Wastegate

[slighty_sykotic]

Hi,

Does anyone know what can cause a external (tial, so not a cheap one) to suddenly run 3ish psi less than before?

It was boosting just a tad over 10 (cheap dial can't tell me exact), and im pretty sure GT4 20 said it was doing around 10.5 on his car (I brought it from him).

Now yesterday when I went to drive it it will only boost 8psi, no matter what I do. Ive given it it's own vacuum line and tried it on different vacuum ports and check there are no leaks in the input to the gate.

I guess if the spring "relaxed" it would go down, but on a genuine tial? and it wasnt being thrashed or anythg (new motor).

Any ideas people?

I will strip it down tomorrow if no one can come up with anything and have a look.


O yeah, its deffently the external that is limiting boost, not a boost leak or anything, as it builds fine until it gets to 8ish and then it external opens (its not plumbed in yet) and the boost stops at 8ish.

--Sykotic

[rage]

have you checked the boost gauge ? u said its a cheapie, maybe its broken

[Inane]

try tapping the boost gauge, it may be lying,

my gauge gets stuck at -15 to -16 tap it and it drops to -19 to -20

and under low boost it gets stuck around 10 or 11 psi, (howwever if i plant boot it the needle unsticks pretty quick)

Im running a cheapy boost gauge.

[slighty_sykotic]

Nah, its not the boost gauge.

It "feels" alot slower.

The needle moves smoothly up the dial until the external opens and then it stops moving.

And I have tried another boost gauge on it anyway to eliminate that.


(its a autogauge, so not cheap cheap).


Any other ideas?

--Sykotic

[evil_si]

have you checked your interccoler hoses?

also check the turbo itself, intake and exhaust housing for oil may have blown the seals,

its a mitsi td04 aye? have you run more than 14psi at all with it? they hate being overboosted and tend to fail.

[Inane]

have you checked your interccoler hoses?

also check the turbo itself, intake and exhaust housing for oil may have blown the seals,

its a mitsi td04 aye? have you run more than 14psi at all with it? they hate being overboosted and tend to fail.

1 bar is overboosting on a td04?? isnt the td04 one of the turbos everyone goes on and on about?

[Dell'Orto]

Nup, the Mitsi TD04's are great upgrades for Starlets etc TD05 is more appropriate for 2L cars

[slighty_sykotic]

Yeah, have checked the piping, and nope, never been above 12psi.

I dont see how it can be the turbo? It is acting for all the world like someone broke into my shed one night and replaced the spring is a 8psi spring.

The wastegate is OPENING at 8, so if it was the turbo, wouldnt the wastegate still be shut and trying to build the boost to 10 but it becuase the turbo is dead it couldnt. Correct?

--Sykotic

[Ako]

Are you positive there is no leaks post turbo at all? No slight leaks on the boost guage hose - it might have a small crack which only gets opened under pressure, and closes up again under vacuum?

Bloody weird one. Never heard of a tial spring relaxing anyway, its got me baffled.

[slighty_sykotic]

Yeah, pretty sure, but I will have another check.

But i still don't get how that works though, if the turbo pipes are leaking at 8psi causing the boost to not get any higher, why is the wastegate opening?

--Sykotic

[Ako]

Are your boost gauge and wastegate both getting their signal from the same place?

[slighty_sykotic]

Yeah, i have tired all different combos with the vacuum lines, and when i get a T from one source to the boost and wastegate, it still shows 8ish.

I have also tried giving the wastegate it's own line, and tried plumbing it into the manifold on different places etc etc.

I just pulled the cap of the wastgate, the diaphram looks good, bit dirty, just gave it a wash in warm water, going to dry it off now and put a bit of silicon on it to lube it up and put it back together.

--Sykotic

[slighty_sykotic]

Ok, put back together and its still doing the same.

I then blocked the line going to the wastegate, and guess what?

It boosts fine now. Boosted to 11ish before I backed off.

So there is nothing left but the wastegate, and there is nothing wrong with the wastegate that I can see (not much to go wrong anyway).


MAYBE, GT4 20 replaced the spring (or whoever had it before him) with a cheap one? And now it's relaxed?

Hopefully he sees this thread and can comment.

--Sykotic

[evil_si]

1 bar is overboosting on a td04?? isnt the td04 one of the turbos everyone goes on and on about?

yup tdo4's dont like being oversped!
personally i hate them, the shaft size is pathetic, they snap easily. and they dont respond very well to compressor stall, ie when your bov goes ch ch ch

sykotic, very wierd about the spring, i havent encountered any of the copies doing this, let alone a genuine tial.
you didnt change the vacuum hose before it did it by any chance?
a couple of small holes or splits will bring the boost up,