sprayed8

iTrader: (1)

just out of curiosity, how much power can my injectors support (ex. dry nitrous )? i have the 33# injectors because of the flex fuel.

00Silv4.8

iTrader: (10)

hmm.. John I may be interested...

not to worry about it hmm? Im running my 4.8 with a cam on stock injectors at 80%... I think the 10.5:1 comp 6.0 with a cam will put them a LITTLE over the max

RandomHero

iTrader: (24)

Not to call you out but the 6.0 injectors aren't 32#. You are thinking of the 8.1L injectors which are rated between 30-31#. The 6.0 injectors(Lq4/Lq9) are rated at the exact same as the 4.8/5.3L trucks. There may be different part numbers, but like Tyler, all my stock file tunes have 25-26# stock injectors.

The only one that is different are the 99 and early 2000 trucks. People say they are rated at 19#, but according to my tunes they are rated at 21#

hog

The 99 and 00 ARE 19 pph injectors, but at 4 BAR of fuel pressure they run at 21.ish IFR.
2001 5.3 run 22 lb/hr injectors with a 25.2 IFR in the PCM tables.

Injectors are rated at 43.5psi or 3BAR of fuel pressure.

Whatever the tunes says, is what the injector SHOULD be rated at at the rail pressure, not what the injector actually flows at the 43.5psi industry standard.
The newer PCM's have injector flow rate (IFR) vs vacuum(MAP) tables because they dont have vacuum referenced FPR's. As manifold pressure decreases(greater MAP), the injectors ACTUAL flow increases. this is because the fuel pressure has less pressure to overcome than it does when there is higher manifold pressure(lower MAP).
Since the newer trucks dont have vacuum referenced FPR's they need these tables to adjust pulsewidth rather than raising and lowering the actual rail pressure.

Look at an early 99-02 IFR vs. MAP table, the value is the same through the whole table, a newer truck will have different values throughout the table(see post #10) as GM dropped the vacuum referenced FPR.

peace
Hog

GMCtrk

iTrader: (27)

Are you sure that the 2000's have 19lb/hr injectors? I thought it was only the 99's that had the smaller injectors. If so, I used the injectors off my 2000 4.8 on my LQ9. I'm wondering if those are too small for 6.0 with some minor boltons (headers, ported tb) and a tune.

RandomHero

iTrader: (24)

it was only the early 2000. IF you have a ecsb 3 door 2000 then you have a good chance of having the 19#ers. If you have an ecsb 4 door then you probably have the newer engine and bigger injectors.

hog

In 1999
5.3 output in 99 was 270hp/315tq
4.8 255hp/285 lb/ft
In 2000
5.3 to 285hp/325lb/ft
4.8 to 270hp/285 lb/ft
In 2004
5.3 to 295/335
4.8 to 295/305


1999 4.8,5.3,6.0 got the 19 lb'rs

2000 was a weird year, 5 speed manual trans 4.8's got the 19's, while
2000 auto 4.8's and 5.3's trucks got the 22's.

2001-04 4.8,5.3,6.0 got 22 lb/hr

2001-04 8.1 got the 26 lb/hr

It all depends what your 2000 4.8 had bolted behind it. if itwas a 2000 manual it had 19's, if it was a 4.8 auto had 22's.

peace
Hog

GMCtrk

iTrader: (27)

Thanks for the post Hog. Mine was a 4 door with auto. So it looks like I got the bigger injectors. But I thought they were 24.7 not 22?

RandomHero

iTrader: (24)

I've never seen anywhere where the fuel injectors are rated at that low. 99's had 19#, 00-up had 24# and 8.1L had 30-31#

hog

You are quoting the IFR flow ratings AFTER 60 psi of fuel pressure has been applied(00+ smallblock and bigblock), and other for which the correction has NOT been applied(99).

The industry standard of 3BAR is usually referenced.

The 8.1 trucks flow 26 lb/hr@43.5 or 30.02 lb/hr at 4BAR or 58psi FP.
99-some 00 got 19@3BAR or 21.94(22)@4BAR
some 00-04 got 22 at 3BAR or 25.4 lb/hr at 4BAR

It all depends at what fuel pressure you reference. For accuracy I quote the industry standard test pressure of 3 BAR or 43.5psi.

peace
Hog