Overboost problem

[AUDIS$]

Had my motor out and replaced the turbos with F21's, running AWE stage 3 tune with green top injectors. Hitachi MAF. Car runs well but seems to be overboosting. Even if i change to stock mode. Things i have done to troubleshoot this problem-

1) Checked wastegate lines, used bike pump to apply pressure. made sure the rods were both moving.
2) Unhooked the N75 valve Saw boost pressure max out at 10-12psi
3) Replaced with new N75 valve.
4) Tried Changing both ECU tunes Stock/pump still boosting well past 25PSI

I have not done a pressure test, at this point that will be next. anything i am overlooking?

Here is a log of blocks 114/115/003 I am new to logging so some of this is foreign to me.

https://docs.google.com/spreadsheets...it?usp=sharing

[CELison]

You aren’t tuned for the cracking pressure your F21s are set at.

[AUDIS$]

You aren’t tuned for the cracking pressure your F21s are set at.

really, so its a matter of getting a tune specific for the F21's? or do you mean physically adjusting the wastegates? Also i would think in stock mode the ecu would tell the n75 the wastegates need to open?

[m_haiser]

Had the same thing happen. F21 wastegates are usually set at 14psi. You can tune to compensate or adjust wastegates. Given your smallish injectors I would advise adjusting the gates.

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[AUDIS$]

Had the same thing happen. F21 wastegates are usually set at 14psi. You can tune to compensate or adjust wastegates. Given your smallish injectors I would advise adjusting the gates.

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Thats what i dont get, if the cracking pressure is at 14psi why am i able to boost past that point with the N75 plugged in. isnt the tune or for that matter the stock ecu saying "there is 14psi of boost time to open up the wastegate"

[m_haiser]

Not quite. It goes by n75 duty cycle. Say on a stock engine it takes 80% duty cycle to make 10psi well because your car THINKS it's got stock wastegates its going to use that same 80% which would make you boost closer to 20 or 25. You car doesn't use the n75 as an on off switch but rather modulates it for a smoother power delivery

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[AUDIS$]

Not quite. It goes by n75 duty cycle. Say on a stock engine it takes 80% duty cycle to make 10psi well because your car THINKS it's got stock wastegates its going to use that same 80% which would make you boost closer to 20 or 25. You car doesn't use the n75 as an on off switch but rather modulates it for a smoother power delivery

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ok, That makes sense now. thank you!

[AudiSportB5S4]

What turbos did you have before? RS4-K04s? Why the change?

[AUDIS$]

What turbos did you have before? RS4-K04s? Why the change?

K03's before.

[AudiSportB5S4]

K03's before.

Oh okay.. So you swapped in F21s during the engine pull and bought an AWE fueling kit to go along with it? Just FYI, you are leaving power on the table.

[AUDIS$]

Oh okay.. So you swapped in F21s during the engine pull and bought an AWE fueling kit to go along with it? Just FYI, you are leaving power on the table.

so i have heard, :( im contemplating selling the ecu and injectors and going with a tune from blake and 52# injectors. Thoughts?

[AudiSportB5S4]

so i have heard, :( im contemplating selling the ecu and injectors and going with a tune from blake and 52# injectors. Thoughts?

Definitely the right decision to sell what you have and go the custom tune route.. Once you start changing up the hardware outside of what AWE designed their kit for, or any kit for that matter, you're going to be losing power from the adjustments that the ECU will be making to try and keep things kosher so the car at least runs. The ECU will do a pretty good job of keeping things in a state so that you can drive the car, but when it comes down to WOT you really need the hardware the tune was designed around. Even though F21s are pretty similar to K04s, they're different enough that as already mentioned N75 duty cycle will be most likely requesting too much boost from those turbos, the fueling won't be right, etc. If you've already invested (VERY loosely speaking ) in swapping the turbos, do yourself a favor and get a good tune on it.

[erykv1]

@Corradovolksb can also hook you up with what you need

we are so far along with these cars and the ME7 ecu there is no point in running an off the shelf tune anymore

[m_haiser]

@Corradovolksb can also hook you up with what you need

we are so far along with these cars and the ME7 ecu there is no point in running an off the shelf tune anymore

Agreed. Get a wideband and get the power you paid for with those f21s. Mine was base tuned by Daz back in the day and was a pretty serious machine for only being stage 3-

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[apaluilis]

Agreed. Get a wideband and get the power you paid for with those f21s. Mine was base tuned by Daz back in the day and was a pretty serious machine for only being stage 3-

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Thanks guys! I think that is the route im gonna go.

Hopefully get it running well soon. A couple pics. Have a few things still left to install


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[zachattacker]

What bi-pipes are those?


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[Silverex]

Stock with some CF wrap?

[chris86vw]

Apr logo on the passenger side pipe

[AUDIS$]

What bi-pipes are those?


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APR Bipipe Carbon dipped.

[AUDIS$]

Got the wheels on, lowered..need a clean filler plate..52# injectors and 3bar MAP should be here tomorrow.

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