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I'm trying to get a better handle on how the EFI system works and I'm having trouble finding specific information, so I'm hoping you guys can help me.

I'm curious about the flow rate of the stock HD injectors and if it gets to be a restriction in bigger motors. When I put the Jim's 120" (out of the box stock) on my '04 Wide Glide I used a HorsePower Inc 51mm throttle body and the stock injectors.

As far as I can tell, the stock injectors flow at 4.35 gm/sec (?). Does there come a time in street applications for a motor like this where the stock injectors just can't deliver enough fuel? Is there a benefit to going to higher flow rate injectors, like 6 gm/sec?

I have pretty much zero knowledge in this area, so I hope this question at least makes a little sense.
 

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Snaps said:
I'm trying to get a better handle on how the EFI system works and I'm having trouble finding specific information, so I'm hoping you guys can help me.

I'm curious about the flow rate of the stock HD injectors and if it gets to be a restriction in bigger motors. When I put the Jim's 120" (out of the box stock) on my '04 Wide Glide I used a HorsePower Inc 51mm throttle body and the stock injectors.

As far as I can tell, the stock injectors flow at 4.35 gm/sec (?). Does there come a time in street applications for a motor like this where the stock injectors just can't deliver enough fuel? Is there a benefit to going to higher flow rate injectors, like 6 gm/sec?

I have pretty much zero knowledge in this area, so I hope this question at least makes a little sense.
I'm assuming that the injector flow rate you are referencing come from the EFI Tuner software. Remember that when calculating flow rates, fuel pressure is also a factor. If you change the fuel pressure, then you must re-calculate the flow rate. Here is the formula: New flow rate = old flow rate * sqrt (new pressure/old pressure)

The O/E Delphi Injectors should feed that motor with no problem. I built a 124" that blew 154 tq with O/E injectors and was in no danger of overrunning the injectors.

If you have questions, drop me a note @ [email protected] I don't always check this forum.
 
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