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High compression small turbo SR20

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    #16
    Originally posted by irsa76 View Post
    What sort of compression ratio are you aiming for? Given Saab were running 9.25:1 @1 bar with a TD04 on 95RON from the factory 30 years ago with no issues, not unheard of for them to go 400,000km with no problems even when people use low octane in them, I don't think anything under 9.5 or even 10:1 would be an issue depending on chamber design, ecu, fueling system and tune on E85.
    Stock turbo is 9:1
    stock Na I think is 9.5 in a s13 and 10:1 in s14/15 motors

    have seen some CP pistons in 11:1 so leaning towards those

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      #17
      Similar but bit different experience here. My factory stock NA 2ZZGE motor runs 11:5 compression and around 11 psi boost from a very inefficient roots style supercharger and a pretty hopeless A2A mid mounted intercooler. This on 98 pump fuel. Does heaps of circuit work. So far so good.

      So 10 to 11:1 compression and moderate boost is no problem I'd say.

      2 suggestions:

      1) Run Water/Meth. I do.
      2) Run E85. I would it it were readily available.

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        #18
        In theory keep the boost level moderate, have a good fuel and ignition and ECU, clean up the edges in the chamber and a good tuner and you should be ok. Advantage of E85 is it's knock restance and cooling abilities which is why you can get away with higher compression and boost.
        BUT, I say all this based on what I've read and watched on EngineMasters, skid factory, MCM and the Haltech YT channel.

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          #19
          The small frame billet high tech turbos are my pick for sr20s and other engines in the same basket 100%.

          I had a lot of setups on SR20s and the very best one was a t2 gtx2863r on a basically stock s15 motor with some cams and e85 by miles. Still made 240kw on 18psi with internal gate and

          I'd suggest 10.1 for this build based on my dad's car which is a kit car with a 2.0 duratec and a gtx2860 it feels like a monster and on 98 petrol 6 psi made 180kw. Totally stock engine cast t2 manifold .6 rear and water2air cooler. It was damn near as soft tune as they could make it at the time. The standard clutch slipped any higher and the car being 700kg means it has stayed that way atm but I am supremely confident it would make 230kw without a doubt on 14 psi and basically drives like it has a v8. Compression ratio for those is 10.8 according to the internet.

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            #20
            Originally posted by (Locky) View Post

            Stock turbo is 9:1
            stock Na I think is 9.5 in a s13 and 10:1 in s14/15 motors

            have seen some CP pistons in 11:1 so leaning towards those
            stock CR in a turbo motor is 8.5:1, so its a big jump
            S13 NA are 9.5:1, Pulsars and S14+ are 10:1

            I've always been wary of tiny turbos on them. AVO or someone used to do turbo kits for K20A with a ball bearing T28. They'd make less power turbocharged, due to high comp (11.5:1) and huge cams that want to breathe. The turbo would just be a huge exhaust restriction, choke it up and make it ping. So the joke was 155fwkw NA, and 145fwkw turbocharged. Putting a 3076 on them would see 250kw @ 5 psi, so its not like they don't like boost.

            However, have seen Z guys put stock turbos on a VG30DE, which are 10.5:1, with E85. Appear to be absolute animals, they're always on boost. So running GTSS will probably be fine on a 10:1 comp motor with E85. You might hit some sort of ceiling but you'd be living in torque city.

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