Injector calculations

Based on information found in Four-Stroke Performance Tuning by A. Grahamm Bell there are some basic calculations that can be done on injectors to see how far they scale. I’ve used these calculations in the injectorlist below.

Injector static flow = (Required flow * 100) / (injectors per cylinder * duty cycle)

Required flow = (maximum horsepower * K) / number of cylinders

Where:

• K = 4.6 for NA engines
• K = 5.6 for turbo/supercharged

Combined for the Speedster/VX220:

Max power == SF * (D / 100) * 4 / K

Where D is the duty cycle in percentage.

To recalculate the flow of an injector at a different fuel pressure, the following formula can be used:

new flow = old flow * sqrt(new pressure/oldpressure)

Without specification injector flowrates should be at 3bar. The z22se runs the fuel rails at 3.8bar.

For prolonged use at high rpm’s it is best to keep the duty cycle of an injector below 80%.

Injector list

Based on a lot of searching on the web I’ve found the following injectors which seem interesting for use on the Speedster/VX220 2.2 because they are the right type and have the correct connector.

Standard Z22SE injectors

Part number:

• GM 12565474

Brand:

• Siemens Deka

Flow:

• 225cc/min @ 3bar
• 252cc/min @ 3.8bar

Standard engine:

• Z22SE @ 147hp

Power:

• NA: 252cc @ 80% == 175hp
• SC: 252cc @ 80% == 144hp

Z22SE compressor upgrade injectors

Part number:

• GM 12593904

Brand:

• Unknown

Flow:

• 370cc/min @ 3.8bar (not sure)

Standard engine:

• Z22SE compressor @ 200hp

Power:

• NA: 370cc @ 80% == 257hp
• SC: 370cc @ 80% == 211hp

Standard LSJ injectors

Part number:

• GM 12790827

Brand:

• Siemens Deka

Flow:

• 352cc/min @ 3bar
• 396cc/min @ 3.8bar

Standard engine:

• LSJ @ 205hp

Power:

• NA: 396cc @ 80% == 275pk
• SC: 396cc @ 80% == 226pk

Stage 1/2 LSJ injectors

Part number:

• GM 12599778 (single injector)
• GM 12597995 (4 injector kit)
• GM 12597996 (4 injector kit)

Brand:

• Siemens Deka

Flow:

• 451cc/min @ 3bar
• 507cc/min @ 3.8bar

Standard engine:

• LSJ stage 1 @ 236hp
• LSJ stage 2 @ 241hp

Power:

• NA: 507cc @ 80% = 352pk
• SC: 507cc @ 80% = 289pk