PE: Aircharge vs PRatio - when does ECU use which?

Hi

I'm tuning a 3.8 Jeep with a S/C. I'm seeing seriously rich fueling at WOT with a STOCK* tune - 10.3:1 (0.7 Lambda).

Why would I see such rich commanded EQ? When does the ECU use Aircharge vs PRatio and why?

You can see the the EQ being commanded at 6:26 onwards in the log.

Any advice would be appreciated

Attachment 101371Attachment 101372



* some minor changes but no changes to VE, PR or Aircharge

On GPEC2A controllers default is aircharge. There is even a switch to toggle between aircharge and pratio. Not sure why GPEC2A has a switch but GPEC2 and earlier controllers don't?

GPEC2A
Attachment 101373

GPEC2
Attachment 101374

You're pretty much staying in Open Loop fueling that's why your EQ commanded is showing the way it is.

You've got lots of issues going on in this tune if it's boosted.

Thanks Homer, no such switch on the NGC4 though

Quote:

---

Originally Posted by Mag0842

You're pretty much staying in Open Loop fueling that's why your EQ commanded is showing the way it is.

You've got lots of issues going on in this tune if it's boosted.

---

But that EQ is lower than either the Aircharge or PRatio tables - I could see an EQ that low if the ECU was doing EQ = Stoich + Aircharge + PRatio, then it would make sense. It would make the diagnostics easier if I knew how and when the tables were being used and if they are combined or used individually.

I think my ETC/TPS maybe faulty, so I've ordered a new one to be sure. What are the other issues you're seeing? Any areas I should change? The Jeep is fine in Closed Loop and near undrivable with horrible MPG in Open Loop. Like I said this is STOCK tune issue, I haven't even started on adjusting anything for boost.

Quote:

---

Originally Posted by chillman

But that EQ is lower than either the Aircharge or PRatio tables - I could see an EQ that low if the ECU was doing EQ = Stoich + Aircharge + PRatio, then it would make sense. It would make the diagnostics easier if I knew how and when the tables were being used and if they are combined or used individually.

I think my ETC/TPS maybe faulty, so I've ordered a new one to be sure. What are the other issues you're seeing? Any areas I should change? The Jeep is fine in Closed Loop and near undrivable with horrible MPG in Open Loop. Like I said this is STOCK tune issue, I haven't even started on adjusting anything for boost.

---

You're probably hitting Catalyst Over Temperature Protection. Check in [Engine] [Fuel] [Temperature Control], increase the targets and maximum thresholds to their limits, and zero out the FA Adders. After that, you should be able to make sense of the commanded EQ Ratio.

You say you're running a mostly stock tune with boost. Have you installed a 2 bar MAP sensor, or are you still on a stock 1 bar? Probably a bad idea to run on a stock MAP sensor and stock tune when running with boost. Timing is going to be way too high, and fueling won't be rich enough. That would be a very bad combination.

Do you have a wideband o2 sensor installed?

Quote:

---

Originally Posted by B00STJUNKY

You're probably hitting Catalyst Over Temperature Protection. Check in [Engine] [Fuel] [Temperature Control], increase the targets and maximum thresholds to their limits, and zero out the FA Adders. After that, you should be able to make sense of the commanded EQ Ratio.

You say you're running a mostly stock tune with boost. Have you installed a 2 bar MAP sensor, or are you still on a stock 1 bar? Probably a bad idea to run on a stock MAP sensor and stock tune when running with boost. Timing is going to be way too high, and fueling won't be rich enough. That would be a very bad combination.

Do you have a wideband o2 sensor installed?

---

Thanks Boostjunky. I'll make the adjustments you recommend.

I agree pure stock tune with boost is a horrible idea. I have a SplitSecond FTC piggyback controller with 2 bar MAP which retards the timing and activates a 7th injector in the S/C to richen mixture and provide charge cooling under boost using the SplitSeconds own maps. I run a boost gauge and wideband, which get logged to the SplitSecond.

I want to sort out the fueling on the stock ECU before trying to tune AFRs via the SplitSecond. Once I'm in the ballpark with AFR for both the stock ECU and the SplitSecond, I'll put it on the dyno. I'd just be wasting money on dyno time until I can get some of these issues sorted.