R34 Gtt Two Stage Boost

[mature gent]

Hi How do I disconnect the factory two stage boost system on my R34 GTT

Cheers

Steve

[jrm]

Easiest way - unplug the solenoid.

It should be located to the right of the turbo & wastegate - a small metal cylinder with two sets of vacuum lines running into it and a plug. Off the top of my head, you should see it right behind a black fluid reservoir on the passenger-side strut tower.

[boostn0199]

Theres a thread in the DIY section about grounding one of the wires on it which gets rid of it or you could completely not use it and just run a hose from you cooler pipe to the actuator.

[jrm]

The DIY section about grounding the solenoid does not get rid of it - quite the opposite. It basically makes the solenoid always open - which will leak an unknown level of boost with factory ECU tuning and restrictor sizing, all depending on exhaust size, wastegate size, etc.

For me, with a 10psi wastegate actuator, the boost solenoid was leaking nearly 5psi - in-effec running my still standard turbo at 15 psi - way more than I wanted. By disconnecting the boost solenoid I get a solid 10psi. With the factory wastegate, disconnecting the solenoid you should get around 5psi.

Also note you can program the boost solenoid to some extent if you install a nistune. There are a number of threads on the nistune forums about it.

Really, a lot of this comes down to the reasons why you're wanting to disconnect it. If you're installing aftermarket boost control, you'll probably want to bypass the solenoid completely. Can you shed some more light on what you're trying to achieve?

[QWK32]

^^^ yeah but that's with a 10psi actuator though. with the stock one of 4-5psi, grounding out the solenoid gives you 7psi on a stock exhaust. I saw a constant 10psi with a grounded solenoid and full exhaust. With the stock ecu and tune, the solenoid becomes static at around 3000rpm, so basically the same as grounding it out.

Even though nistune will show the boost solenoids duty as a 3D map, the stock values in the map make the solenoid behave in an ON/OFF way. I played with the duty to test it out (had to alter the piping as well), was basically the same as a jaycar iebc to setup, just in 3D instead of 2D.

[KiwiRS4T]

Here are instructions on how to bypass the solenoid and adjust the bleed to acheive different boost levels (courtesy of SK):

This is the 10 minute no cost boost to 0.5 bar rerouting of the vacuum hoses [thanks to SK]. Disconnect the two vacuum hoses from the solenoid. Then connect the boost feed (from the cross over pipe on the left of the picture) to the standard T piece. Connect one side of the T piece directly to the wastegate actuator (on the right of the picture). The remaining connection on the T piece goes back into the inlet via the BOV return pipe (on the standard fitting). Make sure to put the standard brass restrictor in that vacuum hose to bypass the desired amount back into the turbo inlet. The standard bypass hole of 1.25 mm bypasses enough air flow for 0.5 bar. (See photo)

PS: If you want more boost you can drill out the bypass, 1.5 mm = more boost (around 0.7 bar) 1.75mm = a bit more (around 1.0 bar).

OK, this is the picture of the vacuum hoses. The boost pressure comes out of the intercooler return pipe (that's the big black one on the left) via the standard fitting. It travels down the vacuum hose to the standard T piece.

The right hand side of the T piece goes to the wastegate actuator via another short piece of vacuum hose. It has 2 standard spring clamps on it. So that "some" of the boost pressure goes to the wastegate actuator.

The left hand side of the T piece is connected to another (longer) piece of vacuum hose that goes to the standard fitting on the BOV return pipe. You can't see that fitting in the picture as it is hidden by the (big black) turbo to intercooler pipe. I squeezed the standard restrictor into that vacuum hose, it is tight fit, so be patient and use some lubricant (RP7 in my case).

The restrictor limits the amount of boost pressure that is bled off, so that the "some" pressure that goes to the wastegate actuator is actually less than the boost pressure. This means you get more boost before the wastegate opens at its usual 4-5 psi. How much more depends on the size of the hole in the restrictor, the bigger the hole the more it bypasses and the higher the boost.

The standard hole is ~1.25 mm and gave ~0.5 bar on my Stagea, which has standard everything else (no exhaust, no FMIC, std filter, etc). If you have mods, you may not get the same boost pressure, so you may have to adjust the size of the hole in the restrictor, it is brass so you can easily solder it up and redrill the hole smaller if necessary.

[mature gent]

The DIY section about grounding the solenoid does not get rid of it - quite the opposite. It basically makes the solenoid always open - which will leak an unknown level of boost with factory ECU tuning and restrictor sizing, all depending on exhaust size, wastegate size, etc.

For me, with a 10psi wastegate actuator, the boost solenoid was leaking nearly 5psi - in-effec running my still standard turbo at 15 psi - way more than I wanted. By disconnecting the boost solenoid I get a solid 10psi. With the factory wastegate, disconnecting the solenoid you should get around 5psi.

Also note you can program the boost solenoid to some extent if you install a nistune. There are a number of threads on the nistune forums about it.

Really, a lot of this comes down to the reasons why you're wanting to disconnect it. If you're installing aftermarket boost control, you'll probably want to bypass the solenoid completely. Can you shed some more light on what you're trying to achieve?

Hi thanks,I was reading the steps to get a bit more out of it,step 1, inlet, 3" exhaust,disconnect two stage boost and set the plugs at around .8 mm to remove any flat spots.I am always ready to listen to advice

Cheers

Steve

[jrm]

Disconnecting the solenoid will lower your power - not increase it.

GROUNDING the solenoid will increase your power below 4500rpm (as it will essentially bleed out and remove the 4500rpm solenoid switchover).

At those levels of modification, 0.8mm is also probably overkill - I wouldn't bother, and if you were having issues, I'd probably be thinking fresh coil-packs prior to a smaller plug gap. Unless you're running much higher boost, its almost certainly un-necessary and will also rob you of power.

Realistically, 3" exhaust, FMIC, ground out the solenoid (or even better - EBC), nistune + retune.

Look at things like coil-packs / plugs if you see flat-spots / mis-firing at that point. If you already have flat-spots, mis-fires, you should get that stuff sorted before trying to get more power out. Start from a solid base.