HP Tuners, L77, Random extreme lean spots occurring in different area each log.

Hi Guys,

I am playing with a 2011 VE SS Sportswagon. The vehicle has a VCM16 cam kit fitted and a DOD delete. The car has been tuned with the MAF still fitted by a well respected tuner in my part of town.

The owner had mentioned of random very rich smell form the exhaust. Apart from that no other issues was noticed. On a recent Dyno Day we ran this car and it had a off the scale lean out during the first run. The second run was aborted for the same reason. On the first run the vehicle leaned off and then returned to normal AFRs by the end of the run. The lean spot started about 3000 and was over by 4000.

Owner wanted to go Mafless tune and OTR. I am new to HP Tuners and followed the procedure in the course. I will attach the tune file I converted to mafless and am using to try to tune the vehicle.

The issue is this random extreme lean area that moves around during steady state tuning. Each time I do some steady state the area is in a different spot. I have not gone to try power runs yet.

I thought it was the wide band playing up so I connected a second wide band and both read exactly the same. So it appears this is a real lean out.

If I remember correctly the base fuel pressure is around 5 bar.

I will attach tune converted to mafless and untouched and a screen capture. Happy to hear any suggestions. Sorry for some reason it will not allow me to post the log file. It is in HPL format

So essentially you're seeing the same sort of lean area when the car was running a MAF as well as MAFless? I'd be suspicious that you have an issue outside of the ECU such as the fuel pressure dropping away perhaps. Have you logged commanded AFR and confirmed this is staying where you'd expect? I'd also log the injector pulse width and see if this is tracking the lean area you're seeing - ie does the injector pulse width reduce at the point the engine leans out?

Thanks Andre,

I have found a crack in the flange that I suspect was expanding as it got hotter and drawing in outside air into the exhaust. I did study the log file and saw that the factory O2 sensors were reading as expected and only the wide band fitted to the tail pipe was reading lean.

Once the crack has been repaired and I rerun the vehicle I will post a confirmed fix.

Sounds like a definite possibility. Good spotting!

Hey Guys,

Confirmed fix. No more random lean spots and a normal looking VE table.

Both collectors had cracks repaired and all is normal.

Darren