L92 Injector Duty Cycle over 100% with new intake (minimal mods)

[markislive]

Hello…

I recently installed a new Varram RAM air intake in place of the Outlaw intake I had on my Sierra. After the install my WOT AFR was pretty lean (around 13.8:1) so recalibrated the MAF to get my AFR back to what I am commanding (12.7:1). Truck is really running well now. I noticed in my latest scan that my injector duty cycle goes up to 101%. With the old intake calibrated to 12.7:1 the highest it would go up to is 92%. How it possible to go over 100%? Anyway, I read that with anything over 80% duty cycle an injector upgrade is prudent.

Do I have anything to worry about? I am fixing to add headers and I’m sure that will require a little more fuel when I re-cal the MAF.

Any help would be greatly appreciated. I also attached my log file...

Thanks

[murphinator]

anything over 100% means your injectors have gone "static" cant close without being asked to open again.

it is probably time for injectors but make sure you have a fresh fuel filter and enough voltage to your pump

[markislive]

Thanks for the reply. Ouch, Is really time for new injectors? All I have done so far is intake, exhaust, and a tune...If so that sucks!

[69lt1bird]

Either we need the config file you used or your LM1 wideband reads about 12.49 or so the whole time even when the commanded is 14.68.

Like dogn said, your tune file is need and the config file.

It is hard to believe that the minor mods you did would run you up to 100%+ DC.

How are you setting up everything to tune the MAF?

[midevil1]

I'm still running the "stock" 30lb injectors and not anywhere near 100%. Something is "afoul" with your tune. I'm making alittle bit of power with quite a few mods.

[carlrx7]

maybe your pump is putting out low psi, and you absorded that into your maf table..

compare your maf table and a stock one, shouldn't be more than a 10% difference with your listed mods.

your commanding 12.71 but getting 12.49, try getting it closer..

if you run e85, i can see the inj duty % going to 100% with only your listed mods.

[LSX378]

If you have the regular 42lb injectors: for example our LS7 running E85 at full song just gets past the mid 90's on DC with 42lb'ers, so something wierd going on.

[Mep_q8]

I've seen 3 faulty pumps on the L92 platforms and a few on the the newer 5.3.. Changed them out and things were reading fine... any noise from the left rear of the truck that sounds out of place?

[BBA]

maybe i am looking at this wrong... 12.49 afr 24/7? it never changes from idle to max tps.. now i am not using 2.22 to view it... but it never reports more then 12.49afr on my end.. if in fact this is correct 12.49 is way rich for anything other then wot.. i would tend to think the wb is not set correct as i do see the 02's switching and i don't see the trims taking fuel out like it would/should to return to stoich if the afr is in fact 12.49. please let me know if it is changing when you view the wb readings..

Looking at the log, looks like you are running high 12's AFR based on stock O2 readings, which is about right for WOT. The sensors do switch, as seen in the frames before you went WOT so they probably work ok.

If you had to make drastic changes to MAF tables to get the mixture down, you might want to do as others said, definitely post your tune and check/make sure you have good fuel pressure under WOT and fix any fuel related issues (filter/pump, etc...). If the MAF is so far off, try clocking it to different positions until you get the smoothest response from it, then start tuning.

[BBA]

BTW: Do not be concerned about commanded not matching actuall at times, there are a few things that will cause this, such as COT (it takes over mixture while active).

[markislive]

Thanks for the replies, my wideband was disconnected during that logfile, 12.49 is the reading displayed when it's not connected. I have verified that my actual WOT AFR matches the AFR I am commanding (12.71:1) My LM-1 display also shows 12.7ish under WOT when connected.

FYI, It reached 101% duty cycle at the top of 1st gear. 2nd gear topped out at 95% and 3rd gear topped out at 93%

I attached my tune and config file...

Here are the steps I use to calibrate my MAF...

1. Remove drivers side primary o2 sensor, connect my LM-1 wideband o2 sensor.
2. Copy original tune
3. Copy High Octane Spark Table to Low Octane Spark Table
4.Engine-->Fuel Control-->
a. Fuel Cutoff--> DFCO Enable Normal Set enable temp to 284F
b. Power Enrich-->EQ ratio vs. RPM set to desired a/f across the board (i.e. 1.155 = 12.7:1 afr)
c. Long Term Fuel Trims to Disabled
d. Closed Loop Enable ECT-vs-IAT to 284°F (ensure you go into open loop)
e. Turn off COT (Catalytic Overtemp Protection)
5. Reset Fuel Trims using VCM Controls in Scanner
6. Take a drive make a few WOT runs, I like to get a MAF Freq. High cell count to at least 50
7. Use the Wideband % Error from the histogram and Copy/Paste Special into my tune's MAF Freq. High table.
8. Repet until I get my error % near 0(reset fuel trims between each run)
9. Once MAF table is adjusted copy it back to your original tune. (easier than removing all the edits)
10. Disconnect wideband o2 sensor replace with factory sensor.

[markislive]

I'm still running the "stock" 30lb injectors and not anywhere near 100%. Something is "afoul" with your tune. I'm making alittle bit of power with quite a few mods.

That Yukon Denali you have must be fun to ride in. What were your duty cycle #'s before and after the CAM?

BTW how is your 6L80 holding up to all that power? Tranny still stock?

[markislive]

compare your maf table and a stock one, shouldn't be more than a 10% difference with your listed mods.

Looks good.. about 8% increase across the board compared to stock MAF High Freq tables...

[69lt1bird]

Is your stock file a 2007 Denali? I just pulled down a stock tune and there is so much changed in yours from a stock tune its hard to say where to start. Who tuned it?

[markislive]

Is your stock file a 2007 Denali? I just pulled down a stock tune and there is so much changed in yours from a stock tune its hard to say where to start. Who tuned it?

Yes, You might be looking at the stock file I posted in the repository. I attached just incase. I do my own tuning...

[69lt1bird]

No, I got it from the repository and it is very different from yours.

Have you checked the fuel pressure?

[markislive]

Have you checked the fuel pressure?

No I haven't...For grins I will reload my stock tune and datalog. If the Injector duty cycle is still high under WOT I will try that next.

I found an old logfile. My injector duty cycle would get up to 92% back in Oct 07', the truck was only a few months old.

[BBA]

Did you check your WOT fuel pressure yet? Sounds like you still need to get the duty cycle down a bit.



Honestly, for WOT AFR, the way I like to do it is while running the normal tune, I'll scan for calculated torque/delivered torque and go trial and error on PE looking for the higest torque. Takes a few times to get the highest numbers but it eliminates guess work about what AFR my car runs the best at (so I could care less what the actual AFR is in the end as long as it makes the most torque.)

[markislive]

Did you check your WOT fuel pressure yet?

No not yet. Any tips for checking fuel pressure with the vehicle in motion.

[69lt1bird]

A fuel pressure gauge with a long hose and duct tape it to the windshield.