Hey guys,

I recently switched over to open loop cruise and idle. Before switching I ensured my trims were within +/- 5%.

After tuning in my preferred AFR for idle and cruise, I am seeing something strange.... To me.

After extended driving, maybe 40+ minutes, the AFR will start to lean out between 0.5 and 0.8. Example cruise AFR was set and working at 15.6:1, however after driving for awhile it's starts to lean out to 16.4:1.

I figured the Walbro may be worn and so I bought and installed a new Walbro, unfortunately it did not resolve the problem.

Any ideas guys?

 

Temp rising?

 

certainly seems like a compensation is having a effect. I cant recall all of the temperature compensations to IPW etc, but I would try to correlate it to the temperature of something changing. Whether it be fuel temp as IAT heatsoaking from return, or MAF (or post turbo for SD IAT).

 

Corrected the timeframe.. Usually requires 40+ minutes.

Temps stay consistent.

Do trims affect cruise afr (ipw) when in open loop?

 

I always thought they did. Which is part if the reason as close to zero as possible and letting them settle before tuning wot. But I had never seen that proactively reflected on here.

You can play with the hz crossover points andaybr achieve better results. Do you still have some closed loop happening ?

 

Nope, I'm in OL 100% of the time.

Maybe I'll re-enable closed loop and check trims for the third time

I vaguely remember a thread about trims affecting OL IPW, but that could have been for the Evo X I used to own and not the Evo IX I own now.

 

Did you used the periphery bit to switch to open loop?

Try to keep it on open loop by increasing the min temp required for closed loop to a value which wont be reached.

I can remember having some weird timing variations when switching to open loop via periphery bits, so I always used the min engine temp to stay in open loop.
With this method, AFR and timing were always dead-on, even on very long journeys with the engine running >7h non-stop...
(which gives you incredibly huge logfiles if you forget to stop/start logging for over half of the time )

 

I didn't use the periphery bit, I used the open loop rpm and load tables.

After switching back to closed loop I found my med trim at -10. I forgot I found a boost leak after my initial tuning.

I guess trims do affect open loop cruise!

Im back to dialing in the trims again and plan to report back to this thread.

 

So you guys are saying that even though you've disabled closed loop control that the ECU still records and stores LTFTs and changes open loop fueling? Seems odd...

Does this change if you disable the rear o2 with periphery? I dont think LTFTs change when you disable the rear 02 with periphery. Maybe it was another setting, but I remember having that issue before and wondering if a side benefit could could be to use that for this purpose.

 

IIRC the ECU applies the last stored fuel trims to open loop but doesn't correct/change them any more. So you need to reset your trims to 0 (unplug the ecu or battery) before switching to full-time open loop. What happens if you change the "min temp for CL" value to stay in OL? does it still correct trims?

 

My understanding of the OP's explanation is that he is thinking that the -10 LTFT has an effect on open loop fueling. And pointing to that as a reason for his problem of AFRs leaning out during long cruise implies that the LTFTs are changing while he is driving.

Id be surprised if LTFT had any effect on open loop fueling and certainly shouldnt be changing when in open loop. But if they do...Id really like to know.

 

That's my theory and I'm trying to prove it

Can anyone else confirm?

 

I have an issue where my open loop cruise fueling starts out lean (where I set it 15.3:1), and richens up slightly (14.7-ish) by the end of my 30 min drive. My trims are completely zeroed, and the rear O2 is disabled in the peripheries, so that none of the trims are active. I like a closed loop idle, so I've altered the open loop tables accordingly. Over 1500rpm is all zeros so that I get STFTs still.

I had it tuned, trims zeroed, everything nice...then disabled the rear O2 in the peripheries...and had to retune?! It got richer, no idea why.

 

Exactly, something causes this!!

We're taking about 2006 cars here, so I'm sure someone has seen this before... Chime in and help

 

I'm confused.

After switching back to closed loop and re-tuning for trims that are +/- 2%, I'm still seeing drifting O2's during open loop cruising.

During my daily commute today I saw 15.3 during the morning commute, and on my afternoon commute I saw it drift from 15.3 to 16.3 after 1 hour.

What can cause this?