On my previous mega-powered vehicle I had a part-throttle fuel control module installed to fatten up my AF during part-throttle boost. As a matter of fact, we were very concerned with 2-3 PSI when not in open loop.

Anyway, my point is I'm seeing 14.7 AF with 10 PSI during closed loop; is this normal?

 

We are on the same page! Now with this new tune I'm seeing 14.7AFR when the car feels like it's pulling way too hard. I don't have a boost sensor yet but can monitor AFR and whether in open or closed loop at the same time with this PLX gauge. It seems like at lower throttle openings but at high engine load the car holds on to closed loop too long.

I think the Split Second Enricher box would work real well for partial throttle/closed loop tuning. I'm almost there, just sorting hardware issues then looking forward to some tuning.

 

I'm happy to see I'm not the only one going through this, but I'd be even happier if Clint would respond to the email I sent him regarding the matter. He must be very busy or on vacation, as he usually responds to emails very promptly.

 

I just sent Clint a second email. I'll post up the results later.

 

Grip Grip,

You know who this is. The PTFC was needed to address closed loop boost concerns on your previous Hemi. However, on your factory Supercharged SRT-6, 14.7 afr under boost is not an issue as it would be for a modified N/A engine as your previous Hemi. This is with the assumption you are running factory boost. The engine and the ecu program are designed for the condition. Otherwise they could not warranty it. My former SRT-4 was exactly the same.

From your sig are you running 20psi? If so, then 10psi closed loop is likely abnormal. Your tune should address, but depends on whether you are getting any short term knock. PM me to discuss.

 

I spoke to Clint last week and his wife is expecting so he told he would be out of the office for a week and for me to talk to Jerry. Jerry hasn't answered my email but I'm making plans under the assumption that he read it. I just started loging AFR's and boost and it doesn't start adding fuel until around 10 lbs. After my new tune on Wednesday, when I'm more comfortable running hard I'll get better info.

Les

 

Good point. I was under the impression that the ecu would request a richer mixture at the higher boost levels, by that's not the case with my tune. I'll just have to get used to seeing 10psi+ and a 14.* A/F. It's a little unnerving to me.

 

So you're positive you're seeing the ecu add fuel in closed loop?

 

That would be impossible. Closed loop means 14.7.

 

I was told by another member with an SLK that his adds fuel at part throttle. I don't think it's implausible for the computer to request a richer mixture in closed loop just as it seeks a 14.7 mixture. It does monitor boost levels, so couldn't it request a richer mixture when higher levels are reached?

 

It will add or remove fuel to keep your mixture at 14.7.The only way to change your mixture in closed loop is to fool the ECU by changing the O2 sensor output voltage.
After 10psi Les must be breaking into open loop mode and seeing the "tune" mixture.

Re-read your post Grip. I didn't think it would be possible for the ECU to request a different mixture at different engine loads. If it could then we could throw away our widebands and tuning cables and run a feedback loop all the way to redline.

 

No. I was guesstimating at the PSI. I only ran the car WOT twice after getting the wide band in as I was too worried about the tune. The lowest AFR I saw with the wide band was 13.3. On the dyno it hit 12.7 but was hotter. At part throttle I only see 14.7 to 15 but I'm going to analyze the part throttle when I have WOT fixed. I don't think Eurocharged makes any AFR changes except at WOT.

Les

 

Some new vehicles are moving to use of a wide band sensor giving the ecu greater control over afr in all conditions, thereby staying in a closed loop mode at all times. That design could adjust to any afr desired by the ecu.

With a narrowband sensor, it is only accurate around the midpoint voltage so the ecu ticks on either side to obtain an average 14.7 afr. O2 sensor offset can add some fuel while in closed loop, but it will not be more than a coarse adjustment as sensitivity of the narrowband degrades the farther one moves from midpoint.
What did you see for closed loop boost before cranking up the boost?

 

Thanks for the explanation, as that was just what I needed to hear. Unfortunately I didn't install the gauges until after I increased the boost, so I don't know what the norm is.

A couple days ago I saw 14psi in closed loop and I believe the max boost these make stock is the same. That's what scares me.

 

my stage 3 computer in my srt4 calls for an afr of 9.8 at wot lol

 

I think that is more than stock boost. Can you log to see if any knock retard is present? I would consider an EGT gauge to see what your temps are running. I would consider adding water/meth spray as that will help cool the combustion chamber.

 

He is not in WOT, but still in closed loop.

9.8 in WOT is super pig rich and leaving a lot of power on the table.

 

yes it is. Ive heard they did it to use fuel to cool down the cylinders