DIY boost leak fix

[VWindahouse]

I'm thinking disconnect the N75 and see if that changes anything boost wise first. How long were the stages? Also thinking sustained punishment could have sent something into safe mode.

[Stuwey]

Gauge, yes. Code reader plugger-inner, no.

[VWindahouse]

Cool, do a couple of short runs with the N75 disconnected and see what boost you make.

[h100vw]

Cool, do a couple of short runs with the N75 disconnected and see what boost you make.

The N75 is inline between the inlet manifold and the wastegate actuator. With it connected the ECU can restrict the boost that gets to the actuator by opening and closing it quickly. This is usually called duty cycle. The higher the duty ( the more time the N75 is closed, maybe think about coils charging/dwell) cycle the less boost to the actuator and the harder the turbo goes.

With lower duty cycle you get more boost to the actuator.

With the N75 electrically disconnected, the line is wide open. The actuator is set to open at 6 PSI. So as the turbo spools and 6 PSI appears at the actuator the WG opens and bypasses the hot wheel, so the turbo slows down. Boost drops and the actuator closes a bit. then this continues ad infinitum.



Here's the Forge actuator on Anthony's billet baby. Yours is the same but made of steel. The 2 nuts either side of the wastegate arm can be moved up and down to set the cracking pressure (6PSI) of the wastegate. So make sure that they are tight. 10mm stubby spanner is the winner for that job. Be careful of everything behind there if the car hasn't been stood for an hour with the bonnet up.

If they have backed off or have disappeared then the WG will be opening early or be getting blown open and the hot wheel getting bypassed, so no boost. This sounds likely to me.

Gavin

The turbo is the other way up, so the actuator is against the firewall. Also, you can see the wastegate flap in the edge of the turbo outlet.

[VWindahouse]

Gav what's APR's valet boost level again? Do you think valet mode could have been accidently activated? Just thinking 3 to 4 psi is even too low for a boost leak??

[h100vw]

Gav what's APR's valet boost level again? Do you think valet mode could have been accidently activated? Just thinking 3 to 4 psi is even too low for a boost leak??

Not sure you could turn it down that far? Worth checking though.

Gavin

[Stuwey]

Gav what's APR's valet boost level again? Do you think valet mode could have been accidently activated? Just thinking 3 to 4 psi is even too low for a boost leak??

Only the one APR program loaded, no valet setting here.

Would setting the tune back to standard reset anything of sorts?

I assum the N75, like anything else, can fail.

[h100vw]

Only the one APR program loaded, no valet setting here.

Would setting the tune back to standard reset anything of sorts?

I assum the N75, like anything else, can fail.

If it failed, it would be open and you would get 6PSI so that doesn't work for me. A scan would be a really good idea. I'd expect that cycling the ignition, would clear anything that going to the std tune would do.

Any other VWs in the Rally that might have a scanner?

Gavin

[Stuwey]

Wastegate rod still attached and tight.

All engine bay plumbing appears to be ok, looks like it'll be a long day of searching!

[Stuwey]

Well, removed, cleaned, checked all plumbing from turbo to throttle body.

Found one hose had come awry on the steel turbo charge pipe behind the engine cover. Left the battery of while checking everything else, put it back together and we have boost again...

With a big whistle noise