Hello all! I'm hoping I can get an idea of where to look with something I'm seeing.

I have a 91 euro GT with an Andy Keel supercharger setup. I just recently added an X pipe and Super MAF. I retuned it using a combination of the autotune and shark plotter. I did all of the tuning with the NB02 disabled. With the NB02 disabled it idles fine at around stoich. When I enable the NB02 in the sharktuner it starts adding fuel and brings the AFR down to around 12. I installed a new NB02 when the x pipe went in and didn't have this issue previously. Any ideas? Otherwise the car has been transformed from before the sharktuning and SMAF. It is running freaking amazing!!!

thanks

Brian

 

Hi Brian,

Nothing to add except that I have the same issues on my 91GT. Car goes PIG rich with the NBO2 loop enabled. My solution was to run open loop. Not ideal, but it works. Wish i could run the O2.

 

I'm just starting out with the Shark Tuner on an S3 with an Andy Keel setup and have little experience.

The manual states when in in Auto Tune the NBO2 is "open Loop", what I've found was get the Idle Auto tuned sitting at Idle and maybe slowly moving the throttle a bit and do a save.

Then when tuning the Base map for Cruise (no Idle checked) for a 14.7 AFR, sometimes it will automatically go back and change some of the idle cells. So I save the Cruise base map and re adjust the Idle cells and re-save as once again as my new Idle and cruise base map.

Like I said before I'm totally new at this, but this worked for me and I'm running closed loop with AFR at 14.7, but still tuning, have yet to get to WOT or enrichment maps

I'm sure other more experienced w/ the S4/Gt's will speak up, you may also want to review the TwinScrew thread, if you havn't all ready done so, it is rather long though.

Keep us updated please,

Dave K

 

Did you Autotune at all rpm or just above (say) 2000rpm ?

Tuning around idle is not very successful due to the time lag of the exhaust gases.

I never tune by either Autotune or Sharkplotter around idle speeds/loads. Suggest you revert to stock map values in that area.

Although the O2 loop is disabled when tuning, you can get over the adaptation issue by just disabling the adaptation. This still leave you in closed loop when driving.

 

Dave,

This is an issue for when all the tuning is done, and you want to re-enable the NBO2 loop to let the computer do its job and fine tune things. You will see the STer shows that the O2 adjustment goes from 0 to 20% and the car goes super rich. I'm not sure if this is a "bug" in the STer code, or something else. I gave up trying to fix it a long time ago and decided I would just run open loop.

 

I do leave the adaptation disabled all of the time. I did tune at idle and cruise at all rpm ranges. If the sharktuner was altering the cells around idle during the cruise mapping then I would see the low AFR with the NB02 open loop while at idle. What I'm seeing is that the maps are tuned good at idle and everything is fine until it goes closed loop and then the computer thinks it needs to start adding fuel when it doesn't. Everything says it's running at stoich but the computer thinks it's lean an starts adding fuel.

 

Presumably you have eliminated the "idiot" errors and ST2 understands the correct injector size, MAF type etc.

If the above are correct and the error is occurring across the full rev range then I have no explanation for what you are seeing. It should be noted that at full load the stock mapping gives AFR's close to 12 so the obvious question is whether the brains think the motor is at full load when it is not. A failure of the full load switch usually leaves the motor stuck in cruise mode.

I do not have a NBO2 sensor in my system and if one tunes correctly with ST2 I see no need for one given it is a custom tune albeit I appreciate there may be federal implications.
.
Regarding idle I find that an indicated WBO2 AFR of 14 seems to give the best result with some additional advance over stock but the idle is still far from perfect but maybe I have other issues

 

The low AFR is occuring at idle as it fluctuates across the load range. When I'm cruising at lower load and rpm it is right around 14.

I appreciate all of the comments!

 

So it is tuned OK at idle cruise as the OK loop is working and keeping the fuelling at stoic.

There seems to be confusion about the O2 loop: switching off the adaptation does NOT switch of the O2 loop. It just inhibits the longer term adaptation that the LH does automatically to try and centre the fuelling in the middle of the loop range, to cope with varying temperature and battery voltages.

It is perfectly acceptable to get a good tune and leave the adaptation off.

If your mixture is OK at light throttle, (idle cruise) but going out at higher loads where the LH automatically goes open loop (nothing to do with the WOT switch until you are really at WOT). It sounds like you tune is out at the higher loads/rpm.

See my comments on another ST thread running at the moment.

 

Thanks John for the comments and yes, I do understand that the adaptation has nothing to do with open or closed loop. I have also read the manual several times along with all of the sharktuner posts.

I spent today at 3rd coast on several lengthy high speed runs. I was logging the entire time open loop, NB02 force disabled, in sharktunner. I took a look at the logging runs in sharkplotter and made some adjustments using my AFR target map. Overall the AFR plots didn't look too bad. I reloaded the maps and it is running exceptionally well. Most all load ranges seem to be in line with my target AFR map.

When I enable the NB02, obey coding plug, it goes rich. Drops from the 14ish AFR at idle to ~12.5. The richness does continue on to higher rpm and load ranges where initially I thought it was only at idle. I will be doing a number of logging runs with it enabled so that I can compare the two. If I'm not able to figure it out then I will probably just drive it with the NB02 disabled since I'm not running cats and probably won't have any issues.

Thanks again.

 

Have you checked the engine temperature sharktuner is indicating? As I remember the ST2 has two indications which I understand are outputs from the temp 2 sensor. If this is reading incorrectly and the brains think the motor is cooler than it actually is it will have a cold enrichment increment added.

The running temperature when warm should show something around 85C to 90C and be the same within about 1 degree on both channels. I doubt this is connected to your problem but stranger things have happened and you should eliminate this as a possibility.

 

The coolant temp during all logging runs was at 89 - 92 C. I logged the temp on the ignition variable side. Are there any other indications that temp II sensor may be bad?

 

OK, understood. Do you have CO pot "disabled" ?

If you are you are forcing non cat mod I think this means you have been tuning the non cat map. (Where's Jim Corenman when you need him?)

I'm not an expert user and so after 12 years my understanding is a bit rusty.

Maybe copying the tuned map to the other cat map would help.

 

Next time you are out just check on the fuel display page that the temperature aligns with that on the other page give or take a degree.

As I said earlier I doubt this is your problem but eliminating potential issues is part of system diagnosis.

I had a problem with my full throttle switch and if that does not contact you do not get the full throttle mapping [additional fuel]. I chose to map the cruise map and told ST2 to ignore the full throttle maps thus the full throttle contact is mostly irrelevant- but the one currently fitted works.

 

Although mine is a euro it did come with factory cats and without a CO pot but I do have it disabled. I'm using version 6.3 of sharktuner that allows forcing open loop without having to use the non cat maps. I have verified that I'm tuning to the correct map.

I have put my WOT map to zero and have tuned to my cruise map.