[Odan.be]

Hey,

I hope you guys have some insights in this matter, because i really, really can't wrap my head around it.

I regulary do some logging.
A week ago i noticed some weird "lag"

Everytime i mashed the throttle , there is a really small delay.
So i went to the logs, So i thought there was a boost leak. But boost building is working as intended. WG functionality is normal, and i am hitting peak boost everytime.
Then i started to look at the acceleration pedal/throttle body behaviour.
Everything seems normal, Throttle body is a bit behind accel pedal maybe , but nothing to weird.

Then i noticed that when I go WOT , the moment there is no boost building, there is actually no RPM increase either... Obviously no rpm increase... no boost... thus "lag"
But the strange thing is, at that time throttle body is wide open @ 80%.

Does someone have some experience or thought about this ?

This is a Log where you can see the flatline at the start of WOT:

http://datazap.me/u/odanbe/mhd-stage...&solo=4&mark=9

And this is zoomed in on that specific part...:

http://datazap.me/u/odanbe/mhd-stage...om=4-14&mark=9

[SM335i]

I have similar symptoms, when I mash the pedal it feels like there is hesitation, I thought it was misfire, but coils/plugs/injectors are behaving normal.

[TBN54]

Could possibily be carbon build-up. Walnut blast may be needed.

[xcusem3]

I have similar symptoms as well, replaced coils, injectors, plugs a few months ago. Boost builds to peak, WG cycle is normal.. I know I need a walnut blast done but that doesn't seem like it would affect the car this drastically. It's like no boost, no boost then bam! the car rockets off. The cobb shows full boost the entire time but never over boosts.

[mike@x-ph.com]

+1 for walnut blast

[Odan.be]

Ok,

then i might just shedule a walnutshell blast...

How come clogged / dirty inlet ports will cause this ?


Had an accident this week, so I might as well do everything together

[Flex68]

Originally Posted by Odan.be

Ok,

then i might just shedule a walnutshell blast...

How come clogged / dirty inlet ports will cause this ?


Had an accident this week, so I might as well do everything together

Is your car on YouTube that has the akrop exhaust that sounds insane ?

[dawhiz]

I've been getting weird throttle behavior as well. Enough so that I think it's either the adaptations from driving too slow and throwing off calculated values?? or my throttle position sensor is going bad. It is hit or miss each day as to which way it behaves but essentially some days it's fine and other days it rockets off to exactly the same rpm through gear shifts. In a weird way.

[Gohan335i7]

Carbon Blast for sure !! Go from there!

[SM335i]

not to threadjack, but after I ran DP Fix for a while this started happening to me. Can it be fuel trims?

[Odan.be]

Originally Posted by Flex68

Is your car on YouTube that has the akrop exhaust that sounds insane ?

nope, not mine.
I have catless downpipes on a stock exhaust system

[Velocity26]

Just a random comment, are you making sure to turn traction control all the way off before logging? If you have not, the ECU will chop the throttle when it detects wheel spin and cause exactly what we are seeing in your logs.

The only other thing that I see is that your fuel trims indicate that you are running very rich and are doing their best to lean out the car. I can see where your A/F ratio was in the 11's & 12's.

[SM335i]

Originally Posted by Velocity26

Just a random comment, are you making sure to turn traction control all the way off before logging? If you have not, the ECU will chop the throttle when it detects wheel spin and cause exactly what we are seeing in your logs.

The only other thing that I see is that your fuel trims indicate that you are running very rich and are doing their best to lean out the car. I can see where your A/F ratio was in the 11's & 12's.

what causes the car to run very rich? Bad Coils or injectors?

[Odan.be]

Originally Posted by Velocity26

Just a random comment, are you making sure to turn traction control all the way off before logging? If you have not, the ECU will chop the throttle when it detects wheel spin and cause exactly what we are seeing in your logs.

The only other thing that I see is that your fuel trims indicate that you are running very rich and are doing their best to lean out the car. I can see where your A/F ratio was in the 11's & 12's.

Traction control is totally off,

Don't know what you are talking about AFR wise.
But AFR is fine to me Starts at normal 14 ish at low revs and then more rich near top end...
to more lean you run near the top end , the higher your temps get in the manifold/turbo's...

[Velocity26]

Take a look at your short term fuel trims, the ECU is pulling a lot of fuel out of the mix, I can see -19% near the end of the boost runs.

Then look at the A/F ratio under boost and you will see where it is consistently in the 11's.

I cannot see what is causing the throttle closures, but the rich mixture is the result. The throttle is closing and restricting the air flow into the engine while the injectors are adding fuel for a larger amount of air. The resulting mix is rich and the ECU pulls fuel to lean it back out.

Log more parameters and see if you can find the reason for the throttle closures.

[Odan.be]

Originally Posted by Velocity26

Take a look at your short term fuel trims, the ECU is pulling a lot of fuel out of the mix, I can see -19% near the end of the boost runs.

Then look at the A/F ratio under boost and you will see where it is consistently in the 11's.

I cannot see what is causing the throttle closures, but the rich mixture is the result. The throttle is closing and restricting the air flow into the engine while the injectors are adding fuel for a larger amount of air. The resulting mix is rich and the ECU pulls fuel to lean it back out.

Log more parameters and see if you can find the reason for the throttle closures.

I think the large throttle closure is due to boost overshoot,
trying to solve that with making the throttle plate less sensitive, because it was set really sensitive.
it is only Stft 1 that is so high , i presume that is bank 1 ?

maybe it is carbon build up, not allowing the valve so seal correctly ?

what could be a possible other cause ?

[Velocity26]

Both of your STFT go negative at the same time.

[Two Snails]

I had this issue before I flashed my car. It seemed like throttle input lag where when I would drive around normal with it, the car would get use to it. Then when I go WOT it would take a moment to realize I wanted to go.