AFR goes to 11.5 but creeps back to 14.7 in boost

**xsports33** · 03-09-2011

I just got my truck tuned and when i go WOT the AFR goes to 11.5 as commanded, but then works it's way back to 14.7 while i'm still in boost. Shouldn't i stay at ~11.5 the entire time i'm in boost? why would by AFR start creeping back to stoich? it takes about 2-3 seconds for it to get back to 14.7.

do i need to adjust any tables?

thanks!

**Bill@HPTuners** · 03-09-2011

This maybe ? http://www.hptuners.com/forum/showthread.php?t=18672

**xsports33** · 03-09-2011

Thanks for the link, Bill. I got all excited reading it thinking i had it covered, but unfortunately not. My commanded AFR stays at 11.7 the whole time.

However, watching the STFTs on my log they are pulling fuel. I thought the STFTs are disabled in boost?

**5_Liter_Eater** · 03-09-2011

Are you saying that the commanded AFR is reverting back to 14.7 or the AFR as measured by the wide band is creeping back to 14.7? If the latter then you need to tune your MAF table and/or PE.

**DSteck** · 03-09-2011

Make sure your car is meeting the PE requirements before it goes into boost.

**LSxpwrdZ** · 03-09-2011

Most boost setup's I alway's set the enable TPS significantly lower than normal and set the MAP point to around 85-90kpa that way PE enables anytime a load is on the motor.

**xsports33** · 03-09-2011

The AFR that is measure by the wideband creeps back up to 14.7, the commanded AFR stays at 11.7 while in boost.

PE is set at 1.13 across the table BE is set at 1.25 across the table. It's 2bar SD, so the MAF has been completely disabled. PE requirements are definitely being met as kPA is set at 95 and BE is set at 100kPA. Also, TPS is set at 45%.

**LSxpwrdZ** · 03-09-2011

If that's the case then you need to do some VE tuning then. The goal is to get actual the same as commanded.

**Montecarlodrag** · 03-09-2011

Originally Posted by xsports33

The AFR that is measure by the wideband creeps back up to 14.7, the commanded AFR stays at 11.7 while in boost.

PE is set at 1.13 across the table BE is set at 1.25 across the table. It's 2bar SD, so the MAF has been completely disabled. PE requirements are definitely being met as kPA is set at 95 and BE is set at 100kPA. Also, TPS is set at 45%.

Log % injector duty cycle, it is possible your injectors are too small and aren't unable to supply enough fuel at higher demands.

If commanded AFR is 11.7 always under boost but it just doesn't happen at the wideband, it may be something is not calibrated properly, or the fuel delivery is not enough.

You know the injectors are too small when under boost the AFR=commanded at low RPM's, but as RPM increase, %IDC also increases reaching 100%. Then AFR starts to climb and there's nothing you can do.

**carlrx7** · 03-10-2011

needs more pump

**xsports33** · 03-10-2011

when i turn off STFT and LTFT and disable STFT Openloop my AFR is spot on. So, my VE table and multipliers are correct.

it's when i enable STFT and LTFT when the AFR works it's way back to 14.7 Commanded is 11.7, as soon as i mash the pedal the AFR goes to 11.7, but slowly (~2 sec) works it way back to 14.7 WHILE STAYING in boost.

**SSUte01** · 03-10-2011

What are your STFTs doing during the boost when this is occurring? I've never used OL STFTs because by very definition that is Closed Loop and frankly I don't see the point of the feature, so I don't know what the Commanded EQ does when they are active. If I were you I would disable the OL STFTs for a start and then show us a log showing Commanded AFR, STFTs, WB, NB Voltage and all the other standard usual PIDs that you'd want.

**xsports33** · 03-10-2011

During boost STFT's show -20 to -25 because they are pulling fuel going back to stoich.

But obviously, i don't want them to pull fuel because the VE is correct providing 11.7 which is what is commanded.

Question is: Why would my STFT's be pulling fuel trying to get back to 14.7 in boost, when the commanded AFR is 11.7 and VE w/the multiplier provides 11.7?

**5_Liter_Eater** · 03-10-2011

Post the tune and log of the behavior.

**xsports33** · 03-10-2011

Here's the log and the tune. We were using an Innovative Wideband that was hooked up externally, so it's not shown on the log. BUT, you can see the STFT's pulling fuel while in low boost and the commanded stays at 11.7

Frames 575-675 and 875 - 925 show what i'm talking about. Low boost, commanded 11.7 AFR and the STFT's kicking in and pulling fuel.

Again, with STFTs and LTFTs off AFR is as commanded... at most 1-3% rich

**12secSS** · 03-10-2011

From what I see ...

You have STFT enabled so that is correcting the fule back to Stoich.
PLUS: your PE Enable TPS is set to 37% at that RPM ... that enable TPS is your current Throttle Position (SAE) (which is at 43%) minus the Throttle Position (SAE) at Idle (which was 6%), which gives you 37%.

Makes sense to me that it is going lean, you are crossing under the PE Enable TPS threshold. Try lowering the PE Enable TPS threshold by 5 and it should help. Also as noted, disable STFT during Open Loop, because there will be times when your go out of Closed Loop but have not met PE qualifications yet ... that is where STFT in Open Loop work.

**5_Liter_Eater** · 03-10-2011

Try setting the the STFT Openloop to Disabled.

**xsports33** · 03-10-2011

Thanks guys! i will try that now.

12secSS - you moved TO Simi Valley? I just moved FROM Simi Valley to Chicago (military orders). You helped me out more than a few times on pt.net Glad to see you're still around.

**xsports33** · 03-10-2011

Ok. That didn't work. I disabled STFT Openloop and lowered my PE Enable TPS values by 5 and STFT's are still pulling fuel while in boost. It does it a little slower, but never the less does pull fuel.

Here's another log. It shows 2 pulls frames 40-60 and 150-160. Again, AFR drops down to what is commanded but slowly works its way back to 14.7 even though i'm still in boost.

**xsports33** · 03-11-2011

OK. After much trial and error, i finally figured it out. It had nothing to do with any of the above suggestions (unfortunately, otherwise i would have been done a long time ago).

For some reason, and i'm REALLY hoping someone can explain this to me, under ->Engine -> Torque Management ->General... one or potentially all of these tables were causing my STFTs to pull fuel while in boost:

Maximum Torque vs. RPM
ETC TPS Max
Torque Loss % vs. Spark Retard

I changed the above tables back to what i had before my last tune, and now the STFT's stay off in boost and i can hold AFR again... can someone shed some light on this?

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AFR goes to 11.5 but creeps back to 14.7 in boost