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G4+ NGTR ECU - idle and rev limiter issue


judasentinel

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Hello all,

First time here, and happy to join this community.

I have recently upgraded my R33 GTR ECU to the Link G4+. Got it tuned on the road and am very happy with the results. The car has some mods (bigger injectors, turbos, exhaust, LS2 coils, etc.), and the tuner did a good job of getting it running. However, there are two issues that I am struggling with right now:

 

1. The idle remains a bit erratic. The revs go up and down a little bit, as do the AFR (air-fuel ratio)...from 13 to 15.5. In addition to this, if I rev the car a little bit (a blip of the throttle), the revs go up as they should, but then come down very slowly. The idle does eventually settle down to 1000 rpm, but I am wondering what the cause of the erratic idle and afrs could be, and how to fix it.

2. The rev limiter is set to 7500 rpm, but the car cuts out sometimes at 6900 or at 7100 rpm max. I am not able to rev to even 7200 rpm. Any ideas as to why this could be? Prior to the Link ECU, I was running Nistune ECU with MAF sensors. Now with the Link, I am using MAP and IAT sensors.

I would appreciate if someone could help me with these issues.

Thanks.

Judas

Base.pclr

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The rev limits and MAP limits in Link ECU's are the absolute max that you never want to exceed.  They have what we call a limit control range which is the range over which the cut will be ramped in from minimum to maximum.  The default control range for the RPM limit is 200RPM, this means you will start to get a gentle cut 200RPM before your set limit, and if RPM continues to climb then the limit % will increase.  

In your current tune your RPM limit is set to 7400 (not the 7500 you mentioned originally), so the limiter will start coming in at 7200.  

In the log it appears the fuel cut starts to come in at 7175 but that is just due to the logging rate and RPM filtering not allowing you to see the the little spikes of RPM that will be higher than that.  So it appears to be working correctly.

If you want to only start limiting at 7500RPM, then you should set your limiter to 7700Rpm.  

MzlsWNd.png

 

Your "idle slow to return after a blip" is due to your base position table being no where close to where it should be.  When its warm it looks like it needs 40% idle position to idle at the target RPM, but your base position table has 52% in it.  So after you blip it the idle valve goes to 54% (base position + hold step), the closed loop system then sees RPM is too high so it slowly winds the valve all the way down to 40%. This takes like 10 seconds.

X41YAqY.png

 

The unstable AFR at idle is due to closed loop lambda gain being too high causing it to oscillate.  I suggest you either set your RPM lockout to disable it at idle of change to Auto mode so you have more control over gain and update rate. 

v513gLs.png

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