Boost Leak

[Sirocco20348]

Hey guys,

Edit: I might give some context to this problem. I installed my front mount intercooler and had the system smoke leak tested by Alba European. He confirmed that there are no boost leaks and the car felt strong (20psi), butmade a funny whistle noise at full boost. I contacted Jimmy and he ensured I had no leaks, so i thought it must be air passing through the new pipes and created a whistling noise. (??)

Anyway as the weeks went on I went from a max boost of 20 psi to a max of 18psi and then a max 15 psi last week! Which made be want to action it. So i thought I must have a boost leak? Maybe?

Boost test:

• I fabricated up an attachment to connect into my TIP with a nitto attachment on it to connect to an air compressor.
• I set the air to be regulated to the minimum setting.
• I also unplugged the hockey puck and plugged the hole to avoid pressurising the sump.
• Do i need to do anything else?

Anyway I start the test, and I get a really high pitch whistle happening!!!! Similar to the sound i hear at full boost but a mega version.
I freak out and then unplug the nitto coupling which makes the big whoosh sound.

https://youtu.be/2821FhrB3lM

Please watch and if I am doing anything stupid please let me know....Does it sound like a boost leak somewhere?
I'm scared to do the test again in case I'm damaging something.

How do you regulate only a certain amount of air into system? Eg. I only want 1 bar of pressure for the test.

[DAM GTi]

compressor has a regulator on it?
theres a youtube video that goes for 12 mins. thats good..mexican dude.
also smoke test works good-could get a mate revving up the car for pressure...

oil cap off..should keep things safe..plumb a guage into the pvc tube you made for the tip should be good..worked for me..dv
yours sounds like a split in the hose on a guesstimate..bitch of a thing and annoying as all hell
all the best

[Sirocco20348]

Yeh no regulator which is obviously not ideal which is why I set the air pressure to minimum.

And yes oil cap was off, I forgot to mention that.

I'm pretty sure this is what I need. Can you confirm?

Air Pressure Regulator Relief w/ Gauge Hose Quick Release Compressor Fitting 1/4 | eBay

I'll make sure my boost leak test is 100% accurate before proceeding.

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[DAM GTi]

yeah rok that do it!

taper pressure up in lots of 5 to be safe if your paranoid..i would just smash it with air and zone in on that fkn farting noise personally,least you know its there and not in your head lol..these rides do your nut in!

[Sirocco20348]

Ok I ordered that to help out.

I have noticed my turbo inlet pipe does not have a clamp on it.... i guess the coolant hard line keeps it on. The pipe is under vacuum, should I put one on?

[DAM GTi]

wouldnt hurt

[Sirocco20348]

I logged various blocks in vagcom yesterday and one value that was highlighting concern was the n75 Duty Cycle.

It had no idea what it was doing! Most the time it was 0%!! Which means valve open and the car relying on wastegate pressure for boost. I will post logs when I get a chance.

How much psi would be required to open the wastegate?

This might explain the whistling noise being the Wastegate opening slightly under pressure.. maybe?


I might see if someone has a spare n75 to test out.

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[h100vw]

I logged various blocks in vagcom yesterday and one value that was highlighting concern was the n75 Duty Cycle.

It had no idea what it was doing! Most the time it was 0%!! Which means valve open and the car relying on wastegate pressure for boost. I will post logs when I get a chance.

How much psi would be required to open the wastegate?

This might explain the whistling noise being the Wastegate opening slightly under pressure.. maybe?


I might see if someone has a spare n75 to test out.

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Call me when you have a break mate.

[Sirocco20348]

Ok so I upgraded my vagcom cable and it logs much better now.

As expected n75 duty cycle stays maxxed at 99.6% throughout the rev range. This indicates that I do have a leak.

I'm awaiting my air pressure regulator to arrive to hone in further to find out what the hell is going on.

I ordered a new n75 anyway, I'll place it on the shelf until this one fails completely.

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[h100vw]

Sorry i haven't called back. Been so busy at work. Call me tomorrow. It's looking reasonably quiet ATM

[Sirocco20348]

Sorry Gavin yesterday was crazy for me at work.

UPDATE: Boost leak detected with newly upgraded leak tester.

It was a coupler used for the intercooler piping, it started leaking at 5psi! So at 20psi would be mental loud.

I just have no idea how the smoke test performed by Jimmy would not have identified this leak the first time?.... Does anyone know how much psi pressure is applied during a smoke test? I smsd Jimmy and didn't get a reply....

Anyway I'll vagcom my car tonight. Hopefully it's the last leak in my car 😁

[dubster99]

What size fitting did you use for the leak tester?
Also what did you block off to do the test? Oil cap off, pvc pipe clamped shut?

[Sirocco20348]

What size fitting did you use for the leak tester?
Also what did you block off to do the test? Oil cap off, pvc pipe clamped shut?

What are you referring as the fitting?

Both the threaded pvc tube and the end cap i bought from Bunnings, The thread for both of these is like an inch long.
The PVC tube fits my APR silicone turbo inlet pipe perfectly. Clamp it down TIGHT because the PVC pipe does not have a lipped end!
I drilled a hole in the top of the black end cap a fraction smaller than the threaded Nitto style male coupler. I then forced the coupler to create its own thread in the black end cap.
All threads I used plumbers tape to ensure no air leaking.

Oil cap off
I remove the hockey puck from the TIP, and then clamp a Co2 canister in there TIGHT!. It is a perfect fit, but watch out it doesn't slide into the TIP and make sure it does not become a missile.
https://i.stack.imgur.com/OVvrz.jpg

[Sirocco20348]

UPDATE: Just logged my car and I still have boost leaks. n75 duty cycle still maxxed out.

HOWEVER, The car is much better thou as acceleration is really strong through the rev range. Kinda crazy to think there is still more power after I finalise these leaks. I really think I am down to the tiniest of leaks now.
I only tested to around 7 psi today because my TIP clamp is quite stuffed.

Just an aside, my FMIC was working really well. The air intake temps were within 10 degrees of ambient air temps.

Attached logs for people who are curious. 2x runs, WOT in 3rd to around 6000rpm.

https://1drv.ms/x/s!ArCKuFTQ_s3egZtOvsKHmnT6VC4Rzg

[Sirocco20348]

I drove the car to the train station this morning, and gave it wot 3rd from 3000rpm off the highway offramp.

The boost strangely slowly built up to 15psi??.. but I should have been on boost already at 3000rpm, car felt flat unlike the other night when it felt fantastic.

Has any one experienced this slow build up of boost before?

Gavin sorry I haven't called you yet, we have been busy moving offices atm.

Any ideas?





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