Idle issues on Evo IV, hardware or software?

[JB9]

Hi all. I just bought an Evo IV GSR -97 with G4+ Plugin in it. The car is supposed to be properly dyno tuned, and it drives fine, but I'm not sure the tuner has set up the idle correctly, or if I might have a hardware issue.

Idle is fluctuating +-150rpm, and I've tried pretty  much everything with the idle control settings in the ECU now. I can't get it to a point where it's stable, not even in open loop mode.

At first, I couldn't get it to go below 980rpm or so at all, so that's when I learned about the base idle screw in the throttle body, and from Mitsubishi/DSM forums it seems like the guys with oem ecu does some kind of base setting of the screw with the ecu idle control disabled, but I can't find a way to disable it in pclink, so I tried disconnecting the connector on the throttle body instead... But even then, I can't really get to a stable idle by adjusting the "BISS" screw. Could this be because the fuel map is badly tuned at idle? Or is it definitely a hardware issue with the throttle body/stepper motor thingy?

How do you guys have the Evo 4-6 idle set up?

EDIT: I should probably add that I have a spare Evo IV throttle body laying around I could try with (took a better condition BISS screw from it already), but I'd like to avoid and find out it if it's a tuning issue first.

Thanks.

[cj]

can you post you map & a log file of it trying to idle? If you disconnected the idle control valve and its still fluctuating there are still half a dozen things in the config that could be causing it do this. 

[Monsterbishi]

Put me down for one vote towards bad idle stepper controller and base idle set screw incorrectly set.

[JB9]

On 8/25/2019 at 7:32 AM, cj said:

can you post you map & a log file of it trying to idle? If you disconnected the idle control valve and its still fluctuating there are still half a dozen things in the config that could be causing it do this. 

Sorry for the late reply, haven't had time to work on the car.. Here's the map and 3 logs. The rpm gap varies between the logs, that's because I'm trying different BISS screw settings from time to time.

Idle is somewhat stable if I open up the screw so much that it idles above 1350rpm. If I set it so it idles around 950, it's fluctuating at first but stabilizes somewhat after a while. If I go lower, it fluctuates all the time.

 

Car is an Evo IV with a Evo VI engine, E85, bigger injectors, fuel pump, 2,75" exhaust, better elbow, better intercooler, ARP rod bolts, etc. The usual.

 

JB9.pclr Log 2019-08-30 8;06;19 pm.llg Log 2019-08-30 8;12;45 pm.llg Log 2019-08-30 8;24;12 pm.llg

[cj]

what injectors do you have and can you get short pulse adder data for them? You are running ~0.7ms @ idle which is probably in the non linear range for the injector and so the ~0.1ms change in fuel the ecu is requesting may be 20 or 30% difference in actual fuel injected. ignition angle, stepper motor dont change at all so its not the ECU changing them badly. VVT is not set up, and especially on the run where you have the idle screw set at ~1krpm, the fuelling is the only thing changing with rpm. you might be able to tweak the fuel table up or down a tiny bit in the cells its bouncing between at idle, but better injector data is probably the long term fix.

[JB9]

Sorry, could have mentioned that earlier. They are Bosch 2200cc/min @ 3bar, 0280158821.

This is the info I keep finding everywhere for them:

 

Coil Resistance: 9.1 Ohms 
Dead Time: 0.45ms at 14 volts
Static Flow Rate @ 43.5 PSI ( 300kPa ) w/Gas: 2200 cc/min = 210 lb/hr
Static Flow Rate @ 58 PSI ( 400kPa ) w/Gas: 2550 cc/min = 240 lb/hr
Static Flow Rate @ 78.5 PSI ( 500kPa ) w/Gas: 2865 cc/min = 273 lb/hr
Static Flow Rate @ 88 PSI ( 600kPa ) w/Gas: 3155 cc/min = 300 lb/hr
Static Flow Rate @ 101.5PSI ( 700kPa ) w/Gas: 3350 cc/min = 320 lb/hr
Connector: Denso / Sumitomo
Injector Length: O-Ring to O-Ring: 1.5. / 37.5 mm
Injector Body Diameter: 16mm
O-Ring: 14.5mm Viton
Acceptable Fuels: Gas/Petrol, alcohol/methanol, E85, CNG

 

Looking at that -- Would you say the tuner has set it up wrong? Or perhaps a "normal" idle is too much to hope for with those? I've never had a car with anything "bigger" than 875cc before so I wouldn't really know.

 

EDIT:

Found this info on one site as well:

Bosch 2200cc 0280158821

43psi / 58psi / 70psi / 80psi

8 V 1.45 / 1.67 / 1.82 / 1.96

10 V .95 / 1.10 / 1.17 / 1.27

12 V .68 / .78 / .84 / .93

14 V .47 / .57 / .64 / .70

16 V .36 / .46 / .49 / .52

Static Flow Rate: 2200cc @ 43.5psi / 3bar

Static Flow Rate: 2550cc @ 58psi / 4bar

 

Car runs the stock Denso 3260 FPR which is set to 3bar/43psi AFAIK.

[cj]

those dead times are very close to what's in your tune already. I dont think dead times are the problem. 

At the lower end of the static flow rate slope, injectors start to flow non-linearly. Some manufacturers put out short pulse adder tables to allow compensation for this, but I cant find one for those injectors online. You could try emailing bosh directly? A 2200cc injector at idle will almost certainly be running in the non linear range.

Or you could try very gently adjusting the couple of cells it is moving between at idle until you get it pretty close. 

[JB9]

Thanks CJ. I adjusted the dead times to what that table says, and it made a small difference.

After that, I copied the settings from the Injector Dynamics ID2000, which is their 2200cc injector. I figured the characteristics should at least be similar. This helped a lot, so fueling definitely seems to be the culprit here. It's not 100% ok yet though, but I now have a somewhat stable idle at 980-1020rpm. I'll do some more fiddling to see how close to the stock 750rpm I can get.