Seems like I have a possible overfueling issue. 4.8 with a Cam Motion stage II truck cam (pretty mild). LTFT are usually around -15%. It was a mail order tune. I have HP Tuners so I copied all the stock 4.8 fuel trims over to the mailorder cal and no change. I left the "flow rate vs kpa" table alone since the stock (regulator on rail) setup was 25.2 across the entire table.

Besides the cam, the motor is stock. I'm running a corvette regulator with 6an braided hose to a later style non return fuel rail. Fuel pressure at the rail when running is 65-66. Have not driven vehicle yet because I'm waiting on driveshaft. Rarely starts on first crank. But, the smell from this thing will make your eyes water!

Is that enough extra fuel pressure to hose up my LTFT that much?

Thanks in advance!

 

" I left the "flow rate vs kpa" table alone since the stock (regulator on rail) setup was 25.2 across the entire table."

Given the Vette reg is not vac referenced, the fr vs kpa should be scaled.

FWIW, we use the Vette reg on many applications, and I don't recall having seen 1 w/ that much psi. Gauge accuracy verified?

 

The last 3 vette regulators I used had 65 PSI at idle with a Walbro 255 and 75 PSI at idle with a Walbro 400.

 

****, I had plans to run a Walbro 255/ vette regulator on my 6.0 but keep seeing people having high fuel pressure issues with the vette regulator makes me second guess it.

 

you need it tuned correctly.

 

65 psi aint too bad. you need to tune it.

you got a wideband right? turn off the fuel trims and dfco and maf.

search "afr error % histogram", set that up get your VE dialed in using copy>paste special>multiply %

do that like three times just cruising around hitting all the cells, smooth throttling up and down.

then put it back on the maf and set up a maf afr % error histogram, turn off the VE table and drive around on that for awhile...same thing copy>paste special>multiply % in the maf scaling table.

turn the trims & closed loop and ve table back on and you should be under +/-2% trims


just did this with my latest swap...damn it runs so good!

 

Sorry, mail order tune had the scaled fpr vs kpa already in it. I used those and then compensated for the higher fuel pressure using the calculator in hp tuners.