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98 Impreza STI Type R - Link G4x - Idle fluctuation


IncepTioN

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I recently got a G4x installed and mapped but its having issues idling. Once you start the car its fine but then after a few minutes it starts bouncing from 1200-1500rpm. Ive tried changing values on the idle base position table, idle target rpm table and tried changing values for the overrun fuel cut table but nothing seems to be fixing the issue. I cant get my car in at the moment to get looked at so that is why I've tried to see if I can fix it. 

PC Datalog - 2023-01-27 4;12;51 pm.llgx

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In that log it is bouncing off the overrun fuel cut which looks like it might be set to around 1400RPM.  So that would indicate 2 problems:

  1. The over-run fuel cut is set too low - I would normally have it up around 17-1800 on a car like this.
  2. Since it is hitting the over-run fuel cut when its meant to be idling with the throttle closed that means there is enough air entering the engine from somewhere else to acheive more than 1400rpm.  This could just be an incorrect idle valve setting or if this problem has just recently developed it could be an air leak or the throttle blade not fully closing.  

In the log your idle valve doesnt close more than 25%, so you should still have a little bit of wiggle room to close that valve a bit more.  Without your tune it is hard to guess why the valve is not closing any further (assuming it is in closed loop mode).  Start by checking the minimum clamp is not set to 25% and the integral gain is not 0.  Or attach a copy of your map and I can make some suggestions.  

Why is the target idle speed 1200RPM when hot? - that seems a bit extreme unless it is some fairly wild engine?

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This is the original map before I started tweaking stuff, any time i try changing anything and it doesn't work i put it back to this map. I've took my idle control valve off cleaned it and put it back together with new seal and gasket. I don't think i needed to do this since all was working ok on the original ecu but i did it just in case.

Ive no idea why any of the targets are set the way they are I would need to get talking to the guy who set it up and mapped it. 

Its a fully forged engine but still a 2.0 and everything else is standard apart from the fuel pump which is a rcm 2338.

 

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Are you sure you attached the correct map?  There is not even any idle valve assigned in that map and idle ign is turned off, so you have no idle control working at all.  

What model is this? a V4?

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I just loaded in that map and its running sweet. Ive data logged it here but will also let it get up to temp and see how it is and log that aswell.

 

 

just took a log of it up to temp and also took it for a wee spin up the road. 

 

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Yeah it looks a lot closer to how it should look now.  I would update the idle base position table to the example below.  One problem is your "driving wheel speed" is not working so the speed lockout isnt working, this is the cause of the near stalls a few times in the 2nd log where RPM dips down to a bit under 600RPM, I think possibly when you are in overrun coming up to traffic lights or a give way or something.  Try turning the pull-up on on GP speed 1 to see if that is needed to make the speed work.  

Other stuff that will likely need a bit of tuning are the offsets for startup/fan/AC/power steering and dashpot.  

KKs709F.png

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Updated the base position table. Also set the pull-up resistor to on for GP speed 1. Still having same issue of dipping down to 600rpm but this happened when stationary as well as pulling up to a junction and traffic lights. 

1st log is start up. 2nd log of me taking it up the road.

 

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A couple of changes I would suggest, in Idle Speed Control Setup, reduce the speed lockout to 6kmh. In Idle Actuator settings, try increasing the min clamp to about 30%.  Those should hopefully reduce the dip when coming to a stop with the clutch out.

The dip at 0:06 seconds is not clear what caused it but possibly dash pot settings as it was after you blipped the throttle a few times. 

Then there are a few near stalls in the log such as at 0:44.5secs where there is really no explanation but the ecu was already doing about as much as it can do, the ecu has the ign advance pegged at max, the idle valve is open more than normal and quickly being opened more, but still RPM is low.  You can see the MAP is increased so extra load is coming from somewhere there are no fans or AC active - this looks more like the driver dragging the clutch or something.  Possibly a fuel related issue but there is no wideband so we cant say.  

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I can manually adjust the idle control valve to be closed off more and then see if that helps? As its sitting about in the middle of the adjustment slots on the valve body.

 

Also just noticed my map calibration is set to subaru v7-8 instead of subaru v1-6. would changing this help at all?

PC Datalog - 2023-02-9 6;15;01 pm.llgx

PC Datalog - 2023-02-9 6;19;58 pm.llgx

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1 hour ago, IncepTioN said:

I can manually adjust the idle control valve to be closed off more and then see if that helps?

No, it wont make any difference.  You you still have undershoot entering idle then you will have to experiment with the dashpot settings. 

 

1 hour ago, IncepTioN said:

Also just noticed my map calibration is set to subaru v7-8 instead of subaru v1-6. would changing this help at all?

If MAP reads the same as BAP when the engine isnt running then you have the correct calibration.    

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