SD tune issues - chasing fueling

[kjlindgr]

Hey folks,

I have a swapped setup here with a 5.7L engine and supercharger on it. It's running a SD tune. The problem I'm having is very inconsistent fueling between tuning sessions. One day I will get it all dialed in very closely. I will come in the next day and it will be super rich. I will pull a lot of fuel out of it, get things dialed in fine, then the next day it will be really lean. I'm just swinging back and forth and chasing my tail.

I believe that I have all of the dynamic fueling turned off, failed MAF correctly, etc.

Has anyone else ever run into this with SD tunes on the Gen3? Anything in my tune file that stands out as being a problem?

Any help is appreciated.



Thank you!

DYNO_small_lower_e85_retune_oldve_coldstart_0039.hpt

[bk2life]

If you dont have your engine in the exact same as it was when you tuned it, it will be off.
Meaning, if you tuned it at 210 degrees engine, 85 ambient, going 75 mph, that is what you need to scan it at.
If you try to look at it at 172 degrees and 60 ambient, itll be different.

How much boost are you running, and why SD?

Also, a few weeks ago i was chgasing my tail all over with fueling. My issue, i wasnt driving far enough to get it all really settled in. I had a nice 10 mile loop i would use, and that ended up being too short to get the entire vehicle up to operating temp and everythig settled.

[kjlindgr]

Thanks for the response. This setup is running about 12 pounds currently. It's running SD for a couple reasons - less complication of MAF placement and frequency restriction with planned higher boost, and because it should be able to run SD with no issues.

Let me put my issue into more context. I'm not talking about a 1-5% swing of fueling due to humidity and ambient conditions, I'm talking +20% fueling swings. The tune is dead on (+/- 2%) one day, and 25% fat/lean the other. It can always be dialed in with fueling changes, but why it isn't consistent is my issue.

[mjc79]

Have you checked for vacuum leaks? Or exhaust leaks? Those will create issues like you are seeing. Could also be a faulty afr sensor as well. If it has intake sealing issues and you are using the steel backed felpro gaskets, that could be the problem. My tahoe had a similar issue and it ended up being those gaskets. Swapped out to oem style BTR gaskets and have not had an issue since. Just a couple things to consider.

[Alvin]

Hey folks,

I have a swapped setup here with a 5.7L engine and supercharger on it. It's running a SD tune. The problem I'm having is very inconsistent fueling between tuning sessions. One day I will get it all dialed in very closely. I will come in the next day and it will be super rich. I will pull a lot of fuel out of it, get things dialed in fine, then the next day it will be really lean. I'm just swinging back and forth and chasing my tail.

I believe that I have all of the dynamic fueling turned off, failed MAF correctly, etc.

Has anyone else ever run into this with SD tunes on the Gen3? Anything in my tune file that stands out as being a problem?

Any help is appreciated.



Thank you!

DYNO_small_lower_e85_retune_oldve_coldstart_0039.hpt

200 LB injectors? Do they need to be that big? Injector data needs to be spot on especially when they are that big.

You'd likely be better off with the Transient min fuel to 0.


I have a employee with a rather unstable fueling car. With a gauge on it the fuel pressure bounces around 5-8 psi and not with vacuum. With injectors that big that's going to matter a lot too.

[kjlindgr]

Injectors are Fuel Injector Connection 1600's. Greg Banish does the injector calibration for them so I have fairly high confidence the data provided is accurate.

Thanks everyone for the suggestions. I will make some tweaks and report back.

[kjlindgr]

Here's an update. I smoked the intake and there are no leaks. I even swapped ECU's just to try something new. I've attached the tune file. More interestingly though, I have 3 log files attached. They were all done back-to-back with a few minute wait in between with the car left running. First run was rich ~3%, second was much closer to target being rich 1-2%, and the third was lean by 4-5%.

To pick a spot in the log to focus on for differences, I picked each run at 5500RPM. The calculated cylinder airmass all looks very similar. Intake air temps are difference since things are heat soaking a little bit. Injector pulse width is lower in the leaner log, but I'm not certain what may be driving this value.

Here is the tune file: DYNO_small_lower_e85_newecu_0043.hpt

Run 1: new_ECU_run_0003.hpl
log3.png

Run 2: new_ECU_run_0004.hpl
log4.png

Run 3: new_ECU_run_0005.hpl
log5.png


Any other thoughts would be much appreciated.

Thanks!

[blindsquirrel]

What filters are you using, to make sure you aren't including things like EVAP purge...?

[kjlindgr]

This setup doesn't have any EVAP system on it and no plumbing accomodations for it.

[1TANK]

What ever happened with this ?

[2000Phoenix]

I would go back in to closed loop and turn your narrow bands back on and call it a day. I could not keep my fuel trims from swinging based on the up and down temps. As for people running speed density and not using some type if a resistor there is something not being said that has to be done to stop the swings is my guess. I’m banking on the fuel transient as there is no real step by step on how to do it properly. There are only definitions defining things and theory’s. Maybe soon one of the more experienced tuners or hptuners will shed light on this and how to properly update those areas in a step by step format. If their was a book I definitely would buy it. Good luck.