M

MAF

Mass air flow

MAP

Manifold air pressure.

MAT

Manifold air temperature

mbt

maximum brake torque.

ME

Mechanical efficiency

Mean Effective Pressure (MEP)

The combustion pressure above the piston on the power stroke.

MEP

Mean effective pressure (generic for cylinder pressure). The Mean Effective Pressure (MEP) is a theoretical parameter used to measure the performance of an internal combustion engine (ICE). Also, since the torque is divided by the engine capacity, the mean effective pressure parameter can be used to compare internal combustion engines of different displacements.

MFR

Mass Flow Rate.

Mass Flow Rate is the mass of air flowing through a compressor (and engine!) over a given period of time and is commonly expressed as lb/min (pounds per minute). ... As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow.

mm

millimeter.

N

Nm

Newton meter (See Torque)

Number 5252

"a permanent value for the purpose of computation. For example, in the torque and horsepower formula, 5,252 is the constant that enables the calculation of torque, horsepower, or engine speed if any two values are known.

O

O-Rings

Non-moving seal which prevents oil or air getting between different components.

O2

Oxygen

OEM

Original Equipment Manufacturer (OEM) vs. Aftermarket

An OEM refers to something made specifically for the original product, while the aftermarket refers to equipment made by another company that a consumer may use as a replacement.

On-Centre Turbine Housings

On-centre turbine housings is an old design turbine housing with a centred turbine inlet pad.

Overbalancing

The practice of adding a small percentage more than the normal weight of 50 percent to the bob weights when balancing an engine. It helps smooth the engine’s operation at high RPM.

Overlap

A brief period in camshaft timing where both valves are partially open at the same time.

Overspeeding

Is a term used when a turbo is operating well above its normal operating limits.

P

Petrol

Petrol

Pi (π)

pi (π): 3.1417 - Pi or π is used when calcualting circles or other round objects.

Pin Height

Distance from the centerline of the piston pin to the top of the piston. Formally known as the compression height.

Piston

Vital engine part

Piston Rings

Type of seal commonly used in turbochargers to prevent air, gas or oil getting where it shouldn’t. A pressure differential seal.

Post-Turbo Flow Loss

Pressure drop across Intercooler, Piping, and TB.APS DR525 publishes this pressure drop as 1.0psi.

Power Curve

A graphic representation of an engine’s torque and horsepower output per RPM. On a graph, the torque and the horsepower curves cross at 5,252 rpm.

PR

Pressure Ratio

Pre-Turbo Flow Loss

Flow restriction of Turbo inlet tube, Air Induction Tube, and Air Filter.

Pressure Ratio

Absolute outlet pressure divided by absolute inlet pressure. To demonstrate: (Boost + DPIntercooler+ Atmos) / (Atmos-DPAir Filter) = Pressure Ratio

Pressure Ratio

The ratio of artificial boost pressure to ambient atmospheric pressure. Calculated by adding boost pressure and ambient pressure then dividing by ambient pressure.

psi

Pound per Squeare Inch

psig

Gauge pressure