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I'm pulling my hair out, please help. Late 2nd Tubby, low boost.


Scott

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Ok long story short my 2nd turbo popped so i had them both replaced. Since then i have been seeing strange boosting issues. I have checked all the technical articles and searched my arse off trying to find the answer but it seems i have a bit of a strange one.

 

I have:

 

Double De-cat 3"

RSR II Exhaust 3"ish

1.2Bar Restrictor ring

FMIC

Mines ECU (FCD etc)

 

Symptoms:

 

1st turbo starts making boost at the right time but only boosts to 0.5bar. The 2nd turbo doesn't come online until around 5krpm which is very late. When it does i am only seeing around 0.9bar. In TTC mode the boost doesn't hit till just under 5krpm and i also only get 0.9bar.

 

I have checked the vac lines and replaced one that had a small crack in it. I have ran the car in TTC mode to check the pressure tank, pipes etc and it seems fine (both actuators stay open & holding pressure).

 

Is it possible that i have a small leak? I'm thinking that if some of the pressure was lost, perhaps 0.5bar from the first turbo isn't enough to open up the EGBV and therefore the 2nd turbo isn't being pre-spooled making it come in late. Then when the 2nd turbo comes online the pressure is still down due to the small leak?

 

I'm going to take off all the pipes and go over all the vac lines with a fine tooth comb. I'm also going to check all the intercooler pipes/couplers and make sure they are all tight.

 

Any other ideas?

 

Thanks

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Ok long story short my 2nd turbo popped so i had them both replaced. Since then i have been seeing strange boosting issues. I have checked all the technical articles and searched my arse off trying to find the answer but it seems i have a bit of a strange one.

 

I have:

 

Double De-cat 3"

RSR II Exhaust 3"ish

1.2Bar Restrictor ring

FMIC

Mines ECU (FCD etc)

 

Symptoms:

 

1st turbo starts making boost at the right time but only boosts to 0.5bar. The 2nd turbo doesn't come online until around 5krpm which is very late. When it does i am only seeing around 0.9bar. In TTC mode the boost doesn't hit till just under 5krpm and i also only get 0.9bar.

 

I have checked the vac lines and replaced one that had a small crack in it. I have ran the car in TTC mode to check the pressure tank, pipes etc and it seems fine (both actuators stay open & holding pressure).

 

Is it possible that i have a small leak? I'm thinking that if some of the pressure was lost, perhaps 0.5bar from the first turbo isn't enough to open up the EGBV and therefore the 2nd turbo isn't being pre-spooled making it come in late. Then when the 2nd turbo comes online the pressure is still down due to the small leak?

 

I'm going to take off all the pipes and go over all the vac lines with a fine tooth comb. I'm also going to check all the intercooler pipes/couplers and make sure they are all tight.

 

Any other ideas?

 

Thanks

 

Dundee on here had identical symptoms to you,turned out to be a tiny split on one of the vac hoses where it went onto one of the hard pipes.

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Dundee on here had identical symptoms to you,turned out to be a tiny split on one of the vac hoses where it went onto one of the hard pipes.

 

Cheers mate, fingers crossed i can nail the sucker on friday then.

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Scott you ain't havig any luck with those twins, wish I could help, get a small single wacked on :D

 

You buying bud? :D

 

I'm hoping that its just a small niggle, if so i'm happy, if not..... anyone wanna buy an almost working facelift black TT with fresh re-spray? lol

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Have you checked the intercooler and pipes for leaks...?

 

Not extensively. I had a look over everything and i couldn't see anything out of the ordinary but i haven't pressure tested any of it. I want to be sure i'm looking for a leak though, no point in looking for a hooker in a monestary...... or is there :sly:

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Hey,

I've only recently bought a twin turbo, my firstturbo dont come in till just over 3krpm @ 0.5 bar and second comes in at just over 5krpm and 1.2 bar, is this normal?

 

Cheers

 

Nope thats very wrong, sounds even worse than mine.

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Ok i managed to get a little groundwork done today. 1 of the lines had a little tear in it and another one was too long so it had a bit much angle on it. I trimmed the long one and replaced the torn one. It appears that its running much much better but the reading on the boost gauge is still a little low.

 

I've got the dump valve off for tomorrow, as thats my next test, and i'm planning to check out the boost gauge plumbing.

 

The symptoms are now:

 

2000rpm 1st turbo starts to make boost, by around 2800rpm i'm making 0.6bar boost, by 3200rpm this tails off to 0.5bar boost. At 3800rpm the boost drops dramatically and then at 4000rpm the 2nd tubby hits hard at 1bar when all hell brakes loose. During the changeover i would say that it goes as low as 0.1-0.2bar.

 

Does this sound reasonable if the boost gauge was under-reading?

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