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Thread: Setting up launch control with auto

  1. #1
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    Setting up launch control with auto

    So I'm looking to set up some sort of launch control for my 2jz with a gtx4202 to try and get it on boost sooner on the line so the dicks at the drags don't keep waving me on while I'm sitting there.
    Is it as simple as retarding timing and adding a bit of fuel?
    I had a bit of a play with it and as soon as it starts it will not pick up more revs.
    Also wondering do I put the rev cut setting where I want it to stall to or a little less?
    I've since had the convertor loosened more so hoping that will help but just want an idea of if I'm doing it wrong or not.
    Ecu is a haltech elite 2500
    Last edited by Skippy; 27-05-17 at 06:05 AM.

  2. #2
    sack riding 10sec rx7's Avatar
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    you want to add timing and pull fuel out normally.. i run up to 40deg on the transbrake, once we get to target rpm then dump timing to get the boost to build quickly..

    if you dont have a trans brake you will need to use the brake switch to activate the controls you want to use
    im a cunt
    and apparently i dont know shit...

  3. #3
    <3 Gate Rollin's Avatar
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    Well that's counter intuitive.

    Sent from my GT-I9505 using Tapatalk
    Quote Originally Posted by jmac
    But on seatbelts - I don't think they should be mandatory for adults, but for under 18s. I reckon make them mandatory up till then, and provide plenty of graphic evidence supporting their use to school age children, and then if they hit adulthood and don't choose to wear them, think of the future without these fucken idiots around...

  4. #4
    sack riding 10sec rx7's Avatar
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    what is??
    im a cunt
    and apparently i dont know shit...

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    How do you expect it to get on the converter while making less torque by pulling timing? Gotta make power to get there then change how it makes power to suit launch (i.e. Make boost).

    add some timing to it to play and progressively reduce timing as boost becomes positive, then adjust the retard to suit desired converter rpm. With that small of a turbo I'd almost guess you could foot brake it from idle for better results.

    add fuel once its positive pressure to control egts and get some post ignition if it needs it. But youll have turbo rpm through the roof very quickly.
    Quote Originally Posted by Bosshoggett View Post
    If your planing to drive this on the road and enjoy it, id suggest a second opinion, someone with a history in Australian Rally or Fink River . If your just playing dyno comps. Then ok

  6. #6
    Registered User burn is weird's Avatar
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    Rollin, remember you have a transbrake to load up against.

    building boost while free revving in a manual gearbox is a different thing all together.

    Oo___oO


  7. #7
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    I assumed foot brake car being JZ. Treating it like a manual will see it doing 600rpm with no oil pressure firing every 3rd stroke. Trick with no transbrake is you have a 3-5hp window to target and maintain to keep stall speed up, while transitioning to boost. Transbrake you can make 50hp too much, car still won't break a tyre or push a wheel.
    Quote Originally Posted by Bosshoggett View Post
    If your planing to drive this on the road and enjoy it, id suggest a second opinion, someone with a history in Australian Rally or Fink River . If your just playing dyno comps. Then ok

  8. #8
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    Yeah it's foot brake unfortunately as I'm trying to keep the Toyota auto and do a 9.
    This is a video on the footbrake as hard as possible and handbrake also.
    Had a look at the log of my run and I left the line on 9.3psi.
    I think it is setup with road speed Vs tps activates the launch control

    Last edited by Skippy; 27-05-17 at 10:21 PM.

  9. #9
    <3 Gate Rollin's Avatar
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    I just assumed you'd already have the timing advanced as much as possible to be making the most power (therefore exhaust gas therefore boost) possible, so advancing further would just break things.

    I'd have thought pulling a little timing in the 0psi-to-low-boost parts of the timing map would spool the turbo, and as it comes onto boost proper it gets a bit more advance to make power with that boost.

    Obviously I'm wrong, so to me it's counter intuitive - 40* advance and lean under load sounds like a recipe for disaster, but 10sec rx7 knows more than I do.

    Sent from my GT-I9505 using Tapatalk
    Quote Originally Posted by jmac
    But on seatbelts - I don't think they should be mandatory for adults, but for under 18s. I reckon make them mandatory up till then, and provide plenty of graphic evidence supporting their use to school age children, and then if they hit adulthood and don't choose to wear them, think of the future without these fucken idiots around...

  10. #10
    sack riding 10sec rx7's Avatar
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    you pull timing you will not get it up plain and simple.. if you pull timing any more than 500rpm before the 2 step it wont get to the 2 step..
    im a cunt
    and apparently i dont know shit...

  11. #11
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    Yeah i think that's my problem then.
    So I should advance the timing in the launch control table at lower revs to get it on the convertor and reduce it about 500rpm before the rev cut.
    Will it damage it throwing in timing?
    It is running united e85 so I should be good?
    Also if it makes a difference it is running open loop boost control.
    Is it worth changing it to closed loop and what else do I need to change if I do?

  12. #12
    sack riding 10sec rx7's Avatar
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    try adding 5 to the launch control and see what happens,

    open or closed loop boost wont effect anything
    im a cunt
    and apparently i dont know shit...

  13. #13
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    Way I think of it, and I'm happy to be wrong.

    Try and understand whats actually happening to get the process a lot better/clearer, and be able to troubleshoot. You are injecting potential energy (fuel), and asking it to do one thing...Convert that energy to kinetic energy as efficiently as possible by forcing a piston down. (and heat, duh). The magic of cars/internal combustion engines.

    On a foot brake car, you now want to turn that energy (as much or as little is required) into both kinetic energy to rotate the engine, and also gas velocity & gas pressure differential...Through expanding gas law (too smart for me), and in doing so you're attempting to load up as much potential energy in the converter differential as possible (shear point between stator and rotor). So to have the engine free rev to 3000rpm, it might take 15 horsepower in neutral...Only thing fighting you is compression, valve train, oil pump and alternator. However against a converter you need to make say...150 horsepower as you're asking to transfer a fuckload of mechanical energy in to heat (gearbox fluid).

    Then you also need to transfer energy to the turbo to increase it's RPM (which takes energy). So in effect you're very carefully balancing two distinct destinations for the energy to go to, through one process, with one fuel. Your method to do so is purely when you ignite that energy, and how much of it you inject. Pulling timing reduces the energy put towards turning the engine by a huge amount, hence the engine will slow down/never reach stall. As I said above, add as much power as you can possibly make, and then transition to maintain that same power to the crank whilst also giving energy to the turbo, and also take advantage of the increase in air density coming in. It takes a lot of fuel. Once you're nearing stall RPM you can pull more and more timing as the crank energy increases less and less with every few digits less ignition. Took hours and hours of fucking around in the ute. It's a balancing act and you're limited by heat (egt, auto).

    That said leaving with positive boost pressure is kind of not the aim here anyway, it's leaving with as much turbine RPM as you can safely make and with enough engine RPM to then not slow the turbo down from being so far over the surge line. Boost is a restriction to flow and acts against that turbine speed. Leaving at 15psi may not actually give any real benefit compared to leaving with 2-3psi for a variety of factors like wastegate response, converter slip etc. Trial and error really; the ute never did a 0-100 faster with 12psi vs 3psi on fairly crude tailshaft rpm vs time log. But there is probably far better ways do things than I was doing too.
    Quote Originally Posted by Bosshoggett View Post
    If your planing to drive this on the road and enjoy it, id suggest a second opinion, someone with a history in Australian Rally or Fink River . If your just playing dyno comps. Then ok

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