3SGTE over boosting?

[ST185GT4]

Hi guys (mod on),

I have got the GT4 rego'd an on the road, wahoo!!!

It's running better than ever, it's stock as (apart from a .20" bore) and I still have a set of headers to go on, maybe later...

The last remaining problem: When I throttle up (in the non-restricted gears 3-5) it boosts up to 10-15 psi and then gets the turbo sensor error and goes into limp mode cutting spark when it gets to 0psi from vacuum.

It seems to be alright in 1st and 2nd. It's running awesome apart from this.

It is the actuator or do I need a new turbo sensor or ???

Thanks in advance....

[OnAll-FOUR]

It sounds like your hitting the boost cut

[ST185GT4]

Thanks for the quick reply.

Yeah I agree, but why it is?

I'm not flogging it at all and it gets there really easy.
Not sure on the revs but not very much maybe around 4000 to 6000.

[td42gq]

From memory that model has two vacuum lines to the wastegate solenoid. Is it possible they are on back to front?

Aaron

[Cuts]

^^that wouldnt matter^^^ as they both just go into the actuator.

[OnAll-FOUR]

Are you running any boost controller?

[ST185GT4]

Nope. Not yet. It's all pretty much stock. Althought it does have a GFB Bov which is connected (as I got it) to the same line as the turbo pressure sensor...Hmmmmm.
Could that be it???

[jonathan yee]

stock turbo? do you have an aftemarket dump pipe? the ebay one's have a tendency to interfere with the wastegate so it could be inhibiting it/not allowing it to open fully and hence your boosting more than you should.

stock wastegate pressure is 7/8psi and the tvsv allows 10psi stock.

[ST185GT4]

Mate thanks heaps for that cooler it seems to have solved my water/oil prob.

Re: over boost
Yep all stock.
One of my mates sayed he had that prob you mentioned with his et pulsar.
Maybe i've upset the wastegate when I replaced the old exhaust manifold.I think i'll check the turbo pressure sensor and go from there. If its good i'll put on my new headers on and check the waste gate.

[mattysshop]

try just connecting the wastegate to the turbo housing.. not tvsv or what ever it's called.. see if it still has that problem..

also are you refering to a turbo manifold as headers?

[OnAll-FOUR]

Try to narrow down your problem, do as Mattysshop says and also block the seccond port on the wastegate. This should give you the same boost as first in all gears. If this is working properly then reconnect in the TVSV and this will give you back the higher boost in the other gears.

If you haven't touched anything it should hold closer to 10psi psi no problems. Check all your vacume lines expecially around the wastegate. A stock setup shouldn't be seeing 15psi

[ST185GT4]

Alright. I disconnected the tvis and blocked it and it worked.

It was boosting to 4-5psi in all gears. So it's the tvis vsv and onward that is the problem?

Looks like we're getting closer. Thanks again for the help guys. Us newbies need calming down and pointing in the right direction. Loving the learning curve.
PS Sorry about the headers thing. Its turbo manifold from now on, cheers.

[OnAll-FOUR]

Okay so is you put the VS back in, does it hold 8-10 psi boost then creep up to 15psi further up in the rev range?

Or does it shoot stright to 15psi and boost cut when you put your foot down?

[ST185GT4]

If I reconnect the tvis vsv the boost shoots straight to 15psi and cuts.

Once I put the foot down. i.e. its not boosting to 15psi at less than 4000-6000rpm.

But when it does it goes up quick.

[OnAll-FOUR]

Maybe the VSV is not working or maybe a vacuum leak?

Either way maybe disconnect the VSV and buy a boost controller = more boost in all gears

I'm not sure about the 4000-6000 rpm wheen on boost. with a CT26 turbo you should be on boost 2500-3000 rpm