Wiring/hoses On Rb25det Engine

[ClumpyDog]

My series 1 R33 GTS-t up until very recently was fairly modified, and the police thought so as well when they pulled me over and gave me a fine, and gave me an invite to the EPA.

I have since decided to make my vehicle more legal, and have taken the car to a workshop to remove some mods, the main ones being the injectors and the Microtech MT8 computer, going back to stock ECU, AFM, etc.

The car when I got it back is very uninspiring, has horrible torque holes, unpredictable power and is generally running poorly. The car has not been dyno tuned yet on the original stock parts, other than tuning by the workshop that changed my car back - but I have noticed a couple of things on the wiring/vacuum hose that I am not sure are quite right. I purchased the car with the Microtech, so it didnt have an AFM or some of the loom wiring- and didn't need it.

Not much point getting it tuned, if something is unplugged that is causing my problems..

Two things seem to be obviously missing:

- There is a prominent plug that looks like it needs something plugged in it about where the throttle butterfly is, going in to a black box. Nothing is plugged in there, and there is definitely no plug in the loom that matches it. Is this supposed to have something there?

- A small vacuum hose is hanging loose with just a screw in it to prevent vacuum loss- This is next to the power steering reservoir, behind the air box. One hose goes to the pressure side of the intake, the other goes nowhere. Where is this supposed to go to?

Any help appreciated.

Thanks,

Alan

[Abo Bob]

1. No, see that plug hanging just below it? That's the wiring for that one. Weird but true.

2. I can't see it.

[ClumpyDog]

1. No, see that plug hanging just below it? That's the wiring for that one. Weird but true.

2. I can't see it.

Thanks for that, 1 down, 1 to go

Attached is a hopefully easier to see picture...

The red arrow is the gold colured valve part where the hoses are going to.

The blue arrow is where the vacuum/pressure is obtained, this goes on to the valve part, the lower hose point.

The green arrow points to the loose hose with the plug. This goes in to the valve part on the upper hose point, the other end hanging loose..

Sorry for my dodgy terminology, I don't know what it is supposed to be called.

[RBwhatever]

Red Arrow --> Stock boost solenoid (Bleed Valve). Controls boost.

Blue Arrow --> Pressure Side, Pressure flows to the solenoid through this hose.

Green Arrow --> Bleed Hose, any air that is bled off by the solenoid goes through this hose. From factory that hose plumbs back into the "plumb back" pipe coming from the BOV. So any air that is bled off to create more boost, is bled back into the intake before the turbo.

I don't know why that hose is blocked off. Unless your car is using another boost controller.

Because it is blocked off, and if the car is using the stock boost solenoid to control boost, then it would not be able to bleed off any air to increase boost.....so the turbo would only be making 5psi max and not 7psi.

Anyone please correct me if i'm wrong.

[ClumpyDog]

Great, thanks for that. This clears things up a bit..

This car did have a boost controller, but no longer. It may not have been put back 'stock' correctly.

The car has been meauring 0.6-0.7 bar of boost (8-10psi) so boost seems high if anything for the stock wastegate.

Since your post, I checked the car, and indeed there was a hose going in to the wastegate return... it was connected via a T piece going in to the 'blue arrow' hose... so we have effectively 1 hose connected to the pressure and the non pressure side, which this solenoid is supposed to measure? It obviously was not doing a great deal, as the pressure goes straight back through the return. If effect, the solenoid would never be told that the pressure was too high, it would always be measuring lower than boost pressure.

I think this T piece used to go to the the boost controller, but was just plumbed back wrongly.

I have disconnected the T piece, and have replumbed 'green arrow' hose back to the wastegate return, and directly attached the 'blue arrow' pressure side to the solenoid. It looks neater now at least.

I took the car for a drive, and it didn't make it any worse, but didn't make it any better either. Boost in unchanged at 0.6-0.7 bar, power is erratic. I guess it is time for the dyno tune...