Injector resizing. Rb25det and Deatchwerks 740cc injectors

[crans]

Havin alot off issues resizing my injectors and I am starting to think it is a hardware problem(With the injectors)

Did the resize 370cc stock injectors to 758cc(From flow test results) K Const come out to 91
Adjusted latency value to 1300(Flow test shows 1.3ms @14v <- On warmup my car sits at 14v)

I let the car warm up AFR's are sitting on 10arf and slowly build up to 14.

As car warms up to 74Deg voltage drops to around 13.5V

AFR on idle is all over the place. car sounds like it is constantly missing.
Driving on deceleration its poping and farting everywhere (Thought the was fuel cut)

On boost is is running richer that with the stock injectors but seams to be smoother than idle

I tried adjusting the K const with NB input disabled and getting it smak bang on 14.9 makes the car run like complete shit.

Any ideas of where im going wrong?

[bachig24u]

yep, had similar problems with RB20 with seimens deka 870's.

The way I started was to adjust K so the car free revved nicely.
Idle as very rich, 12's or lower.

then had to lower TTPmin down.
adjust K' so the car free revved nicely without hesistation and cruise was on the mark.
later installed an adjustable fuel regulater to tidy up the idle mixture.

the popping is often too much fuel on decel.

[crans]

Matt,

Been talking to Deatchwerks over the issue and they have suggested Nissan ECU's report latency incorrectly

Stock Rb25 latency is around 570us but on my rb20ecu running rb25 maps the latency says 740us

Deatchwerks want me to set latency at around 700us but Ive already done this with the default figure already being around 700us.

Starting to think i just have a dodgy set of injectors

[Matt]

suggested Nissan ECU's report latency incorrectly

I have verified using an oscilloscope that the injector latency adjustments are correct. In that the modification of the time in uS matches the adjustments seen on the screen (remember this in addition to the additional injection time determined from the maps).

So the scaling is correct at least. You can raise/drop the latency until your AFRs appear better around idle once Injection Multiplier is correct (as this is the only real area you will notice its effect due to the minor time adjustment it allows)

[crans]

When idling at an afr for 14 - 14.9 the car missfires and runs really rough.

Is this more than likely a tune issue or hardware issue?

If K const and latency are incorrect but its at the correct afr it should still idle smooth? <- this is what makes me think i have faulty injectors

[Matt]

Personally I've mainly seen this issue with AFMs not working properly or a vacuum leak. Whilst the AFRs appear to be okay the fluctuation and misreading of actual load vs required load for injection time seems to fluctuate and can even cause misfiring etc

Not so sure with injectors causing to run that bad as I havent seen that first hand

[crans]

Interesting. I have long suspected an intake leak, but never found anything even after compressing all the pipe work.
I do how ever think my AFM wiring is dodgy 1 knock and it cuts out. I was going to wait till the injector resize worked before connecting my Z32 but i might just do it now.