Closed Loop at WOT?
Race Director
Joined: Sep 1999
Posts: 12,438
Likes: 919
From: CONCORD NC
while you could program the stock ecm to never to into closed loop, I don't think there is a way to calibrate it to read a wide-band O2 sensor. Plus, in open-loop, it always trys to achieve the same afr, usually 14.7:1. Unless you want the car to run rich ALL of the time, you would not be able to program both part-throttle and full throttle to run safely without using open loop
Thread Starter
Instructor
Joined: Aug 2006
Posts: 129
Likes: 0
Thanks for the informative replies!
What I was hoping was that running WBO2s would allow closed loop all the time, which might simplify the tuning particularly at WOT. For example, program the PCM to run 12.5 AFR at WOT and 14.7 at cruise.
Anyhow, this approach doesn't seem feasible & a normal dyno tune is not all that expensive.
What I was hoping was that running WBO2s would allow closed loop all the time, which might simplify the tuning particularly at WOT. For example, program the PCM to run 12.5 AFR at WOT and 14.7 at cruise.
Anyhow, this approach doesn't seem feasible & a normal dyno tune is not all that expensive.
Burning Brakes
Joined: Feb 2006
Posts: 903
Likes: 5
From: Miami FL
Yeah, you can run this method, however it's called an Open loop speed density tune. You tune the car based on wideband readings only. Tune for 14.7 everywhere and tune WOT to your desired afr.
I run this OLSD(open loop speed density) method on my GTO.
Dougie
I run this OLSD(open loop speed density) method on my GTO.
Dougie
Advanced
Joined: Jan 2005
Posts: 51
Likes: 0
From: Charleston SC
Originally Posted by gtodoug
What would be the purpose to run closed loop with widebands?
i just wrote up two articles differentiating SDvsMAF and OLvsCL, cause i've seen too much confusion about it on the forums, so this thread is perfect for plugging these:
http://redhardsupra.blogspot.com/200...on-part-1.html
http://redhardsupra.blogspot.com/200...-2-olvscl.html
Former Vendor
Joined: Dec 2004
Posts: 678
Likes: 0
From: Trenton NJ
just to add a little more to Red's Blogs heres a pretty simple breakdown of the modes your computer can enter http://www.hptuners.com/forum/showthread.php?t=8994
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Le Mans Master
Joined: Oct 2001
Posts: 5,145
Likes: 125
From: The Motor City
Once we have AutoTune, you'll effectively be able to run closed loop off of the wideband. Instead of just updating trims, it will be updating the VE table directly.
(Wait, I'm not sure if RTT will be available on LS2s.)
(Wait, I'm not sure if RTT will be available on LS2s.)
Burning Brakes
Joined: Feb 2002
Posts: 885
Likes: 18
From: McFarland WI
VE tables in LS2 ecm
It is my understanding that the 07 ecm doesn't use VE tables as such but a rather complicated mathimatical formula to constantly calc and update afr. Is this correct???
Tech Member
Joined: Dec 2005
Posts: 80
Likes: 0
From: Claremont CA
Originally Posted by jwbert
It is my understanding that the 07 ecm doesn't use VE tables as such but a rather complicated mathimatical formula to constantly calc and update afr. Is this correct???
It involves using predicted air charge (PV=NrT) and Measured air (MAF) So if the engine controller has a MAP and a MAF then it is using both, (DYNAIR) if there is no MAP then it is using measured air, (MAF) and if there is no MAF then it is using Speed Density.
If you have a desired AF then all you need to know is how many grams of air are entering the cylinder and the how many grams of fuel the injector can flow. Mapping this out for the entire load range the engine will be operated in is called tuning. If you have your math right then there will be little error in the AF, this is where the narrow band sensor is used to correct for this error which should be within 5% in all cells where STOICH is desired.
If you have any further questions please let me know.
Regards,
Scott Brown