Announcement

Collapse
No announcement yet.

High compression small turbo SR20

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    High compression small turbo SR20

    So as title suggests is this a bad idea?


    The motor needs pistons as it has to be honed to. 5mm oversized the plan was originally an oem refresh but things have snowballed.
    Getting 'step 1/drop in' cams
    Valve Springs
    Head studs
    Currently running. Gt-ss hks turbo ( Pretty much a disco potato 2680rs) don't feel like it's ever going to get a massive turbo, maybe just one size up eventually if this dies.
    Along with all the usual suporting mods

    Now it needs pistons (and might as well rods) and not wanting to lower to an 8.5:1. That seemed to be the go to for a lot of off the shelf setups as has just been the done thing for a big boost pump fuel forged motor in the past I guess.


    All the info I can find is from mid 2000s before e85 was a thing.

    Is track only and will be running pump e85 with a small turbo. Just looking mid 200kw but wondering if a bump in compression is worth it.
    A responsive low to mid 200kw setup has suited my driving and never felt the need for a 300kw setup.
    Just wondering if bumping up the compression will make it even more responsive/ meater mid range


    Thinking 10:1 or even 11
    Last edited by (Locky); 09-07-21, 08:05 AM.

    #2
    I think some IPRA guys were doing this back in the day. 10.5:1 plus E85, or race fuel of some description..

    I've run a 9.0:1 SR20 with the stock T25 for years as a rally car with few issues, but you're looking at significantly higher compression.

    Subscribed

    Comment


      #3
      The challenge in IPRA is all around response within the flow rate of the restrictor to make the car as drivable as possible and produce as much boost as low as possible. My 3s motor basically didn’t increase its power after about 5000rpm but it could easily rev to 7500+rpm just no more power. Restrictors are a PITA but thems the rules

      Similar theory applies to non restricted hi comp motor. Makes for a very responsive drive. How much boost are you planning on using?

      Comment


        #4
        Originally posted by davel View Post
        The challenge in IPRA is all around response within the flow rate of the restrictor to make the car as drivable as possible and produce as much boost as low as possible. My 3s motor basically didn’t increase its power after about 5000rpm but it could easily rev to 7500+rpm just no more power. Restrictors are a PITA but thems the rules

        Similar theory applies to non restricted hi comp motor. Makes for a very responsive drive. How much boost are you planning on using?
        Mines is just a scumbag drift car so no restrictions or anything like proper rules.

        Was running 14 psi but that was on a un tuned 98 spec.
        was just going to go till the tuner says no more point

        Comment


          #5
          i have nothing to add other than to say i always wanted to do this to an SR20. At least 10:1 with a late model T28 frame garrett turbo and cams.
          Originally posted by gerry;n7288577
          having done my fair share of snorting white powder, made by a bikie in a garage, off a dirty cistern in a night club, means I find the argument about not knowing whats in the vaccine slightly perplexing.

          Comment


            #6
            Cossie55 on here is your man. His was a beast in his 1200 IPRA car

            Comment


              #7
              Still 2 main schools of thought, low comp more boost more timing, high comp less boost less timing.

              Really depends what your eventual tuner or engine guy prefers. Also what the head is like and turbo etc. Personally I'd go more comp and a small new style turbo with billet wheels that spin up fast and make bulk hp even at tiny size (go smaller than bigger if response is key)

              Sent from my HTC One M9 using Tapatalk

              Originally posted by 50RTD
              Dave, have you uploaded the data from the carby?
              Originally posted by Dogsballs;n7259704
              Bit harder to Wank to without Wendy, but got there in the end

              Comment


                #8
                If its going to be run on E85, then from everything I have learned in JZ land over the past decade, high compression builds are the only real choice. Everyone doing big builds is going 10:1 or 10.5:1, rather than the lazy 8.5:1 needed to run big boost on pump fuel.

                Its a win win, as long as your tuner is proficient in tuning on corn juice, and to answer your question, yes, your response and meaty midrange will be insane.

                Comment


                  #9
                  Dogsballs is right and it’s a bit of personal preference between those two options. I like to go for area under the curve for a circuit car and responsiveness. I haven’t drifted but I imagine that it would be better to have a responsive motor with lots of torque than a dyno queen with a nice peak number on the sheet of paper. This would help with transitions and recovery from any mistakes if you happen to make one.

                  Combustion chamber shape is a big factor. That’s probably the limiting factor on an SR as it will limit the peak dynamic compression ratio before detonating. E85 helps a lot so you can probably raise the sun comp by 10-15% (at a guess). You can calculate what your current combination gives (14psi at x rpm and 9:1 comp) and figure out how much boost will give the same dyn comp at 11:1. Then you can check the turbo maps and see that the small turbo with a modern front wheel will give you a really good option. Then you can decide if you want 10.5:1 instead of 11:1. Watch for head lift in the SR but you probably already know that.

                  at the end of the day, talk to your engine guy and tuner to see how far they recommend you push it. You aren’t going for huge numbers to it should turn out OK

                  Comment


                    #10
                    The tuner I have always used on my other car has been doing e85 for years.

                    That is a street car with an unopened s14 sr20, just cams and valve springs. With a gtx2860r running 1.5 bar and straight e85 and no issues for 3+ years and the 3 years before that it spent in another drift car with a td05 also on e85

                    ​​​It currently has a fat mid range
                    / area under the curve which is what I like and hoping that bumping the compression on the motor I'm building will enhance this.

                    Seeing how budgets go i may ditch the gt-ss and get a more modern t2 flange turbo

                    Comment


                      #11
                      I helped build a SR20DE + a small BB turbo...Such a beast. it nudged 200kw and had a mountain of torque...

                      Comment


                        #12
                        Is it worth getting a wrecker na motor and swapping the Boltons onto it?

                        Comment


                          #13
                          Originally posted by Roadsailing View Post
                          Is it worth getting a wrecker na motor and swapping the Boltons onto it?

                          Thats all I'd do. buy 2 and keep a swap-n-go style spare.

                          Comment


                            #14
                            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.

                            Comment


                              #15
                              Originally posted by Roadsailing View Post
                              Is it worth getting a wrecker na motor and swapping the Boltons onto it?
                              Prices of sr20s have gone mental like everything else
                              otherwise I would have just chucked another running motor in

                              2-3k for turbo motors needing rebuild
                              1500+ for running NA
                              5k for a unknown turbo motor running condition


                              This was ment to be a oem refresh with bearings and rings,
                              then head studs and new oil pump
                              now small mark on the bore so needing some kind of oversized pistons

                              Comment

                              Working...
                              X