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  • gt4088r.....A/R?

    I've had really bad luck lately on my cars.

    Threw a rod on my S-10, week later threw a rod on my quad 4 achieva.

    Last x-mas, popped a head gasket on the cutlass.

    So I'm rebuilding the cutlass because I don't have the time to finish the drag achieva.
    And i miss my car and want a street toy.

    So... pulling the motor, LQ1, out later next week for a full rebuild, complete with new and stronger lower end, some p&p work, injectors etc....
    I have/had a dodge truck turbo to drop in there but upon tearing it down....it's junk.

    So, following Mars advice, and trying to learn more about boost, I looked into the GT4088r.
    I've learned how to read the boost maps, I understand the maps....i think.

    Now how to apply that data to understanding if my motor can handle that. How much can she breath to avoid the "surge" I've read about? And on the turbine side, what is .89 A/R vs the other 1,2,3,4 models that they show with different A/R's? How is that going to effect or what is that going to effect?

    Still an automatic, high stall converter being made, and beefing up the trans, with help from a tranny guru.

    My goal is, to not have another M5 pull on me like I'm in reverse, and still drive this thing daily, no emissions required. thx
    sigpicHow to make High performance Emissions:
    A "true" High flow converter, straight pipe.
    Low/No flow EGR valve, block off plate.
    Carbon canister and purge valve mod, place in large 30 Gallon can, cover, and place curbside, the city will do the rest.
    PCV valve and vent tube, reroute to exhaust to dump where it belongs, on the ground. Or add breathers and let it all free.

  • #2
    surge on a LQ1 would be hard, with a properly sized compressor... if you look at turbo maps, you'll see the surge line to the left of the map, and with the map going airmass from left to right, you can deduce that surge happens at lower airflow for a given pressure. seeing as how the LQ1 breathes deep, should be hard to get into. that's the simple explanation anyways.

    also simple ex: turbine A/R basically determines what RPM (at WOT) you'll start making boost at. lower A/R = lower boost threshold. however, too low of an A/R will essentially choke the top end and you'll end up with a LOT of pressure between the head and the turbine, which kills power, increases EGTs, lots of bad stuff. on the other side of the coin, a REALLY big A/R will significantly the raise boost threshold, so the engine will essentially act N/A until that point, but when it does make boost...... monster torque multiplier.



    ideally.... you'll make a comprimise somewhere between the two extremes for turbine A/R. while a really high A/R would make awesome peak HP/TQ numbers, it wouldn't be anywhere near as much fun to drive on the street and would probably be slower on the strip than a car with a more reasonable A/R.

    the garrett turbo website has a decent introduction to turbos. http://www.turbobygarrett.com/turbobygarrett/

    if you really want to spend money.... the variable A/R units are just magical in operation.
    1995 Monte Carlo LS 3100, 4T60E...for now, future plans include driving it until the wheels fall off!
    Latest nAst1 files here!
    Need a wiring diagram for any GM car or truck from 82-06(and 07-08 cars)? PM me!

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    • #3
      I've got a .95 turbine on mine, and I'd go smaller on a 3500 if I was to do it over. (well now that I'm planning a 3.9, it'll likely be OK)

      Don't go any bigger than a .95 I say on your DOHC. It'll still sream on the top end and it'll spool at a decent RPM.
      11.92 @ 122 MPH 3400 91 Cavalier Z24 Intercooled S/C. -totalled-
      10.56 @ 130 MPH 3900 LZ9 87 IROC Z28 Intercooled GT4088 Turbo

      Comment


      • #4
        rgr that thx
        sigpicHow to make High performance Emissions:
        A "true" High flow converter, straight pipe.
        Low/No flow EGR valve, block off plate.
        Carbon canister and purge valve mod, place in large 30 Gallon can, cover, and place curbside, the city will do the rest.
        PCV valve and vent tube, reroute to exhaust to dump where it belongs, on the ground. Or add breathers and let it all free.

        Comment


        • #5
          On the GT4088R, turbine A/R was pretty large compared with what people are used to for a T4 turbo. All of them should work, but the smaller ones trade top end for spool and the larger ones trade response and low end for power.

          Consider this turbo. Borg Warner S300SX FMW.

          It's much newer and cheaper than the GT4088R. The GT4088R is an awesome turbo, but this should get you the same or better performance for less $$. It's also only oil cooled, so you wouldn't have to worry about running water lines to the turbo.

          Tim
          1995 Z34 - T04E "60" trim, 42.5 lb/hr injectors, AEM WBO2, FFP UD&DB, 3" exhaust, 2800 stall, shift kit, tranny cooler, Powerslot, Hawk HPS, rear disc conversion, KYB, Eibach, HMS F&R STB, Fittipaldi Force 18" wheels, big stereo, lots more coming eventually...
          325 whp 350 lb-ft

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          • #6
            ^ jesus I like the sounds of that turbo as well...
            11.92 @ 122 MPH 3400 91 Cavalier Z24 Intercooled S/C. -totalled-
            10.56 @ 130 MPH 3900 LZ9 87 IROC Z28 Intercooled GT4088 Turbo

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