The reason I play around with my tune before I changes my engine is that the engine don’t perform as well as it should. And I am afraid that this is not related to the engine it selves.
After I have studied lots of logs, and have thought on when the engine act strange I think that the problems are fuel related. Most of my earlier loggings and auto ve were done just after engine warm up. Then when logging a longer trip in summer temperatures the values changes. I have a feeling that this might be because the fuel warms up.
I have a home made return fuel system with the regulator placed on top of the engine. I have also tried some different solutions for the EVAP system and found pretty much vacuum in the tank sometime. The engine is in an impala ss clone. The in tank fuel pump is a Granatelli hp pump, but it is mounted on a 91 caprice in tank module. That means that it just sits in the middle of the fuel tank without any baffles or the more modern “turbo system”.
My fuel gauge is wrong as on most of these cars. When it shows half it is less then ¼. I have found that on Impala ss forum there is a lot of people that have the problem that the lt1 engines acts strange when the fuel level is down on1/4. When they dragrace this cars they newer do it with less then a ¾ tank of gas. I think that my feeling that the car loses power is because my fuel pump drags air on heavy accelerations. It is also possible that the fuel pressure changes do to the heating of the fuel pressure regulator or vacuum in the fuel tank.
This entire theory and tuning attempt and most of the problems could probably be solved if I borrowed the fuel pressure gauge that I have on work. I could have used it for weeks if I wanted to. On the ls3 I am going to place the fuel pressure regulator under the car or use the corvette fuel filter with the regulator inside.