STFT negative after dialing in VE/MAF - getting 02s to agree with wideband

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05-31-2016
dunce79

STFT negative after dialing in VE/MAF - getting 02s to agree with wideband

I've tuned my VE and MAF tables to within 1-2% error, then enabled closed loop (LTFTs off) and did some logging. Each time my STFT are showing negative 4-8 in the 4000 and lower cruise type driving I'm doing. Actual AFR around 15.1 in this range where as in open loop having tuned VE/MAF my AFR was much closer to 14.7 most of the time. After logging in closed loop a few times I would make some small changes to MAF and VE but my STFTs want to stay negative and by adding fuel it seems the STFTs are going increasingly negative each time.

LS1, LS6 intake, PRC 225 heads, TSP Torquer v2 cam, stock maf, long tube 1 7/8 headers. O2 sensors just after the collectors.

Found this:
http://www.hptuners.com/forum/showth...ts-to-Match-WB

After researching a bit more I'm not quite clear what direction to take. Anyone else been down this path tuning closed loop AFR with Long tubes?

Basically I'm not sure if the plan of attack should be to adjust the O2 switchpoints or if adjusting the table(s) that account for the transport delay should be adjusted first? I'm no expert by any means but it appears the o2s are oscillating nicely its just that being farther away from the head than in a stock configuration they are potentially colder, being effected by the cam and thus reading differently. On the surface adjusting the switchpoints seems like the quick fix but maybe thats masking the real issue and would create others?

If not starting with switchpoint, what table(s) and method for identifying the needed changes should be used?

When my wideband says i'm running 14.7 at steady cruise, the O2s are around 800 so the computer thinks its rich and consistently pulls out fuel.

I may just go openloop and forget it but figured it couldn't hurt to play around with this as time allows.
06-03-2016
dermotw

link is broken...
06-03-2016
BigMike42

What wideband is it? Have you verified the wideband gauge is matching your wideband reading in hptuners?
06-03-2016
GHuggins

O2 integrator delay airflow mode - typically increase this - some say multiply by 1.5 to 1.9 / Closed Loop Proportional airflow - typically you decrease this to reduce the amount of fuel it's adding or subtracting to induce O2 switching - don't go too low or closed loop fueling can become uncontrollable... Then you can shift your main airflow mode table to the left to aid in controlling O2 switching...

Hope this helps get you going.
06-05-2016
dunce79

Here's the link: http://www.hptuners.com/forum/showth...ts-to-Match-WB

Before I started tuning I hooked up the LC-2 wideband to the laptop via serial and saw that HP tuners and the wideband gauge software were reading basically the same.

Thanks GH, I'll check that out. If my o2s are switching well do I still need to play with proportional airflow? By shifting the main airflow table (ve table?) to the left would that mean the values increase? (sorry, still learning here)
06-05-2016
GHuggins

Quote:

Originally Posted by dunce79

Here's the link: http://www.hptuners.com/forum/showth...ts-to-Match-WB

Before I started tuning I hooked up the LC-2 wideband to the laptop via serial and saw that HP tuners and the wideband gauge software were reading basically the same.

Thanks GH, I'll check that out. If my o2s are switching well do I still need to play with proportional airflow? By shifting the main airflow table (ve table?) to the left would that mean the values increase? (sorry, still learning here)

Fuel - Open closed loop - airflow mode - mode vs. airflow... I haven't played with this much to confirm or deny it's effects on O2 switching, but others on here have said it works rather well for bucking issues caused by headers and cams...