O2 issue
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 3,011
Likes: 9
From: Dublin GA
O2 issue
Does anyone know of a reason that my O2 sensors are not "cycling" at idle on my SD tune>> 
I have a 98 that has a 02 PCM. at idle (up to around 1400 rpm) the O2s stay in the 900s and the AFR is in the 12s. If I rev it up to around 1400 in gear, the O2s cycle perfectly and the AFR is close (VE needs tweaking)
I purchased new O2s and it didn't help, so the original ones are actually in it right now
I have been fighting this issue for around a month,
but a crazy work schedule, the holidays and consistent rain every weekend has hampered any testing. I'm ready to get this thing back on the road
I have a 98 that has a 02 PCM. at idle (up to around 1400 rpm) the O2s stay in the 900s and the AFR is in the 12s. If I rev it up to around 1400 in gear, the O2s cycle perfectly and the AFR is close (VE needs tweaking)
I purchased new O2s and it didn't help, so the original ones are actually in it right now
I have been fighting this issue for around a month,
but a crazy work schedule, the holidays and consistent rain every weekend has hampered any testing. I'm ready to get this thing back on the road
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
I believe on a SD tune the front 02's-MAF and fuel trims are NOT being used---so their reportiing is not important----An SD tune uses the VE table solely to command fuel----Even on a stock OL/CL tune at WOT the 02's are not being used--the fueling is commanded by the PE table in your tune---
Safety Car
Joined: Aug 2011
Posts: 4,449
Likes: 409
From: Portland OR
Tom,
It depends on how the tune is set up.
SD most certainly will run in closed loop. I have my turbo car running CL and it's a 3 bar SD tune. Works very well.
It's also possible to set up any tune to be open loop at idle and switch to closed loop at 1200 or so rpm.
Ron
It depends on how the tune is set up.
SD most certainly will run in closed loop. I have my turbo car running CL and it's a 3 bar SD tune. Works very well.
It's also possible to set up any tune to be open loop at idle and switch to closed loop at 1200 or so rpm.
Ron
Burning Brakes
Joined: Jul 2006
Posts: 968
Likes: 12
From: Regina Sask
I believe on a SD tune the front 02's-MAF and fuel trims are NOT being used---so their reportiing is not important----An SD tune uses the VE table solely to command fuel----Even on a stock OL/CL tune at WOT the 02's are not being used--the fueling is commanded by the PE table in your tune---
Blow Torch, post your tune.
Russ Kemp
Last edited by Russ K; Feb 9, 2016 at 11:35 AM.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
I agree somewhat---However there are several versions of an SD tune----Some use OL some use CL and some use both---But a true SD tune uses neither---No MAF NO fuel trims--NO 02 input---This type of tune is generally used only on dedicated race cars---
Most people running an SD tune have no idea which version of an SD tune their tuner used----
Most people running an SD tune have no idea which version of an SD tune their tuner used----
