Steve,
I sorta disagree provided that you aren't using fully matched/tested injectors for this workload. The, reasoning behind disagreeing is that with the higher the duty cycle there is a greater the chance that the fuel injection spray pattern is altered and that can/usually does reduce fuel atomization which leads to less power if that is the intent. Typically we hear that it is not recommended to run an injector at more than 80% due to the above reasoning. One of the reason that injectors are tested past 80% is to be sure that that the injector is large enough to support the engine during normal operating conditions and will not starve the engine for fuel. Fuel pressure also plays a role in this combination that some don't think to take into account either.
I'm no injector expert, but my basic understanding is a little different. Sequential fuel injection allows injectors to be individually fired during a specific window of crankshaft rotation. Obviously this would be timed with the intake valve openings and the period of negative intake pressure to assure fuel was moving in the right direction. The duration of injector opening during this available window is a time over time measurement and referenced in duty cycle percentage. If the injector was opened during this entire window the duty cycle would be 100%. Injector spray pattern does not change with duty cycle. They are opened or closed. A smaller injector has better atomization than a larger one, it has smaller holes. This is better for low speed operation and emissions. The OEM cars these days run their duty cycles into the low 90s routinely. This is all driven by emissions, not peak HP goals. Running bigger injectors than you need is the safe way to go for easy WOT tuning even though in
theory it may cost you low speed power. I think we would need a a very sophisticacted test session to ever figure that one out. I purposely left the stock injectors in that 107 build after someone told me they would not work. With a different cam, more overlap and duration, may have gone lean and never made it to the same HP level? I'm not telling others to do it, but I had no issues and better than expected results in the driveability department with injector duty cycles in the low 90s.
Maybe on the next one I will run out of fuel?
Ride safe!
SG
PS- On any fuel injection that does not allow individual cylinder tuning, getting the injectors flowed and matched as
you mentioned is very important. I had all 8 of the injectors flowed and matched on my little 635" Pontiac. Front tires still look like new!
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Topic: Dyno Test! Stock heads and TB VS CNC heads and 58TB (Read 18596 times)