duty cycle defined

[Doctor 30]

What does duty cycle actually mean.

If I am running at 2000rpm at 40% then that would be twice as rich as 4000rpm at 40% because the injector would be twice as long at 2000rpm when compared with 4000rpm. Or does the computer allow for this?

[Sydneykid]

What does duty cycle actually mean.  

If I am running at 2000rpm at 40% then that would be twice as rich as 4000rpm at 40% because the injector would be twice as long at 2000rpm when compared with 4000rpm.  Or does the computer allow for this?

RPM is irrelevant, 40% means it is open for 40% of the time, that can be 40% of 1 second, 40% of 1 minute, or 40% of one hour.

[Doctor 30]

So realistically for a given manifold pressure it should read

1000 rpm 20%

2000 rpm 25%

3000 rpm 35%

4000 rpm 45% etc

Is that correct?

[Sydneykid]

So realistically for a given manifold pressure it should read

1000 rpm 20%  

2000 rpm 25%

3000 rpm 35%

4000 rpm 45% etc

Is that correct?

Sorta. On a fuel map, rpm is one axis and load is the other axis. So you can have a lower duration at 3,000 rpm than at 2,000 rpm, if the load is lower. On a Skyline the load sensor is the AFM, manifold pressure is irrelevant. If it has no AFM, it is usually mapped for rpm against throttle position, again manifold pressure is sometimes irrelevant.

[Doctor 30]

Yeah, I was thinking other things being equal (IE load) Mine runs from RPM and MAP (I don't have an AFM. TPS is only used for extra enrichment which mine is set at 50% throttle.

So my car is probably running ridiculously rich down low and dangerously lean up top. Thanks for sorting that out for me.

I now need to find out what is a good duty cycle for varying loads and rpms for the RB20DET. Anyone that can help that would know would be very useful!!!

[benm]

What is a safe maxium load for RB25DET injectors?

[RB30-POWER]

Ideally you want to go to about a maximum of 80% or so, at maximum power/boost for your motor.

Its not a good idea to run injectors close to 99% all the time as they weren't really intended to be pushed that far, and could shortern their life considerbly.

Therfore when choosing injectors for a certain motor, you want them to be at a maximum of 80%. This will allow safety margin, if you need a bit more injector on time, maybe when its a cold night or such.

Another thing, if you get massive injectors that you only run up to say 40% at full power, it makes it very difficult for the tuner to control them as acurately.

In fact microcraps and other cheap ecu arent the best for massive injectors if outright accuracy is wanted in the tune at low loads and light throttle. Autronic and Motecs are much better at controlling very large injectors at low duty cycle.

[Doctor 30]

hang on, who's hijacking this thread!

I also have a MASTER FUEL section. WTF is that about?!

[Sydneykid]

hang on, who's hijacking this thread!  

I also have a MASTER FUEL section.  WTF is that about?!

Moves all the fuel load points on the map up or down. It makes changing from say 370 cc injectors to to 750 cc injectors real quick, just subtract 50% on the master fuel correction. Then fine tune the load points that need it. Much quicker than punching in every individual load point.

[Doctor 30]

so really I should reset the whole thing. Set the master fuel ,then the Row Fuel, then the individual load points..

I can't be stuffed. Well maybe I can

[Doctor 30]

As no one can tell me what it is set at I am going to get the car retuned at rematch in Thomastown. I will then post every single value so that anyone that buys a Link ECU can just copy it and let the fun begin! Aren't I the charitable one?!