What is the maximum amount of injector opening time (mls)

[To The Max]

Hi Guys,my standard injectors on my 103 peak at about 17 milliseconds at 6400 rpm , can anyone tell me if that exceeds the limit . Max

[strokerjlk]

Hi Guys,my standard injectors on my 103 peak at about 17 milliseconds at 6400 rpm , can anyone tell me if that exceeds the limit . Max

not really . that is about 90 % duty cycle. very good for 6400 rpms

[Sunny Jim]

Gidday to the Max fromAustralia( West) . Welcome to a truly spine tingling, temple twisting extravaganza of knowledge. Cheers!

[To The Max]

Gidday to the Max fromAustralia( West) . Welcome to a truly spine tingling, temple twisting extravaganza of knowledge. Cheers!

Thanks for the welcome Jimbo.

[To The Max]

Hi Guys,my standard injectors on my 103 peak at about 17 milliseconds at 6400 rpm , can anyone tell me if that exceeds the limit . Max

not really . that is about 90 % duty cycle. very good for 6400 rpms

Thanks very much for that Srokerjlk i was hoping for the high 80s but that will do very well.Max

[joe_lyons]

Hi Guys,my standard injectors on my 103 peak at about 17 milliseconds at 6400 rpm , can anyone tell me if that exceeds the limit . Max

The limit is %100 but its suggested to go to the next size larger at %80 duty cycle.

[strokerjlk]

Duty cycle is a calculation of injector pulse width vs rpm of the engine. Injector Pulse Width is a set number.

Let's say 20 milliseconds is the fastest it can pulse. If your engine is at an RPM where it takes 50 milliseconds to complete a cycle (that's two revolutions, because two revolutions equals 1 engine cycle) than your injector is at 40% duty cycle because 20 milliseconds is 40% of 50 milliseconds. The injector's open time is 40% of the time it takes for the engine to complete 1 cycle.

Once the rpm reaches a point where it takes 20 milliseconds to complete a cycle, you are at 100% duty cycle and the injector is staying open. If the engine spins any faster, obviously the calculation passes 100% because the engine is taking 15 milliseconds to complete a cycle, but the injector pulse width is 20 milliseconds. The injector is still static open at 100%, but the calculation can surpass 100% because the engine is spinning faster than the injector can open.

Duty cycle is just a calculation of injector open time vs rpm

[hrdtail78]

Hi Guys,my standard injectors on my 103 peak at about 17 milliseconds at 6400 rpm , can anyone tell me if that exceeds the limit . Max

The limit is %100 but its suggested to go to the next size larger at %80 duty cycle.

I follow the 80% rule of thumb.  You might be at 90% with a regular WOT pull targeting 13, but that pw/ duty cycle is going to go up when it is targeting 12.6 or 12.4. 

[strokerjlk]

It's possible to have 115 % calculated duty cycle , and still have plenty of injector .

[joe_lyons]

Yes your right.  My bad.  But if the injector is open that much then you are pissing up a rope and need a bigger injector.

[strokerjlk]

Yes your right.  My bad.  But if the injector is open that much then you are pissing up a rope and need a bigger injector.

Not really . If you can still ask for more fuel and it gets it .

Once the rpm reaches a point where it takes 20 milliseconds to complete a cycle, you are at 100% duty cycle and the injector is staying open. If the engine spins any faster, obviously the calculation passes 100% because the engine is taking 15 milliseconds to complete a cycle, but the injector pulse width is 20 milliseconds. The injector is still static open at 100%, but the calculation can surpass 100% because the engine is spinning faster than the injector can open.

[hrdtail78]

100% is 100%.  Yes, you can calculate past 100% but what for?  You can not run an injector higher than 100%.  100% means the injector is statically open 100% of the time.  How do you open it up any longer than open all the time?  You can't.

Yes your right.  My bad.  But if the injector is open that much then you are pissing up a rope and need a bigger injector.

I agree.  100% equals lose of control.  Bigger injector or more pressure is needed.

[BVHOG]

Keep in mind fuel pressure has a huge effect on injector sizing

[joe_lyons]

I guess the question is if the bike is still making any power at that rpm?  If it stops making power at 5500 then 6400 is pointless.

