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lsvtec build

Discussion in 'Engine Building' started by JDM91SIR, Jul 24, 2005.

  1. JDM91SIR

    JDM91SIR Member

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    Yes i was plaining on building a lsvtec and i was reading a bunch of things about the bottom end not being able to handle the rev that the b16a head can give out. So i was wondering what maybe a good set up on the bottom end so it can handle it.
     
  2. sohcslammer

    sohcslammer Senior Member

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    You could de-stroke the motor by around 5mm effectively creating a near perfect rod/stroke angle and thereby increasing the rpm capabilities.

    Or something like that. :p

    Edit - Wow. I actually just went and did the math and to have a "perfect" rod/stroke ratio of between 1.75:1 and 1.8:1 you would need to de-stroke the motor by 13mm, if you are using the LS rods. 76mm of stroke seems about perfect. Which is also mysteriously the stroke of a B16 engine from the factory.... :p


    BTW- to get your rod/stroke just divide your rod lenth by your stroke. For example -

    Ls rods = 137 mm
    LS stroke = 89 mm
    137 / 89 = 1.53:1 which is poor, yes.
     
  3. 97CTR

    97CTR Senior Member

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    If you want to rev high on your ls block a little more "safely". Replace your stock rod bolts with ARP. Get a crank girdle, aftermarket or oem(but not totally necessary).

    Revs are mainly determined by the head and not the block. And a perfect R/S ratio is all theoretical numbers any way. A gsr I beleive is 1.58:1 not much different than an ls and I rev to 9500 to 10,000. Its all in the head.
     
  4. 94CivicSlow

    94CivicSlow Senior Member

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    I have a B16 SIRII head and LS block. The head has upgraded valvetrain and the block has a built bottom end. It sees 9k everyweekend
     
  5. sohcslammer

    sohcslammer Senior Member

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    :blink:


    WTF are you talking about? There is nothing theoretical about it. For minimal cylinder wall loading you want your stroke to be exactly 57% of the length of your rod. If you had a 100mm rod then a 57mm stroke would be considered "perfect". R/s ratios have more to do than cylinder wall loading though, it also affects piston speed as well, which in turn affects power and gas consumption. Also by running a longer rod you increase the "dwell" time of the piston at TDC and create more torque with the same piston speeds.

    You obviosly need to read up a little more on engine building before you go calling r/s ratios "theoretical".
     
  6. 97CTR

    97CTR Senior Member

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    sorry let me clarify, when I said that no perfect r/s ratio exists I was reffering to making power. There is no set or standard r/s ratio that is going to make you the most power.
     
  7. sohcslammer

    sohcslammer Senior Member

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    Yes there is. There is a reason that Bizi de-strokes his f22 down to 1.8:1 r/s. It's considered "perfect"
     
  8. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    No... that's just the "best compromise" between streetable power and cylinder wall side loading. If you want to rev even higher, you can take your ratio up to 2:1 or more- great for extremely high revving power like motorcycle engines, but horrible for torque down low. It's all about compromise. Bisi knows this too.
     
  9. sohcslammer

    sohcslammer Senior Member

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    Fucker. :p
     
  10. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    :p
     
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