Hoping that the saga here ends. The corollary in tuning is that you first make certain all the mechanical bits are operating on nominal levels, ie they're working the way they're supposed to work. Otherwise you'll be chasing your tail tuning around the deficiency. As part of a recent rehab of my motor, which included a freshly rebuilt short block, it was necessary to replace my Accel injectors. After 10 years, they'd pretty much given up the ghost with the #7 secondary having a deteriorated aerator which caused fuel to simply stream into the cylinders creating a lean condition. That in turn brought about knock ultimately cracking the top compression ring in 4 places. So enter a new set of injectors which are advertised as flow matched to within 1% of each other.
In the course of tuning, the plugs did not show an even burn among the cylinders however, so I had my suspicions. I waited for an reason to pull the plenum and a blown alternator gave me the opportunity. I had the injectors flow tested and I have attached pics of the actual flow for both left an right banks. IOW, each primary was flowed along w corresponding secondary. The diagnostic report w the values for each injector is also attached.
As you can see, these injectors were NOT within 1% of each other, essentially confirming what I was seeing on the plugs.
With the information of the flow test I was able to match up pairs of the injectors so that I was able to tighten the range of fuel flow(on a cylinder to cylinder basis) from 10ml down to a difference of only 2ml. when operating on all injectors. To me this also strengthens the argument for running all injectors during LT5 engine operation.
For idling operation, I was able to lower overall fuel and reduce the disparity between banks by 50%, albeit 1 ml.
The SOTP is readily discernable. Engine smoothness and responsiveness, is pretty obvious. It feels like it has more power altho I don't have any measurements yet. Along w a change in calibration and spark plugs (NGK BKR6E @ .035"), knock is pretty much eliminated. The LT5 is a noisy motor, and when modified becomes even noisier so my objective was to eliminate any knock that was consequential, which appears to have been achieved.
I would make injector flow testing a basic part overall "tuneup" regimen. The $112 the flow test cost me



was more than well worth it and would recommend it to anyone.

N. B. My injectors have 5k+ miles on them, so I am not being accusatory of any vendor's claims. Just saying that "trust but verify".

 

 

Another update on this. The re-balancing of the injectors has had clear impact on how the motor is running. Much smoother and quieter. However, I have found that in doing the necessary re-mapping of the VE tables, I have taken out about the 3-5% fuel, resulting in better mpg(>1.5mpg) and cleaner exhaust as evidenced by my exhaust tips. But since all fueling is dependent on the VE tables, I am also needing to re-visit my Acceleration Enrichment. Removing fuel from the VE tables is requiring me to put it back in for AE. I have been getting audible knock in certain circumstances resulting from an insufficient “pumpshot” due to reduced fuel. So AE now needs to be not only increased, but also lengthened in terms of duration.
This also would affect the PE parameters for WOT, but I’d rather do that on a dyno.

 

Wow! What a difference! Increased AE, AE delay and the duration of AE phaseout. No knock. Thanks again to RBob for his help on explaining the code.