Injector size

[RTMike]

Upgrading a 13 RG ,is the stock injector gps 4.3?

[Ohio HD]

Yes, 4.35.

[RTMike]

Thanks

[Ohio HD]

 

[chas]

If i'm going to a larger cam on a 03 ultra should i be thinking of using a larger injector?

[Ohio HD]

No, stock are fine.

[Jamie Long]

Here is some helpful info from the FM University website:

OEM injector sizes for H-D Delphi injected models:

4.38 gm/s – 2017-later Milwaukee-8
4.35 gm/s – 2008-2017 Twin Cam Throttle by wire
3.91 gm/s – 2006-2017 Twin Cam w/cable throttle
4.35 gm/s – 2001-2005 Twin Cam

We put together the following chart to illustrate what we consider to be the optimum injector size based on rear wheel horsepower. This is to be used as a general guideline and may vary based on the application.

[Ohio HD]

Nice visual for the injector ranges.   

[kd]

Very interesting graph. By classifying them in "optimum" size, what percentage of gm/s injector output is the graph line.  For example at 100% under WFO it likely would not sustain that range for long if the load increases. (wind, elevation, incline etc)  Are the graph levels at a more comfortable 80% or other level below 100% max output? In other words, on the graph, if I wanted to feed 150 HP, would I chose a 6.0 gm/s instead of the 5.5 gm/s the graph shows is capable of getting there?

[jty]

Great article on the website
Jamie, there seems to be a small typo there, I guess
"Twin Cam Cable throttle 2006-2017" should say 2006-2007

[Buglet]

  Twin Cam Cable throttle was use up to 2017 on sum models, not all were FBW.

[Pirsch Fire Wagon]

Very interesting graph. By classifying them in "optimum" size, what percentage of gm/s injector output is the graph line.  For example at 100% under WFO it likely would not sustain that range for long if the load increases. (wind, elevation, incline etc)  Are the graph levels at a more comfortable 80% or other level below 100% max output? In other words, on the graph, if I wanted to feed 150 HP, would I chose a 6.0 gm/s instead of the 5.5 gm/s the graph shows is capable of getting there?

Use the 80% Rule when moving to a larger Injector.

[kd]

Very interesting graph. By classifying them in "optimum" size, what percentage of gm/s injector output is the graph line.  For example at 100% under WFO it likely would not sustain that range for long if the load increases. (wind, elevation, incline etc)  Are the graph levels at a more comfortable 80% or other level below 100% max output? In other words, on the graph, if I wanted to feed 150 HP, would I chose a 6.0 gm/s instead of the 5.5 gm/s the graph shows is capable of getting there?

Use the 80% Rule when moving to a larger Injector.

Thanks for that.  I didn't know about the article on Jamie's web site either.  It's a good read.  My 120 was spec'd to be 150 HP (and it is) so I used 6.2 yellow band injectors with a 62/64 HPI throttle body.  It worked out great top and bottom but is more like 88% duty cycle.

[jty]

  Twin Cam Cable throttle was use up to 2017 on sum models, not all were FBW.

Oh, did not know that, thanks for the correction

[itsafatboy]

I used 6.2 gms in a 116 , have no issues , i kind of figure get the fuel in quick open fast get it there then close , kind of like a woods cam ,