[strokerjlk]

If the Op'er would have been at 20 ms P/W at 6400 he would have been at 106 % duty cycle .
So relying on duty cycle to determine if the inj is used up , is not the best practice .

Sure  a bigger inj can be used at this point . But just because you have 90 % duty cycle at 6400 isn't a reason to swap injectors and re tune .

[hrdtail78]

Keep in mind fuel pressure has a huge effect on injector sizing

Absolutely.  It's about controlling the right amount of fuel for the application.  More fuel will flow at a higher pressure out of the same injector for same pw.  A secondary benefit is at low RPM.  The higher pressure can spray right into the combustion chamber as the valve is opening.  Less cross talk. 

Injector DUTY CYCLE is the best thing to rely on.  If you are at 100%.  You have lost control.

Here are a couple of things written by guys that seem to be in the injector industry.

http://docinjector.com/info1.htm

"What do the terms "static" and "duty cycle" mean?
An injector in an engine turns on and off very quickly to control the amount of fuel delivered. The amount of time an injector is turned on and delivering fuel is known as the duty cycle. This is measured as a percent, so 50% duty cycle indicates that the injector is held open and held closed for an equal amount of time. When the engine needs more fuel, the time that the injector stays on (its duty cycle) increases so that more fuel can flow into the engine. If an injector stays on all the time, it is said to be static (wide open, or 100% duty cycle). Injectors should not go static in a running engine. If an injector is static in a running engine (open 100% of the time), that injector is no longer able to control fuel delivery. This could be an indication that the injector is too small for the needs of the engine. Injector duty cycle should usually not exceed 80% in a running engine at any time."

http://injector-rehab.com/shop/idc.html

"I have seen it more than once that people report they ran a duty higher than 100%... it is not possible. Your injector has completely maxed out and only ran 100%, you just ran it past its operating range and the calculation shows that. It is impossible to physically run an injector HIGHER than 100%."

[strokerjlk]

Injector PW is the best thing to rely on

the op'er is fine at 17 ms @ 6400 rpms

[hrdtail78]

Typo on my part. I meant duty cycle.  Let's not confuse reported pulse width with what actually is going on with an injector.  The ECM can only report what it wants. There is no feedback telling you how long the injector is open.  That is why we use duty cycles. 100% is 100%. There is no such thing as 106%

[m1marty]

 Im hitting right at 19ms at less than 6k on my build.....thinking its new injector time.

[joe_lyons]

Im hitting right at 19ms at less than 6k on my build.....thinking its new injector time.

Yes sir

[strokerjlk]

Im hitting right at 19ms at less than 6k on my build.....thinking its new injector time.

What would you expect to gain if you changed to a bigger injector and your Pw was 15 ms instead ?.
Where your at now you can still command more fuel and get it right?
At 19 ms you can still add enough fuel to kill power .
If your making changes that warrant another tune ,Then yeah buy some bigger injectors .
If your doing it just to see a gain , or you think you gonna wear your injector out . Save your money, unless its a bonniville bike .

[m1marty]

Stroker- Im wanting to go to an S&S throttle hog.  I figured while Im there- new injectors would be a good idea for the eventual 113 thats replacing this 103ci.

[strokerjlk]

Stroker- Im wanting to go to an S&S throttle hog.  I figured while Im there- new injectors would be a good idea for the eventual 113 thats replacing this 103ci.

makes perfect sense .

[To The Max]

Great discussion guys, I think 80% to 85% is ideal and 90% is very borderline I think we need to allow time for the injector to actually open and close after the signal which is how duty is measured and for changes in engine temp, air temp and battery voltage which can all change the ms,so I think 80% is better than 90%. another thing that concerns me is if you extend the d/ cycle where does the injector stop spraying( does it spray onto a closed inlet valve ? ). my t/max has adjustable injection advance but I don't know if it adjusts injector opening or closing point. I did change this setting to 360% and it made a big difference to my cold and hot idle , light load cruise under 2300 rpm and hp but I don't really know why?? Max

[joe_lyons]

It would be nice to have injector time control with the Delphi ecm.  Maybe they will be releasing that in the future?