Gen 3 tune question

[jcschimmels]

Hey everybody. I am new to HP Tuners but not necessarily new to tuning software. I am having a strange issue with my LM7 and I cannot for the life of me figure out where the mix up is. I have the tune file I am currently using. The tune on the PCM is for a 6.0 which I know is not correct as well as the chamber volume and am going to fix that next. The intake, maf, pcm, and 65lb injectors were all used on a 6.0L block before the previous owner switched everything to the 5.3 bottom end. At 5500 rpm its as though I hit fuel cut/rev limiter. It stops climbing instantly in rpms and breaks up really bad. It should rev out to at least 6500. Recently I have heard about fuel boiling in the rails due to the returnless setup but i haven't been able to verify if that really happens. The specs on it are 5.3L LM7 (earlier non flex fuel version), stock heads with trunnion upgrade, 65lb injectors, gm performance hot cam with .525" intake and exhaust lift with 219 degrees intake duration and 228 degrees exhaust duration @ .050" on a 112 degree centerline, walbro 255 fuel pump with corvette filter/regulator. Its in a 1996 240sx with factory 4.08 rear end. Any insight would be greatly appreciated.

[B52bombardier1]

At 58 PSI at the rails, it is very unlikely that fuel can boil at that pressure at typical underhood temperatures.

Rick

[Just Chuck]

Post a data log.

From the tune, looks to me like you have 52lb injectors If you really have 65# injectors, you are going to be overly rich. Fuel pump should be enough unless its getting starved for fuel.

[kingtal0n]

you really need a wideband or its just shooting into the dark

I looked in the tune file briefly and the ve table gets crazy after 5200rpm so I would say its probably drowning in fuel (guess)