R34 Gtt Boost Issue (driving Me Nuts)

[seriesII]

Hi all...want to see if someone can help out with this...I bought this low 70k 34 a year ago..ever since its had boost issues... so today I wrote down the max boost I recieve with my boost controller turned off and using my internal wastegate..

1st gear I get 7psi !

2nd gear 8psi

3rd gear around 9psi

4th gear just under 10psi

5th full boost of 10 psi.

I use a hks evc 5..when this is on I revive a little higher boost of course..If I'm set to hi mode..15psi in 5th gear..though any Lower gears less boost..1st will only ever reach around 9psi.. 2nd 10psi.. 3rd 12psi and 4th can be 13psi and 5th full boost..I can't find any leaks..All hoses have been changed.ive changed my intake as it was custom made and way to short..changed bov incase the turbosmart that came with It was leaking..

New tune on my nistune board by toshi.

Changed spark plugs..coil packs to splitfire.. All hose clamps are tight..

Car has

nistune ecu

z32 afm

Tomei poncams 252

Full 3inch exhaust

Just jap return flow intercooler

Custom metal intake.

Walbro 255 fuel pump

splitfire coils

Large garret turbo. It came with the car and had only about 3k on it. It does have a larger intake connection then a stock skyline turbo..3 inches. So my intake that joints to it us 3inches.. A guy looked up my turbos serial number and was saying may be a gtx garret..It did seem to have double fins on each fin when the intake was installed..

Does anyone have any ideas or why my car has down low boost issues ?.. is there a sensor stopping this or can it be a faulty boost sensor ? Is their anything I can look at with my consult cable to check if anything is maxing out a voltage somewhere ? ...seems some days I can get 1 or 2psi more if km lucky or the car is cold..Thank you

Edited August 25, 2015 by seriesII

[seriesII]

Oh to add..when I've had it on high boost 15psi. I've seen my turbosmart boost gauge go to 13psi or 14 then it will drop to 10psi in 3rd and 2nd gear..I've had it feel like it launches with power then the boost drops down by 4psi or so and back down to 10psi.. until I hit 5th gear which will hit 15psi. Getting so annoyed with this car..and it's in perfect condition not even a oil drop out of the car

[GTSBoy]

Are you telling us that this is all on standard management?

[Ben C34]

Take care to a place capable of tuning it.

You are not going to be able to.

[seriesII]

It's has a nistune board installed..not stand engine management.. and was tuned by toshi for 16psi.. so I should get a retune again ,.?.. If it keeps the issue up while tuning I guess it could start costing a bit though..

Toshi is a top notch tuner known by many and one of the best.. even he had this boost issue tuning my car..3rd gear would spike up to 15psi then drop down to 10 psi within 2 seconds.. another tune with this issue seems like it could be a waste of money if I can't find what the issue may be..was unaware the ecu would control boost except for the boost pressure sensor on the 34s.. just seeing if anyone has any ideas I have missed on to why this is going on.

Edited August 25, 2015 by seriesII

[KiwiRS4T]

Sounds like your boost controller is faulty or set up wrongly. Can you borrow a manual boost T and see if its any different? Have you tried pressure testing your pipes?

[GTSBoy]

Sorry, I missed the Nistune buried in the middle of the list.

What sort of dump pipe is on it?

[seriesII]

Boost controller seems perfect..well its set up perfect.. I tried a turbosmart the piece.the duel when I got the car..It did the dawn thing. Maby ill hook up the stock solenoid and see what is does ? . I have not tried to presure test..good idea ..can any place just do that ?..I guess I would have to take my pipes of ? ..

Gtsboy..that's okay..I had a lot of info .. It is a all in one dump and down pipe..

[seriesII]

If my boost controller was faulty or set up wrong..would it still hit full boost in 5th ?

[VeYzZii]

Internal or External wastegate?

[seriesII]

It's a internal gate.. was thinking maby my wastegate is leaking..I'm not to sure how to tell though

[seriesII]

It does seem when the car is cold..10 mins of warm up and then driving I can get around 9.3psi in 2nd and the other gears.. Once it's a lot hoter seems to not make it to that

Edited August 26, 2015 by seriesII

[scotty nm35]

You need an upgraded actuator for the wastegate.

[seriesII]

Wastegate is upgraded that came with the gtx garret

[Dose Pipe Sutututu]

pressure test the hot/cold side.

[seriesII]

Will do.. looking to get this done next week and a smoke test..hopefully it comes up with some leaks to be a easy fix

[benl1981]

You say upgraded intake. Is it all metal? Does it have anywhere it can collapse?

I had a home made snorkel on the standard air box (to allow for the FMIC piping) that was collapsing under the suction created at high boost so I'd go from 18psi down to 0psi at about 5k rpm. Worse in the higher gears since more load / air being pulled in.

Looked at everything before that.. May not be the same issue but worth having a look at your intake, especially pre turbo to make sure there's no weak points

[benl1981]

Just had another read. Your getting higher boost in higher gears so may not be the problem I wa describing. Might be some kind of leak as mentioned above. Hope it's an easy fix.

[scotty nm35]

A smoke test only pressurises the intake to .0001 psi, your leak may only appear at 10psi. I always use a compressor and put 20 to 30 psi in the intake, you would be surprised how many leaks I can usually find.

Do you know what pressure the actuator is supposed to hold?

[seriesII]

Thanks so much for the time to reply guys..so appreciate it... its funny as I have paper work that has just before I bought the car for a new waste gate that is set to 14psi..so wtf..yet max I get is 10psi if I use just the intrenal gate to control my boost ...I might try this pressure test with a compressor.. Scott when you say intake..would I just remove my pod filter and pop 20psi in there ?..or I could remove the engine oil breather line on my metal intake and pop the compressor in there ? Thanks

Definitely today in first gear using the waste gate with stock solenoid connected..7psi in first.. 8 ish in 2nd and 9psi in 3rd.grr

Edited August 28, 2015 by seriesII