BACK

# Formulas

## Engine

Brake Mean Effective Pressure
This is a calculation that gives you a measurement in bar (pressure). It is intended to be a way to compare engines and their output. It gives you output with respect to engine size as well as RPM (better than just HP/Liter).

(HP * 894.84) / (liters * rpm @ peak HP)

Peak Horsepower
Engine size (liters)
Rpm @ peak Horsepower

Here are some calculations of common Tercel engines, and similar car's engines:

 Engine BMEP 3E 7.99 3E-E 9.69 1st Gen 4E-FE 10.08 2nd Gen 4E-FE 10.39 4E-FTE 14.18 1st Gen 5E-FE 9.34 2nd Gen 5E-FE 10.41 5E-FHE 10.27 1NZ-FE 10.26 4A-GE 10.59 4A-GZE 14.54 4A-GE 20V 11.93 1ZZ-FE 10.69

Horsepower
Your basic calculation for horsepower. Everyone who tinkers with engines should know this one.

RPM x Torque / 5252 = Horsepower

Torque
RPM

Injector Horsepower Capacity
Calculations for estimating horsepower and injector size.

Horsepower limit of injectors = (Injector flow rate / 10.5) * Max Injector Duty Cycle / Brake Specific Fuel Consumption * Number of Cylinders

Maximum Injector Flow Rate (cc/min)
Maximum Duty Cycle (.8 recommended)
Brake Specific Fuel Consumption (.5 for NA, .6-.65 for turbo/supercharged)
Number of Injectors

Ideal injector size (cc/min) = (Maximum Horsepower * Brake Specific Fuel Consumption) * 10.5 / (Number of Injectors * Maximum Duty Cycle)

Maximum Horsepower
Brake Specific Fuel Consumption (.5 for NA, .6-.65 for turbo/supercharged)
Number of Injectors
Maximum Duty Cycle (.8 recommended)

Optimum Muffler Flow Rate
The ideal flow rate for your muffler. Too small and it will cause restriction and thus power loss.

Ideal muffler flow rate (CFM) = HP X 2.2

Maximum Horsepower

## Suspension

Springrate
A rough calculation of spring rate.

Spring Rate (Lbs/In) = 11,250,000 * Bar Diameter ^ 4 / 8 * Number of active coils ^ 3

Bar Diameter
Number of Free Coils

Bar & Tube Stiffness
A calculation to measure the stiffness of a bar. Very useful for increasing sizes of sway bars or any type of support bars.

Diameter ^ 4 = Stiffness

Bar Diameter

If you have a hollow tube, first calculate the outside diameter stiffness. Then, calculate the hollow diameter as if it were solid. Now subtract the first calculation from the second.

Bar Outside Diameter
Bar Inside (hollow) Diameter

BACK