Made another run during my TTS tuning and got the following message. Not sure at what point I should upgrade, and to which. Bike is a 110 with TW7 cams, and a DD Fatcat.

 

Do you know what power level you realistically are shooting for?

Needs for gasoline typically go about .5lbs per hp/hr. You injector should be sized to provide that plus enough over so they aren't wide open at peak power.

Example 100hp = 50lbs for fuel per hour, divide by two (two injectors). So they'd be 25 lbs per hour at WFO. At 85% duty at max, that puts you at about 30lb/hr injectors.

 

Honestly I wasn't expecting cams and a pipe to max the injectors out. I think it will do somewhere around 120tq/106hp based on the dynos I've seen. So 85% is the max? The bike is already over 90% in the upper revs and isn't completely tuned yet....

 

You need to know the size of the injectors you have. Also, the rating is just that. A rating. If you're on the edge, you need to know the ACTUAL flow rate.

The thing is, if the injectors are maxed out, and the fueling is controlled via sensors, what happens when the injector gets a little varnished up? Or when you a running WFO at a lower altitude than when you tuned it?

You also have to honest with yourself about how you actually use the bike. You can always set the rev limiter to keep it from reaching an RPM where max duty cycle is needed.

I can tell ya, having a motor starve for fuel at high rpm ain't pretty and it happens quick.

 

The most important question here is how often and how long are you ride the bike in the 90% DC rpms?
If you are infrequently running that high in the rpms or running at that rpm+ for periods of time, you should up the injector size.
That said, I tune bikes everyday that will go over 80% but only at a area where the rider doesn't spend time there.
Duty cycle does not indicate lean or rich, just how many much of the available time the injector is in the "on" state.
In other word, an engine can run exactly the same with injectors that are running @ 90% DC as with injectors that require only 50% DC.
The difference is in mainly life span of the injector. Also there is a bit of control differences.
Big injectors tend to be a little sloppy in the real low demand areas and small injectors tend to control fueling better in the low demand areas.
So, IME, it's best to use the smallest size injector that doesn't need to run over 80% for periods of time. A spot 90+ DC is acceptable IF the engine doesn't spend time at that state.
Hopefully this doesn't muddy up the waters,
Bob

 

Thanks for the reply, Bob. I ride fairly hard and the TTS is still recommending additional tuning, with already being above 90% in the higher revs. I'm assuming if I were to go to a larger injector all of the tuning I've done thus far has been for naught?

 

Again, pay more attention to how long you would/will be at those revs/load and if not long, you're fine where you are and require no change.
If you are racing this bike and will be spending a considerable time period at high rev/loads by all means a larger injector is better, albeit without power gains.
Bob