Turbo #2 not coming on line

[Ian C]

Hi all.  I've removed both turbos from the engine (what a greusome job) and no.2 is intact.   Why, then, would I get the symptom of boost (and associated power) loss as soon as #2 is brought online at 4000rpm?  Obviously, #1's boost is going somewhere other than the engine at this point, so it's probably cycling through #2 backwards and back into #1's intake again.

 

So, the reason boost from #1 can pass through #2 with no resistance is probably because #2 isn't spinning when the IACV opens.  The reason it wouldn't be spinning?  I would have said damaged impeller, but it's peachy.  Any other ideas?  Before I put it all back together again?!?

 

It's not all wasted effort, as I'm putting the hybrids off the damaged engine back onto the new one.  They survived the incident without a scratch.  And I checked by manually spinning the vanes - J spec ceramic ones are indeed easier to spin up than steel, by a very noticeable margin!!

 

-Ian

[Guest Martin F]

I don't want to hijack Ian's thread here, but allegedly on stock cars there is a vacuum pipe diagram on the air box.

 

Would it be possible for somebody to take a picture of these (UK spec and Jap spec) so that those of us who do not have this diagram could learn (and potentially fix) something.

 

Or does anybody know if they are already up on the web somewhere ?

 

Ian, i am pretty damn sure that this is one of the many actuators or VSV's for the sequential system, but i don't know enough to be of any help.

 

 

 

 

[Gordon F]

Ian

 

I think if you had a damaged impeller, turbo or turbo bearing you would have some kind of noise coming from the engine. I would think that there is some kind of valve or actuator not working correctly. Didn't look too much awry when you came past me last week.:smile:

[Branners]

Im pretty sure that the wastegate is located on the 2nd turbo, so the first turbo can spool up okay, and once you open up the flap to get both on line all the boost is just running out the wastegate which might just be jammed open.

 

Try checking the actuator on the wastegate and see if it is operating. I think leon pressurises it up to a set PSI at which point it should open up, sometimes he has seen them jam open or closed.

 

btw, if you still have your old engine and turbos then Leon might be interested in buying them off you. He wants a full engine sitting there ready in case anybody else blows theirs.

 

Hope that helps.

 

JB

[Ian C]

JB - unfortunately in my learning about the whole TT setup, I have found that there isn't in fact a wastegate on the 2nd turbo  There is a bit of kit that looks like a wastegate, but it's the prespool device, which allows a small amount of exhaust to spin up #2 and exit via #1's exhaust pipe.

 

However, some of this plumbing may not be working as it should, so swapping the old turbos back on should prove that.

 

I've swapped out the vsv's for the #1 wastegate and the Exhaust Gas Bypass Valve (EGBV) to no avail - the same performance and boost falloff at 4000rpm.  I'll use the IACV from my old engine and see if I can swap the EGBV as well while it's stripped down...

 

I have my old engine and two perfectly OK j-spec turbos if Leon wants them.  Let's face it, I need the money :biggrin:

 

Gordon - you are right, there are no nasty noises, so it's got to be a bit of the plumbing somewhere.  I'm going to try tagging the actuator arms with easily-breakable stuff, so I can tell if they actually move

 

-Ian

[Guest Martin F]

Quote: from Ian C on 12:42 pm on Dec. 22, 2001[br]JB - unfortunately in my learning about the whole TT setup, I have found that there isn't in fact a wastegate on the 2nd turbo  

 

-Ian

 

Errr beg to differ on this. The wastegate sits at the bottom of the first second turbo and can quite easily be seen from the drivers side of the car. It's usually tapped into for those running boost controllers.

 

If there wasn't a wastegate all cars would blow their turbo's within 100 miles :biggrin:

[GavinL]

Quote: from Martin F on 11:56 pm on Dec. 21, 2001[br]I don't want to hijack Ian's thread here, but allegedly on stock cars there is a vacuum pipe diagram on the air box.

 

 

 

I have looked at my car which still has the stock box and the diagram is for the main belt not the pipe work.

 

regards.............

[Ian C]

Quote: from Martin F on 1:53 pm on Dec. 22, 2001[br]

Quote: from Ian C on 12:42 pm on Dec. 22, 2001[br]JB - unfortunately in my learning about the whole TT setup, I have found that there isn't in fact a wastegate on the 2nd turbo  

 

-Ian

 

Errr beg to differ on this. The wastegate sits at the bottom of the first second turbo and can quite easily be seen from the drivers side of the car. It's usually tapped into for those running boost controllers.

 

If there wasn't a wastegate all cars would blow their turbo's within 100 miles :biggrin:

 

Ahem.  Beg to argue the point

 

#1 turbo, the one closest to the front of the car, does indeed have the wastegate attached, as it's the one boosting constantly.

 

I only said that #2 turbo, the one nearest the firewall, doesn't have a wastegate.  It's a bypass valve to allow prespooling at 3500-4000rpm, but it looks suspiciously like a wastegate.  The giveaway is that it's downstream of the impeller - open or not, all exhaust gas would go through the impeller anyway!  I'm not 100% sure how the system regulates boost from the 2nd turbo yet, I think it's to do with electronically controlling the wastegate and the exhaust passing through it as the path of least resistance.

 

-Ian

[Syed Shah]

From what i have read and heard (Leon etc) the TT has only ONE wastegate, that services both Turbos.

[Branners]

I just talked to Leon and he's interested in buying your engine, and if you do him a deal then he can probably do you a favour and take a look at your boost problem.

 

JB

[Ian C]

Cheers, JB.  Hopefully the tried and tested methodology of 'take it apart and put it back together again' will fix my boost prob, but if not I'll speak to Leon after Christmas.  I don't know what the going rate is for a 25k mile old engine with a duff cylinder and two good J-spec turbos + associated manifold and intake plumbing - any reasonable suggestions?

 

-Ian

[Guest Martin F]

Quote: from Ian C on 2:47 pm on Dec. 22, 2001[br]

Quote: from Martin F on 1:53 pm on Dec. 22, 2001[br]

Quote: from Ian C on 12:42 pm on Dec. 22, 2001[br]JB - unfortunately in my learning about the whole TT setup, I have found that there isn't in fact a wastegate on the 2nd turbo  

 

-Ian

 

Errr beg to differ on this. The wastegate sits at the bottom of the first second turbo and can quite easily be seen from the drivers side of the car. It's usually tapped into for those running boost controllers.

 

If there wasn't a wastegate all cars would blow their turbo's within 100 miles :biggrin:

 

Ahem.  Beg to argue the point

 

#1 turbo, the one closest to the front of the car, does indeed have the wastegate attached, as it's the one boosting constantly.

 

I only said that #2 turbo, the one nearest the firewall, doesn't have a wastegate.  It's a bypass valve to allow prespooling at 3500-4000rpm, but it looks suspiciously like a wastegate.  The giveaway is that it's downstream of the impeller - open or not, all exhaust gas would go through the impeller anyway!  I'm not 100% sure how the system regulates boost from the 2nd turbo yet, I think it's to do with electronically controlling the wastegate and the exhaust passing through it as the path of least resistance.

 

-Ian

 

ROFL..............i've just read my original post 'first second turbo'  What's that then ??

 

Maybe i was pre-empting my own mistake.

 

I thought the turbo charger at the front was No2 but you are right it is No1 and as you say there is only one wastegate on our cars.

 

From the TRSM :-

 

During a high speed operation, it is the waste gate valve that executes the boost pressure control of the entire system, in place of the exhaust bypass valve.