Internal Gate Boost Control Problems

[SimonR32]

I have a Apexi AX53B70 internally gated (aftermarket actuator) 380hp turbo on my RB20DET, but I have heard people with similar problems with HKS and Garrett internally gated turbos as well.

I am having problems with the boost creeping as the engine rises through the revs and it can not be controlled to hold less than 20psi approaching redline. This is NOT a boost controller problem as it is unable to hold boost to less than this with the actuator line connected straight to the turbo outlet. Is there any way to fix this as sometimes i would rather use low boost to conserve my engine (eg: drift and track days)

The car used to only creep up slowly towards 1 bar when it arrived from japan, but now i have increased the intake and exhaust flow (by changing the dump pipe, larger FMIC and air filter) it will not be controlled to anything under 1.4bar.

I am assuming that this has to do with internal gates lack of abilty to flow enough air to lower the boost pressure. Therefore I have been approached with 2 options that may work...

1. Buying a aftermarket manifold to suit a external gate application, weld the internal gate shut and use a external gate to control boost.

2. Improve the flow of the internal gate by using a larger actuator flap and grinding out a larger hole to improve flow

Neither of these options appeal to me as they would involve modifying my expensive turbo. Also the first option which i know has been known to work on other cars is a fairly expensive process when you have to buy a external gate, manifold and new exhaust to suit the high mount.

Does have any bright ideas or solutions to the problem, i know it is not only me struggling with this so any advice for a cheap solution would be much appriciated

Thanks in Advance

Simon

[grim32]

sounds like maybe the actuator arm needs more travel, can you disconect the actuator from the waste gate and then wire the wastegate fully open, mine wont even make 1psi if i do this so it should give you a good indication of what the problem is

[SimonR32]

good idea... i shall have a try on the weekend

by the way my actuator arm is adjustable, i have not touched it since it came over from japan

any more other suggestions/solutions?

[BHDave]

I think grim may be on to something.

I would expect that a properly designed internal wastegate is capable of flowing enough for the turbo, particularly as it is an aftermarket model designed for 1+ bar.

What type of dump pipe are you running? could it be preventing the wastegate opening properly. I've seen it before.

[R31Nismoid]

I am assuming that this has to do with internal gates lack of abilty to flow enough air to lower the boost pressure. Therefore I have been approached with 2 options that may work...

thats totally backwards dude.

It wont have a flow problem with less air.

Its only more air/backpressure that would be a problem

try dropping the exhaust, from the cat, then see what happens

[SimonR32]

there is no cat 3 inch front pipe and 4 inch cat back

the dump pipe is a hks copy china split dump, it has been ported to improve flow as some of the welds are a bit dodgy standard...

i talked to a very reputable performance workshop mechanic today and he said that they have to port the internal wastegates on all rb25 highflowed turbos otherwise they have the same problem... he also said that a bit of porting to direct the flow to the wastegate helps as otherwise the exhaust gases will just flow past cause of their high speed.

so it looks like its die grinder time. ill have to take the turbo off and find out how much i can increase the diameter of the wastegate without changing the flap, hopefully should be about 3mm or so.

may as well also give the dump pipe a little more of a port and match as well to help improve flow even more

[SimonR32]

thats totally backwards dude.

It wont have a flow problem with less air.

Its only more air/backpressure that would be a problem

try dropping the exhaust, from the cat, then see what happens

<{POST_SNAPBACK}>

if the internal gate is too small it will not allow enough air to flow through creating a larger pressure in the manifold and the only way this air can flow is through the turbine blades... which cause them to spin faster and therefore increase boost pressure

hense why engines making more horsepower need bigger external wastegates

Edited October 7, 2005 by Cerbera

[R31 POWER]

I have the same problem atm.HKS GT2535 on the RB20.

Ok when I installed this turbo with the standard RB20 actuator it would go to 12 psi and sit there all the way to redline.I recently got a tune but this time no cat and now boost will go to 12psi and creep upto ~15psi with no boost controller!!!

I have a profec B boost controller and with my high boost settings at 17psi it will creep upto 18-19psi.Low boost it will hit 12psi and creep upto ~15psi.

I disconnected the actuator rod and took it for a fang and boost went to 1psi for like a second and then it was all vacume.I have even tried another RB20 actuator and it was the same.

So maybe not having the cat is causing this?? I might pop it back in and see what happens.

[paulr33]

i recall reading some time ago about wastegate sizes and a large like the 42mm gates where only needed when u wanted to run a small amount of boost a bigger turbo. that was the only reason you needed larger wastegates and the argument of bigger is always better was not valid (for once!). but you guys are using int gate so i have no idea.

[Cubes]

the dump pipe is a hks copy china split dump, it has been ported to improve flow as some of the welds are a bit dodgy standard...

