Closed loop questions

pcn

New Member
From what I understand now, most people only use the Closed Loop function while tuning, not while racing. Why is that? What negative is there to having the Closed Loop on? It seems like it would be an extra level of safety. How do you disable the Closed Loop function, just set the "On" setting to a very high RPM that you won't ever reach? Finally, how much gap do you put between your 2-step and the Closed Loop "On" when tuning? I understand the 2-step will skew the numbers, but I think I want as little a gap between time on the 2-step and when I can start recording data. So how little a gap can I use? This is for a BS3 in particular, but I would think the theory would apply to all in general. Thanks for any help!
 

HighPSI

Moderator
Staff member
I have very few customers who turn off the WOT O2 correction. You can turn the WBO2 off on the 2 step be several methods 1) raise the minimum rpm like you posted 2) set the O2 correction limits to zero at where you are on the 2 step 3) wire the 2 step into the PA tables and disable the WBO2 when activated
 

pcn

New Member
Depends on how fast the processor is...

Are you saying this would apply if we were comparing a dyno tune were you could slowly load vs. a race were the acceleration is much faster? I can't see a difference between tuning at the track vs racing at the track. I should have been more detailed - I am trying to tune at the track. I can see if there was significant lag the computer could make a change in the wrong direction if the situation were to change from lean to rich for example and actually move the A/F in the wrong direction.

So if processor speed makes a difference, how fast is fast? Or, how fast is fast enough? What speed processor would you leave on? Thanks for the input.
 

pe_turbo

Member
I typically tune turbo/supercharged cars rarely if ever do nitrous cars so I can't speak for the bottle fed guys but I almost always run closed loop especially when I'm tuning so the feedback covers what little bit the tune is off. I'm one of the few lucky ones who can do a couple dyno pulls prior to going to a track so the tune is within 02 feedback limits. If I do a two-step/brake or need some heat and the system is setup for it, I will stay in closed loop but just put the target at 13.8-14.5. Thats not always feasible but when you can it works and it keeps you from having to modify your VE table to make it lean where you want your car to spool on the chip.
 

pcn

New Member
I typically tune turbo/supercharged cars rarely if ever do nitrous cars so I can't speak for the bottle fed guys but I almost always run closed loop especially when I'm tuning so the feedback covers what little bit the tune is off. I'm one of the few lucky ones who can do a couple dyno pulls prior to going to a track so the tune is within 02 feedback limits. If I do a two-step/brake or need some heat and the system is setup for it, I will stay in closed loop but just put the target at 13.8-14.5. Thats not always feasible but when you can it works and it keeps you from having to modify your VE table to make it lean where you want your car to spool on the chip.

What is the typical end result of leaving the VE table alone and not adjusting the target? Mine is set around 12 at where the 2-step is (4k, 7 psi) and I see numbers jumping around in the 13-14 range. If the 2-step is cutting out spark, wouldnt the numbers show a rich condition? Thank you for your input!
 

pe_turbo

Member
You adjust the target in the PA feature so that only when you are on the two step it goes to 13.5-14 no matter where in the map it is, otherwise it defaults to the VE table. Some guys don't have room to do this because all of their PA features are used up with other things.
 

pe_turbo

Member
pcn, I just relooked your question I think I misunderstood it the first time. In closed loop, if you adjusted the VE table only and not the target, the 02 feedback would correct the mix to try to meet the target until it reached the limits you assigned in the software. In open loop, if there are no other corrections being made, ats, cts, etc, what you put in the VE table is what goes. When you are on the 2Step the 02 is going to bounce around which youve mentioned but it should show lean; haven't actually scientifically tested it but i'm assuming it's because of the massive amounts of unused air vs what the 02 sensor normally sees when the fuel/air is burned.
 

pacecarta

LOGGED OUT
Staff member
with the 2step nocking out cylinders it causes unburnt air (O2) to enter exhaust which is read as lean, the sensor reads O2 not fuel
if you are running closed loop on the 2step with + correction set high it would make the actual AF in the cylinders become richer than your target as the correction based on a lean sensor ads fuel to reach target

set the + correction on the row(s) that you hold the two step to 0 (i use +5 ) to limit the ecu from throwing fuel at it,
 

pe_turbo

Member
Here was the PA I was talking about using while on the brake/2-step. You can make all your fuel changes on here without changing your VE table whether its open/closed loop. You can set the closed loop to 18 or you can disable it and set a certain amount of enrichment or a certain value..timing can be modified as well although not quite as many choices. I think there are even seperate tables completely for one of the PAs for fuel/boost/timing but I don't use them yet
 

Attachments

  • PA.jpg
    PA.jpg
    68 KB · Views: 104
Top