Have a 6.2 liter in a 2003 silverado, has a summit 8706 cam and an aftermarket air intake. Pretty much all.
Tuner says it's hitting .90 up to 1.00 in the upper rpm ranges.
What exactly does this mean? I thought it was normal.
file deleted
Have a 6.2 liter in a 2003 silverado, has a summit 8706 cam and an aftermarket air intake. Pretty much all.
Tuner says it's hitting .90 up to 1.00 in the upper rpm ranges.
What exactly does this mean? I thought it was normal.
file deleted
Last edited by Jason B; 04-08-2023 at 08:10 AM.
Do you have logs or a tune?
What injectors and stuff like that is installed?
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Tune file attached
file deleted
Last edited by Jason B; 04-08-2023 at 08:11 AM.
It has a NBSS intake, 92mm tb, 243 heads, iron Gen 4 block bored .030, shorty headers, Dual 2 1/2" exhaust, 4" aftermarket air intake, summit 8706 cam, 33 pound flex fuel injectors running at 50 psi with a Gen 3 fuel rail and stock vacuum referenced FPR.Originally Posted by 5FDP
Update the cylinder volume for the .030 engine size increase. I know it's minor but it does make a difference in how values are calculated. It's currently still at a 6.0 engine size and not a 6.2 engine size.
Are those factory flex fuel injectors rated 33lb/hr at 50psi or 58psi? The 50psi seems low for a return style fuel system, those usually stay up around 55-58psi with a good pump.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
It's actually a 6.1 come to think of it, it's .035 short of 6.2. So it's a 6.0 bored .030 Sorry about that.
Injectors are 25326903 They are rated at 33 pounds with the flex fuel rail that has the vacuum referenced regulator like I have. Non flex fuel has a 58 psi regulator and non return rails are regulated at 58 psi.
50 psi is the spec for flex fuel trucks (with the vacuum hose disconnected for testing) And in the stock tunes for all vin Z trucks that use this part number injector have 33.05 in the injector data.
I've looked at that a lot so this is what I know.
Does this guy saying my Cylinder Airmass being high seem off? I did edit the first post and attach the run file.
Thanks
I went through the injector debacle a couple years ago when upgrading. The different fuel pump psi ratings and the different regulators play a role in injector flow rate math. I would get a known good fuel pressure tester and check to see what it says with the engine running and regulator vacuum line disconnected and plugged just to be 100% sure its at 50 psi. Then you can do the proper math on the injector flow rate table. Otherwise its just guessing and will never be right.
Edit: Is your truck a factory flex truck or non-flex?
Last edited by mjc79; 04-01-2023 at 12:30 PM.
02 Tahoe, Rebuilt 5.3, PRC 2.5 heads, BTR Stg2 V2 cam, 50lb Injectors, Speed Engineering LT's, Offroad Y, Magnaflow catback, Built 4L60, NP241 swap etc etc...
the airflow model is about 5-9% high, the cylinder airmass will come down once the MAF/VE curves follow commanded AFR at wot. right now its rich. falsely increasing Cyl airmass.
L59 is one of the rare ones that used the same injector across the switch from return-style to returnless, there was also a base pressure change at the same time.
Non flex fuel.
It has 50-52 psi with the vacuum hose disconnected, even under load. And I did a pressure hold test on the system and it held within 2 psi for maybe 40 minutes until I called it good.
EDIT: One thing that bothers me a bit is the vacuum referenced regulator. Changing cams and altering manifold vacuum seems like it's a guessing game by design since the regulated pressure is always changing.
Last edited by Jason B; 04-01-2023 at 03:25 PM.
I've actually researched this a lot. Especially looking at a lot of trucks in several junkyards. The L59 with vacuum referenced FPR's use 25326903 injectors at 50 psi, and the L59's that use returnless rails use 12580426 injectors at 58 psi.
25326903 is not a current part number for anything. The current number, ACDelco 2171626 or 12580426, is for all 2002 thru 2007 L59s regardless of fuel system type.
No, you have that backwards. Constantly varying the rail pressure actually keeps the pressure delta across the injector the same at all times, since it changes 1:1 as manifold pressure changes. It's the returnless systems where pressure at the injector tip is changing with engine load but rail pressure remains fixed where the PCM has to do the weird math to derive the current flow rate/pressure delta.
And for everybody else, in the service manual it lists:
2004 Tahoe (VIN Z return style, all others returnless)
2005 Tahoe (all RPOs returnless)Gasoline: 385-425 kPa (55-62 psi)
VIN Z Ethanol: 335-375 kPa (48-54 psi)
385-425 kPa (55-62 psi)
25326903 is a Denso part number, but is the correct stock replacement for the 02-07 flex injector. My 02 tahoe had a couple mixed in with the stock GM 12580426 injectors when they got swapped out for the 50's
02 Tahoe, Rebuilt 5.3, PRC 2.5 heads, BTR Stg2 V2 cam, 50lb Injectors, Speed Engineering LT's, Offroad Y, Magnaflow catback, Built 4L60, NP241 swap etc etc...
Now I'm confused.
I HAVE 25326903 injectors so why would I say any other number?
In fact I have several sets of those.
And I have a pile of regulators that read 45 or so with the vacuum line connected and 50 to 52 or so with it disconnected.
These came off a factory stock vehicle and are being used the exact way they came off the vehicle.
https://ibb.co/X7MfMz2
https://ibb.co/9r1xpHq
https://ibb.co/tCyYHGf
https://ibb.co/TmBsXsg
Are you telling me this stuff doesn't exist?
I'm clearly not seeing your point.
Last edited by Jason B; 04-08-2023 at 08:12 AM.
That's an old part number, no longer used for current production. The parts with the new number on the side are an exact replacement for the parts with the old number on the side. Stock replacement parts aren't stock replacement if they are of different specs that would require PCM calibration changes. Everything that was originally built with 25326903 injectors can use the new ones with no changes. Because they are functionally identical.
With a vacuum-referenced regulator, fuel pressure specs are always given as with the vacuum line removed. This is called the 'base pressure' - meaning the pressure before any corrections are added (or subtracted - whatever!). I have never seen a spec for what pressure should be with the line connected, because it will vary depending on how much idle vacuum the engine makes, and they are not all the same (what idle speed? is it hot or cold? are the intake valves all carboned-up? etc.). The returnless systems have no vacuum line to remove so they are always at base pressure.
Here's my stock 02 tahoe 5.3 flex tune if you want to compare all the injector data 02 Tahoe 5.3 Flex Stock Tune File.hpt
02 Tahoe, Rebuilt 5.3, PRC 2.5 heads, BTR Stg2 V2 cam, 50lb Injectors, Speed Engineering LT's, Offroad Y, Magnaflow catback, Built 4L60, NP241 swap etc etc...
So what does this have to do with my first post?
I took injectors, rails, regulator, off an L59 and used it's injector data in my tune.
How does your information apply to this?
Thanks for the information. It just seems a little off topic. Or tell me what you're thinking, maybe it's me.
Thanks!
I have seen that data before, mine is slightly different. Yet I do have some flex fuel tune files that use the data I'm running. I need to figure out how mine is different. Or just use yours.
I was using the 12580426 injectors at one time, I pulled them off a truck along with the rails PCM and all and used the data out of that PCM.
So just to be sure I think I need to use the data you have. I do have several PCMs with that data too, maybe I need to make better notes on what came out of what.
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