Help Understand GTT Boost Setup

[DraftySquash]

Hi everyone,

Apologies in advance if this feels like a topic covered multiple times. I'm only asking because some of the old topics I found are missing images now.

I'm in the process of getting a manual boost controller (BC). Nothing fancy, just getting a manual one for now as I don't plan to go crazy with it and would not go over 10 PSI. My car is not jacked up on boost steroids to do crazy numbers.

I want to understand the OEM setup of the boost solenoid and vacuum lines on the R34 GTT so I know what needs to be changed when I do install the BC. I sketched the current setup to the best I could see and it's on the diagram attached.



If the boost controller 'Wastegate Arrow' goes from nipple 1 to 2. My understanding is that the red vacuum line's "F" connector-end should be connected to BC nipple #2?
Nipple #1 is meant to have the "pressure source" so what vacuum line would that be? Is it the green vacuum line? 

From what I have read here, the OEM boost solenoid is not used at this point. So that can come out and then I can just plug the nipple that usually connects to the blue vacuum line? 

So would the final setup look something like this?

 

Thanks in advance. I don't want to already be knee-deep into pulling out vacuum lines before understanding this. I'm a noob when it comes to boost setups so trying to learn as I go.

[GTSBoy]

The stock boost solenoid is just a valve. Power it and it is open. Unpowered, it is closed.

When it is closed, there is no boost bleed out through the solenoid back to the inlet. The wastegate sees all the boost pressure, thus you get the wastegate's spring pressure as your boost pressure. 5 psi.

When it is open, it lets some boost escape. This causes the static (boost) pressure in the line to the wastegate to be lower than the pressure in the intercooler pipe. There is probably a small restrictor in the solenoid or one of its lines to limit the flow rate of the escaping air, which limits how far the static pressure can fall, which limits the extra boost. The boost has to climb above the original/wastegate setpoint until the wastegate sees 5 psi. You get 7 psi in the intercooler pipework.

A manual boost controller is exactly the same setup, just without the ability to change it on-off. It's always set to whatever you set it to. There is a small leak from the boost controller. The more you screw the adjuster in, the more it leaks, the lower the pressure seen at the wastegate and the higher the boost will be.

So, yes, your diagrams are correct.

[DraftySquash]

@GTSBoy that’s good information and thanks for sharing that. 
I’ve read the GTT has 2 stages of boost? 5psi or so at lower RPMs and then 7psi. 
So I assume, with a boost controller it will be one standard pressure. I got no issue with that until I invest in an electronic boost controller.

With the setup after the boost controller, should I still keep the solenoid plugged in to power? Just so the ECU is happy? Or does unplugging it and completely removing it cause no issues? 

I’ve got myself booked in for a Nistune install and tune next Monday so pretty excited 😝 

[GTSBoy]

The ECU doesn't care if the solenoid isn't there. There's no sensing/feedback from the solenoid. The ECU just gives it power, or not.

Make sure that you Nistune tuner knows damn well how to tune a Neo. They suck. You have to take a lot of care to override bullshit to do with the boost sensor and a few other things to stop them being a dick.

[Milkmun]

Who's doing your Nistune install and tune? 

Could always ask them to install the MBC.

[DraftySquash]

  On 11/02/2025 at 10:51 AM, Milkmun said:

Who's doing your Nistune install and tune? 

Could always ask them to install the MBC.

Expand  

It’s Shane at CMS performance doing the tune. 
 

CMS performance was the only place in VIC I could find that would supply, install and tune (and had good feedback)

Yeah that might be a good idea 😂

Less chances of fkn it up 

Edited February 11 by DraftySquash

[Milkmun]

  On 11/02/2025 at 11:04 AM, DraftySquash said:

It’s Shane at CMS performance doing the tune. 
 

CMS performance was the only place in VIC I could find that would supply, install and tune (and had good feedback)

Yeah that might be a good idea 😂

Less chances of fkn it up 

Expand  

Big drive from the west to Seaford. Good luck man, let us know how it all goes.

[DraftySquash]

  On 11/02/2025 at 11:15 AM, Milkmun said:

Big drive from the west to Seaford. Good luck man, let us know how it all goes.

