My 04 heritage (specs below) has stock injectors (as far as I know), and with all those mods it puts out right around 120 tq/hp at the rear wheel. Am I going to gain anything on that with hi-flow injectors?

If yes, any recommendations on what I should go with and how easy/difficult are they to replace in a home garage? Thanks!

 

First, I need to assume you have had the bike dynoed, and have seen the air-fuel ratio curve versus rpm.

IF that curve is already sufficiently "rich" (say AFR = 13 to 13.5), you won't gain any power, because the injectors are already supplying enough fuel to make the correct ratio. IF however you are running lean, then the larger injectors may make more power.

However, there is another factor. Injectors are supposed to be turned on only a maximum of 80% of the time in order to have a decent lifetime. If your injectors are operating above 80% duty cycle, they will likely fail prematurely, and of course, never at a convenient time.

So, to answer your question, you need to know what duty cycle your injectors are currently experiencing with the tune you have.

Although there are math formulas that will get you in the ballpark, they are too broad (e.g. 0.4 to 0.6 lb of fuel per hour per horsepower) to answer the question.

While it may sound like going bigger on injectors "can't hurt", it actually can. If the injectors are significantly larger than they need to be to hit the 80% duty cycle, their part throttle and idle performance is significantly degraded, which can hurt performance, smoothness, and fuel mileage.

I suspect there is engine tuning software that can read your current duty cycle, but since I have never had to do this, I don't know which tuning software does it and what screens to access.

Sorry I could not be of more help, but you have a start here.

Jim G

 

Yep, had it on a dyno a few years back, which is how I found out the power output. I did see the AFR curve at RPM. However, at the time of the dyno run, I had a Daytona Twin Tech on it and now I'm running Thundermax. I'll have to see if the software can pull up the duty cycle on the injectors. Thanks for the response!