at what point should we got to larger injectors?

 

If you use the calculator on the RC engineering site RC engineering , then a duty cycle of 80%, bsfc of .55, a fuel pressure of 100 psi and six injectors delivering 240 cc/min (stock 4th gen injectors) results in a crank power of 300 hp. We know that 4th geners are making over 300 hp at the wheel using stock injectors, so something isn't quite right. If you assume a duty cycle of 100% and a fuel pressure of 85 psi, then you get 350 hp at the crank, or about 300 hp at the wheel for a 5 speed (15% powertrain loss) which seems more realistic. At any rate, it appears that if you go much over 300 hp at the wheel you enter the danger zone with respect to duty cycle and injector pressure. Some people are running over 100 psi fuel pressure without problems, but it's kind of risky. There's no safety margin if an injector malfunctions.

 

while on the subject, I'm still kinda confused as to how Mardi is running the 370s "properly" w/o ECU reprogram?? I never saw the clear answer...anyone care to shine some light?

 

I thought his ecu was modified? however, i was unaware that you had to reprogram the ecu when u added larger injectors. If so, how would us 99's add larger injector isf they no make an ecu for our cars.

 

I am running ~30psi base fuel pressure, normal is ~40. With less pressure the stock ECU can handle the fine tuning of the larger injectors. I use an FMU to ramp up fuel pressure under boost.

 

What damage is done if an injector failes? I know when using nitrous you're screwed, because just the nitrous and air will ignite.

Will enough combustion take place w/o fuel to do damage, or will you just lose power?

 

If an injector fails, your engine may fail, and your wallet will fail again.......

 

"Fail how?" is what I'm asking.

 

Injectors can fail a number of ways. One way is if they run at a high enough duty cycle for a long enough period of time that they overheat, the solenoid winding insulation fails (due to the heat) and they short out. Normally fuel flow carries away heat generated in the solenoid windings of the injector, but heat transfer to the fuel may not be sufficient if the duty cycle is high enough for long enough periods of time.

Another way an injector can fail is by overpowering it with fuel pressure. The injector solenoid acts against the fuel pressure in opening the injector. If the fuel pressure is high enough, the injector will lock up. This can also happen due to a gradual weakening of the injector over time (due to overheating, for instance).

An injector can also get clogged with debris, resulting in less than full fuel flow when needed.

The result from the different types of injector failures is all the same - a lean operating condition resulting in detonation when boosting.

 

Can we use bigger bosch injectors in our cars and are our injectors high empedance?