CRAZYCUTER4.8

iTrader: (2)

the injectors wwere bought here at dealership. Where are you getting these flow rates, I was told the flow rate was the same. Can you give the info on where these are coming from?

BigTex

iTrader: (16)

Thats your problem. Without telling the PCM that you have larger injectors installed, its assuming you still have the small ones. That means its running extremely rich.

LS1 Edit - engine cal - Fuel tab. Injector flow rate button. Stock number in every cell here should be 3.12, but your bigger injectors should be something like 5.15. I'm running those injectors and found that anything between 5.10 - 5.20 worked pretty well.

Make that change and put everything else you've been messing with back like you found it. Start tuning it from there.

Speartech

iTrader: (14)

And then get bigger injectors and retune again. 600 - 700mv and 33 ms injector on-times means you are very lean, not rich.

Retuning the injectors you have will only help it run right at idle and low speeds.

BigTex

iTrader: (16)

I can't see a stock LQ9 taking enough boost to need more than a 42 pound injector with an FMU. The stock 24# injector with an FMU can put down well over 400rhwp.

Then again, the 600-700mv is an issue. Maybe its 1600-1700mv.

TurboBerserker

iTrader: (1)

IFR values are just a conversion into g/sec from lb/hr assuming that your fuel pressure matchs the flow rating of the injector (e.g. you flow 58 psi and you have the 58 psi flow rating of the injectors).

My truck runs great with flowmatched injectors rated at 43.75 lb/hr @ 58psi and PCM values at IFR of 5.52 (g/sec) and a properly adjusted VE table. 5.20 worked (but then again, so did 4.99, 5.05, 5.10, 5.15, etc.) with adjusted MAF and IFR, but its better, IMO to set your IFR where it should be and adjust your VE to the proper scale.

Black Blown 02

Do we know for sure he has 42 pounders? If he's going lean, I'd say he just has the 8.1 truck versions. We need to find out for sure what injectors he has.

Speartech

iTrader: (14)

If he bought them at a GM dealership they are not marine injectors. They are just the 30# stock 8.1 truck injectors more than likely.

lm7

iTrader: (8)

another vote for the wrong 8.1 injectors.the WRONG injectors have the part # 25323974 and 4 holes in the bottom of the injector, these are the normal 8.1 injectors..sounds to me like you are running very lean...be very careful. you want to buy the right 43lb injectors from ASM at 400 they are a bargain. i bought mine from RC engineering before ASM sold these at over 700 bucks! with those u can remove the FMU and tuning will be a lot easier.

Black Blown 02

Heres what you want---
http://www.azspeed-marine.com/muii43lbin.html

CRAZYCUTER4.8

iTrader: (2)

they are they marine injectors, I went back & check the #'s. The odd thing about this is that when we first tested with the fmu screw out 1 turn the truck ran awsome! the Fuel trims were @ 0 to +2% as we drove I noticed the O2 sensors were dropping around 800 mv, we turned the screw in all the way and the O2 sensors were at 900-950. We get back to the house & I am thinking this should be easy! I adjusted the injector flow rate from 4.9 to 4.7 & adjusted the power enrichment up about 23% thinking that I can always turn the screw on the fmu to lean it out if needed. We drove it & the fuel trims were a tad rich @ -5% then at wot it started cutting out a little. I watched the O2's the first couple of times & they were @ 990. It never cut out until the 4th time we hammered it.

the odd thing is my dad keeps telling me it did not start until we had the cats cut off & the cutouts were installed. He then noticed that he lost a few pounds of boost, so we had ati send another pulley, then we noticed the injectors were pegged. So we get new injectors & the saga continues! The truck ran damn good before all ths started.

The fmu is working, we saw 100 psi of fuel pressure. I am wondering if the excess in fuel pressure is causing the injectors to lock up. I still am wondering how to tune using VE tables. I also am curious if anyone has an edit file similar to this one.

THANKS AGAIN FOR THE INPUT!