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compresion ratios

Discussion in 'Forced Induction' started by kermit5327, Dec 16, 2007.

  1. kermit5327

    kermit5327 New Member

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    ok about my compresion ratio lets say i have a d16z6 with some stupid sized turbo like idk a t70 now we know that a stock z6 isnt going to spool that untill like 4th gear so what if i was to put a little higher compresion pistons in the motor like lets say stock is 9.2:1 so maybe like 10:1 would that help in aid to spooling the turbo quicker

    i guess my main question is how can i spool a huge ass turbo in a little ass motor
    should i just open the head up as much as i can and still go low comp pistons or open the head up and go with a little higher than stock comp pistons
     
  2. jtornado

    jtornado New Member

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    Well what im thinking is that the higher the compression ratio the faster rpms, which pushes the exhaust out faster than lower compression but im am not certain that this will make you spool faster. Basically the turbine a/r is determined how fast it will spool. The smaller the a/r the faster it will spool and the bigger the a/r the slower it will spool. You can have a huge turbo in a little motor and still spool fast but what are the options for your turbine a/r, like the .48 a/r could start spooling at 2.5-4 rpms and the .57 a/r could start spooling at 3.5-5 rpms. Here is what you can do to make your big turbo spool fast. Small turbine a/r, 3-4" Exhaust (including the DP), lighter compressor and turbine wheels, and maybe higher compression ratio but that is a question I do not know. Keep in mind that larger turbos generally take longer to spool up, so you could lose some low-end performance. Also, if you attach a turbo that is too large for the exhaust system, you can make the car slower. With N/A cars you actually want back pressure but with F/I cars you actually DON'T want back pressure. The less back pressure the quicker the exhaust can flow out. I'm pretty new too but I researched for about 1 year and learned over the years but I am no Master Tech so don't take all my words and tips for granted. Good Luck with whatever your doing;)
     
  3. kermit5327

    kermit5327 New Member

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    wow that was deff a big help im trying to do something stupid to honda build that i dont think will eben work but im gonna try to squezze a t70 turbo on my single cam 93 4 door i have a y8 block but i was gonna go all z6 parts sept in the head i was gonna go after market everything with a little machine work and higher comp piston heads stock rods (yeah i know bad idea but the build is wallet permitting lol) i was thinking about a 25 or 50 shot with it just to spool it
     
  4. jtornado

    jtornado New Member

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    yea that would be kinda the same thing as having higher compression in a way cause that is like canceling the turbo cause the turbo might not spool at low rpms but then again, Bigger Turbos=More Top End/Less Low End and Smaller Turbos=More Low End/Less Top End. I guess it all depends on your goals. What are your goals?????
     
  5. kermit5327

    kermit5327 New Member

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    just proving ppl around here wrong they say that there is no way that i can get a t70 to spool and push more than 8 pounds in a single cam
     
  6. daveholiday

    daveholiday Do work

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    Not necessarily true. You can take a fully built motor and slap a tiny ass probe gt turbo on there, but if it's built and tuned right and you can set your wastegate high enough, that thing will keep pushing. You can have a bigger turbo, and brake boost it and launch at full boost.

    There's an article on compression ratio, but I don't know if you'll actually read the whole thing.
    http://hondaswap.com/turbo-information/static-vs-effective-compression-29102/

    Are you using this as a DD or track car or what?

    Compression is more or less how tight everything is together in the combustion chamber at time of combustion. If you're going F/I, you don't want to raise it too much, especially if you're running a huge turbo.

    Higher compression, unless I'm proven wrong by a higher up, will not make it spool faster. IF you up your compression though, when that thing is fully spooling, you're compression is going to be outrageous and dangerous.
     
    Last edited: Dec 17, 2007
  7. kermit5327

    kermit5327 New Member

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    im wanting to have it as a dd toy
    and what if i keep it at low boost
    so what can i do to keep a t70 spooling on stock comp or should i still go low comp and open the head up as much as i can
     
  8. daveholiday

    daveholiday Do work

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    as far as the head, turbo cam = low duration high lift, get matching springs/retainers, but that's won't spool it faster.

    You have 2 choices.
    Make it a track car,
    or get a smaller turbo.

    If you keep it at low boost, you're still not going to spool up quick, and you'll just not get as much power out of it. Get a t25 or t3/t4. I don't know the t3/t4's for sure, but I know t25's spool up around 25k.
     
  9. kermit5327

    kermit5327 New Member

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    in your own what would be the highest comp ratio that would be safe in a z6 or y8 block
     
  10. kermit5327

    kermit5327 New Member

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    so what if i went high comp everything in the head and had the head decked got shorter rods and stock comp piston heads to boost a y8 to like somewere around like 10 :1 or just got 10:1 pistons and a high comp head with like 6 pounds out of a t3/t4
     
  11. daveholiday

    daveholiday Do work

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    You'd be fine there, just make sure you get some good tuning
     
  12. kermit5327

    kermit5327 New Member

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    i dont really have a horsepower goal at all its more of wallet permmitting goal and realiablity also a just for the hell of it kinda thing but i do under stand were you coming from i think ill just go ahead and keep my t3t4 or goto a gt28rs if i can get the money and run stock boost out of it
     
  13. kermit5327

    kermit5327 New Member

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    ill say i wanna sit prolly right around 300
     
  14. kermit5327

    kermit5327 New Member

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    ok what about this idk if it will work or not and im sure someone will correct meif im wrong but shot peend d15 rods for smaller stroke the lowest comp pistons i can find what are they like 9.1:1 like some z6 pistons in a y8 block y8 head 2 layer y8 head gasket that should put my comp at around 8.66:1

    now question because my buddie thinks im wrong if i build a head for high comp will it rase or lower my comp and will it decress or improve the performance of my motor
     
  15. reikoshea

    reikoshea HS Troll...And Mod Moderator VIP

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    Thank you blanco...you said everything i was thinking.

    This was the first time i looked at this thread and i got the urge to push an old man down the stairs just from reading all the anal spew.
     
  16. kermit5327

    kermit5327 New Member

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    will d15 rods fit in a y8 block
     
  17. Matts96HB

    Matts96HB . Moderator VIP

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    Wait a second, I have a question. Many people have told me that shorter gears will make the turbo spool faster.

    Say you have a B16 tranny on an LS. Doesnt it just seem like its spooling faster? Since the rpms will be increasing faster than say an LS tranny? Because if the RPMS are increasing faster, the exhaust pressure is there faster, but you're also getting closer to the shift faster. Right?
     
  18. reikoshea

    reikoshea HS Troll...And Mod Moderator VIP

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    correct.

    it feels like its spooling up faster, but in reality, it just means you have to shift faster, and you are out of your powerband sooner.

    thats why you see so many people talk about mating an LS transmission with their build. The LS tranny can keep them in the powerband longer. While they might not get as good of a 60' or even 300' the 1/8 and 1/4 mile times will, on the whole be better (Im generalizing here, so bare with me).
     
  19. Matts96HB

    Matts96HB . Moderator VIP

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    Gotcha. So that is why people with B16 trannys will use an LS 4th and 5th gear. I was thinking of using a GSR 4th and 5th in my build, because I don't really have the money to go switching transmissions.
     
  20. reikoshea

    reikoshea HS Troll...And Mod Moderator VIP

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    the other reason is that at 60mph in 5th gear youre only doing 2,500 or so RPMs with an LS transmission. In a B16 its closer to 3,500. More RPMs = More gas.
     
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