Update to SEL affecting AFR...

mbox · 12-01-2005, 08:52 AM

Original Post

Quote from DAP:
"The SEL adaption channel is going to scale down the specified engine load (SEL) which is an axis on those maps. So by changing the load, you are changing where the ECU looks in those maps for its data values for boost, fuel, timing, etc..."

Personally, I thought the exact same thing as DAP but I wanted to do a minor test regardless. I had my MBC in parallel set ~20 and SEL cranked to 83% which put me ~16psi and had been running this exact setup w/ no tweaks for around 10 days.

This morning I checked my PT LTFT's and they are set to -3.9% so w/out resetting my codes I changed SEL to -90%, a +7% change, thinking that my PT LTFT's would move.

After driving ~25 miles of varying speeds, I parked and checked my LTFT's again and whaddyaknow.. -3.9% PT LTFT. I know it's only been 25 miles, but I would think that with a +7% SEL tweak, my PT LTFT's have got to move a little bit.

So was Doc right in thinking SEL does not affect AFR?

Imolavirus@BuehnEngineering · 12-01-2005, 08:57 AM

Mike2kS4 · 12-01-2005, 09:47 AM

But in order to measure it, you're looking in the wrong place. Part trims should be relatively unaffected since SEL really plays a minor role when you're not in boost.

We have a MAF: That's what meters fueling. And you'd still want the same approximate AFR under boost. You might see a difference in WOT O2 settings, if you reduce SEL to the extreme and you're *NOT* controlling boost with the N75.

mbox · 12-01-2005, 10:05 AM

sent my injectors off to be cleaned.

12-01-2005, 08:52 AM	#1
mbox AudiWorld Super User Garage is empty, add now Join Date: Jan 2005 Posts: 2,724	Update to SEL affecting AFR... Original Post Quote from DAP: "The SEL adaption channel is going to scale down the specified engine load (SEL) which is an axis on those maps. So by changing the load, you are changing where the ECU looks in those maps for its data values for boost, fuel, timing, etc..." Personally, I thought the exact same thing as DAP but I wanted to do a minor test regardless. I had my MBC in parallel set ~20 and SEL cranked to 83% which put me ~16psi and had been running this exact setup w/ no tweaks for around 10 days. This morning I checked my PT LTFT's and they are set to -3.9% so w/out resetting my codes I changed SEL to -90%, a +7% change, thinking that my PT LTFT's would move. After driving ~25 miles of varying speeds, I parked and checked my LTFT's again and whaddyaknow.. -3.9% PT LTFT. I know it's only been 25 miles, but I would think that with a +7% SEL tweak, my PT LTFT's have got to move a little bit. So was Doc right in thinking SEL does not affect AFR?

12-01-2005, 08:57 AM	#2
Imolavirus@BuehnEngineering AudiWorld Super User Garage is empty, add now Join Date: Mar 2002 Posts: 17,943	are you mbc only? __________________ -Jacob ^^^CLICK SIG FOR BUEHN ENGINEERING WEBSITE^^^ <big><big>Website Here!!!</big></big> <big>Items For Sale</big>

12-01-2005, 09:47 AM	#3
Mike2kS4 AudiWorld Super User Garage is empty, add now Join Date: Jun 2002 Posts: 12,096	I wouldn't think a minor change in SEL would affect AFR... But in order to measure it, you're looking in the wrong place. Part trims should be relatively unaffected since SEL really plays a minor role when you're not in boost. We have a MAF: That's what meters fueling. And you'd still want the same approximate AFR under boost. You might see a difference in WOT O2 settings, if you reduce SEL to the extreme and you're NOT controlling boost with the N75. __________________ 2002 S4 Avant, 6spd. Bone stock. <a href="http://www.autospeed.us"> </a> Caveat: Any advice I express regarding potential tuning and such is purely informational. If your knowledge and abilities are not up to the task, no amount of advice can assist.

12-01-2005, 10:05 AM	#4
mbox AudiWorld Super User Garage is empty, add now Join Date: Jan 2005 Posts: 2,724	parallel right now b/c I'm on stock fueling. sent my injectors off to be cleaned.

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