LQ4 Tune Question

**YungTyph** · 08-27-2023

Originally Posted by 2xls1

It's not back pressure that is needed. It is you don't want O2 sensors anywhere close to open exhaust so outside air doesn't effect their reading oxygen only in the exhaust. This means absolutely no exhaust leaks anywhere near the O2s. Especially upstream of them and within a couple of feet downstream.

I am confident there are no leaks beforehand, I can investigate further- but the PCV and injector issues certainly need addressed. Thanks for all the help

**YungTyph** · 08-28-2023

Set up a barebone PCV setup and roughed in some injector data from a GTO... From what I looked into- a good VE table should balance out what I haven't touched.

Set my default&minimum injector width to 1ms off a few HPTuner posts- from what I saw flow rate and VE apparently can handle the rest, O2s still switch at 700 mV, Catalytic Converter Protection disabled (COT to my knowledge), DFCO disabled

Idles just grand with MAF enabled, with it disabled- again some weird behavior. Minor lurching on low throttle, to be expected with a rough VE.

https://log.tunezilla.com/s/X8rJbfTt

The car drives OK at best, but better than it has been. When cruising, it seems to cut spark at a certain rpm/load but I didn't get a good log of this. Don't think it knocked, but unsure.

I want to confirm I don't have exhaust leaks AFTER my O2/wideband (they are right next to each other, so not sure why they ever contradict) as well as calibrate the MAF.

**Whitelightning603** · 08-31-2023

This is not going to help you, but I wanted to give props to 2xls1 for his StartupTune_Baselineo2.bin. I have a manual trans behind a 5.3 LM7 and have been trying to get start/idle, deceleration and dying at stops cured and I used this baseline bin and it works great! Thank you guys for sharing your expertise!

**YungTyph** · 08-31-2023

Originally Posted by Whitelightning603

This is not going to help you, but I wanted to give props to 2xls1 for his StartupTune_Baselineo2.bin. I have a manual trans behind a 5.3 LM7 and have been trying to get start/idle, deceleration and dying at stops cured and I used this baseline bin and it works great! Thank you guys for sharing your expertise!

Glad to hear that's working for you, did you seg swap? That bin is a 6L and has different injector flow rates

**Whitelightning603** · 08-31-2023

Originally Posted by YungTyph

Glad to hear that's working for you, did you seg swap? That bin is a 6L and has different injector flow rates

I used Universal Patcher to compare my existing tune to Startup bin and only changed a few items pertaining to start and idle. It is very drivable but by no means tuned for max performance....yet. This 5.3 was in a early 07 Silverado with automatic trans. After a mail order tune it 'identified ' as a 4.8 with manual trans. I haven't got deep enough to check on Injectors yet. But I have to admit it's interesting to program these engines as I learn more.

**2xls1** · 09-01-2023

Don't segment swap anything into that 6.0 M5 file. You will screw up a lot of the things in the engine cal that are unique to a M5 engine file.

**2xls1** · 09-01-2023

Originally Posted by YungTyph

Glad to hear that's working for you, did you seg swap? That bin is a 6L and has different injector flow rates

The injector flow rates would only be different of the 5.3 you have was Flex Fuel. Non FF 5.3 would use the same injectors as a 4.8 or a 6.0.

**YungTyph** · 09-10-2023

Update for all. Tune is feeling MUCH better now. Disabled the O2s and went full open loop off the wideband, seems much more predictable. With the O2s enabled my long term trims were massively negative, with my wideband still reporting decent AFRs. Fueling and airflow feels pretty good for the most part, just need to continue to cruise and smooth it out.

https://log.tunezilla.com/s/BjFP0kDM
https://log.tunezilla.com/s/OmRnlRHD

**YungTyph** · 09-24-2023

Originally Posted by YungTyph

Update for all. Tune is feeling MUCH better now. Disabled the O2s and went full open loop off the wideband, seems much more predictable. With the O2s enabled my long term trims were massively negative, with my wideband still reporting decent AFRs. Fueling and airflow feels pretty good for the most part, just need to continue to cruise and smooth it out.

https://log.tunezilla.com/s/BjFP0kDM
https://log.tunezilla.com/s/OmRnlRHD

Another update for the crowd- changed injector data to known LS2 data, and the car drives even nicer. With that change I nudged the VE table a bit (still in closed loop SD) and the tune generally feels amazing.

HOWEVER, when giving it a gradual (although faster than normal) increase in throttle I had the car backfire pretty badly. The wideband went full lean, and i coasted to the side of the road to investigate. Is there any possibility I am actually too rich? At this point I dont even look at the O2 sensors for reference, pretty confident they are junk.

Here is the log showing this event at the end (right before the throttle defaults down to ~17%) Is this just too much throttle for SD? I will dial in the maf soon too, but I want to know its not in my timing or spark or something else.

I have ordered new O2s and will be messing with the PE aspect of the tune, wondering if I just wasn't kicking in nearly soon enough.

https://log.tunezilla.com/s/OpWcF3EX