RB20DET with Link G4+ Idling Issues

[Cormac]

Hi All, 

I currently own an R32 Skyline with RB20DET engine and a Link G4+ ECU. The car intermittently has problems idling and sometimes will cut out. 

Firstly, apologies if any of my questions seem basic. I am new to the world of aftermarket ECUs so my knowledge is limited. 

The car sometimes has an erratic idle, when hot or cold. It will fall to almost 0 rpm before rising back up to  ~1200 rpm before falling back down to idle, or sometimes cutting out. 

The issue is more apparent when coming to a stop and pressing the clutch. It also seems to happen more frequently when turning the steering wheel and coming to a stop, or when using the rear window demister and A/C. I believe this is due to these systems requiring more engine power to run, and the idle suffers as a result. 

A search on google suggests that the Idle Air Control Valve gets gummed up on these engine, and requires a clean out, and then a reset of the idle. I did this yesterday and installed with a brand new gasket. However it did not make a difference. What was even more unusual is that the position of the adjustment screw on the IACV doesn't make any difference to idle speed at all. 

So my questions is this - is the IACV used by the G4+ ECU to control the idle? Or is another method used altogether?

I'd appreciate any suggestions on this issue! 

Cheers

[Adamw]

Assuming it is a skyline plug-in ECU then yes the IACV is used, often idle ignition is used also to stabalise idle.  For help you really need to do a PC log of a drive and attach the log and your tune here.

[Cormac]

Hi, apologies for the delayed response. It took some time to get a tuning cable and go for a test drive. 

Unfortunately I couldn't recreate the issue on the test drive, due it being intermittent. However I did manage to sort of re-create the issue by turning on and off the headlights when idling. 

I am attaching three log files.

1) Test drive log.

2) Base map from my ECU.

3) Shorter log of turning on and off headlights.

There also seems to be one fault code logged on my ECU - "ECU Fault Code 46: An Temp 2 above Error High value".

Thanks for the help!

R32 Test Drive Log File.llg r32 base map.pclr R32 Log turning headlights on and off.llg

[Adamw]

I have made some small changes to idle control in the attached map if you want to try it.  However, I'm suspicious a lot of your problem maybe related to injectors or fuel.  In the "headlight test" the idle valve position is stable, the ignition timing is stable and the fuel table number is stable, yet RPM is bouncing around a lot.  You dont have a lambda connected so we dont have any feedback on the fuel side, but since you only have 1.5ms pulswitdh at idle I suspect your injectors maybe a bit erratic at that pulsewidth.  You may see an improvement by richening up the idle region a little.

r32basemap idle tweaks.pclr

[Cormac]

Hi Adam, 

Thanks a lot. I will download this base map and try it when I next get a chance. 

Just a couple of questions,

1) I noticed that there doesn't seem to be a lambda sensor anywhere in my exhaust system and you noted that there is none connected. Is it ok to run the engine without one? I was surprised myself when I couldn't find it. 

2) I understand the pulsewidth of the injector refers to how long it stays open. Could I try increasing this?

3) When you say problems with injectors or fuel, could that be an issue with the physical components themselves or just the tune?

Thanks again.

 

[Adamw]

15 hours ago, Cormac said:

1) I noticed that there doesn't seem to be a lambda sensor anywhere in my exhaust system and you noted that there is none connected. Is it ok to run the engine without one? I was surprised myself when I couldn't find it. 

Obviously you need a lambda probe for tuning but if you arent doing the tuning then you dont specifically need one (nice to have tho).

 

15 hours ago, Cormac said:

I understand the pulsewidth of the injector refers to how long it stays open. Could I try increasing this?

You would really want a tuner to do this.  It may be as simple as a small adjustment to the idle cells and just running it with a richer idle.  Or if it is already rich at idle then it may be as complicated as lowering the fuel pressure so the inj PW can then be increased without making it even richer.  The whole fuel table would then likely need to be checked/tweaked.

 

16 hours ago, Cormac said:

When you say problems with injectors or fuel, could that be an issue with the physical components themselves or just the tune?

That is really just my hunch as most other parameters that affect idle are quite stable in your log and since we dont have anyway to view fuel mixture (no lambda) that would be high up my list of possibilites.  It may not be a fuel related problem but that looks most likely to me.  If the PW is so low at idle that you are operating in the non-linear region of the injector that usually means either your injectors are just shit, or they are too large for the engine size/fuel type/power goals.

[Cormac]

7 hours ago, Adamw said:

That is really just my hunch as most other parameters that affect idle are quite stable in your log and since we dont have anyway to view fuel mixture (no lambda) that would be high up my list of possibilites.  It may not be a fuel related problem but that looks most likely to me.  If the PW is so low at idle that you are operating in the non-linear region of the injector that usually means either your injectors are just shit, or they are too large for the engine size/fuel type/power goals.

Thanks. I'll avoid tweaking the injector PW at idle myself since. I understand it would be safer to let a tuner do this with feedback on the mixture/lambda. 

I'll give you some further information on the setup just in case it gives you any idea as to a potential problem on the fuel side of things. 

The car was initially tuned with this setup in March 2017 and hasn't been altered since (previous owner). 

The car made 330 HP (282 HP at the wheels) at ~15.6 psi. The injectors are 560cc with an R32 GT-R fuel pump. It has a stock Fuel Pressure Regulator. 

The car was mapped and is run on 95 RON fuel which is the only widely available fuel here.

The injectors were flow tested and cleaned before being installed in the car before tuning. 

I haven't noticed any issues with how the car runs otherwise, no breaking up / misfire under load or full boost etc. I don't have any current plans to make any changes to the power level, just trying to sort out the annoying Idle issue 

[Adamw]

16 hours ago, Cormac said:

The injectors are 560cc

When you had them flow tested did they report back the actual flow numbers?  From the settings in your tune and the logged pulse width I get the feeling they may flow more like 800cc...  

[Cormac]

7 hours ago, Adamw said:

When you had them flow tested did they report back the actual flow numbers?  From the settings in your tune and the logged pulse width I get the feeling they may flow more like 800cc...  

It was the previous owner that had them flow tested. So I only have a receipt that says they were flow tested and cleaned. No figures on the flow numbers. 

I can take a closer look at the injectors later this evening and see if I can get any information on them. All I have to go off at the moment is a spec sheet that says they are 560cc. 

I guess if they are really 800cc, that would explain why the pulse width is so low. Injectors might be just too big for my setup?

[Cormac]

Just reporting back to close this out. I eventually went back to the original tuner to get the idling problem checked out.

It turns out that it was running too lean on idle. All the other components checked out (IACV etc), so he added more fuel to the idle region as you suggested Adam. Also he changed the behaviour when pushing in the clutch and coming to a stop. The revs now stay at 1200 rpm for a few seconds before stabilising around 950 rpm. This has stopped the cutting out issue when stopping. The idle is also much more stable in general. 

Thanks for the help along the way