<{POST_SNAPBACK}>

I'd say this is more than likely part cause of your problem. Prior it was fine at 1bar with the old dump, now its having issues with creep to 20psi.

FMIC and pod won't cause what you are experiencing.

Those cheap china hks copy's are only 2.5" and they don't flare when the wastegate joins in either.

No doubt better than stock but not better than a open mouth 3".

Enjoy the 20psi, get it tuned to suit.

Edited October 7, 2005 by Cubes

[Sydneykid]

I agree with grim32, I find it very hard to believe that IHI (they make the Apexi turbos) made a mistake calculating the size of the wastegate by that much.

I have seen exactly the same problem several times with adjustable actuator arms straight from the factory. The wastegate actuator simply isn't travelling far enough. This means the wastegate flap isn't opening far enough to bypass the necessary exhaust to control the boost. To test if this is happening in your case, simply disconnect the wastegate actuator and wire the wastegate fully open.

If this doesn' t resullt in very low boost, then you have another problem. I have seen (rarely) split dumps where the wastegate pipe actually stops the wastegate flap opening far enough. That is easy to test, just disconnect the wastegate actuator and check that the wastegate is fully opening. Maybe check this just before you do the above test.

cheers

[SimonR32]

as i said before this is not only a problem with IHI (Apexi) turbos but i have seen it happen with HKS 2530 and HKS 2535 as well as Garrett 3071's

i will test to see what happens when i dissconnect the actuator arm tommorrow...

if it is to do with the actuator not opening enough would the solution be as simple as just adjusting the arm to be longer?

it is not a problem with the dump, as the car had a standard dump on when it came over from japan and when i put on the china dump it actually made it a little better

[Cubes]

How did it make it better when you said prior it was creeping to 1bar now it is creeping to 20psi?

[SimonR32]

ok

here goes the story

-came over from japan standard dump, standard boost hit 1 bar

-china dump added and only creeped to .9 bar

-new filter and power fc tune went to 1.2bar

-100mm front mount replaced old GTR went to 1.4bar

sorry if i got confusing

[R31 POWER]

Fark it lets put RB25det actuators on Cerb 5/7psi here we come lol

[SimonR32]

i have a apexi actuator...

i thought about taking the actuator arm off last night, this would be useless as taking this off would make the car not run any boost so it would be making a lot less power and hense not pushing the same amount of exhaust gas as it would if it was boosted by the turbo...

therefore sydneykid is wrong, pulling off the actuator arm will not test to see if the internal gate flows enough air

any new suggestions

[Cubes]

Thats right Cerbera,

Say you push 10psi through it, the wastegate may very well have the ability to bypass enough exhaust gas to hold 10psi, 12psi may be ok then all of a sudden at 13-14psi you find it wants to creep.

That dump pipe you are running is crapo though.

[Sydneykid]

i have a apexi actuator...

i thought about taking the actuator arm off last night, this would be useless as taking this off would make the car not run any boost so it would be making a lot less power and hense not pushing the same amount of exhaust gas as it would if it was boosted by the turbo...

therefore sydneykid is wrong, pulling off the actuator arm will not test to see if the internal gate flows enough air

any new suggestions

<{POST_SNAPBACK}>

Nope, your at looking at it as if the wastegate is either fully open or fully closed and this is not the case. Plus you are thinking of this as if it is the only test. It is one of a sequence of tests to eliminate the possibilities. There is no one test that will eliminate all of the posibilities, so I have to do them one by one in a logical sequence.

If I wire the wastegate flap fully open and it still builds excessive boost, then I know it isn't the wastgate flap that is causing the boost to build. One item eliminated and I can start looking elsewhere.

Plus the very process of wiring the wastegate flap open by itself will tell me if there is an obstruction to its full opening. Another item eliminated.

If the boost builds with the flap fully open, then I drop the exhaust at the entry to the cat and see if that stops the boost build. If it does then I know the issue is cat back. If it doesn't, then I know it is between the engine and the cat. Another item eliminated.

If I wire the wastegate fully open and it doesn't build boost, then I need to check that the wastegate actuator is actually capable of fully opening the wastegate. I do this by tightly tieing a cable tie onto the wastegate actuator shaft such that it is pushed along the shaft by the action of actuator body moving the shaft. I then go for a drive, build some boost and then check how far along the shaft the cable tie has moved. I compare that to the full movement of the wastegate flap to make sure the actuator has sufficient travel. If not, I then adjust the length of the shaft to achieve more flap opening. I have to be careful as lengthening the shaft also increases the preload on the wastegate actuator spring and thus increases the boost level at which the activator moves.

I have carried out this elimination process on a number of Skylines, and I have ALWAYS found the problem. The most common of which is insufficient wastegate flap opening, either from obstruction or poor adjustment.

Hope that clarifies

cheers

Edited October 8, 2005 by Sydneykid