Engine Theory, Build, Etc Discussion.

Discussion in 'Engine & Transmission Mods' started by BlkCurrantKord, Oct 15, 2007.

  1. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    Ok, this thread is so you can ask questions about engine parts, terms, names, how to setup rod/piston combo's, compression ratios,....you get the point.

    If there's something you don't know or dont quite understand, I and the rest of the members will do our best to help you understand and have some sense of a working knowledge when it comes to engine talk. Keep in mine there's gonna be some things that I or other members don't know enough about so you may end up searching google.com on your own.

    So...start it up....
     
  2. CHID0

    CHID0 Well-Known Member

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    Here it goes......If I'm thinkin about runnin 12+ lbs of boost whats the best CR for the block build? How do I achieve that compression?

    I'm an engine noob......:(
     
  3. Kid2000EX

    Kid2000EX Well-Known Member

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    So everyone knows and we can stop writing it:

    K20 Pistons and F23 pistons both have a bore of 86mm so they will fit. Because of the compression and raise and proof through Honda-Tech, it wouldnt be wise to put K20a2(RSX-S) pistons or your copression would rise to 12-14:1 and your motor would blow. K20a3's would be perfect because your compression would be right at about 11:1-11:7. F23a5's would be at about 10:7!

    Hope this Helps,
    Mike
     
  4. Kid2000EX

    Kid2000EX Well-Known Member

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    Honestly 12lbs of boost would be okay on a stock block. I say anything above 15lbs, your compression would need to be at least 9:0:1 and under. So forged pistons would have to be ordered. Most companies that do forged set the CR at 8:8:1 or 8:5:1 which should be sufficient enough for over 15lbs. Dont forget that you will also need piston rings forged rods as well as your main bearings to fortify the short block. JackHunt told me that he has always used stock rods in his engines, though I agree with him, if you have the money, go with forged rods. If anyone wants to add to this(ahem Greg) please do.
     
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  5. Roadrage

    Roadrage Well-Known Member

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    Complete noob on this. I would like to do the cheap NA build that was already posted in the other thread. what all is needed to get the job done minus the labor. Like i said im a complete noob on this. eg, pistons, rings, pnp, will the stock engine work or will i have to convert to something else, different plugs or wires. you know ish like that.
     
  6. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    Anywhere from 8.5:1 to 9.0:1. There's multiple ways to achieve this compression ratio. The easiest being to use an aftermarket rod which is the same length at the stock unit (aka Crower) to handle the abuse of 12+ lbs of boost, and a piston with a dished or recessed dome.

    Other things that come into play are if you mill the head, use flat faced valves, a longer/shorter rod, change the compression height of the piston, etc.
     
  7. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    There's a little more to it..

    The F23 and K20 have the same bore and compression height in their pistons. The only difference is the dome or dish of the piston itself. This is what greatly changes the compression ratio. Also, your motor will not blow with 12-14:1 compression, it'll just require 93+ octane fuel or race fuel and some really good tuning.
     
  8. Kid2000EX

    Kid2000EX Well-Known Member

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    Sorry about that, I shouldve added that you must use 93+ octane gas for the motor to work with the CR. But I doubt that anyone on here has easy access to 94+octane gas.
     
  9. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    Ok, you have an a5 correct? I posted everything needed parts wise. The only things that you would want done by a shop are..

    1) Hot Tank - cleans the block
    2) Hone Job - preps the cylinder walls for new pistons
    3) Balance and Assembly - unless you have some background or knowledge, leave it to the pros.

    I'm not really sure what you mean by "will the stock engine work or convert to something else". Plugs and wires will stay the same, there's no reason why those would change.
     
  10. Kid2000EX

    Kid2000EX Well-Known Member

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    I can see this thread being 200 pages long and it will also attract more people from other forums. Im surprised no F20bvs. H22 questions yet!
     

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