Jump to content
SAU Community

2 stage boost on R34 - please prove me wrong

DatsunBanana
 Share

Recommended Posts

DatsunBanana Enthusiast

DatsunBanana

Posted
Posted
2 stage boost on R34 - please prove me wrong

This is really bugging me since I did a NEO +t conversion and used a GTT ECU. Nearly every discussion says there is 2 stage boost on an R34 - that over XXXX rpm the solenoid bleeds off some air and gives higher boost. That is except a few posts out there saying that the boost solenoid is always bleeding under normal operation and only closes in limp mode and reverts to actuator pressure.

There's been some discussion with the +t guys that the pin 104 signal from GTT ECU can do a similar job to pin 104 on the GT ECU which controls the plenum butterfly valve on the NA engine.

The R34 service manual clearly explains the way pin 104 works for the GT - it turns the solenoid on at idle and off above 3500 rpm. But all it says for GTT pin 104 is that it's off at idle and at approx 2000 rpm it comes on when the engine is suddenly raced. Where is it documented apart from hearsay that it switches at over XXXX rpm for the GTT?

To satisfy my curiosity I went out for a drive with a voltmeter connected across the solenoid plug from pin 104. Under any acceleration ("engine raced") the voltmeter showed a steady voltage (solenoid open). As soon as I relaxed the throttle the voltage dropped to zero (solenoid closed). I took it right through the rev range and as long as it was above 2000 rpm and accelerating the voltage never changed at 4500, 4700, 3500 or any other rpm. If I relaxed the throttle at 5 or 6 K rpm then the voltage dropped back to zero - it didn't maintain the 'solenoid on' voltage even at those high revs.

So what I saw seems to agree with the service manual. But where is the idea of two stage boost coming from, I just can't see how it would work on the basis of what the manual says and what I saw in my test.

I hope I'm wrong and can have it explained why so I can try using pin 104 to control the butterfly valve.

GTSBoy Grand Master

GTSBoy

Posted
Posted

Of course it's a boost control.  Of course it's not "2-stage boost".

The factory actuator gives 5 psi.  When the bleeder solenoid valve is switched by the ECU, you get 7 psi.  The ECU does this when the ECU wants.....but in general, it has nothing to do with RPM.  It is nothing like the actuation of the plenum butterfly.  It is primarily intended to give lower boost in 1st gear.  I wouldn't be surprised if the ECU also drops the boost when it is doing traction control, but I have no evidence of that....just seems logical.

  • Like 1
DatsunBanana Enthusiast

DatsunBanana

Posted
  • Author
Posted

Thanks. I fully expected replies from people saying that their gauges are clearly showing that there are two stages of boost and that I'm completely wrong. There are so many posts on different forums about grounding a pin to keep the boost high so what's all that about? From what you've explained that's a waste of time if the system is already at high boost except under certain conditions.

Is the R33 different and is that causing confusion with people?

GTSBoy Grand Master

GTSBoy

Posted
Posted
1 hour ago, DatsunBanana said:

Is the R33 different and is that causing confusion with people?

Nope.  Same same.  Except for the possibility of small differences like maybe traction control interaction, because R33 had no TC.

Johnny's right about being able to control boost from Nistune, but he's missed the point that you want to use the boost control output to run your plenum valve.  However, there are intriguing possibilities to do as he says and use the output to try to run your valve, with the 3D table he talks about.  It's just that....it may work, or it may be a pain in the arse.

Kinkstaah Grand Master

Kinkstaah

Posted
Posted
5 hours ago, DatsunBanana said:

? From what you've explained that's a waste of time if the system is already at high boost except under certain conditions.

Is the R33 different and is that causing confusion with people?

It's to make sure it's under high boost under all conditions all of the time. Certain conditions from Nissan are very conservative for a person who wants more power at the cost of a paperclip ;)

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

If you need Nistune boards or a Nistune board fitted I can organise them for a good price. Also have the ECU bench tested and loaded with a base map with whatever injectors and afm mix you have so your car is driveable to your favourite tuner.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Duncan
      Mistakes were made, my R34 Story

      By Duncan · Posted

      Have a look at that (shitty) pic I posted. You can see AN -4 braided line coming to a -4 to 1/8 BSPT adapter, into a 1/8 BSPT T piece. The Haltech pressure sender is screwed into the long arm of the sender and factory sender (pre your pic) into the T side. You can also see the cable tie holding the whole contraption in place. Is it better than mounting the sender direct to your engine fitting......yes because it removes that vibration as the engine revs out 50 times every lap and that factory sender is pretty big. Is it necessary for you......well I've got no idea, I just don't like something important failing twice so over-engineer it to the moon!
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      Yup. You can get creative and make a sort of "bracket" with cable ties. Put 2 around the sender with a third passing underneath them strapped down against the sender. Then that third one is able to be passed through some hole at right angles to the orientation of the sender. Or some variation on the theme. Yes.... ummm, with caveats? I mean, the sender is BSP and you would likely have AN stuff on the hose, so yes, there would be the adapter you mention. But the block end will either be 1/8 NPT if that thread is still OK in there, or you can drill and tap it out to 1/4 BSP or NPT and use appropriate adapter there. As it stands, your mention of 1/8 BSPT male seems... wrong for the 1/8 NPT female it has to go into. The hose will be better, because even with the bush, the mass of the sender will be "hanging" off a hard threaded connection and will add some stress/strain to that. It might fail in the future. The hose eliminates almost all such risk - but adds in several more threaded connections to leak from! It really should be tapered, but it looks very long in that photo with no taper visible. If you have it in hand you should be able to see if it tapered or not. There technically is no possibility of a mechanical seal with a parallel male in a parallel female, so it is hard to believe that it is parallel male, but weirder things have happened. Maybe it's meant to seat on some surface when screwed in on the original installation? Anyway, at that thread size, parallel in parallel, with tape and goop, will seal just fine.
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      How do you propose I cable tie this: To something securely? Is it really just a case of finding a couple of holes and ziptying it there so it never goes flying or starts dangling around, more or less? Then run a 1/8 BSP Female to [hose adapter of choice?/AN?] and then the opposing fitting at the bush-into-oil-block end? being the hose-into-realistically likely a 1/8 BSPT male) Is this going to provide any real benefit over using a stainless/steel 1/4 to 1/8 BSPT reducing bush? I am making the assumption the OEM sender is BSPT not BSPP/BSP
    • funkymonkey
      Jacks that fit under GTR lips that can reach the subframe?

      By funkymonkey · Posted

      I fashioned a ramp out of a couple of pieces of 140x35 lumber, to get the bumper up slightly, and then one of these is what I use
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      I wouldn't worry about dissimilar metal corrosion, should you just buy/make a steel replacement. There will be thread tape and sealant compound between the metals. The few little spots where they touch each other will be deep inside the joint, unable to get wet. And the alloy block is much much larger than a small steel fitting, so there is plenty of "sacrificial" capacity there. Any bush you put in there will be dissimilar anyway. Either steel or brass. Maybe stainless. All of them are different to the other parts in the chain. But what I said above still applies.
×
×
  • Create New...