very lean AFR @ +/-3000-3500 rpm [SOLVED]

[RJBijsterbosch]

Thanks for the advise Matt

[Torque]

Since you said that the car was fine before the injector change / tune would you mind posting the .bin that was in place before the tune?

[RJBijsterbosch]

I don't have this file because I bought nistune when the problems occured. Maybe my tuner has this file.

[RJBijsterbosch]

Trying to get extra fuel in the engine but nothing seems to help.

What if there is something wrong with the ignition @ the specific piont @ 3200 rpm? What AFR would you see when there is a missfire. I'm assuming a lean AFR because the oxigen inside the cilinder is not used for combustion.

[Eric]

Hello Robbert, have you tried bypassing/removing the BOV yet ? (like I suggested some time ago, when you came to me for advise)
..I think you're forgetting to mention the lean condition is usually accompanied with a hissing/surging sound.

I am not sure if we already tried this, but another thing you can test/try is disconnect the (standard) O2 sensor and go for a drive to see how it behaves without the sensor connected.
(you can also contact/call me, if you want to do some more investigation into this problem.)

-Eric (DTA Motorsport)

[Matt]

What if there is something wrong with the ignition @ the specific piont @ 3200 rpm? What AFR would you see when there is a missfire

Likely a short period of time you may get a lean spot but more obviously a cut in RPM

[RJBijsterbosch]

Hello Robbert, have you tried bypassing/removing the BOV yet ? (like I suggested some time ago, when you came to me for advise)
..I think you're forgetting to mention the lean condition is usually accompanied with a hissing/surging sound.
i did not remove the BOV yet, i need to find a way to block the outlet @ the BOV of the intercooler piping. The hissing/surging sound is something i don't hear. I only opened the BOV to look for any damage, no damage found. With the smoke test the BOV was airtight.

I am not sure if we already tried this, but another thing you can test/try is disconnect the (standard) O2 sensor and go for a drive to see how it behaves without the sensor connected.
I have adjusted O2 sensing to 205 C in Nistune. This should do. Or am i wrong?

(you can also contact/call me, if you want to do some more investigation into this problem.)
Thanks, i know you are willing to help.

-Eric (DTA Motorsport)

[RJBijsterbosch]

Tested the car with removing the BOV. By placing a valve (rubber ball) on top of the BOV flange. At first it seemed to work but the problem is still there.

It looks like i''m running out off options, of what the problem is.

[Torque]

????
Can we have some more detail please?

[RJBijsterbosch]

????
Can we have some more detail please?

I''ve tested the car again today and the problem still occurs.

[Torque]

Sorry to hear that ....

[RJBijsterbosch]

I''m going to focus on the injectors right now.

Measured the resistance on the injectors and injector wiring loom.
Inj 1 coil: 12.1 Ohm
Inj 2 coil: 12,0 Ohm
Inj 3 Coil: 12,2 Ohm
Inj 4 Coil: 11,9 Ohm
Inj 5 Coil: 11,9 Ohm
Inj 6 Coil: 11,9 Ohm

Looks Ok?!

Injector Wiring loom is ok. All wires have a resistance of 0,2 or 0,3 Ohm. Wires are not damaged.

I will inspect the injectors them selves as well.

Because the problem is rpm related, can it be that there is some kind of electrical interference by maybe the alternator or something?

[Matt]

Injector resistances look fine

I wrote:

That seems a big drop in your AFRs for only 0.1V of extra airflow (noted injection time is only slightly lower). If you increase fueling at this point to get around 3.21 -3.30ms injection time, what are AFRs then.

You replied 3rd sep:

Trying to get extra fuel in the engine but nothing seems to help.

Can you provide the updated tune file (and matching log) with the extra fuel added to fuel map to get around 3.3ms injection time (and also note the AFRs) here.

I want to see how much extra fuel you needed to add to get 3.3ms and if the AFRs stayed consistent here. If the AFRs were still lean but the injection time is still solid at 3000-3500rpm compared to before/after this vehicle - it is no longer an ECU tuning related problem

[RJBijsterbosch]

Fucking hell guys, i finally have the "bull by the horns" in dutch "de koe bij de horens". It's a dutch saying when you pin point a problem.
The problem is caused by my own fucking mistake.

I was focussing on the fuelside of the engine. Because a vacuum leakage wasn't found.

I pulled out the injectors to inspect them. Injecters were clean and the filters in the injectors were also clean, so i assumed the injectors are ok.
Fuelpump is brand new. So what couldt be more?

Eric mentioned the sissing/hissing sound. This sound was coming out of FPR and i also mentioned this @ my first tuner who had done the first mapping after the rebuild, but he said this was no problem. Why doubt a expert? So i didn't spend much attention to this sissing/hissing sound.

I went thinking about this sissing sound out of the FPR. It apeared to me that it had something to do with a inconsistend fuel flow/pressure. I am a service engineer of high pressure centrifugal/plunger pumps/compressors in the oil and gas industry (Lewa & Sundyne) and we often use a pulsation damper to decrease flow/pressure spikes. Then i looked @ the r33 sevice manual to find some information to figure out a way to check if there is something wrong with the fuelside of the engine causing inconsistend fuel flow/pressure. When i was looking @ the picture of the fuelrail/injectors i saw that there is already a fuel dampener in the return fuel line.

Then i gave myself a slap in the face. I didn't mount this fuel dampener after the intake conversion. I had thrown a lot of old fuel/intake hoses into a box because i didn't need them anymore. I also had thrown the fueldampener in this box, for a unknown reason. (brain fart ) so i missed that when when installing everything back.

Mounted the fueldampener today and the problem is gone. I'm so fucking happy that i found the problem, because i was running out of options to solve the problem.

I tested the car without the bov (was still off), just to be sure that the dampener did the trick. Tomorrow i will put back the bov.

I made a log, so that you can see that the problem is gone. The engine is running much smoother now. I haven't done WOT because the bov was of.

I will try this tomorrow, when the bov is on.

i want to thank Matt, Torque, Eric for looking into my problem that i caused myself. My apology.

Now i can focus on learning to tune and understanding Nistune and ask a lot of other stupid questions.

[Torque]

Good news, and thank you for the 'report'
That was a well obscured issue ... who would have thought of the harmonic damper?
Interesting when you think about it, possibly a resonance causing a pressure wave and unstable rail pressure ..

Well, have fun enjoying your car