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Big overall fuel trim adjustment after changing big cc/min injector

Posted: Sat May 05, 2018 7:16 am
by CHB
Hi Hondata,

I just replaced the some 1000cc/min injectors (Bosch 14mm High Impedence 12ohm). Before I did the change, I warmed up the car and A/F was steady at 14.5AFR at idle.

Changed the injectors, changed the injector size value in kManager to 1000cc, and also changed the injector dead time table accordingly.

The car started straight up with no hesitation, in fact it started better than the stock keihin 270cc injectors, but.... AFR was around 25AFR.

I have to adjust "Overall fuel trim" to +75%, only then the idle AFR will be at 14.5-15.0 AFR.

I'm using Kpro4 in PND on K20A3 DC5, using stock PND Air Fuel Ratio Sensor.

Does this seems correct?

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Sat May 05, 2018 2:08 pm
by Hondata
What dead time values did you use? What fuel pressure are you running? I think some of the 1000cc injectors are around 850cc/min unless you are at very high fuel pressure.

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Mon May 07, 2018 7:42 pm
by CHB
I have not installed fuel pressure gauge, and still on stock fuel pump.

The injector is Raceworks (Australian brand) which uses Bosch injector core.

Attached is the dead time setup from the manufacturer. I've entered the values on 43.5psi (3bar).

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Mon May 07, 2018 7:56 pm
by CHB
Just to add on, these injectors have been tested flowing 1000cc @ 43.5psi 3bar.

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Tue May 08, 2018 5:48 am
by Hondata
What sort of injector are they? If they are the Bosch EV6 or EV14 then the dead time at 14V is going to be around 1.2ms, not 0.88ms

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Fri May 11, 2018 8:40 am
by CHB
They are EV14

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Fri May 11, 2018 9:15 am
by Hondata
Dead times are going to be around 1.2ms @ 14V

Re: Big overall fuel trim adjustment after changing big cc/min injector

Posted: Sun May 13, 2018 9:21 pm
by CHB
I've used the default ID1000 table and fire it up, works great.. idle dead stable at 13.8-14.0AFR with 0% overall fuel trim.

Thanks Hondata.