PromtEngine

Calculators

145 calculators on 43 pages for engines, fuel, gearing, tyres and vehicle performance. Every calculator explains its inputs, shows its formula and works in metric or imperial units.

Engine 6 pages

Compression ratioStatic compression ratio · Chamber volume for a target compression ratio · Theoretical compression pressure3 calculatorsEngine airflowAirflow required by an engine · Volumetric efficiency from measured airflow · Power supported by an airflow3 calculatorsEngine displacementDisplacement from bore, stroke and cylinders · Bore from displacement and stroke · Stroke from displacement and bore · Bore-to-stroke ratio4 calculatorsFiring interval and frequencyFiring interval in crank degrees · Firing frequency · RPM to frequency3 calculatorsPiston speedMean piston speed · Maximum RPM for a piston speed limit · Rod ratio, piston velocity and acceleration3 calculatorsTorque, power and BMEPPower from torque and RPM · Torque from power and RPM · Brake mean effective pressure (BMEP) · Specific output per litre4 calculators

Fuel 5 pages

Air–fuel ratio and fuel pumpAir–fuel ratio to lambda · Lambda to air–fuel ratio · Fuel pump flow required3 calculatorsBSFC and thermal efficiencyBSFC from power and fuel flow · Fuel flow from power and BSFC · Thermal efficiency from BSFC · Energy content of fuel4 calculatorsFuel economy and trip costFuel economy unit converter · Trip fuel and cost · Annual savings from better economy3 calculatorsFuel injector sizingInjector size for a target power · Power an injector set can support · Injector flow at a different fuel pressure · Duty cycle from pulse width4 calculatorsFuel savings and break-evenBreak-even distance for a more economical vehicle · Fuel price at which two vehicles cost the same · Running cost per 100 km3 calculators

Forced induction 3 pages

Boost and pressure ratioGauge boost to absolute pressure and pressure ratio · Compressor pressure ratio with system losses · Boost needed for a power increase3 calculatorsIntercooler and superchargerIntercooler effectiveness · Supercharger speed from pulley sizes · Pulley size for a target supercharger speed · Theoretical power gain from boost4 calculatorsTurbo airflow and powerAir mass flow of a boosted engine · Power supported by compressor airflow · Compressor outlet temperature3 calculators

Vehicle 5 pages

Acceleration and quarter-mileForce and power for a target acceleration · Theoretical best 0–100 km/h time · Quarter-mile time and trap speed3 calculatorsBraking and stopping distanceStopping distance · Brake energy and disc temperature rise · Deceleration from a measured stop3 calculatorsCornering and steeringLateral acceleration in a corner · Maximum cornering speed · Turning radius from wheelbase and steering lock · Ackermann steering angles4 calculatorsDrag and top speedAerodynamic drag force and power · Rolling resistance · Top speed from power · Frontal area estimate4 calculatorsPower-to-weightPower-to-weight ratio · Torque-to-weight ratio · Power needed for a target ratio3 calculators

Towing and loads 3 pages

Axle load and weight distributionAxle loads after adding a load · Centre of gravity from axle weights · Weight transfer under braking or acceleration3 calculatorsRoad grade and hill climbingPercentage gradient to degrees and ratio · Degrees to percentage gradient · Force and power to climb a hill3 calculatorsTowing and payloadPayload capacity and what is left · Trailer tongue weight · Combined weight against GCWR3 calculators

EV and electrical 4 pages

12/24 V wiringVoltage drop in a cable · Minimum cable size for an allowed drop · Fuse rating3 calculatorsBattery capacity and runtimeAmp-hours to watt-hours · Runtime for a load · Charging time · Ohm’s law: power and resistance4 calculatorsEV charging time and costCharging time · Charging cost · Electric versus petrol or diesel running cost3 calculatorsEV range and consumptionDriving range from battery and consumption · Energy consumption unit converter · Battery health and capacity loss3 calculators

Tyres and gearing 5 pages

Gear ratio and road speedRoad speed at a given RPM · Engine RPM at a given road speed · Overall ratio and wheel torque3 calculatorsGearing changes and shift pointsEffect of a new final drive ratio · RPM drop between gears · Shift RPM to land at a target RPM · Crawl ratio and crawl speed4 calculatorsTyre sizeTyre dimensions from the size code · Compare two tyre sizes · Speedometer error after a tyre change3 calculatorsWheel offset and fitmentOffset and width change · Offset to backspacing · Backspacing to offset · Pitch circle diameter from bolt spacing4 calculatorsWheel torque and tractive forceTractive force and acceleration potential · Traction limit of the driven wheels · Drivetrain loss from crank and wheel power · Estimated crank power from a wheel dyno figure4 calculators

Hydraulics and pneumatics 4 pages

Air compressor and pneumaticsCompressor capacity for your tools · Receiver tank fill time · Annual cost of an air leak3 calculatorsHydraulic cylinderPush and pull force · Extension and retraction speed · Cycle time · Oil volume4 calculatorsHydraulic hose sizingHose inside diameter for a flow · Oil velocity in a hose · Pressure drop along a hose3 calculatorsHydraulic pump and motorPump flow from displacement and speed · Hydraulic power and pump input power · Hydraulic motor torque · Hydraulic motor speed4 calculators

Machinery 4 pages

Excavator productivityHourly production · Passes to fill a truck · Trucks needed to keep the loader busy3 calculatorsField capacity and tractor workEffective field capacity · Time to work a field · Fuel per hectare · Drawbar power for an implement4 calculatorsGenerator sizing and fuelGenerator size for your loads · kW, kVA and current · Fuel consumption and runtime3 calculatorsMachine cost per hourTotal cost per operating hour · Buy or rent: break-even hours · Remaining value by hours used3 calculators

Ownership 3 pages

Coolant mix and oil top-upCoolant quantities for a fresh fill · Strengthening a weak coolant mix · Engine oil to add from the dipstick3 calculatorsTotal cost of ownershipTotal cost of ownership · Yearly depreciation rate · Projected future value3 calculatorsVehicle loanMonthly payment and total interest · Loan with a balloon payment · How much can I borrow?3 calculators

Reference 1 pages

Unit converterPower: kW, hp and PS · Torque: Nm, lb-ft and kgf·m · Pressure: bar, psi, kPa and atm · Engine displacement: cc, litres and cubic inches · Speed: km/h, mph, m/s and knots5 calculators

A–Z

How these calculators work

Each page groups closely related calculators with an explanation of every input and result, the formula used, a worked example and a table of typical values. Every formula is checked against reference values before publication. Results are theoretical estimates; follow manufacturer specifications for maintenance and safety.

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