MK6 GTI - K04 and Surging?

[Killerwatt]

No diverter or dump valve or a too large turbo will cause surging, its basically more air than the motor can ingest which is not possible for a K04 on a GTi. Fit a T76 to your GTi then you will experience compressor surge.

How do you determine its not possible on a GTi or similar 2.0TFSI motors?

You check your car's flow rate and compare on a Turbo graph

Correct, volumetric efficiency in cfm vs turbo flow rate in lbs/min

Nope, Its pressure ratio vs flow rate. CFM and Lbs/min are both a measure of airflow.

To stay out of surge on the K04 you need to be above 150ish g/s at a pressure ratio of 2.5. So yeah most k04 logs that i just googled actually come really close to the surge line.

[Zubair]

How do you determine its not possible on a GTi or similar 2.0TFSI motors?

You check your car's flow rate and compare on a Turbo graph

Correct, volumetric efficiency in cfm vs turbo flow rate in lbs/min

Nope, Its pressure ratio vs flow rate. CFM and Lbs/min are both a measure of airflow.

To stay out of surge on the K04 you need to be above 150ish g/s at a pressure ratio of 2.5. So yeah most k04 logs that i just googled actually come really close to the surge line.

If VE CFM is not up to air volume in pounds you will get surge, been doing this and plotting maps for years, also I still see fueling and timing errors being confused with surge, the term surge gets thrown around loosely.

[M3THANOL]

very informative I love threads like these!!!!!

[ruan9n]

.. the famous exhaust whaap whaap whaaap push and pull with dyno curves all over the place!

correct - you would hear that when the car is surging

Dankeschon... thought I was right on this one! I heard it on an mk6 with 2 metric fucktons of boost thrown at it.

[mika1803]

Thread revival
So how does one cure this disease?

[Hoosier Daddy]

Thread revival
So how does one cure this disease?

Drop boost

[mika1803]

That kills the point of K04

[Hoosier Daddy]

That kills the point of K04

On a compressor map there is a surge line and a choke line with efficiency islands. You want the turbo to be at the centre island for as long as you can. Upping boost kind of kills the time in the sweet spot. The surging can also be hardware related... If you can't hold boost at a certain flow rate or your compressor is not the right size... you'll surge

[Unobeat]

very informative I love threads like these!!!!!

Totally agree

send from my Umsotho GT using tapatalk!!

[mika1803]

I have checked all hardware, adjusted the actuator, changed intakes and plugs. Could a faulty N75 valve cause surging? Car has been back to the tuner 4 times

[PoLonY]

Change tuner lol

[Benji’sMk6GTi]

I know it’s an old thread, but what can I do to stop the surging from happening? I understand the concept of the engine not being able to take in the air that the turbo is producing at certain rpm’s, so do you just get your tuner to reduce requested boost at certain rpm’s? I get that sound when I’m in 3rd-4th gear at low rpm’s and throttle at about 50% but as soon as the rpm gets a little higher it goes away, I’m assuming because the engine at that point is able to take in the extra air that the turbo has produced? I noticed that the sound is more prominent now that I’ve got a GFB DV+, I think it’s because it can’t divert the air as quickly as the stock DV setup or because the spring in the DV+ plunger is too heavy? I dunno, help please!!!

[Ashveer03]

Where did U buy the gfb DV from? There's a bunch of fakes going around from random sellers on the web, which jam and cause more flutter than there should be.