Help With Turbo Boost.

[Wheely]

Guys - please help as Cupra TDi still unwell.

Up to the point my turbo blew (turbine shaft let go - no engine damage) car had been running like a dream. Since turbo replaced for an OEM part, the boost has not bee picking up until >2100rpm and theres lag when changing gear (even when keeping revs high). On top of that you can barely hear that lovely whistle you get with the windows down as the turbo spools up.

Its not the maf
VNT is operating/actuating
Thought it was blocked cat - but proved not the case by removing it temporarily.
No CEL lights - although did have a couple of negative pressure deviations. All hoses good and checked.

So what is it ?? Can the new turbo be defective or the VNT not set exactly right ?? Do you know of an exact procedure for setting VNT shaft linkage distance ??

It will probably need to go back to the garage who changed the turbo - but convincing them to change it out again is going to be a nightmare !!

Your thoughts please

 

[UncleFester]

You haven't got oil / crud in your intercooler pipework have you? Have you had vagcom on to scan for faults? What about a split actuator hose - mine had this where it had been rubbing on the exhaust heatshield. Or failing N75 ....

 

[glynnd]

it will be the map sensor, when 3 liters of oil went through my engine after turbo failure it buggered the map sensor. They are about £30 from vw and its located in the front boost pipe.
Glynn

 

[Wheely]

Mmm car going back to the garage this week. I think its either the turbo itself or the setup of the VNT.

Vac hose seems ok - but will get that changed. Put the VNT hose straight onto the vac supply (bypassing the N75). Did some low rev driving (so as not to overboost) - and nothing from the turbo still until >2000 revs.

So vac hose (unlikely) or turbo/vnt actuator setup !!!

Unless I have missed something ? Rolling road dyno shows a flat right and a big aggressive boost/surge at around 2850.

Mark

 

[Wheely]

...also checked my vacuum today - Tee'ing a gauge into VNT vac line. At idle this was pulling about 35cm Hg. Also crimped the line and turned off engine - the vac held fairly well, proving hose is not split. Driving car the vacuum decreases as it should as the revs go up. Changing gear shows and immediate drop of vacuum and a full charge on throttle. Certainly seems nothing wrong here.

Looks so much like d defective new turbo - or VNT needs adjusting (but surely not on a new turbo !!).

And come on helpful guys - why the lack of replies here ???!!???

 

[Bogwoppit]

Have you replaced/checked the MAP sensor as mentioned above?

 

[Wheely]

Have you replaced/checked the MAP sensor as mentioned above?

I have by-passed N75 / airflow control by putting VNT hose straight onto permanent vacuum outlet. And still the same turbo lag / slow spool up.

I have been spending so much time reading up on everything. And remember the car was running absolutely 100% fine until turbo turbine shaft snapped.

So if 100% VNT actuation gives poor turbo boost then (and correct me if i leave something out) :

1. VNT setup wrong
2. New turbo crap (too much friction). Remember its also down about 30Hp on rollers.
3. Exhaust blocked -- but not this as same dyno with cat removed from turbo outlet
4. Inlet blocked. Most hoses look clear - but will check bottom IC one this weekend. No reason to suspect this tho.

As Jonny 5 says "more input required"..............................

 

[Muttley]

Wheely wrote


I have by-passed N75 / airflow control by putting VNT hose straight onto permanent vacuum outlet. And still the same turbo lag / slow spool up.

VNT vanes are spring-loaded to the fully open position. Attaching the vacuum line from the actuator to unswitched vacuum should result in the vanes being pulled to the minimum opening setting, the low-rpm setting, intended to get small amounts of exhaust gas moving quickly. This should result in overboost and limp mode as soon as you get going. The fact that it doesn't suggests:

1) leaky or blocked VNT actuator vacuum line
2) What you think is permanent vacuum isn't
3) VNT actuator sticky or jammed
4) VNT actuator not connected to vanes

in addition the original fault may be due to

5) N75 valve faulty
6) N75 valve pipes connected incorrectly
7) N75 valve electrical connector faulty


- for a start.

Where did you get your "permanent vacuum" connection from?

Fault is almost certainly associated with the installation of the replacement turbo and its connections.

It might be worth finding out what kind of turbo they have installed - check the invoices. It may just be a faulty turbo, but the things get checked at the manufacturer. It may be the wrong type altogether - stranger things have happened. It's a long shot, though.


I have been spending so much time reading up on everything. And remember the car was running absolutely 100% fine until turbo turbine shaft snapped.

Hmmm. Why did the turbine shaft let go in the first place?


So if 100% VNT actuation gives poor turbo boost then (and correct me if i leave something out) :

1. VNT setup wrong
2. New turbo crap (too much friction). Remember its also down about 30Hp on rollers.
3. Exhaust blocked -- but not this as same dyno with cat removed from turbo outlet
4. Inlet blocked. Most hoses look clear - but will check bottom IC one this weekend. No reason to suspect this tho.

1) VNT settings not done properly, VNT vacuum connection faulty, N75 valve faulty, vacuum system connections screwed up.
2) Wrong turbo, VNT actuator not set properly, oilways partially blocked. You could be headed for another blown turbo
3) If lots of oil had gone into the cat it will be buggered. Has it been checked - remember diesel cats don't get checked at MOT
4) Possibility of oil blockage in intercooler.



I hope that they replaced oil and filter and washed out the oilways and sump after your turbo blew? Shaft failure is likely to have put metal particles into the oil return, choking the filter.

 

[DelMonte20]

Help!

I'm having this exact same problem.

Turbo went last week, new one fitted, everything cleaned and flushed out as it should be, and now no boost until around 3k rpm in 2nd gear upwards (1st gear hardly anything).

Lost that lovely whistle sound and what did sound like a recirc dump valve (not sure if the TDI FR has one as standard?). Also used to almost get a kind of waste gate chatter sound (knowing that it wasn't), but still sounded good.

It was chipped and running a nice smooth linear curve on both power and torque (201bhp and 318lb/ft). It now feels like a 150bhp car with no power until I've nearly run out of revs!

I've had three chats with my mechanic, but he's adimant to wait a couple of weeks to let the residual oil burn off, new oil and turbo to run in. I'm sure there's something else wrong here and am a little concerned it may/can cause damage?

Did you get to the bottom of your problem?

Thanks

Mike

 

[Wheely]

I'm having this exact same problem.

Turbo went last week, new one fitted, everything cleaned and flushed out as it should be, and now no boost until around 3k rpm in 2nd gear upwards (1st gear hardly anything).

Lost that lovely whistle sound and what did sound like a recirc dump valve (not sure if the TDI FR has one as standard?). Also used to almost get a kind of waste gate chatter sound (knowing that it wasn't), but still sounded good.

It was chipped and running a nice smooth linear curve on both power and torque (201bhp and 318lb/ft). It now feels like a 150bhp car with no power until I've nearly run out of revs!

I've had three chats with my mechanic, but he's adimant to wait a couple of weeks to let the residual oil burn off, new oil and turbo to run in. I'm sure there's something else wrong here and am a little concerned it may/can cause damage?

Did you get to the bottom of your problem?

Thanks

Mike

Hi Mike

Although I no longer have the car (now an Audi driver), I did get to the bottom of this - see this post for the root cause http://www.seatcupra.net/forums/showthread.php?t=213048

Check this very carefully.

As for a turbo running in - thats bollox. Once I had a decent new turbo the car was instantly bionic once again.

Hope ya get it sorted

Mark (who still checks out this forum far to often)

 

[Muttley]

So I was right - VNT actuator sticky or jammed

Although to be fair I did suggest just about everything that could have gone wrong . . . .