Individual throttle bodies build

Discussion in 'Technical' started by Rutger, Apr 30, 2013.

  1. Rutger

    Rutger New Member

    Had to figure out how to legally drive the car to the dyno and I got it all worked out this week. So I went to the dyno today. Last week it ran perfect, but it started hesitating very bad yesterday so I was worried all was gonna fail. The fuel system was good, and the timing was set correctly at 15 degrees. I didn't knew anymore where to start. So I went with some of the basics, refitted a poorly grounded harness cable and cleaned the AFM and CAS harnesses. Then, all of a sudden it pulled correctly again.

    Now I haven't driven this car in anger before the manifold swap, but it does feel like the standard mapping is not suited to this manifold. If I quickly depress the throttle after a gear shift, there's no response. It also feels somewhat nervous and sensitive to throttle changes, a bit like my brother's Gti-r with the OEM ITB setup. This system really needs a map 'written' for it.

    Anyway, on the dyno all went well. The car pulled 263hp/349nm uncorrected at the rear wheels, on a warm day (29 degrees C) and the coldpipes from the intercoolers got very hot as the 2 coolers they had were not that powerful. I estimate the inlet temp was around 45 degrees C. During the other pulls the power went down as the engine heated up even worse and the operator couldn't get a good pulse from the ignition system, the output was therefore measured in speed not rpm's.

    The blue line is the first pull. The torque values are incorrect, they had some trouble getting the dyno system to correctly convert. Explains the weird 800+nm spike. Realistically, it's about 350nm at the wheels.


    Now I'm not directly converting the car back to stock, there's another type of manifold that I want to try on the dyno. Roughly the same as this one, but with the stock TB's. Will make a different topic for that.
  2. Anti

    Anti 14.7 x 14.7 = 44.1

    Need to see some back to back testing on a better car! Surely someone local would donate their time?
  3. 8300zx9

    8300zx9 Active Member

    Oooooow those ITB's sound sooooo gooood! :zlove:
  4. Rutger

    Rutger New Member

    There was a 300zx forum here in Holland with several people with tuned vg30dett's but that forum was removed and I lost track of them. I haven't seen a modded 300zx in ages.

    I do have a customer from the UK who's already making 750hp. He wants to buy and test one from me, but I need to design it so that his Border fuel rail fits. And he was having issues with his engine as well he mailed me the other day. So that's not an short term option.

    8300zx9; The sound comes from the dyno roller, the ITB's don't make much noise with a plenum on top of them. But you can still hear the roar when revving the engine like in the first vid I posted.
  5. 1badg35

    1badg35 New Member

    was it discussed what size throttle bodies were chosen? I have a similar project in the works, and am torn between 50mm and 52mm throttle bodies
  6. tassuperkart

    tassuperkart Its a lie I tell you!

    When your feeding a single runner/port in an ITB, the TB size is largely irrelevant as its not a primary restriction in the system like a carburettor would be.
    Carbs need to create a depression to draw fuel and creating a drepression results in restriction.
    TB's ony need to control airflow so you can throttle the thing.
    I would try and choose the smallest TB that will still match the flow of each runner/port.

    Ever increasing TB diameter makes no additional power (unless in the first place its small enough that its the restriction in the system) but results in a choppy light throttle response as so much CFM of air is admitted for a smaller throttle opening. No biggie but a PITA to drive and especially to tune in speed/density (MAP) mode.

    The workaround is to simply choose smaller TB's or make a progressive cable quadrant that mechanically slows down throttle opening at the slow run end.

  7. Chad_

    Chad_ Well-Known Member

    fkn awsome nice work man looks sexy as :br:
  8. mitsoevo

    mitsoevo New Member

    What ended up happening with all of this in the end, sorry to revive a zombie thread
  9. tassuperkart

    tassuperkart Its a lie I tell you!

    Id guess it went the way (away) like of a lot of this kind of stuff.
    The standard manifold isnt really that much of a handbrake on the engine to begin with and individual throttle bodies is more something to do because you can rather than the engine actually needing it.
    It looks sensational and his work is awesome, but in reality, a very expensive modification for modifications sake.

    Might achieve something is the stupidly high Hp/rpm area but Ill stick my neck out and predict it made no difference to Hp at the end of the day.

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