So I started tuning today and I'm already regretting it.....


I haven't touched the fuel tables yet with the exception of changing commanded AFR to 13.8 from 14.6....I realize this will cause an increase in fuel flow but I didn't think it would put me at 112% duty cycle @ 5800rpm . I commanded a lower AFR because I'm having all kinds of false knock issues and I had to zero out the base knock retard table to get rid of it (more on that later) and I wanted a slightly safer AFR to work with.


some help here would be appreciated.......

 

time for bigger injectors

 

How much power is your setup producing? I have The mods in my sig and I'm running around 13:1 A/F at WOT with a max duty cycle of 86% on stock injectors.........BTW, I live a little over an hours drive from Death Valley/Stove Pipe Wells

Stan

 

Wow, you are definitely maxed out on the current injectors. What was the DC before changing the AFR target?
One thing I have seen/heard is that the stock programming will dump extra fuel at high RPM's and WOT to cool down the cats. Not sure if there is a separate field for AFR for those conditions but it would be interesting to see the results.

 

I'm not sure anymore but it's enough to give me a serious grin every time I put the pedal down. I'm seeing a little over 300gms/sec throught the MAF at 5800rpms if that helps

Ridgecrest Huh ??, I'll have to make it out there to meet you sometime. my normal stomping ground is Vegas but I'm not opposed to driving the other way once in a while

 

What does your PE table look like? Are you using the narrow band O2s?

 

Hehe, sometimes you pick up info you would just rather not know. A few months back I put a Vortech S/C on my 5.3 and got a cheap dyno tune. The Vortech changed stock injectors to GM 8.1 Marine injectors, When I wanted more I went to a smaller 3.12" pulley. Life was good. Then I bought HP Tuners.. My first scan showed 113% DC @5600 rpm and MAF readings of 12000 HZ (65.65 lbs/min). I questioned how this could be, so I brought in the guru's guru. Allen laughed and said "Damn that thing is sucking air...."
After three weeks of tweaking and tuning through email with HP Tuners we have come to the conclusion that the little 5.3L that could is asking for more fuel. So it's off to the internet for larger injectors (55-60) and an intank fuel pump. This is a stock 5.3L with a Vortech. Other than the CAI, duals, and 160 thermo, this is a stock setup. We increased shift point to 5800 and saw a noticible increase in both MAF and DC readings.
So with all this said I am left with the dilema of getting more fuel to the engine and getting a larger fuel delivery device. My fix? I just bought a LQ9 and 4L80E to swap into the Avalanche. That will teach those injectors

 

you shure teaching those injectors a lesson alright!!!

 

DC over 100% doesn't necesarilly mean maxed injectors.

In Yelo's case, if you put the AFR back where it is, I would bet you will be fine. AFR plays a HUGE role on that. THe best way to look for injector problems is in PE mode, you will notice the o2's dropping off after a certain RPM or MAF reading. You shouldn't really go by duty cycle.

 

Fla, I'm not sure what to think of your situation. I don't think you would be maxing the injectors that soon. I had the MAF maxing at 60lbs somewhere around 5200 rpm, running the motor all the way up to 6600, and had no problems. This was on a 5.3 with a RADIX and a cam pushing 8 or 9 psi.

I think maybe your tune is running a bit rich and I know for a fact your MAF tables are not what they should be. The MAF should read no more than 60lbs. How much boost are you seeing?