Forced Induction Custom FI Setup Questions

Compression...

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Old Mar 7, 2004 | 06:50 AM
  #1  
Redhatch4u's Avatar
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Default Compression...

I am going to buy a B20B engine in a few months. My question is, if I wanna go turbo what is better: a engine with higher compression or lower compression What is the difference between the two?? I am new and don't know much about compression. I will appreciate any help I can get.
Old Mar 7, 2004 | 09:08 AM
  #2  
Ravage70's Avatar
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Default Re:Compression...

higher will let u achieve ur hp goals with less boost but is a harder tune,
low comp requires more boost for the same hp but u have more room for tuning error.

thats what they told me thats what im telling u
Old Mar 7, 2004 | 09:16 AM
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atLdohc's Avatar
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Default Re:Compression...

basically hes saying if its your first turbo kit then try to keep the compression lower. you'll have less chance of breaking something. its easier to turn up the boost for more power than to buy another engine.
Old Mar 7, 2004 | 06:21 PM
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baldur's Avatar
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Default Re:Compression...

Basically saying, lower compression will allow you more boost on the same fuel.
You can't run 20psi boost on 10:1 compression on pump gas, no matter how you tune it. If you run too little ignition advance you'll just be melting exhaust valves and burning up turbine wheels.
Old Mar 7, 2004 | 10:26 PM
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Default Re:Compression...

Hi boost and lower compression owns
Old Mar 7, 2004 | 11:30 PM
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Default Re:Compression...

Originally Posted by jake2001z001
Hi boost and lower compression owns
Only for top end. Boost, especially with a large turbo (which you'll need to make up for low compression) doesn't come on that quick, so by lowering the compression from stock, you'll hurt your low end, and off-boost driving. So, boost only rules for dragging. For a daily-driver, keep the compression where it is at (except maybe for a type-r, which isn't the best to boost anyway). A cr of 9.2-9.6 is generally considered to be ok for moderate boost levels, and will give you a better-driving car than if you lower it to around 8.5 and jack up the boost. Of course, the b20 has a nice torque curve, so you won't be hurting that much. Just remember, lowering your cr equals not as much fun off-boost. Higher boost = higher trap speed. My .02.

BTW, since you are doing the b20b, look into some different internals. The rs ratio on the b20 is about as bad as they come. But with some different rods and a crank you can improve that and rev it much higher, much safer. Oh yeah, and a vtec head.
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