Expand  

lol I know!!

I’m actually staying over at a mate’s place in SE the night before. 
not because I don’t like the long drive. I just don’t want to drive from West to Seaford around 8am on a Monday 😂

traffic would be wild. 
 

The Skyline actually does the West to SE trip without issues. My family is on that side. 

[DraftySquash]

I think a 60-90 mins drive is worth it, if the mechanic is good and has experience. 
that’s what I’ve heard about CMS, so I’ll let you know how I go after Monday 

[Kinkstaah]

I have a friend who has used Chequered Tuning and CMS. Went to CMS when Chequered had a long wait time which is kind of the norm (for good reason).

Was very happy - I'm pretty sure the very simple thing you're asking will be simple.

[DraftySquash]

  On 11/02/2025 at 10:31 PM, Kinkstaah said:

I have a friend who has used Chequered Tuning and CMS. Went to CMS when Chequered had a long wait time which is kind of the norm (for good reason).

Was very happy - I'm pretty sure the very simple thing you're asking will be simple.

Expand  

@Kinkstaah yeah I initially checked with Chequered as I've used them with a previous car. But they have stopped sourcing and installing Nistune chips. They only do tuning now.

I did not want to pull out my ECU and send it away somewhere to have the chip installed. That would mean no driving the Skyline  

[Kinkstaah]

Ah my friend, messing with the engine and looking for more power is the gateway into "no more driving the Skyline"

Tread carefully 

[DraftySquash]

@Kinkstaah

I've got my list.. but most of them is to do if I ever win the lotto

[Kinkstaah]

Just putting it out there, that's a decent list.

You would be better off *not* doing *any* of that and buying someone else's modded car. Like mine. Or anybody else's. Yes it's lotto dependent and all this and that but that 70K (remember, double your guesses) could go elsewhere. Keep it stock, save your money, go lowball @Dose Pipe Sutututu :p

[Milkmun]

Big list. Get security asap I reckon.

[Dose Pipe Sutututu]

If someone walked up to me and offered me an amount that I can't refuse, please take it away, I'll throw in half my tools, the boxes of brand new OEM spares, anything in the house I can find that's Skyline related. 

Want the lot gone.

 

(don't mod your car, you'll regret it)

[Dose Pipe Sutututu]

  On 11/02/2025 at 11:57 PM, Kinkstaah said:

"no more driving the Skyline"

Expand  

........... aint' that the truth.

[Kinkstaah]

You know what, I'll double or nothing. Save your money, buy a V8 Manual Mustang in 2 years and have a more fun street car with better support and all that. I often tell people "if I could do it all again, I wouldn't".

Sell your R34 GTT to someone, spend the 20k in difference between that and a 2018 Gen2 V8 Manual Mustang. I'll bet you will have the $ in your pocket by the time you spend the ~20K differential on mods and get them installed.

Just planting this seed for future regrets. Blah blah, wisdom of people who would do it differently who are at the end of the road you are just starting on, etc. Car modding is often death by a thousand cuts as you wait to afford the next big mod.

Imagine a 2 door Skyline with a 330KW N/A V8 Revving to 7500rpm like the RB25, with 315's all round.

[MBS206]

I'd do it all again in a heart beat.

Well, not all, I'd make some different choices in which mods. But I'd definitely still spend all the money.

[joshuaho96]

  On 12/02/2025 at 11:57 AM, Kinkstaah said:

You know what, I'll double or nothing. Save your money, buy a V8 Manual Mustang in 2 years and have a more fun street car with better support and all that. I often tell people "if I could do it all again, I wouldn't".

Sell your R34 GTT to someone, spend the 20k in difference between that and a 2018 Gen2 V8 Manual Mustang. I'll bet you will have the $ in your pocket by the time you spend the ~20K differential on mods and get them installed.

Just planting this seed for future regrets. Blah blah, wisdom of people who would do it differently who are at the end of the road you are just starting on, etc. Car modding is often death by a thousand cuts as you wait to afford the next big mod.

Imagine a 2 door Skyline with a 330KW N/A V8 Revving to 7500rpm like the RB25, with 315's all round.

Expand  

Yeah if the goal is to drive something then modifying a car is a bad idea.