Gt3540iw Over Boosting

[walkoau]

hi guys

i recently put a gt3540 with internal waste gate on my r34. the prob im having is it still makes boost after the waste gate has opened, i have moved away form the aftermarket actuator sold with the turbo as its spring too heavy.

i have since made up a solid braket and mounted my standard r34 wastegate actuator and i can feel the actuator (and see Via boost gauge) open up just before 10psi, but then as the revs increase to 4000rpm and higher the boost also creeps higher and im talking a big increase to like 20psi with the waste gate open.

so fare i have tried using tie wire and tying the wastegate flap open, take it for a test drive and i would have thought it would make next to NO boost although through the higher gears form 3rd anyway the boost is at 0psi till i get to about 3500rpm then it creeps up to 5psi at around 4000rpm and if i countinue to push the revs higher it reachs about 8-9 psi at 6-7000rpm. ALL THIS WITH THE WASTE GATE FULLY OPEN!!!

can anyone shed some light for me? i want to clear this problem up before i take the car into get tuned.

i should also make it clear that there is no restrictions in the exhaust so there should be no back pressure it is a full 3'' exhuast from the turbo and only one straight through cannon muffler.

and the problem cant be with the boost controller because if i take the actuator pressure hose straight after the compressor cover directly to the wastegate actuator...(meaning that if the actuator is rated at 14.7psi it should open at that pressure exactly. no boost controller to interferr with the pressure sigal.

any helpful surgestions appreciated guys

thanks

Justin

[Crans]

Is this turbo off an xr6 turbo?

Bigger port and flap

[mikel]

I read in a recent Zoom or HPI an article by Martin Donnon discussing how over boosting is a significant issue for internal gate turbos when you put a free flowing exhaust on and reduce back pressure significantly. Basically the internal wastegate is not free flowing enough to allow sufficient exhaust to bypass the turbine (ie with a free flowing exhaust, a component of the exhaust finds it easier to keep going through the turbine rather than going through a restrictive wastegate).

If you're making boost with the wastegate fully open then the wastegate is clearly not able to flow enough exhaust.

The answer in the magazine was some trimming around the wastegate port and increase the size of the flap.

If I remember I'll have a look tonight to find the article.

[discopotato03]

A couple of important things to know .

Firstly what turbine housing is on it (please say Garrett GT35 IW) and in what A/R ratio .

I wouldn't think too many waste gate systems would let you run your engine at full load to the redline and not make any boost at all . To do so would require enough valve area to pass all of the exhaust gas out of the engine - at any load and RPM and not spin up the turbine .

Cheers A .

BTW make sure the waste gate valve is opening up completly and not being restricted by the dump pipe .

Edited February 28, 2008 by discopotato03

[walkoau]

A couple of important things to know .

Firstly what turbine housing is on it (please say Garrett GT35 IW) and in what A/R ratio .

I wouldn't think too many waste gate systems would let you run your engine at full load to the redline and not make any boost at all . To do so would require enough valve area to pass all of the exhaust gas out of the engine - at any load and RPM and not spin up the turbine .

Cheers A .

BTW make sure the waste gate valve is opening up completly and not being restricted by the dump pipe .

its a gt3540 IW with .63 rear and .7 front

and the wastegate valve is def opening fully, its not restricted by the dump pipe. that was the first thing i checked.

thanks

Justin

[Cubes]

The .82 IW GT35's don't creep on the 25t's; as for .63 thats a little bit of an unknown.

What sort of dump do you have? Is it a split or a bell mouth?

Bell mouths are best for IW's UNLESS you match the opening of the dump pipe to that of the back of the turbo.

When the flapper opens it reduces the opening area of the dump pipes wastegate section; this is where you run in to issues if you simply slap in a 2" pipe for the wastegate and hope for the best.

[walkoau]

The .82 IW GT35's don't creep on the 25t's; as for .63 thats a little bit of an unknown.

What sort of dump do you have? Is it a split or a bell mouth?

Bell mouths are best for IW's UNLESS you match the opening of the dump pipe to that of the back of the turbo.

When the flapper opens it reduces the opening area of the dump pipes wastegate section; this is where you run in to issues if you simply slap in a 2" pipe for the wastegate and hope for the best.

its a split dump pipe. so i guess i can weld in a larger wategate pipe section. i can give it a go.

thanks

Justin

[dangerman4]

can you show us a pick of your current dump pipe?

ive got a gt3582r-iw which is the correct name for your turbo.

and ive had it low mounted and now highmounted.

never had any issues with creep and my dump pipes have all been a split design that i make myself from 316 stainless.

[discopotato03]

Some would say that a 0.63 A/R is a little small for a GT3582R given the 68mm turbine and 82mm compressor .

Sorry to sound negative but I think I'd have gone for a GT3076R and a 0.82 A/R IW turbine housing . IMO the trouble with small turbine housings on bigish turbos is they limit the gas flow through the hot side once it all gets going .

Some people in the US have made the best of that situation by fitting port shrouded T04S compressor covers but you also have to be careful to get one that actually works . I think Precision Turbo (PTE) in the US does one that seems to work .

Cheers A .

[PM-R33]

What ECU are you running man? You said its going to get tuned soon, so its running on a stock ECU? Or aftermarket? My turbo used to run on stock ECU and would overboost like a bitch due to the ECU retarding the timing. Microtech went in, no more overboosting

[walkoau]

can you show us a pick of your current dump pipe?

ive got a gt3582r-iw which is the correct name for your turbo.

and ive had it low mounted and now highmounted.

never had any issues with creep and my dump pipes have all been a split design that i make myself from 316 stainless.

dangerman

i was hoping you would reply to this thread as i have seen your other threads on the same turbo.

yeah will post a pic up tyomorrow of the dump pipe. why is the correct name for this turbo a gt3582r-iw? i thought it was gt3540r-iw? is the part number different cause of the smaller turbine housing?

thanks

Juatin

[walkoau]

What ECU are you running man? You said its going to get tuned soon, so its running on a stock ECU? Or aftermarket? My turbo used to run on stock ECU and would overboost like a bitch due to the ECU retarding the timing. Microtech went in, no more overboosting

its running an apexi powerfc. and yeah getting it tuned very soon just want to sort out this prob first cause i cant really get much time off work. and dont want to take it to get tuned only to have them say "cant tune it yet, something else must be done first"

thanks

Justin

[PM-R33]

its running an apexi powerfc. and yeah getting it tuned very soon just want to sort out this prob first cause i cant really get much time off work. and dont want to take it to get tuned only to have them say "cant tune it yet, something else must be done first"

thanks

Justin

Oh ok fair enough, not the same problem i had then. Sounds like it would have to be the dump pipe or the internal wastegate to blame then.

[Cubes]

The smaller the rear housing the more exhaust gas the wastegate must be able to pass.

9-10psi with the flapper wired open isn't too bad.

With the stock rb20det turbo on the 3ltr and wastegate wired open with a bell mouth dump I was seeing 6.5psi.

The difference is the boost level would peak then go flat across the rev range.

IF yours continues to rise as rpm rises right until rev cut with the gate wired open then there is a creep issue.