Dual Solanoid For Gtr

[Fat32gtr]

I've just recently purchased a Blitz i-Colour Spec-R boost controller. I have gone through the installation manual and I'm still a bit confused on how to Install it.

I have a twin turbo set up gt2860r -5.

Now my question is- Would I need to tap in a fitting for the hoses on the compressor hosing on both turbos?

There is a diagram In the manual. The solanoid Unit has a Out/In. (Out) T's off and goes to the valve on both actuators and (In) Looks like its T's off into both compressor housings.

Instead of taking off the turbos and tapping in fittings for the (In) is there another way?

Thanks.

[GTSBoy]

Boost signal needs to come from both turbos. Just joint them together and connect to the solenoid.

If you don't want to take off the turbos, then the intercooler pipes immediately after the compressor outlets will do.

[djr81]

Why not take the boost signal from the inlet manifold?

[Ben C34]

You should take the boost signal to the gauge from the inlet manifold.

The line to the waste gates via the solenoid should be done as GTSBoy has said.

As per the diagram the blue line is the pressure source that should go to the new solenoid then waste gates.

Edited May 21, 2014 by Ben C34

[jiffo]

The boost source is the green pipe labeled>

"To bottom of collector, boost source"

The blue pipe simply connects to the induction pipework ahead of the turbo inlets.

[Ben C34]

The boost source is the green pipe labeled>

"To bottom of collector, boost source"

The blue pipe simply connects to the induction pipework ahead of the turbo inlets.

Good point . The blue is the return for the bled air back to the engine for emissions requirements. Can't vent anything to the atmosphere!

[GTSBoy]

You should not take the boost source from the inlet manifold.

[djr81]

Tell the people why.

looking at the drawing Nissan are happy to, although obviously they dont run an EBC.

Edited May 21, 2014 by djr81

[Ben C34]

Every other car takes it from close to or on the turbo.

The gtr is different because racecar.

[GTSBoy]

Note that the first part of this discussion uses the word "plenum" in the sense of the plenum on most cars, not the GTR. The multiple throttles are a complication. So in the above posts the term "inlet manifold" was used. I take that to mean "after the throttles" in the GTR. In any other RB the plenum is after the throttles.

For the purposes of driving a wastegate you want to measure the boost pressure upstream the throttle. If you measure it downstream the throttle then with a partially closed throttle you may have a situation where the pressure in the plenum is much lower than the target boost level but the pressure upstream the throttle is higher. This situation cannot continue indefinitely, but it can exist. At this time the EBC would be trying to close the wastegate to raise the boost (because it's measuring low) but in reality the turbo is pumping more pressure. Because the pressure at the turbo outlet is high but the flow is low (part closed throttle) then you may approach the surge line on the compressor map.

What you actually want is for the EBC to try to maintain the boost that the turbo is making at or less than the max boost you want, rather than allowing the turbo to spin away, effectively uncontrolled.

Now, I acknowledge that a partially closed throttle means that the power output of the engine is under the control of the driver and he is clearly asking for less than max power. It also means that the flow of exhaust gases is being modulated and is therefore less than you would have at WOT. But I think we can all appreciate that under these circumstances you would need a larger proportion of the exhaust flow to go out via the wastegate than the turbine. If the EBC is trying to raise the boost level in the plenum though, then the wastegate will be more closed than needed, meaning more flow through the turbine, meaning more compressor speed. So even with the concept of the driver's ankle being in control, there is a strong possibility of overdriving the turbo relative to what it needs. So we get back to the possibility of surge.

Whether the problem occurs or not may well come down to relative sizing of wastegate to turbine and matching of the exhaust side to the compressor side, which is a lot of variables to play with.

It's all avoided by hooking up the boost signal for the EBC from the turbo outlets.

In a GTR, the plenum is functionally equivalent to the turbo outlet relative to the throttle location, so long as the original throttles are still in use. Single TB conversions are the same as any other RB.

If, in the GTR, the original boost control solenoid is hooked up to the plenum, then that's fine. If it's hooked up to the inlet manifold (which would be the vacuum balance tube underneath) then that opens it all up to the problem I describe above.

[djr81]

So the take off point on the drawing under the plenum is ok for the supply of boost pressure to the solenoids?

The tee is for the boost to the controller.

Edited May 21, 2014 by djr81

[GTSBoy]

Yup, if that connection is to the plenum itself.

In this case though, whilst it will be easier to do that (on the assumption that the standard location is there and available) you'd get better boost control response by keeping all the lines on one side of the engine. Shorter pipes means less pneumatic delay. The original GTR boost control system had to have one pipe go all the way around the engine. But in RB25s and so on, the boost control solenoid was right next to the turbo, for good reason.

FWIW though, the difference won't be terrible and would still work fine.

[Fat32gtr]

Instead of tapping fittings on the turbo compressor housing and going through all the trouble of taking out the turbos. I think I might just end up tapping fittings on both of the pipes that leads out from the housing Where all the decompression charge happens. Less parts to take off and easier. Thanks for your inputs.

[_GTR_]

I recent bought a Greddy Profec Boost Controller and was getting confussed on how to set it up because greddy instructions say to go off the fuel pressure regulator for a signal for the sensor unit. But reading different threads and watching Mighty Car Mods it seems to be a bad practice as you don't want to wreck this signal.

Below I have added my setup which im thinking of doing to my r33 gtr, Just wondering if it would work?

Greddy Setup

Thanks for your input and thanks Fat32gtr and everyone that has put input into this thread so far.

[GTSBoy]

Do not confuse the boost source used for control with the boost source used for display.

The Profec, like most EBCs, is not a closed loop controller. If you look at the installation instructions carefully you will see that the boost signal line they recommend you connect to the FPR signal line is not involved in control at all. it is only the signal that goes to the MAP sensor in the Profec head unit, used for display of boost in the manifold. The actual control boost signal is drawn from the turbo outlet, as shown in their diagram, and the same as instructions given above.

There is very good reason for not tee-ing into the FPR signal line. if nothing goes wrong, then there is no problem. But if you tee in a nice long boost signal hose and it melts or splits or whatever, then you will have a nasty leak in the FPR sense line and your mixtures could go nastily out of control (ie, lean). Not desirable. I think Greddy only recommend that you tee the Profec MAP signal line into there because it is one place that the know will be available on every car that the Profec might get installed into. Saves having to describe a whole bunch of different possibilities for manifold tapping locations.

[_GTR_]

So for the sensor unit signal to supply the control unit can I tee into the factory boost line that supply the gauges inside the car.

And then in my drawing above not tee into the boost source line which go's from the solenoid to the plenum?

[GTSBoy]

Um....yeah. The GTR is complicated. If you hook the sensor up to the plenum you will never read vacuum, because the vacuum is all on the other side of the throttles. So tee the sensor into the other existing boost gauge lines and you will have a true manifold pressure signal.

And the actuator control signal can come from the plenum but would be better coming from closer to the turbo outlets. Your choice.

[djr81]

Is it important to read the vacuum?

Looking at the Blitz unit there are only three wires that go to the dual solenoid unit. Logically one for each solenoid and an earth. So in that instance the display signal is the same thing as the control signal.

[Ben C34]

Yes it is important to read vacuum.

The boost controller doesn't start pulsing the solenoid until it sees 0 vacuum. Otherwise it would be pulsing the solenoid all of the time and wear it out.

[djr81]

Sorry Im a bit dim and dont understand that.