Ibiza cupra tdi no boost

[Jonowilliams87]

Hi there, I've just fitted a new upgraded turbo to my car as the old one was overboosting so I suspected it was sticky vains. To my surprise the turbo was absolutely fine, no play in the shaft no scoring and actuator moving freely.

Anyway I proceeded to fit my new turbo a GTB17/60 essentially and GTB1756 bored out to take the 2260 impeller I beleive. The turbo is new not second hand.

Now it's all fitted to my car I tried to get the stop screw and actuator set up correctly. I've been trying for days to get it correct and covered a wopping 60 miles doing logs.

The best I can do is 50% duty cycle at 4000rpm (measuring blocks group 11) and 96mbar of difference on basic settings group 11.

If I shorten the actuator any more to get closer to 80% duty I lose a lot of mbar on basic settings and I've only got the one thread remaining the unscrew/shorten on it.

The car won't provide full boost until the 3000/3500k range and is extremely laggy up until then. I occasionally get the fault code 17964 - charge pressure control negative deviation. A standard GTB2260 should be at full boost by 2500k.

The supplier and a few other people think I've got a really bad vacuum problem, I've replaced all vacuum pipes coming for the vacuum control unit the actuator held 16inhg for an hour (until I got bored) and didn't drop a bit on my mightyvac. I've seen the tandem pump mentioned but you'd normally get a diesel leak too wouldn't you if that was the case? Also saw something mentioned about the large diameter pipe coming from the servo but that looks fine, wouldn't I have dodgy brakes otherwise?

If anyone has any ideas that would be great I'm lost as what to do now.

Thanks Jono

[Rob69]

Can you try another N75 valve? Sounds like the problem was there before you changed the turbo.

[Doctle Odd]

Can you try another N75 valve? Sounds like the problem was there before you changed the turbo.

+1, you need to do a load of investigative work before buying a turbo. On the plus side there's a market for good 2nd hand turbos

[Jonowilliams87]

Sold the old turbo, but it was also an excuse to but an uprated one.

Struggling to find another n75 that's the same. I may have to order one and just take it on the chin If it wasn't that

[Jonowilliams87]

This is my logs, sorry it's the best I can do for now on my phone the laptop isn't mine so don't have it with me.

Stop screw

Actuator duty

[Doctle Odd]

Sold the old turbo, but it was also an excuse to but an uprated one.

Struggling to find another n75 that's the same. I may have to order one and just take it on the chin If it wasn't that

N75 is cheap part compared with a new turbo. Start by checking all the vacuum hoses and replace any damaged ones. Get the vacuum pump tested as they do fail . You could borrow a known good n75 and try it, this is assuming all the vacuum plumbing is connected properly. The N18 valve is usually mounted close to the N75 they look very similar but they’re not interchangeable

[Jonowilliams87]

I replaced all vacuum hoses coming from the n75, ALL of them.

How do I test the vacuum pump? I've had it on vcds and done basic tests it clicks as it should and after letting the car run and then killing the engine, If I pull the end from the n75 I get a hiss of air being released.

[Doctle Odd]

You need a vacuum gauge, Im still with Rob on the N75

17964/P1556/005462 - Ross-Tech Wiki

[Jonowilliams87]

So my mightyvac isn't gonna be of any use here.... I'll see if I can find one to borrow so I don't waste more money if it isn't that

[Doctle Odd]

A scrappy will have one for about a tenner google the part number on yours they’re very interchangeable and are fitted to many makes and models, TPS, GSF etc sell them for small money, you can buy a Pierburg N75 for 30 notes on a well known auction site