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
Printable View
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
Do you have logs or a tune?
What injectors and stuff like that is installed?
Tune file attached
file deleted
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.
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?
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.
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)Quote:
Gasoline: 385-425 kPa (55-62 psi)
VIN Z Ethanol: 335-375 kPa (48-54 psi)
Quote:
385-425 kPa (55-62 psi)
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.
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 Attachment 129910
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.
There was confusion amongst others about whether the injectors you had were 33lb or 36lb (35), and the answer to which is, yes. They are 33 is it's a 51psi return style '04-down L59, and they are 35lb if it's a '05-up returnless 58psi L59. Then you started arguing that injectors for the same application were different injectors because they had different numbers on them...
His file already has stock injector data in it the same as any other '04-down L59.
Differences in '02 and '03/'04 are minor, they do show an interesting pattern though... Like, in the Offset table, every cell that's different is different by exactly -0.0153? In the plausibly usable regions anyway.
I'd probably use the more recent data. GM has been known to fix things in later years, while leaving the older calibrations as they were. I think the newer calibrations have more refined data in 'em.
Does this look like any kind of progress?
I updated the injector data, and the cylinder volume. The cylinder volume changed the ve table so I manually changed some high numbers.
Then I did one VE correction and multiplied the error by half. I then did a MAF correction and multiplied the error by one (which I think might have been too much)
I didn't get around to hand smoothing anything yet.
files deleted
If the engine is near 100% VE or over it will hit 1.00 gm/cyl air mass or more. My 383 SBC gets pretty darn close to 1.00 gm/cyl. If the engine is moving a large amount of airflow it will drive the gm/cyl reading higher. My buddies LQ4 6.0L in his Chevelle is internally stock with some breathing bolt ons and it gets near 0.90 gm/cyl.
My stock internals 5.3 (Gen 4) will do .83-.84 in good air.
Almost seems like you need a new tuner if he is leaving you with details he should be dealing with.
For a 6.2L with 226/230 cam at that elevation, probably normal. If it was really happy and tuned well it wouldn't seem odd to be higher than 1.00 g/cyl.
(the factory tune on mine pulled all the timing out starting at .64 - they intentionally neutered the 5.3's so as to make the 6.0L TBSS look better than it really was)
I always tune my own stuff, even the OBD 1 stuff.
My local track closed down for good, a new shop opened up. I took it there hoping the guy could clean up the tune I did but apparently not. I have to street tune it and I usually do some of that on the interstate.
Not the most ideal situation.
I'm not even sure I have a problem. Is a 4 second 0-60 slow or fast in a 4000 pound truck with a stock body, suspension and gears? And 275/60/15 radials. And 0 to 90 in 7.5 to 8 seconds. I'm not sure.
Hard for me to see if its been mentioned before.. but if cylinder airmass is too high it's typically because the fueling isn't correct. Either low on fuel pressure, rich, or incorrect injector data. 1 g/cyl is a hard number to hit NA. This setup would not do that.
Yes, it is too rich. Once it hits the lower 12's and goes into the 11's the airmass goes from .9's to 1.0.
Seems like I can get the rest of the tune dialed in pretty good except for the WOT PE.
The injector data is not wrong unless GM made it wrong from the factory.
So thats the VE and/or the MAF airflow?
It seems the VE is a lot easier to get right than the MAF. When I tune the MAF it seems like it doesn't make much of a difference. Like I can tune the MAF error, multiply it by half and paste and it's still off.
I have a feeling it might be the 20 degree bend in the air intake between the engine and MAF. The maf is connected right to the end of this bend.
This is the maf. Fits perfect but I'm not so sure the bend is ideal for function. Could this have something to do with the problem?
This is a new filter, with the smaller filter I had on it I took it off one time and ran it hard and the cyl airmass only went to mid-high .80's
Being right in front of a bend and being right behind the filter is far from ideal. It also looks like the tube is also maybe oversized which will cause a weak maf signal at lower throttle. Add in what looks like a diameter change in the same area and you have the recipe for a bad maf reading.