets the engine run lean at high mean effective pressure, which is why almost every diesel is turbocharged.
Who Uses This Simulator?
Automotive and mechanical engineering students learning IC engines, turbomachinery and the compressor map; technicians and apprentices who need to know what the wastegate, VGT, intercooler and blow-off valve do before they diagnose a boost fault; instructors who want to show turbo lag, surge and the power balance live; and enthusiasts who want to understand why their turbo engine behaves the way it does.
Frequently Asked Questions
How does a turbocharger work?
Hot exhaust gas from the engine spins a turbine wheel. The turbine is on the same shaft as a centrifugal compressor wheel, which draws in fresh air and pushes it into the intake manifold above atmospheric pressure. More air in each cylinder lets the engine burn more fuel, so the same engine makes more power. The shaft spins at up to about 250 000 rpm on an oil-fed bearing.
Does a turbocharger improve fuel efficiency?
Yes, mainly through downsizing. A small turbocharged engine can replace a larger naturally aspirated one of the same power. At the light loads of everyday driving the small engine is throttled less and has less friction, so it burns less fuel for the same power. The turbo also turns part of the exhaust energy, which an ordinary engine throws away, into the work of compressing the intake air.
What causes turbo lag?
When the throttle is opened the turbine has to accelerate the rotor to a much higher speed before the boost arrives, and it can only do so with the surplus of turbine power over compressor power. The rotor's inertia and the low exhaust flow at low engine speed make this take a second or more. Smaller rotors, twin-scroll housings and variable-geometry turbines reduce it.
What does a wastegate do on a turbo?
A wastegate is a valve that lets part of the exhaust bypass the turbine. Once the boost reaches its set point an actuator opens it, so the turbine receives only enough energy to hold that boost. Without it the turbo would overspeed and overboost the engine at high engine speed.
Explore Related Simulators
- Four Stroke Engine Simulator — the Otto and Diesel cycles of the engine the turbo feeds.
- Gas Turbine Simulator — the same compressor and turbine, in a jet engine and a power plant.
- Centrifugal Pump Test Rig — the liquid cousin of the centrifugal compressor, with its own head–flow curve.
- Marine Diesel Engine Simulator — a turbocharged two-stroke ship engine and its scavenge air.
- Pressure Carburetor Simulator — how an aircraft engine meters fuel to the air it breathes.
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