This is one of the strangest things I've seen. For some reason, this car needs 30% more fuel occasionally and I haven't find a reason why.
To put shortly, when I tune the car in dyno everything works. Then, let's say after 20 write calibration only -changes, the car does not start. I reflash once or twice, and then it starts again. I already got used to it last year, but now it's getting worse.
As an example, I was able to nail down idle and low-speed driving at dyno. It was just about perfect, considering the engine is heavily modified with F2, boost-referenced fuel system, 160 lb injectors and so on. Of course the tune is heavily scaled.
Now, after dyno tune I flashed the final changes and drove the car out from the dyno. And it did stall as soon as I hit the pedal. Ok, there was perhaps 15-30 minutes while the car was unstrapped. So engine was bit cooler, but not much.
To get the car running, I had to add 30% into the VE table. Sounds crazy, but that's the way it behaves.
Now the funny part. Three hours later, I started the engine and it was running very rich, so I flashed the tune from the dyno session. And it worked perfectly. Now, RAF may not be fully dialed in at cold temps, but anyway, why an earth it needed 30% more VE after leaving a dyno. And not anymore after three hours?
Next day when driving with original dyno tune, everything is perfect.
Day after and after driving and having a 10 minute break and engine shut off, as soon as I start the engine, it needs 30% more VE.
I have hard time to understand why all this is happening. I mean, fuel pressure stays the same and other things should as well. But for some strange reason, there's this 30% change. Last year it only did it occasionally after flashing, now it seems that you don't need flash, just wait for a next day to see what it wants.
Attached is a dyno tune and about 30% added VE tune to get the car running when it decides it needs more.
One final comment. This is a -98 Vette with 2001 PCM. VIN code has not been changed.
Please help.