need help no boost on my gti

[MikyHRC]

Hi guys, I need a help, I bought 2006 polo gti and it runs Giac KO4 tune with 380 infectors on a 3 bar FPR. I drove it for couple of weeks and everything was ok until I took it for a dyno run last weekend and it only made 100kw at wheels. I drove it back home and I didn't have any boost. I have checked the hoses from IC and turbo and I couldn't find any boost leak, unfortunately I don't have the boost gauge yet to see what boost I'm running

I read somewhere that it could be faulty N75 boost valve. Pls let me know if anyone of you had the same problem I'm kind of stuck and not sure what to check for, I don't want to take it to stealership. Any help appreciated..cheers Mick

[HAR80N]

check the vac lines and the DV i got a audi s3 the other week and went like a nugget and was a split hose that went to the dv fixed that and went awesome with the hose split was just pushing open the dv and dumping all the boost

[seangti]

You can easily check if it's the N75 by disconnecting it and going for a drive. If it feels the same, than that could be the culprit. If the boost leak is of reasonable size, your car could run rough (not always though), and/or you can hear it. I've blown an IC pipe the L shaped one straight off the turbo, huge blow out yet could still drive the car down the highway off boost to get home. With N75 disconnected, it'll boost between 6-8psi, which still feels like no boost. I had a N75 go on my car, but it was intermittent for a while before it was dead. Scanning it will also show a fault if you can get access to a scan tool.

There's nothing wring driving around with the N75 disconnected, just low boost.

My guess is that t's more likely to be a boost leak from the dyno run. Check all hose clamps, pipes are aligned/square, vacuum lines are right. Some cracks/holes can be small, but add boost they expand.

[MikyHRC]

check the vac lines and the DV i got a audi s3 the other week and went like a nugget and was a split hose that went to the dv fixed that and went awesome with the hose split was just pushing open the dv and dumping all the boost

Thanks HAR8ON, I will check the vac lines and the DV today.

[h100vw]

Thanks HAR8ON, I will check the vac lines and the DV today.

So does it have a boost gauge? Because it seems like there's two stories here. I don't see it putting down 100kw making no boost whatsoever.

Gavin

[Bora Sport]

Could it be the old broken wire to the N75 trick. When mine went on the Polo it would boost sometimes and then not. The wire must have been touching occasionally. Eventually of course it felt like it wouldn't boost at all. Soldered the wire back together and the smile returns.

[MikyHRC]

Hi guys I think I found the problem, I've got the hose coming of N75 going down to wastegate actuator a its snaped off right where its connected to WG act. That could be it right? Now the thing is the hose is actually thicker with bigger hole on N75 end and thinner with smaller hole on WG end if I am correct (or I'm looking at the wrong hose?) I don't think the original hose that's in is going to be long enough to reconnect it though. Am I going to be able to get a similar one from Supercheap or Repco? The spare one I have its same size all the way through, is that gonna be a problem if I put this one instead?

[h100vw]

Hi guys I think I found the problem, I've got the hose coming of N75 going down to wastegate actuator a its snaped off right where its connected to WG act. That could be it right? Now the thing is the hose is actually thicker with bigger hole on N75 end and thinner with smaller hole on WG end if I am correct (or I'm looking at the wrong hose?) I don't think the original hose that's in is going to be long enough to reconnect it though. Am I going to be able to get a similar one from Supercheap or Repco? The spare one I have its same size all the way through, is that gonna be a problem if I put this one instead?

If there's no connection to the inlet manifold, the spring is holding WG closed. I have never seen that run on the street. I can imagine that eventually the exhaust would blow the WG open. Not sure what boost you would see.

Don't worry too much about the diameter of the pipe.

Is there enough to take the broken bit off the WG and shove it back on?

[MikyHRC]

No, the original one doesn't seem to be long enough anymore, I'm gonna try to pull the original one out and run it around the other way to make it reach,if its not long enough I just got some pipe from Repco with similar diameter so I'll put that one in and try to make it fit. Hopefully the different diameter is not gonna be an issue��

[sambb]

Yeah the hose that heads down to the wastegate actuator is thick and then tapers where it goes onto the actuator nipple. Mine tore there too. I'm not sure how that's giving you less power though - should be tearing your head off! Or maybe that's the prob, it did for a bit and now its in a limp mode due to the overboosting? not sure
That pipe runs up through a heat resistant sleeve with another hose that goes into the bottom of the turbo inlet pipe. You will be able to pull some extra length through but where you cut off the hose to get a clean end will now be too big a diameter. Just clamp the hell out of it for now and you can just buy some silicon vacuum hose from repco etc. Has to be silicon though so that it has some longevity. Use the existing turd wastegate hose as a pull through to get the new hose down through the heat resistant sheath.
Maybe with that sorted and clear codes you may get your boost back.

[MikyHRC]

Yes, that's what it exactly is sambb.
I tried to reconnect the original hose again but it wasn't long enough anymore so I tried to pull it out completely but there is not enough room to get the hose because is clamped together with the other one that goes into the bottom of the turbo inlet pipe. They are holding together with little bracket looking thing that I couldn't get off because of no room around it. (it might be easier with the car on the hoist). So I went to Repco and got the similar sized hose and clamped the hell out of it. Unfortunately with no heat resistant sleeve arount it.
I took it for a spin around the block and it seems to be working. Car pulls ok but still doesn't feel as good as before, when the boost comes on it is not as sudden as it used to be. I don't know why but it just doesn't kick back so hard as before and there must be still something wrong with DV because I can no longer hear it when I let go of the throttle. ( the sound of the DV was pretty noticeable before). Now it's like it is not even there anymore
I don't know what could be wrong with it, let me know guys if u have any idea. I'm gonna install the boost gauge tomorrow to see what boost I'm getting.
Thanks for your replies.

[seangti]

I think sam nailed it, it may have been overboosting before and gone into a limp mode from the dyno. I've torn that pipe at the nipple, when the vacuum line is off the WG actuator, it overboosts, could be 24+psi boost. Yeah goes well but not safe for the engine. Get that gauge in and see what it's boosting to. Would be worth a scan to validate and clear codes. It seems strange that it's now making power again, almost back to front.

[sambb]

. Get it scanned for errors. maybe it won't come good till you clear any overboost errors (if that's infact what happened). On the DV front, what type is it, the stock one or an aftermarket piston style. Not much to go wrong with the piston ones maybe if its a stocker you've torn the diaphragm in it. To test the stock ones' innards, take it out and push the plunger in with your finger, then suck on the vacuum line to build vacuum in it. keeping the vacuum locked in, then release the diaphragm. The plunger should flobut at and not reseat until you release the vacuum. If the DV passes that test then you need to look at the vacuum lines to from the manifold and the N249 reservoir etc and also the bigger pipe leading to the charge pipe.