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Thread: compression ratio questions

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  1. #1
    Skitt2112
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    compression ratio questions

    So I'm to put it plainly, I'm lost when it comes to compression ratio's and all that stuff.

    So my question is what does the compression ratio do, how it affects the engine and power, it's relation to turbo and lbs of boost, comparing N/A compared to forced induction, and whether higher or lower ratios are better and what the higher ratios benifits and drawbacks are and what the lower ratio benifits and drawbacks are.

    (when I get to working on the engine more I want to know what I'm actually doing and need.)

  2. #2

  3. #3
    Skitt2112
    Guest
    Oh, Didn't even think about that. 0.o lol

  4. #4
    Member allrice4g64's Avatar
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    02-08-2010
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    compression ratio is the pressure inside of you cylinder. Think of it in terms of psi.
    2.4 dohc turbo, 10 psi,small 16g, evo 3 02 housing,98 flashable ecu,maft,3inch magnaflow exhaust,aem wideband,blitz turbo timer,egt gauge,balance shaft delete,a/c delete,battery in trunk,arp headstuds,fmic,mbc, (Wiseco 8:7:1 pistons coming soon.)

  5. #5
    Skitt2112
    Guest
    Ight. Think I got it. Higher ratio=more power off the line Lower ratio=better gas/torque and running boost means you need a lower ratio than normal depending on how much boost your running. High boost lower ratio lower boost can run a higher ratio. Right?

  6. #6
    Member allrice4g64's Avatar
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    02-08-2010
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    More or less.... Sometimes you can run really high compression and depending on the fuel you run make the motor last while boosting. Under higher compression temps get alot hotter inducing knock more easily. Think of how a turbo diesel works they dont have spark plugs the fuel ignites off compresion only. Most of time making the motor last depends 95 percent on your tune. I am a believer that any motor should hold boost fine if the tune is dialed in 100 percent. Sometimes though it takes a pure brainiac and alot of patience to dial a n.a. motor to accept bost safely.
    2.4 dohc turbo, 10 psi,small 16g, evo 3 02 housing,98 flashable ecu,maft,3inch magnaflow exhaust,aem wideband,blitz turbo timer,egt gauge,balance shaft delete,a/c delete,battery in trunk,arp headstuds,fmic,mbc, (Wiseco 8:7:1 pistons coming soon.)

  7. #7
    Skitt2112
    Guest
    So if i'm running just basic unleaded go for a lower compression to avoid knock. and I was thinking now that I just got a second job when I have the money doing the DOHC, 5 speed swap and then going turbo (a 14 running 20 lbs of boost?). In that order. Sound like a good build? although I might do that tranny swap first since I'd have to swap the ecu when I change the heads.

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