Closed loop fuel control delay?

AtaT1T

New Member
Oct 17, 2023
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Hi everyone,

I am a tuner who is looking for some advice regarding an issue. Does anyone know if there is a table responsible for Short term fuel control delay? I am consistently able to produce an issue where going from zero throttle to any throttle, there is a solid delay ranging from 0.5-1.5 seconds until the closed loop fuel control kicks in to correct lambda.

Any insight is appreciated.

Thanks.
 

wheela

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Jun 4, 2021
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Twin Cities, MN
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2015 e84 X1 35i Msport
I have not come across any, but my car does the same. From all the reading I've done, it seems all n55's do this by design. It seems to happen during transients, the thinking is that it's going open loop during times where there may be a delay in response of the sensors. Not sure if it's just running off ltft when this happens or if there are some other tables or logic that come into play for the period where stft cuts out? My AFR seems to stay very close to target when this happens, so I haven't been to worried about it, but it would be nice to know the specifics of what's going on when that happens.

Back in my Mitsubishi days, the cars only came with narrow band O2 sensors, and only ran closed loop during cruise; WOT was always open loop. They had acceleration enrichment tables to add extra fuel during transients to account for delay in sensor response. I'd imagine there must be something analogous with n55 as it's >>>> more sophisticated than an early 2000's Mitsubishi ecu.
 
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AtaT1T

New Member
Oct 17, 2023
2
1
0
I have not come across any, but my car does the same. From all the reading I've done, it seems all n55's do this by design. It seems to happen during transients, the thinking is that it's going open loop during times where there may be a delay in response of the sensors. Not sure if it's just running off ltft when this happens or if there are some other tables or logic that come into play for the period where stft cuts out? My AFR seems to stay very close to target when this happens, so I haven't been to worried about it, but it would be nice to know the specifics of what's going on when that happens.

Back in my Mitsubishi days, the cars only came with narrow band O2 sensors, and only ran closed loop during cruise; WOT was always open loop. They had acceleration enrichment tables to add extra fuel during transients to account for delay in sensor response. I'd imagine there must be something analogous with n55 as it's >>>> more sophisticated than an early 2000's Mitsubishi ecu.
Hey,

Thanks for taking the time to reply.

Glad to know im not the only one experiencing this. I remember back in the old JDM days closed loop was a luxury and open loop tuning was the shit lol, glad those days are gone though shit was a pain sometimes.

I agree with you, it appears to go into some sort of open loop mode. My AFR typically stays close but the problem is when i suddenly floor it, i run rich on ethanol, which results in my fuel pressure dropping. I know the ideal solution here is to fix my fueling map and thats my goal but I'm trying to see if theres a way to avoid this pesky delay.

I was looking at the "related" tables section of the lamba control KLANN in bootmod3 and found this table:

The main table is called KLANN Activation - Lambda Control, which I assume is the Short term fuel correction, and then theres a "Delay Time for Activation Signal which has a value of "0.1". The table itself is named "K_TDKLANN". Do you happen to know if this is it? I was considering setting this to 0.001 to see if there is an improvement in the response of the short term fuel correction.

Thanks again for taking the time to reply.
 
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