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.

Link to comment
Share on other sites
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
Link to comment
Share on other sites
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?

Link to comment
Share on other sites
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.

Link to comment
Share on other sites
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 ;)

Link to comment
Share on other sites

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

    • GTSBoy
      Duncan's V37.......race car?

      By GTSBoy · Posted

      Much less twat-tastic. CF wheels are too garish for civilised use.
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      From there, as the manual says....assembly is the reverse of disassembly, no tricks worth mentioning Much better (for me)
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      In my case, the standard wheel I had was in good condition but the buttons had more wear, so I swapped them across from the original wheel from the car. The plastic rear cover is held on by 4 tabs, and once the wiring is removed you can get access to 2 screws on each side the hold the buttons in From there I just swapped the wiring over. What was interesting is the standard style wheel is 2.0kg but the carbon fibre one is 50% heavier at 2.9kg. It even has a weight inside the wheel at the top to make up for some sort of imbalance in the design. weird
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      Once the airbag is off, to remove the steering wheel.... Undo the 2 plugs into the clock spring, and the horn connector from it's clip. Hit the 19mm nut with a rattle gun (preferably) or if you don't' have one, you probably want an assistant to hold the wheel in place while you use a breaker bar to undo the nut Then, screw the nut back on 3 turns, and pull the wheel sharply towards you. If that doesn't work hit it medium force with a rubber mallet on either side, or possible behind if you can get there. If that all fails (it shouldn't!) you might need a steering wheel puller
    • Duncan
      Duncan's V37.......race car?

      By Duncan · Posted

      So, to next task....the carbon fibre steering wheel was either an expensive factory option or a chinesium special. Either way, I don't like either the flat bottom or thick ring style, so it had to go So...to remove the steering wheel.... First, disconnect battery negative and stomp on the brake pedal for a few seconds. Then, remove the small circular covers on each side of the wheel's rear surround to uncover the airbag clips. You need to push something like a flat bladed screw driver through, to push the steel clip inwards and pull the side of the airbag forward. Once you've done the easy side, same on the centre console side. You can see the tab you are shooting for circled in red Then, disconnect the horn spade connector and for the yellow airbag plug you need to get something small under the black locking tab to pop it out, then the connector releases......airbag is off  
×
×
  • Create New...