Information on the injector sizing selection criteria
Note that this calculator only gives an estimate of the injector sizing. It is your responsibility to make sure
you use the correct injector sizes for your engine.
POWER - this is the power you want your 2JZ-GTE (or 1.5JZ-GTE) to achieve on the dyno at the rear wheels.
RPM - this is the engine rpm that you are making the power specified above at.
AIR FUEL - this is the air-fuel ratio that you want to achieve on the dyno. This depends on the octane
rating of the fuel you are running, but around 12.0:1 is considered safe for normal fuel and boost levels.
For high boost, you would be looking at 11.5:1 or perhaps slightly lower at peak torque.
DYNO - different types of dynos give different rwhp readings so choose the dyno type you will be using. The Dynojet
is used in the USA, the Dyno Dynamics in New Zealand/Australia and the Dynapack in USA/New Zealand/Australia.
WARNING: The Dynapack dyno can be run in a number of different modes. These different modes do produce slightly
different rwhp figures and as a result the injector size calculation for the Dynapack dyno may be slightly
inaccurate.
DRIVING WHEELS - Supras only have RWD but using this calculator you can also calculate injector sizes for the 2JZ-GTE
if installed in a 4WD vechicle.
GEARBOX - select your gearbox type. Note that automatic gearboxs produce lower rwhp readings for the same engine hp.
BASE FUEL PRESSURE - the Supra normally runs a base fuel pressure of 42 psi but higher pressure will result in more
fuel being delivered by the injectors. When running higher fuel pressures make sure you are using a high
pressure fuel pump. Note that the OEM Supra fuel pump is not considered to be a high pressure pump.
FUEL RISING RATE - the OEM Supra fuel regulator has a rising rate of 1:1 hence the 1.0 default. The higher the rising rate,
the more fuel the injectors will deliver. Note that most injectors don't like to run at a total fuel pressure of more than
80psi.
BOOST PRESSURE - you only need to set this if you are altering either the base fuel pressure or the regulator rising rate.
This is because the base fuel pressure will alter the total fuel pressure and with the rising rate, the boost pressure level
will increase the fuel pressure by more than the boost pressure. E.g. 20psi boost at 1.5 rising rate will increase fuel
pressure by 30psi.
FUEL TYPE - Petrol, E10 (10% ethanol), E85 (85% ethanol) and Methanol are the 4 fuel types to choose from. E10
requires 5% more fuel at full boost, E85 requires 40% more fuel at full boost (25-30% more when off boost) and Methanol
requires 100% more fuel.
DUTY CYCLE - this is the injector duty cycle. Using 100% duty cycle is not recommended for more than very short
periods as the injectors can overheat. Most injector articles suggest using a maximum of 80% duty cycle.
Email Kevin if you think this calculator is wrong or you have any suggestions for
improving it.