Open Loop
Thread Starter
Race Director
Joined: Oct 2005
Posts: 14,999
Likes: 200
From: Bay Area Ca.
Open Loop
I was experiencing some ( very little actually ) low rpm surging with the addition of the Vararam. The car was tuned also. Only way to get it to go away was to go Open Loop ( turning 02 sensors off )
What if any concerns should I have other than it will not pass sniffer until the sensors turned back on? I could probably live with the surge ( passenger can not feel it ) But it is smoother with Open Loop.
I was told not to worry but it is in my nature to question.
Thanks for any information
What if any concerns should I have other than it will not pass sniffer until the sensors turned back on? I could probably live with the surge ( passenger can not feel it ) But it is smoother with Open Loop.
I was told not to worry but it is in my nature to question.
Thanks for any information
Supporting Vendor
Joined: Mar 2002
Posts: 13,099
Likes: 671
From: Bristol, Tennessee
St. Jude Donor '09
I was experiencing some ( very little actually ) low rpm surging with the addition of the Vararam. The car was tuned also. Only way to get it to go away was to go Open Loop ( turning 02 sensors off )
What if any concerns should I have other than it will not pass sniffer until the sensors turned back on? I could probably live with the surge ( passenger can not feel it ) But it is smoother with Open Loop.
I was told not to worry but it is in my nature to question.
Thanks for any information
What if any concerns should I have other than it will not pass sniffer until the sensors turned back on? I could probably live with the surge ( passenger can not feel it ) But it is smoother with Open Loop.
I was told not to worry but it is in my nature to question.
Thanks for any information
Closed Loop: O2 feedback loop designed to keep your calibration at 14.68:1 air fuel ratio (considered chemically correct total burn of gasoline)
Open Loop: Factory or tuner preset tables that have an Equivalency Ratio related to increasing fuel (which decreases the air-fuel ratio) to stave off pinging, and or detonation. Open Loop starts at approximately 48% throttle position (rpm dependent) to 100% throttle position. Open Loop air fuel ratios for the LS series Corvettes are typically 11.5:1 (fat)
Any surging you feel would be in Closed Loop and is related to turbulent airflow at the MAF sensor caused by ram air. Near impossible to tune out since it is a physical problem, not a tuning problem.
Our TRIC had this problem bigtime (1999-2000 RIP) and there was only one way to avoid it. Take off the intake or leave the laminar screen in the MAF. Unfortnately, the new style MAF has no laminar flow screens to help with the turbulence and buffeting.
Thread Starter
Race Director
Joined: Oct 2005
Posts: 14,999
Likes: 200
From: Bay Area Ca.
Open Loop does not have any connection with the O2 sensors whatsoever. Closed loop is the stoichiometric loop feedback you are thinking of. No way to turn this off without ruining your car.
Closed Loop: O2 feedback loop designed to keep your calibration at 14.68:1 air fuel ratio (considered chemically correct total burn of gasoline)
Open Loop: Factory or tuner preset tables that have an Equivalency Ratio related to increasing fuel (which decreases the air-fuel ratio) to stave off pinging, and or detonation. Open Loop starts at approximately 48% throttle position (rpm dependent) to 100% throttle position. Open Loop air fuel ratios for the LS series Corvettes are typically 11.5:1 (fat)
Any surging you feel would be in Closed Loop and is related to turbulent airflow at the MAF sensor caused by ram air. Near impossible to tune out since it is a physical problem, not a tuning problem.
Our TRIC had this problem bigtime (1999-2000 RIP) and there was only one way to avoid it. Take off the intake or leave the laminar screen in the MAF. Unfortnately, the new style MAF has no laminar flow screens to help with the turbulence and buffeting.
Closed Loop: O2 feedback loop designed to keep your calibration at 14.68:1 air fuel ratio (considered chemically correct total burn of gasoline)
Open Loop: Factory or tuner preset tables that have an Equivalency Ratio related to increasing fuel (which decreases the air-fuel ratio) to stave off pinging, and or detonation. Open Loop starts at approximately 48% throttle position (rpm dependent) to 100% throttle position. Open Loop air fuel ratios for the LS series Corvettes are typically 11.5:1 (fat)
Any surging you feel would be in Closed Loop and is related to turbulent airflow at the MAF sensor caused by ram air. Near impossible to tune out since it is a physical problem, not a tuning problem.
Our TRIC had this problem bigtime (1999-2000 RIP) and there was only one way to avoid it. Take off the intake or leave the laminar screen in the MAF. Unfortnately, the new style MAF has no laminar flow screens to help with the turbulence and buffeting.
Thanks again
Supporting Vendor
Joined: Mar 2002
Posts: 13,099
Likes: 671
From: Bristol, Tennessee
St. Jude Donor '09
The new probe MAF sensors are ultra sensitive, and Callaway has a baffle of some type that they are offering to keep surging down. All bottom breathers have this issue to some degree.
Maybe their solution would work for you. Check the other threads.
Maybe their solution would work for you. Check the other threads.
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Pro
Joined: May 2000
Posts: 610
Likes: 1
From: Midland Texas
St. Jude Donor '09-'11
I have an '07 manual trans car with Vararam and headers and no surge. Runs fine in closed loop, but I tuned it myself. I don't remember having any surging problems at idle. Is yours an automatic?
Advanced
Joined: Feb 2008
Posts: 66
Likes: 1
open loop maf tuning is easy and it will eliminate surging. Its a good idea and something that is done commonly in Australia.
My car runs open loop SD (self tune)
Surging is more common with aftermarket intakes, Over the radiator style. I always disable Long term trims. Simply not required with e38 pcms. STFT is all I generally uses. And even then you don't need them if tune is correct.
cheers
My car runs open loop SD (self tune)
Surging is more common with aftermarket intakes, Over the radiator style. I always disable Long term trims. Simply not required with e38 pcms. STFT is all I generally uses. And even then you don't need them if tune is correct.
cheers