03 RCSB Z06 Cammed 4.8/NV3500, Injector Duty ~110% - upgrade?

[Closer_2001]

My son and I installed an 01 Z06 Cam in his RCSB about 10 yrs ago...he decided to upgrade to a new car a few years ago and I elected to keep the truck - an '03 RCSB 4.8/NV3500. Not too many around...

I did the original tune with an LC-1 and HPT, simple setup, 4.8, simple drop in CAI from prev owner, GMPP Catback NIB we stole off eBay for under $300 and a used 01 Z06 cam, 204/211, .525/.525 on 114 with a new set up LS6 springs. Oh - and an SLP shifter on clearance for $25. 2009 was very different from 2022 in terms of market opportunity and inflation...but I digress.

The little truck is fun, it has a short first gear and likes to rip to the rev limiter - I'll bury the tach every once and a while and quick shift 1-2 giving a nice bark from the stock G80, 3.42. The NV3500 does not like to shift 2-3 which makes racing automatics a little more complicated...maybe a T56 some day.

I noticed some driveability issues lately, as the truck sat for a while due to life. The front 02s were lazy and the injectors were suspect. I sent the injectors to be flowed and cleaned and replaced the 02s.

Today I only had a chance to give it a down the block and back scan going WOT in first to second. Surprised to see the injectors were at 110% duty. The truck felt great despite high humidity and temps in the 80s. Timing was solid at 26.5, I have it set at 28, but have left some safety nets in the tune, will review where the 1.5 is being pulled. No KR.2022_FinalZ06CamTunev3.hptWOT1stgear_Humid93oct108%Duty.hpl

Is it time to think about bigger injectors? If I'm considering boost - what's that best option? Not planning on 1000HP here, maybe 350-450 and a T56 just to keep people honest...

Tune and Log Attached.

[blindsquirrel]

A stock '03 Z06 has 29lbers and despite the displacement difference you have more go-fast parts than a stock Corvette so most likely making more power... GM doesn't typically leave a lot of headroom in their injectors, so your breaking 100% with just 25lbers makes sense.

It'd be easier to be sure the engine is making what it should with those parts with some more channels logged, like cylinder airmass, MAF Hz (if using a MAF), delivered torque, TPS... missing lots of basics there.

[5FDP]

Commanding 12.0 is sorta rich but usually always safe. If that was changed to a 12.5 and that VE table and MAF curve was cleaned up a little it may drop the duty cycle to around 95-100% again but it's still too high even there.

My opinion on two other things. The timing tables are currently the same and they shouldn't be. The low octane needs less if you are still using knock sensors. And burst knock should be disabled on this vehicle.

[charcoal03silvy]

Put a fuel pressure tester on it and make sure you've got good pressure throughout the rev range.

DSX tuning sells some OEM 50lb injectors that will need a top hat adapter and plug adapter but are good quality, budget oriented injectors.

[Closer_2001]

Thanks for all the suggestions. Will fire up the wideband, make some tweaks mentioned here and see if I can clean a few things up. Then will likely spring from some bigger injectors. If I ended up doing a small turbo down the road, any suggestions on #s? Truck currently is running an essentially new AC Delco pump, kicking myself for not installing the Flex version when I had the bed off... Oh Well, not impossible to replace it again if the pump runs out of juice.

[blindsquirrel]

Play around with this: https://fuelinjectorclinic.com/flow-calculator

Factory injectors with factory data (from stock tunes) can be had up to 50-ish lb-hr and for super cheap, depending on part #.