9N3 Polo GTi boost issue

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madhoshival
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Car Model: 9N3 GTi

9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 12:12 pm

Hey guys, hope you all well.

Have a very strange issue with my 9n polo gti. So I recently bought a complete turbo kit from a fellow member, which consisted of a t28 turbo (internally gated), manifold and adapter, turbo inlet pipe and downpipe. All the parts were in excellent condition and it worked perfectly in his car. Installed the turbo setup in my car and there arised my weird issue, the turbo will only start spooling at around 4500rpm (3rd gear) and reach its max boost of a measly 0.8 bar at 5500rpm which it will hold till redline. This is with the wastegate nipple disconnected (with it connected it's the exact same thing).

Now I really have tried everything to troubleshoot,
•Checked for boost leaks, none whatsoever. (At idle the car also sits perfectly at vacuum of -0.6.
•Checked cam timing.
•Checked for restrictions on the inlet side, charge side as well as the exhaust.
•Swopped out the turbo with another one and the boost curve is EXACTLY the same, so it's not the turbo.
•Removed the exhaust manifold and adapter to check for any warps, also remachined the adapter but it was exactly the same.
•Tighted the wastegate and also added a spring to the actuator, boost was still the same.
•Changed the tune on the car, also exactly the same.

The car was logged in detail and the map is requesting the correct boost level as well as N75/Wastegate duty cycle, the throttle body is fully open, fuelling and ignition timing are correct, but it is still extremely laggy and does not meet requested boost. So I'm now really out of ideas.

Any help would be greatly appreciated.


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Last edited by madhoshival on Mon Nov 27, 2017 12:12 pm, edited 1 time in total.

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Carel040
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Re: 9N3 Polo GTi boost issue

Postby Carel040 » Mon Nov 27, 2017 1:09 pm

Check n75 valve plumbing configuration could have swapped tubes

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madhoshival
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Re: 9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 1:21 pm

Carel040 wrote:Check n75 valve plumbing configuration could have swapped tubes

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Thanks for the reply, N75 is connected correct. I also left it plugged in and ran it with the vacuum going to wastegate opened which should make the car boost to infinity, but the boost never changed.


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Carel040
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Re: 9N3 Polo GTi boost issue

Postby Carel040 » Mon Nov 27, 2017 1:23 pm

If I may ask did u scan with VCDS yet

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Dhir-DKR
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Re: 9N3 Polo GTi boost issue

Postby Dhir-DKR » Mon Nov 27, 2017 1:37 pm

Bro, did you check the fuses?

I had an issue where my car would only hit 0.3 Bar boost, nothing more. Traced it down to a blown fuse, changed it and voila, boosting again.

It's these small push-in fuses.
2007 VW Polo GTi - current
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madhoshival
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Re: 9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 1:56 pm

Carel040 wrote:If I may ask did u scan with VCDS yet

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Scanned and no errors.


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madhoshival
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Re: 9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 1:57 pm

Dhir-DKR wrote:Bro, did you check the fuses?

I had an issue where my car would only hit 0.3 Bar boost, nothing more. Traced it down to a blown fuse, changed it and voila, boosting again.

It's these small push-in fuses.


Nope, not getting any limp mode bro. Throttle is opened 100% and getting 100% wastegate duty cycle.


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Carel040
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Re: 9N3 Polo GTi boost issue

Postby Carel040 » Mon Nov 27, 2017 6:51 pm

Did u find the fault yet

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DCmk3
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Re: 9N3 Polo GTi boost issue

Postby DCmk3 » Mon Nov 27, 2017 7:35 pm

Have you done a compression test on the car?
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madhoshival
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Re: 9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 8:07 pm

Carel040 wrote:Did u find the fault yet

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Not as yet.


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madhoshival
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Re: 9N3 Polo GTi boost issue

Postby madhoshival » Mon Nov 27, 2017 8:10 pm

DCmk3 wrote:Have you done a compression test on the car?


Motor has been rebuilt.
Problem has been there before the rebuild and it's the exactly the same now.
Did a compression test before and all was perfect.Image


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