injector duty question

[rance]

i have a 180 and basic mods fmic,bov,larger dump pipe.exhause, intake etc

i have all stock internals and standard ecu...and my guess is my car is runnin pretty rich

i was checking my avcr the other day..and the injector duty (on idle) was at 89%-90%, while driving is 84% average

i know if it hit over the 80 mark..somethings not right..im right now in the process of looking for a safc II...bacuse im too tight to buy a pfc

my question is...can safc fix the injector problem?...i mean if i up the air flow....i will make more power...but the fuel comsuption is still there....i want to save more petrol...with petrol prices around $1.20 p litre...its hektik

thanks

[SECURITY]

if you up the airflow wont it add more fuel causing it to run even richer?

get your avcr or safc when u get it tuned by someone who knows their shit and they'll find the right balance for you.

Joe

[rance]

i already have avcr ...just wanna know if the safc can actually lower the injector duty....

im 70% sure it does...but just based on my limited knowledge

[MANWHORE]

Safc alone does not necessarily lower the injector duty. Let me try and elaborate. say a car is running a flat 12 afr with a injector duty of 90. By using a FPR and upping the fuel rail pressure, this will make too much fuel get injected. So you use the safc to lower the amount. As a result of the FPR and safc combined, the car is now running a higher fuel rail pressure, yet it is still injecting the same amount of fuel with a duty of 80 and making the same power. raise the fuel rail pressure even more to further lower the duty cycle.

If your car is running rich, that means it's injecting too much fuel. By using the safc to lean out the mixture, that is, inject less fuel for the given air, it is reducing the duty cycle. However, I don't think a slight correcting of the afr using an safc will lower the duty cycle that much.

[rance]

so what u reckon i should do?.... and how do i raise the fuel rail pressure?

[BHDave]

Your car wouldn't run if it was running injector duty of 80% at idle, it would stall instantly. It should be running around 1-3% duty at idle.

Yes an afc will allow you to adjust the duty the injectors are running, how else are you going to adjust the amount of fuel going into the engine down?

Your duty should increase as revs increase and as load increases. For example 7000rpm on 12psi at WOT may be reading 80% where as at half throttle only 60% (only an example) and at 3500 rpm at half throttle maybe 30%.

The duty of the injector basically tells you how much fuel is getting put into the engine (assuming fuel pressure and injector size is constant). The fact that your AVCR is stating duty of higher than 80% at idle tells me that your avcr is reading incorrectly.

[Cubes]

I think you should simply throw it on a dyno and see whats going on.

Having an injector duty of 80-90 or what ever it was on idle is very wrong.