25det Wastegate Issues

[chur]

Praying to the skyline gods for help.

I'm having issues with the boost on my rb25det, it has me totally stumped.

Mods: Factory turbo/wastegate

Front mount Intercooler.

Pod filter

2.5" exhuast from turbo to cat, 3" from there back

Problem: Overboosting

To diagnose the problem I am running a line directly from the plenum to the actuator (no boost controller). The wastegate flapper is moving freely (I have had the down pipe off and inspected the internals).

I took the wastegate actuator off and had it tested by a local shop who told me it is holding pressure.

Some people have told me that adding the exhuast and pod filter could make it boost higher however I fail to see how this is possible as my boost gauge (1 of 2) is reading off the same port running as the actuator. Today I let it boost up to .90 bar and it definetly did not level off.

Finally it seems that everything is pointing towards the actuator being faulty, It isnt obviously jambing as I can pull it open by hand but somethings going on.

If anybody can add anything I've missed it would be much appreciated.

[Cubes]

To determine if it is the actuator simply disconnect it from the flapper.

Mine made almost 7psi with the flapper jammed open but it is a larger motor, a smaller motor may make less boost.

[chur]

To determine if it is the actuator simply disconnect it from the flapper.

Mine made almost 7psi with the flapper jammed open but it is a larger motor, a smaller motor may make less boost.

Good call, I will give it a try, that should prove it!

Thanks Cubes

[13thracer]

does your cooler pipeing have any nasty bends or size changes in pipe i had the same sort of thing which tormented me for 6 months before finally figuring out it was the pipe work. just my experiance with this issue hope it helps

[chur]

does your cooler pipeing have any nasty bends or size changes in pipe i had the same sort of thing which tormented me for 6 months before finally figuring out it was the pipe work. just my experiance with this issue hope it helps

Interesting, I brought a complete fmic kit, none of the bends seemed too harsh however I will bear it in mind. 6 months of not understanding whats going on may cause me to drive it off a cliff (whilst overboosting)

Thanks for your input

[chur]

Ok before I was stumped, now I'm just totally confused. I've completed 2 more tests tonight.

1. using compressed air and a regulator I emulated boost to the actuator, It worked perfectly. Around .5 bar it actuated and moved the the flapper effortlessly.

2. As suggested by Cubes I disconnected the actuator and wired the flapper open........it's still overboosting!! I only took it up to .70bar however I am fairly certain it would have kept going if I hadn't of buttoned off.

Any other ideas, Could a blockage in the exhuast system cause this kind of issue?

I'm kinda hoping somebody will point out the obvious cause, I'm lost!

[Cubes]

When you disconnected the actuator from the flapper did you ensure the flapper was moving freely and was able to open fully?

Start looking at your dump pipe.

[recce]

Where exactly did you run your hose from the actuactor to? Check that it does have pressure. Check every hose that was connected to the actuactor. There might be a leak that bleed the the pressure line to the actuator. Did your intercooler have a nipple in the inlet pipe that run to the throttle? I suspect its the pressure hose to the actuator that is creating that problem.

[chur]

Flapper is nice and free and I wired it fully open for this test. I had the dump pipe off in the weekend everything looked fine. What I'm now wondering is if the cat has fallen to bits, could the extra back pressure cause overboosting... Yes I am totally grasping at straws

Thanks

[Cubes]

What dump are you using? China 2.5" jobby?

'usually' a stuffed cat will cause lack of boost, or boost tapering off in the top end.

[chur]

Where exactly did you run your hose from the actuactor to? Check that it does have pressure. Check every hose that was connected to the actuactor. There might be a leak that bleed the the pressure line to the actuator. Did your intercooler have a nipple in the inlet pipe that run to the throttle? I suspect its the pressure hose to the actuator that is creating that problem.

Hi recce

This all started because while doing the cooler I also went to install an HKS evc4. I put a nipple into the right angle pipe off the top of the compressor. After it failed to work I took the controller out of the equation and plumbed the actuator directly to the plenum (to the nipple below the factory blow off valve line normally used for the carbon canaster, with a brand new length of pipe)

I have also swapped them around and even put the boost gauge in line so I'm fairly sure now that the actuator is actuating.

Now that I have showen that even with the wastegate wired open its still overboosting I think there is something else amiss

[Cubes]

Well as you say.. If it was fine before with the dump its definitely not that.

[chur]

Hmm thats what I thought. A blocked exhaust would cause slow spooling, then again I havnt driven another r33. Dump pipe is a factory dog.

[chur]

I actually had one of these turbos on my L28 powered 280zx, It went really well and certainly never had any problems like this. Thanks for your time fellas and if anyone has ever seen anything like this please let me know, cheers

Special thanks to cubes :laughing-smiley-014:

[recce]

Mate! I don't think the the nipple you tapped into for the actuator is the correct one. Try this last thing before you made any conclusion. Tap it to the hose that connect to the factory BOV. you will need a "T" piece to do that. If that fails, it is something that I cannot help you with. There is a high chance that you have tapped into the wrong nipple. Remember, TAP IT TO THE HOSE OF THE BOV.

[chur]

Mate! I don't think the the nipple you tapped into for the actuator is the correct one. Try this last thing before you made any conclusion. Tap it to the hose that connect to the factory BOV. you will need a "T" piece to do that. If that fails, it is something that I cannot help you with. There is a high chance that you have tapped into the wrong nipple. Remember, TAP IT TO THE HOSE OF THE BOV.

No no I have. Infact at the moment it is connected directly to the port normally used for the BOV. I have proved that the actuator is getting boost pressure and that the actuator is moving. As Cubes pointed out if you wire the flapper open then it definitely should not overboost.

[zebra]

Its not a dodgy boost gauge is it?

Got me stumped otherwise.

Any restriction in the exhaust should cause lack of boost.

GT

[chur]

Its not a dodgy boost gauge is it?

Got me stumped otherwise.

Any restriction in the exhaust should cause lack of boost.

GT

Thanks zebra

I wish it was a dodgy gauge, that would be easy lol

I have two, one is a blitz mechanical, and the other is an HKS digital, both reading about the same. I think I'll just drive it into a wall

thanks brother.

[psi]

how odd..

So, just to get this right, the waste gate is wired so the flapper is in the open postition..

Then there should be no way that thing should be climbing in boost pressure reguardless of where u get the signal from.

arrghh.. question,

can the wastegate actually 'open' all the way? I mean is it only opening say half way or two thirds?

Are you sure there is nothing in the wastegate dump pipe that is blocking gas flow?

well thats all i got! not much help huh?

[lineskee 33]

if the wastegate and actuator are working fine, why not look at other possibilities?

haha i was about to suggest boost controller but u said u dont have one.

i would check vacuum lines and pretty much anything looking for any leaks splits or anything like that.

but hey im no expert.