AFR Fluctuations with turbo kit

[yo.dur]

The problem is that im getting AFR fluctuations on a steady throttle, i even used cruise control to keep the throttle as uniform as possible but am still getting AFR fluctuations. These fluctuations in the AFR seemed to be caused by inconsistent MAF voltage readings. Heres a screenshot of what the tuner sent. The top log is my car and the bottom log is a stage 2 NA car used for a reference. You can see how much more linear the bottom log is in respect to the AFR and MAF voltage.


The tune is by speedfactory ft86, currently set for stock injectors, gt2871r, 270lph fuel pump, 91 oct, 3 bar map sensor for the full blown kit.

So far i have swapped the front o2 sensor, swapped the MAF sensor, cleaned MAF the connector, and checked the wires for physical damage to see if the sources of the problem.

Any suggestions on what could be causing this?

[slowest86]

Boost leak?

[Spartarus]

Well, if I had to hazard a guess, I'd like to see a photo inside and outside your MAF housing where it's welded to the charge piping.

Could be turbulence across the MAF, but I don't know what kit you're using or if it's a custom job.

Granted, I'm guessing at the MAF but it could be o2 sensor related. Who came first? Chicken or the egg. Either way it's hunting for equilibrium. It would really help to disable closed loop in ecutek and see a new data log.

Closed loop f*cks with proper diagnosis, and that would rule in / rule out the o2 sensor.

I doubt boost leak as you aren't in boost on that log. If it was a vacuum leak, you would have a ridiculous LTFT but it would / should stabilize.

[yo.dur]

Originally Posted by Spartarus

Well, if I had to hazard a guess, I'd like to see a photo inside and outside your MAF housing where it's welded to the charge piping.

Could be turbulence across the MAF, but I don't know what kit you're using or if it's a custom job.

Granted, I'm guessing at the MAF but it could be o2 sensor related. Who came first? Chicken or the egg. Either way it's hunting for equilibrium. It would really help to disable closed loop in ecutek and see a new data log.

Closed loop f*cks with proper diagnosis, and that would rule in / rule out the o2 sensor.

I doubt boost leak as you aren't in boost on that log. If it was a vacuum leak, you would have a ridiculous LTFT but it would / should stabilize.

The turbo kit im using is full blowns. I inspected the charge piping before the install and everything checked out. I also did a boost leak test of the charge piping already and it all checked out, no leaks. Yeah the tuner and i were also thinking turbulence across the MAF. But he's tuned that MAF location several times before. There might be turbulence coming from the BOV though

Ive already replaced the front o2 sensor with a new one about a week ago, i also had an extra MAF sensor sitting around so i swapped that on as well. I was hoping those would solve it but to no avail. It might be some kind of electrical interference but thats a little beyond me.

[Spartarus]

Originally Posted by yo.dur

The turbo kit im using is full blowns. I inspected the charge piping before the install and everything checked out. I also did a boost leak test of the charge piping already and it all checked out, no leaks. Yeah the tuner and i were also thinking turbulence across the MAF. But he's tuned that MAF location several times before. There might be turbulence coming from the BOV though

Ive already replaced the front o2 sensor with a new one about a week ago, i also had an extra MAF sensor sitting around so i swapped that on as well. I was hoping those would solve it but to no avail. It might be some kind of electrical interference but thats a little beyond me.

I would still try the same partial throttle data logging with closed loop feedback turned off. That will at least give a final determination on whether it is the MAF or the o2

[yo.dur]

alright sure ill try that later on tonight. Ive got a general driving log here as well using cruise control at 40mph. http://datazap.me/u/rasta42/log-1449...&zoom=694-1663 not sure if the graph will provide anymore insight into the problem but it does show fuel trims that are greater than 10%.

[King Tut]

Does your BOV stay closed at idle?

[yo.dur]

ill check that out right now. I have a boost gauge mounted which shows -17inHG give or take 1 at idle.

[King Tut]

Originally Posted by yo.dur

ill check that out right now. I have a boost gauge mounted which shows -17inHG give or take 1 at idle.

That is a little low. Perhaps you have a vacuum leak as well.

[yo.dur]

Originally Posted by King Tut

That is a little low. Perhaps you have a vacuum leak as well.

Actually its holding -22inHG at idle, remembered it wrong.

[yo.dur]

here are some logs i did this morning on speedfactory's tune. Car drives very smoothly, no noticeable bucks or hesitation. Just this AFR issue.

Cruise Control
http://datazap.me/u/rasta42/ft86crui...og=0&data=6-30

Idle at Operating temp
http://datazap.me/u/rasta42/ft86idle?log=0&data=6-30

Here are some logs on Delicious flash and go tune (speed density)
Idle:
http://datazap.me/u/rasta42/idledel2?log=0&data

Cruise control
http://datazap.me/u/rasta42/cclogdel...&zoom=673-1136

[mato2sk]

I have an AFR fluctuation problem.
In open loop mode, AFR Error max + -1.5%.
But in closed loop mode, there are AFR fluctuations.
During idle speed, even at steady speed with cruise control.
I have my custom job turbo kit with the EFR 7163 Twin Scroll. 9PSI

Bosch MAP sensor 0281002437
AEM 340 Fuel Pump
OEM Injector.
I was looking for leaking of intake pipe, but I found nothing.
Photos of turbo kit design

[Kodename47]

Originally Posted by mato2sk

But in closed loop mode, there are AFR fluctuations.

How much/badly are they fluctuating? Some fluctuations in closed loop are to be expected.

[mato2sk]

Originally Posted by Kodename47

How much/badly are they fluctuating? Some fluctuations in closed loop are to be expected.

I added the log file.
https://datazap.me/u/mato2sk/log-154...a=4-5-11-14-15