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When are you guys firing the injectors I see the default is bottom dead center on intake stroke does that sound right. I would think that it would do better if it was to fire sooner then that
 

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Every Every application is different and requires testing. I've done some that see little affect and other that helped idle and low speed quality some. You should have a tune that is pretty decent before making injector timing adjustments.
 

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Cam card, IVC (xx*) ABDC? Where does the IVO, where does it close? and where on the stroke. You can use the chart to figure it out



If you tune this correctly, You will see accurate Idle AFR's and a crisp throttle response.
 

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Cam card, IVC (xx*) ABDC? Where does the IVO (Intake Valve Opening), where does it close? And where on the stroke? You can use the chart to figure it out:



If you tune this correctly, you will see accurate idle AFRs and a crisp throttle response.
And just for reference (in Holley EFI software), a 0.0° Injector End Angle value, ends the injection event at BDC (Bottom Dead Center) of the intake stroke - before the compression stroke. This is 540° in the four stroke cycle (7th cylinder pictured above). A negative value moves the injection event before BDC, and a positive value moves the injection event after BDC. So a −180° Injector End Angle value will end the injection event at TDC (Top Dead Center) of the intake stroke (as the intake valve is opening). Obviously, a −90° Injector End Angle value will end the injection event in the middle of the intake stroke.
 

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Where would you start with this cam ? Also , what are you guys running for base pressure on the Holley 120 injectors ? ( 26 to 28psi of boost )



 

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Injector timing has a greater affect when the injector placement is poor from my experience.
Excuse my ignorance but how would one know when the injector placement is poor?
 

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I hope this thread keeps going. It is very informative. I would also like to see the response to the above cam events for learning.
Tom
 

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And just for reference (in Holley EFI software), a 0.0° Injector End Angle value, ends the injection event at BDC (Bottom Dead Center) of the intake stroke - before the compression stroke. This is 540° in the four stroke cycle (7th cylinder pictured above). A negative value moves the injection event before BDC, and a positive value moves the injection event after BDC. So a −180° Injector End Angle value will end the injection event at TDC (Top Dead Center) of the intake stroke (as the intake valve is opening). Obviously, a −90° Injector End Angle value will end the injection event in the middle of the intake stroke.
Correct. I tuned a solid roller with a IVC of 56* (596* Crank Rot.) It idled horribly, False lean cond, pump to start, Black soot on bumper, etc. Advanced Inj to 46* (10* under) and this resulted in a steady afr idle, nice throttle response. As said this has really no effect on wot.
 

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Where would you start with this cam ? Also , what are you guys running for base pressure on the Holley 120 injectors ? ( 26 to 28psi of boost )



How does it Idle? Your IVC is 45* ABDC (585* CR). I have good results with Inj ADV to 10* under IVC. So, if I were having difficulty getting afr's right at idle or throttle response sucked, I would try raising Injector timing to 35*.

All setup are different so this is for testing. Don't blame me if your shit stalls. LOL
 

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Injector timing has a greater affect when the injector placement is poor from my experience.
That'd be your transient fueling and fuel puddle issues. Some software allows this to be dealt far more extensively, but it it's not always so simple since we don't have OE-level calibration tools available.

Essentially, the fuel puddles and runs along the wall of the intake and head, eventually evaporating and becoming consumable. I'm speculating that you're injecting on those a bit earlier? What you're seeing by injecting on the closed valve is more time for it to evaporate and become a consumable fuel.

If it's truly poor placement, forcing the fuel at higher pressure is not going to prevent it from still smacking the wall and puddling in my experience.
 

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How does it Idle? Your IVC is 45* ABDC (585* CR). I have good results with Inj ADV to 10* under IVC. So, if I were having difficulty getting afr's right at idle or throttle response sucked, I would try raising Injector timing to 35*.

All setup are different so this is for testing. Don't blame me if your shit stalls. LOL

Idle is great right now .......its carbed . :)
 
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