swapped injectors results not what I expected

[PJG1173]

Ok so after alot of driving around yesterday datalogging I had come to the conclusion that the 4.3L injectors were not cutting it. WOT PE couldn't get the AFR below 14.9 on the WBo2 at high rpm, VE table at 97% and DC in the 70's. Yes I know I could have put more pressure to them, but I figured I was getting up there in DC. So I slapped in a set of 61# injectors copied the injector latency table, flow from a 5.7 bin, and backed the FP down to 13psi. Now I'm globaly lean without changing my ve tables. is there something I'm missing here?:homer: going from 46# injectors @ 15psi (according to the calc they were running 49# at that pressure) to 61# at stock FP should have made it rich doing the math, or maybe I just don't understand. So now what do I do? lower the injector constraint or raise the FP back up?

[gregs78cam]

If you still have some room DC wise I would suggest lowering the Injector flow rate. If not raise the pressure. But I would probably double check the part numbers to make sure that they are 61#ers. What engine/combo is this?

[EagleMark]

If you had just lowered fuel pressure your data log would have gone all lean right? So now you lowered your fuel pressure and changed flow rate to correct of injectors and got same lean right?. You just gave the PCM flow rate to compesate for bigger injectors.

Lower fuel injector flow rate and it will get richer! :thumbsup:

[PJG1173]

:mad1: they are GM5235206 and from a little searching they are the 55# injectors so I copied the info from the wrong bin.

[gregs78cam]

yup that'll do it. So making the flowrate correct should help.

[PJG1173]

so far all the $0d 5.7l bin's Ive looked at have 61# in the constraints and the 5.0 has 55#. more searching has resulted in conflicting information so does anyone know what these truly flow? they have orange/black markings and GM5235206*RPD is etched in the top.

[gregs78cam]

From Fast355 on TGO:


The GM 5235206 *RPD orange/black is 61 lbs/hr NOT 55 lb/hr so stop spreading the false information. I have flowed many of them and clean they are all right around 61 lb/hr +/- 1/2 lb. Most 305s have 55 lb/hr injectors with the green/white color code, again I have flowed many pair of them.

EDIT- I am not trying to be an ***, just once the information gets around, it is impossible to go back. 55 lb/hr designation was given to them many years ago, when in reality they truely are 61 lb/hr. 305 injectors have been given a 40 lb/hr rating in the same WRONG chart (it was the best guess around 10+ years ago). Most 305 injectors really are 55 lb/hr. 40 lb/hr would not even feed the L03s stock 175 FWHP rating.

http://www.thirdgen.org/techboard/tbi/363320-help-injector-specs.html

I would trust him, and that is what I have set in my Camaro. If you need to you can set them to whatever you want, if it makes the engine happy under all conditions.

Mark probably has some sheets from the injector service guy that shows real lb/hr.

[EagleMark]

You guys ever check the links in FAQ?

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?81-GM-Injector-size-color-and-part-numbers

Lower the flow rate...

[PJG1173]

I lowered the flow rate wow what a difference. a real noticable improvement in upper rpm power.

[EagleMark]

There's your sign! :rockon:

We need a Bill Engavall Blue collar Comedy Smiely! :thumbsup:

Did you read the thread on PE for this PCM? Take out the delay to enable PE! Or do you see PE enabled in ADX when WOT?

[PJG1173]

yes I read the thread, I was planning on re-reading all this is alot to absorb being my first time tuning. PE showes up on my dashboard and will show enabled when I hit the tps threashold. I haven't taken the delay out yet since I need to get my VE table realigned with the injector change then I'll go back to PE. I also need to start working on AE. I think its really lacking and have read that vortec heads with aftermarket dual plane intakes need quite a boost. I have a little bit of a "tip in" bog comming off idle. One question though while watching the AFR gauge I go lean after a shift under moderate acceleration (not hitting PE). Is this something that more AE would correct or something I have to work out in the VE table? 10 days till the first mud race its crunch time...

[EagleMark]

Well totally disable PE and highwy lean cruise and you can get more cells filled in to adjust VE. I tried disabling AE but car drives so bad blm data was horrible so I leave it on, it will be there anyway. But everything is based off VE tables. So if they are not close to 128 every where then AE and PE and anything else will be a wrong adjustment, like a bandaid to the real issue then show up somewhere else.

If VE are all close to 128 and you still get lean after shift adjust them in AE MAP or lean tip in then work on those in AE TPS.

PE is a lot easier as it has an entire table to adjust AFR, then check with wideband to see if it's close. 12.8 AFR seems to be a good HP number, some ECM bins need to be set to 12.0 AFR to show 12.8 on wideband for WOT!

No knock during any of this! Then can work on spark advance, then go back and check BLM for VE adjustments.

IMO! :rockon: